Academic literature on the topic 'Polivinil alcool (PVA)'

El objetivo fue desarrollar membranas de Polivinil Alcohol (PVA) y Quitosano (Qo), capaces de absorber solución de Aloe Vera y luego liberarla gradualmente para acelerar la cicatrización de la herida. La metodología empleada consistió en variar la composición de las membranas usando quitosano y Polivinil Alcohol al 5 y 10% p/v, e implementar diferentes relaciones de PVA/Qo de 30/70, 50/50 y 70/30 (v/v), para posteriormente embeberlas en solución de Aloe Vera al 2% (v/v) y formar hidrogeles. Una vez obtenidos, éstos fueron caracterizados por Espectroscopía de Infrarrojo y Microscopía Electrónica de Barrido, y evaluadas por pruebas mecánicas, pruebas de absorción, y ensayos de actividad bactericida.El grado de entrecruzamiento entre el PVA y el Quitosano permitió obtener una matriz con alta capacidad de absorción y liberación controlada de Aloe Vera, con propiedades mecánicas y estabilidad dimensional aún después de rehidratadas. Las pruebas bactericidas mostraron actividad protectora del quitosano y del Aloe Vera, lo cual hace que este compuesto sea adecuado para aplicaciones que ayudan en la curación de heridas.

A B S T R A C TSulfonated polyvinyl alcohol (PVA) can be used as a heterogeneous catalyst in esterification or transesterification reactions during methyl ester production. This catalyst with PVA support has the potential to be used commercially like Amberlyst 46. However, there are several drawbacks in the conventional methods to produce sulfonated PVA compared to Amberlyst 46. In this paper, various processes of sulfonated PVA synthesis will be discussed including the advantages and disadvantages compared to Amberlyst 46. The synthesis of sulfonated PVA catalysts can be carried out using sulfosuccinate acid reagents or other acid reagents that have sulfonic groups that act as the active sites of the catalysts. The use of sulfosuccinate acid as the reagent produces catalysts with better catalytic activity, but the resulting product is not in granule form like Amberlyst 46 and can only be used continuously for seven times. The use of chlorosulfonic acid as the reagent resulted in granular catalysts. However, the catalyst has less catalytic activity and stability, and the reagent has a relatively high environmental impact. For the synthesis performed using sulfuric acid as the reagent, no result regarding catalytic activity has been reported elsewhere. The blending of the catalyst with other polymers resulted in improvements in the thermal stability and mechanical strength of the sulfonated polyvinyl alcohol. After a careful review of the procedures, we propose blending or double cross-linking processes combined with sulfonated PVA synthesis as a promising method to increase the thermal stability and mechanical strength of the catalysts. However, it is necessary to perform further laboratory validations on the catalytic activity of the catalysts produced from the combined method because blending may reduce the acid capacity of the catalyst.Keywords: esterification catalyst, polyvinyl alcohol, sulfonation A B S T R A KPolivinil alkohol (PVA) tersulfonasi dapat digunakan sebagai katalis heterogen dalam reaksi esterifikasi atau transesterifikasi dalam produksi metil ester. Katalis dengan support polivinil alkohol ini berpotensi untuk digunakan secara komersial seperti Amberlyst 46. Akan tetapi, PVA tersulfonasi yang disintesis secara konvensional masih memiliki banyak kekurangan dibandingkan dengan Amberlyst 46. Pada kajian ini akan dibahas mengenai berbagai alternatif proses sintesis PVA tersulfonasi termasuk kelebihan dan kekurangannya jika dibandingkan dengan Amberlyst 46. Sintesis katalis PVA tersulfonasi dapat dilakukan menggunakan reagen asam sulfosuksinat (SSA) maupun reagen asam lainnya yang memiliki gugus sulfonat yang berperan sebagai situs aktif katalis. Penggunaan reagen SSA menghasilkan katalis dengan aktivitas katalitik yang baik namun produk yang dihasilkan tidak berbentuk granula seperti Amberlyst 46 dan hanya dapat digunakan ulang sebanyak tujuh kali. Penggunaan reagen asam klorosulfonat dapat menghasilkan katalis berbentuk granula, namun memiliki aktivitas katalitik dan kestabilan kurang baik, serta reagen yang digunakan cukup berbahaya. Untuk proses sintesis menggunakan reagen asam sulfat belum ada hasil mengenai aktivitas katalitik, tetapi dengan adanya blending dengan polimer lain dapat memperbaiki kestabilan termal dan kekuatan mekanik PVA tersulfonasi yang dihasilkan. Proses blending atau double cross-linking yang digabung dengan sintesis PVA tersulfonasi dapat meningkatkan kestabilan termal dan kekuatan mekanik sehingga metode gabungan ini diyakini sebagai metode yang paling potensial dilakukan untuk menghasilkan PVA tersulfonasi dengan karakteristik terbaik. Meskipun demikian, perlu dilakukan penelitian lebih lanjut disertai tahapan pengujian aktivitas katalitik pada katalis yang dihasilkan dari metode gabungan karena kemungkinan proses blending dapat mengurangi kapasitas asam pada katalis.Kata kunci: katalis esterifikasi; polivinil alkohol; sulfonasi

Abstrak: Tandan kosong kelapa sawit merupakan limbah padat terbesar yang dihasilkan oleh perkebunan kelapa sawit. Kandungan utama tandan kosong kelapa sawit adalah selulosa. Tingginya kandungan selulosa pada tandan kosong kelapa sawit dapat dimanfaatkan sebagai bahan dasar pembuatan nanoselulosa. Nanoselulosa merupakan selulosa yang dihasilkan dalam skala nano dan memiliki sifat karakteristik yang jauh lebih baik dibandingkan dengan selulosa. Pada penelitian ini dilakukan isolasi selulosa yang berasal dari tandan kosong kelapa sawit untuk menghasilkan nanoselulosa yang dapat dimanfaatkan sebagai pencampur (filler) pada polimer polivinil alkohol (PVA), sehingga diharapkan dapat memperbaiki karakteristik pada PVA. Tujuan dari penelitian ini yaitu untuk mengkaji isolasi selulosa menjadi nanoselulosa dari tandan kosong kelapa sawit serta mempelajari karakteristik pada PVA dengan adanya penambahan nanoselulosa. Penelitian ini dilakukan menggunakan rancangan penelitian deskriptif yang terdiri dari jumlah penambahan nanoselulosa (N) dan jumlah PVA (P). Karakterisasi yang dilakukan adalah uji ketebalan, uji kuat tarik, uji FT-IR, uji WVP, dan uji UV-Vis Spectrophotometer. Hasil dari penelitian menunjukkan bahwa penambahan nanoselulosa berpengaruh terhadap karakteristik film PVA. The Effects of Adding Nanocellulose From Oil Palm Empty Fruit Bunch (Elaeis guinensis Jacq) For Characterization of Polyvinil Alcohol (PVA) Abstract: Oil palm empty fruit bunches (OPEFB) are the largest solid waste produced by oil palm plantations. The main content of oil palm empty fruit bunches is cellulose. High cellulose content in oil palm empty fruit bunches can be used for making nanocellulose. Nanocellulose is cellulose that produced in nanoscale and it has better characteristic properties compared to cellulose. In this study, cellulose from oil palm empty fruit bunches was isolated to produce nanocellulose that can be used as filler for characterization of polyvinil alcohol (PVA). The purpose of this study is to examined the isolation of cellulose into nanocellulose from oil palm empty fruit bunches and to investiage the characteristics of PVA with the addition of nanocellulose. This study was conducted using a descriptive research design consisting of 2 (two) factors. The first factor was the total addition of nanocellulose (N) and the second factor was the amount of polyvinyl alcohol (P). The characterization that carried out were a thickness test, tensile strength, Fourier Transform Infra-Red (FT-IR), Water Vapor Permeability (WVP), and UV-Vis Spectrophotometer. The results of the study showed that the addition of nanocellulose can effect the characteristics of PVA films.

Polyvinyl alcohol (PVA) has good compatibility when added as filler in the form of nanocarbon so that it can produce environmentally friendly nanocomposite products. Thus, the addition of nanocomposites to PVA-based films is expected to increase and improve the mechanical properties of the resulting PVA films. This study aims to utilize palm fruit shells as raw materials for nanocarbons and as fillers for nanocomposites, as well as to determine the mechanical properties and thermal strength of nanocarbon nanofibers in the PVA matrix. Composite films were made using the solution mixing method. The research was conducted by mixing PVA solution (3.5 g) with various concentrations of nanocarbon from palm fruit shells (NCCS) and 2 ml of glycerol and 1 g of PEG 400. Film characterization includes tensile test, scanning differential calorimetry (DSC), and conductivity test. Tensile test of PVA/NCCS nanocomposite resulted in tensile strength of 0.314 MPa and an elongation of 4.21925 %. The thermal test of PVA/NCCS nanocomposite with DSC yielded a melting point of around 146.06oC. Electrical conductivity of PVA/NCCS 107.1 (1.07 x 10-3) s/cm. PVA/NCCS nanocomposite based on conductivity scale including a semiconductor material.

A B S T R A C TThe objective of this research was to determine the efficiency of the creatinine transport using chitosan alginate cross linked by polyvinyl alcohol (PVA) 0.1% with 70, 100, and 130 mg/L of creatinine concentration. The subject of this study was the membranes of chitosan alginate PVA, while the object of this study was the efficiency of the creatinine transport. The PVA 0.1% cross-linking chitosan-alginate membrane (1:0.15) was successfully synthesized. The membrane synthesized was characterized by FTIR, as well as tensile and strain test. The FTIR spectra showed that there is a new peak of the amino group of chitosan and carboxyl group of alginate at ca. 1651 cm-1. The hydroxyl group appears at ca. 1088 cm-1 while ester groups at ca. 1088 cm-1 and ca. 1265 cm-1 which indicate the cross binding between alginate and PVA. The water uptake test of the chitosan alginate PVA membrane reaches 257.76% for 6 hours. The tensile test results of the membrane before and after creatinine transport are 2.77 MPa and 12.56 MPa while the strain tests yield 14.24% and 18.51%, respectively. The maximum efficiency of the creatinine transport using the chitosan-alginate cross linked by PVA is 51.02% at 130 mg/L creatinine. This creatinine transport result using the PVA cross linking chitosan-alginate membrane are more efficient than chitosan-pectin membrane (25.24%) with the same creatinine concentration.Keywords: chitosan-alginate PVA membrane; creatinine; cross-link; synthesis; transportA B S T R A KPenelitian ini bertujuan untuk menentukan nilai efisiensi transpor kreatinin menggunakan membran kitosan-alginat tertaut silang polivinil alkohol (PVA) 0,1% dengan konsentrasi kreatinin 70, 100 dan 130 mg/L. Subjek dalam penelitian ini adalah membran kitosan-alginat PVA, sedangkan objek penelitian ini adalah pengaruh efisiensi transpor pada variasi konsentrasi kreatinin. Membran kitosan alginat (1:0,15) tertaut silang PVA 0,1% telah berhasil disintesis. Karakterisasi membran kitosan-alginat tertaut silang PVA diperoleh untuk spektra FTIR membran menunjukkan bahwa telah terjadi pergeseran serapan gugus amino dari kitosan dan gugus karboksil dari alginat pada puncak sekitar 1651 cm-1. Pada bilangan gelombang 3363,86 cm-1 terdapat serapan gugus –OH serta pada bilangan gelombang sekitar 1088 cm-1 dan 1265 cm-1 berasal dari gugus ester yang menunjukkan ikatan silang antara alginat dan PVA. Hasil uji serapan air pada membran kitosan-alginat PVA selama 6 jam mencapai rata-rata 257,76%. Hasil uji tarik membran sebelum dan setelah transpor masing-masing: 2,77 MPa dan 12,56 MPa dan untuk hasil uji regang membran sebelum dan setelah transpor masing-masing: 14,24% dan 18,51%. Efisiensi transpor kreatinin pada membran kitosan-alginat tertaut silang PVA mencapai efisiensi transpor maksimal pada konsentrasi 130 mg/L (51,02%). Efisiensi transpor kreatinin ini lebih tinggi jika dibandingkan menggunakan membran kitosan-pektin (25,24%) pada konsentrasi yang sama.Kata kunci: kreatinin; membran kitosan-alginat PVA; sintesis; taut silang; transpor

Kerusakan tulang yang akan terjadi di Indonesia pada golongan tenaga kerja sebesar 67,76% berupa penurunan massa tulang dan sebesar 28,58% berupa gangguan kepadatan tulang. Scaffold dapat dijadikan sebagai alternatif dari perawatan penyembuhan kerusakan tulang dalam bentuk perancah berpori 3D. Scaffold dapat menyediakan lingkungan yang sesuai untuk regenerasi jaringan tulang. Biomaterial keramik sebagai bahan dasar yang cocok untuk scaffold karena karakteristiknya, namun memiliki kekurangan berupa elastisitas rendah dengan permukaan yang keras dan rapuh. Pada penelitian ini dilakukan penambahan material berupa biomaterial gelatin dan PVA yang mana sangat ideal untuk diferensiasi sel dan kekuatan mekanik dari scaffold. Dalam upaya memperbaiki kualitas produk dan proses pembuatan scaffold, desain eksperimen dengan Metode Taguchi untuk mengetahui parameter yang memberikan nilai kuat tekan yang sesuai dengan tulang manusia. Parameter proses yang digunakan yaitu rasio bubuk hydroxyapatite (HA), rasio bubuk gelatin, dan rasio bubuk polyvynyl alcohol (PVA). Berdasarkan hasil penelitian yang dilakukan parameter proses rasio bubuk hydroxyapatite (HA), rasio bubuk gelatin, dan rasio bubuk polyvynyl alcohol (PVA) sangat berpengaruh terhadap nilai kuat tekan scaffold. Hasil eksperimen konfirmasi diperoleh mean sebesar 3,287 MPa menunjukkan bahwa nilai kuat tekan scaffold berada pada rentan nilai kuat tekan manusia.

Ketoprofen is included in the Class II of Biopharmaceutical Classification System (BCS) which has low solubility. Low solubility will affect the dissolution rate and the dissolved concentration, so the absorption and bioavailability are low as well. Several studies have been conducted to improve the solubility and the dissolution of drugs from these group, such as by solid dispersion system. This study aims to determine the effect of polyvinyl alcohol (PVA) on the dissolved concentration of ketoprofen in solid dispersion and in physical mixture, and to decidethe optimum formula.Solid dispersion and physical mixture of ketoprofen - PVA were formulated with the ratio of 1:1, 1:2 and 1:4, and then compared with the standard ketoprofen. Evaluation of solid dispersion was performed by the intervention test of PVA as a matrix on the maximum wavelength of standard ketoprofen using a UV-Vis spectrophotometer and the dissolution test in artificial gastric fluid media without pepsin using a basket stirrer at pH ± 1,2, the temperature of 37 ± 0.5ºC, and device speed of 50 rpm. The sample was collected at 10, 20, 30, 45, and 60 minutes. The amount of dissolved ketoprofen was determined by a UV-Vis spectrophotometer at a wavelength of 260 nm. The results showed that there was no shifting on maximum wavelength point in both solid dispersions and physical mixtures. The dissolved ketoprofen concentration that was represented in solid dispersion was greater than in physical mixture and standard ketoprofen. The highest dissolved ketoprofen concentration was indicated in solid dispersion formula with the ratio of 1:1.

En la búsqueda por mejorar el uso de los recursos naturales y aumentar el rendimiento y la calidad de los frutos empleando técnicas amigables con el medio ambiente, como el injerto y el uso de nanopartículas metálicas. El objetivo de este trabajo fue determinar el efecto del injerto combinado con la aplicación de diferentes concentraciones de nanopartículas de selenio (Se NPs) encapsuladas en un gramo del hidrogel de quitosán-polivinil alcohol (CS-PVA) en la productividad y producción de pepino injertado. Los tratamientos fueron aplicados al sustrato al momento del trasplante de la siguiente manera: 1, 2.5 y 5 mg de NPs de Se absorbidas en un gamo de hidrogeles de CS-PVA, CS-PVA sin NPs y un tratamiento control, en plantas de pepino con injerto y sin injerto. Las variables evaluadas fueron longitud y diámetro de tallo, peso fresco y seco de hojas, área foliar, longitud de raíz, longitud de fruto, número de frutos y rendimiento por planta. Los resultados mostraron que la aplicación de las NPs de Se tienen un efecto benéfico para las plantas, como un agente promotor del crecimiento y que junto con el injerto coadyuvan a obtener una mayor altura de la planta y peso de fruto obteniendo un mayor rendimiento por planta.

: Polyvinylidene fluoride (PVDF), a piezoelectric material, is commonly used in tissue engineering due to its potential for mimicking the electrical microenvironment of biological conditions for tissue development. In this present research, polyvinyl alcohol (PVA) was introduced into electrospun PVDF fabrication through an electrospinning process, aiming to enhance the nanofibrous membrane's biocompatibility properties by improving the hydrophilicity properties to act as an artificial tissue scaffold. The electrospun PVDF/PVA membranes are found to be optimum at a PVDF-to-PVA ratio of 90:10 due to its excellent mechanical, morphological, and hydrophilicity conductivity properties. Fourier transform infrared (FTIR) spectroscopy verified strong hydrogen bonding interaction formed between the fluorine group of PVDF with oxygen-containing in the hydroxyl group of PVA. In-vitro cell culture showed that the enhanced hydrophilic property of electrospun PVDF/PVA could significantly enhance the cell growth. These positive results indicated that the scaffold could be implemented as artificial tissue material for tissue engineering applications. ABSTRAK: Polivinilidena fluorida (PVDF) adalah bahan piezoelektrik yang biasa digunakan dalam kejuruteraan tisu kerana potensinya menyerupai keadaan persekitaran mikro-elektrik biologi bagi perkembangan tisu. Dalam penyelidikan ini, polivinil alkohol (PVA) diperkenalkan ke dalam fabrikasi pintalan-elektro PVDF melalui proses pemintalan-elektro, yang bertujuan bagi mengembangkan sifat biokompatibiliti membran nanogentian dengan meningkatkan sifat hidrofilik bagi menjadi perancah tisu tiruan. Membran pintalan-elektro PVDF / PVA didapati optimum pada nisbah PVDF-ke-PVA, 90:10 kerana sifat kekonduksian, mekanikal, morfologi dan hidrofiliknya yang sangat baik. Spektroskopi transformasi inframerah Fourier (FTIR) mengesahkan interaksi ikatan hidrogen yang kuat terbentuk antara kumpulan fluoro PVDF dengan oksigen yang terkandung dalam kumpulan hidroksil PVA. Kultur sel secara in-vitro menunjukkan bahawa sifat hidrofilik pintalan-elektro PVDF / PVA dapat meningkatkan pertumbuhan sel secara signifikan. Hasil positif ini menunjukkan bahawa perancah ini dapat digunakan sebagai bahan tisu buatan bagi aplikasi kejuruteraan tisu.

Tutti i tessuti presenti nel corpo umano sono prevalentemente costituiti da network fibrosi (collagene ed elastina) fortemente interpenetrati con una matrice polisaccaridica amorfa di proteoglicani e glicoproteine non collagenose, formando un solido insolubile permeato da un fluido ionico, la cosiddetta matrice extracellulare (ECM)1, all'interno della quale è inoltre presente una componente cellulare, con funzione di apporto nutrienti a tutti i componenti tissutali. Le proprietà macroscopiche del tessuto vengono determinate dalla particolare composizione e dall’assemblamento dei componenti fibrillari e della matrice. La struttura gerarchica dei tessuti a livello dimensionale [scala molecolare (1-100 nm), scala ultramolecolare (0.1-100 μm) e scala tissutale (0.1-100 mm)] assume un ruolo significativo nel determinarne le proprietà fisiche e fisiologiche. La ECM, in seguito ad una specializzazione del tessuto, riesce ad adempiere alle particolari funzioni richieste, come, ad esempio, la resistenza meccanica nei tendini e legamenti, l’estrema durezza tramite calcificazione nelle ossa e nei denti, la filtrazione nel glomerulo renale, l’adesione nelle membrane basali ecc., rendendosi responsabile di tutte le funzioni di supporto meccanico, elasticità, ancoraggio cellulare, determinazione dell’orientazione cellulare e scambio di molecole e fluidi dei tessuti umani. Le differenti funzioni, grazie ai loro specifici ruoli, rendono questi tessuti estremamente distinguibili a livello micro e macroscopici, permettendo di suddividerli facilmente in due tipologie: tessuti soft o molli (muscoli, cuore, nervi, tendini, legamenti, cartilagini, pelle, cristallino, ecc.) e tessuti hard (prevalentemente ossa e denti). Sulla base della natura e struttura della ECM, la scelta dei materiali per la simulazione delle caratteristiche chimico-fisiche della matrice extracellulare è ricaduta sugli idrogel, polimeri idrofili reticolati che in acqua o in fluidi biologici rigonfiano assorbendo elevate percentuali di liquido, pur rimanendo insolubili. Gli idrogeli sono degli ottimi materiali biomimetici grazie alla possibilità di modulare le loro proprietà strutturali, morfologiche e meccaniche sulla base dell’applicazione richiesta, semplicemente variando la loro composizione e il loro grado di reticolazione (come ad esempio gli idrogeli a base di polivinil alcool2-4). Essi rappresentano pertanto dei candidati ideali per l’ingegneria tissutale e per la medicina rigenerativa. L’attività del progetto di ricerca ha avuto come oggetto principale la sintesi e caratterizzazione di materiali biocompositi a matrice idrogelica da utilizzare come sostituti tissutali. Durante il lavoro svolto sono state identificate alcune tra le patologie articolari maggiormente invalidanti e onerose, da un punto di vista socio-economico, tra cui:  L'osteoartrosi (OA) del ginocchio, patologia di tipo degenerativo, caratterizzata dall’assottigliamento della cartilagine, che conduce, nei casi più avanzati, allo sfregamento delle unità ossee con conseguente formazione di osteosclerosi, eburneazione ossea, cisti ossee, sinoviti, versamento e tumefazione del ginocchio e, in larga scala, rigidità e dolore articolare che compromettono le normali funzioni di deambulazione5.  La degenerazione del disco intervertebrale (IDD) (caratterizzata da una netta diminuzione della vitalità cellulare, una riduzione del contenuto d’acqua del tessuto e conseguente apporto di nutrienti, una graduale sostituzione del nucleo con tessuto fibrocartilagineo e la formazione di fessure e fratture nella porzione esterna dell'anulo fibroso) che può condurre al fallimento strutturale dell'IVD comportando disordini spinali più gravi tra i quali l'erniazione del disco intervertebrale, altra patologia estremamente invalidante6.  Le lesioni meniscali da usura prodotte da lavori usuranti o di tipo traumatico in seguito a stress sportivo, che rappresentano una tipologia di infortunio molto comune, caratterizzata da dolore e invalità temporanea, che costringe il lavoratore o l'atleta a brevi-medi periodi di prognosi nei casi più lievi, e al blocco dell'articolazione nei casi più gravi. Tramite chirurgia è possibile asportare la parte di menisco danneggiata ripristinando la funzionalità dell'articolazione, tuttavia l'asportazione chirurgica comporta una modificazione permanete nell'applicazione dei carichi sulla cartilagine articolare e provoca spesso un'insorgenza precoce dell'OA7. Per far fronte agli inconvenienti prodotti dall'OA, patologia altamente invalidante, è stato progettato e sintetizzato un materiale biomimetico che potesse essere utilizzato come sostituto della cartilagine tibiale, scegliendo come materiale sostitutivo un idrogel di polivinil alcool (PVA), reticolato per via chimica mediante trisodio trimetafosfato (STMP) (entrambi materiali notoriamente atossici e impiegati come additivi alimentari)3,8. Al fine di realizzare un materiale biomimetico in grado di mimare al meglio le proprietà della cartilagine,e quindi scegliere le condizioni migliori di sintesi, sono stati sintetizzati e valutati cinque campioni di idrogel con differenti rapporti molari PVA:STMP (1:0.1; 1:0.25; 1:0.5; 1:1; 1:2), ed è stato monitorato l’effetto della variazione di parametri quali pH (11, 12, 13), concentrazione della soluzione di agente reticolante (10%/20% p/v), tempi di reazione (24, 48, 72 o 96 ore) e modalità di agitazione della soluzione (meccanica/magnetica), nonché metodologia di essiccamento [tramite liofilizzazione (_L) o tramite riscaldamento in stufa a 60°C (_E)],valutandoli in funzione della resa di reazione, solidità e continuità della struttura dei materiali. I materiali sintetizzati sono stati in seguito caratterizzati da un punto di vista chimico [mediante Spettrometria Infrarossa (IR), Spettrometria di Massa di Ioni Secondari (ToF-SIMS), Analisi Colorimetria e Analisi Elementare (AE)] per determinare qualitativamente e quantitativamente l'avvenuta reticolazione; da un punto di vista fisico [mediante Analisi Termogravimetrica (TGA) e valutazione del Contenuto d'acqua (WC)] per valutare l’effetto della reticolazione sulla stabilità termica nella matrice di PVA e per valutare la capacità di rigonfiamento degli idrogel; da un punto di vista morfologico [tramite Microscopia Elettronica a Scansione (SEM) e Calorimetria Differenziale a Scansione (DSC)] per valutare rispettivamente la micro e la mesostruttura delle matrici polimeriche; da un punto di vista reologico e meccanico [mediante Analisi Reologica (AR) e Dinamomeccanica (DMA)] per determinare se le proprietà viscoelastiche dei materiali sono confrontabili con quelle del tessuto cartilagineo del piatto tibiale. Infine, sono stati effettuati test degradativi e citotossicologici secondo le norme internazionali vigenti (ISO/FDIS 10993-5 e 10993-13 Biological evaluation of medical device) per valutare la stabilità chimica e la citotossicità dei materiali sintetizzati. Dalle analisi condotte il campione PVA-H 0.5_E mostra caratteristiche similari a quelle della cartilagine del piatto tibiale in termini di idratazione, stabilità, proprietà meccaniche e citotossicità e può essere potenzialmente impiegato nella realizzazione di impianti biomedici volti alla terapia dell’osteoartrosi9,10. Per far fronte ad uno dei disordini spinali più gravi, l'erniazione del disco intervertebrale, dove una fuoriuscita di materiale normalmente contenuto nel disco intervertebrale (nucleo polposo (NP)) entra in contatto con le strutture nervose contenute nel canale spinale, provocando intenso dolore, è stato proposto un idrogel di PVA, sintetizzato per via chimica mediante reticolazione tramite STMP e arricchito con PVP. Il PVP è un polimero altamente idrofilo che, interagendo mediante legami ad idrogeno con le catene di PVA11, ha permesso di diminuirne il grado di reticolazione, producendo matrici con proprietà meccaniche più simili al NP, e allo stesso tempo di incrementare il contenuto acquoso dei campioni fino ai valori del tessuto da sostituire. Per determinare le migliori condizioni di sintesi, sono stati sintetizzati tre idrogel con uguale rapporto molare PVA:STMP(1:0.5), ma con crescenti contenuti % p/v di PVP (1%, 2.5% e 5% p/v). I materiali sintetizzati sono stati in seguito caratterizzati da un punto di vista chimico (mediante spettrometria infrarossa (IR) e analisi colorimetria) per determinare qualitativamente e quantitativamente l'avvenuta reticolazione e per valutare se l'introduzione del PVP producesse o meno effetti di disturbo all'interno della matrice dell'idrogel. Da un punto di vista fisico (mediante analisi termo gravimetrica (TGA) e valutazione del contenuto d'acqua (WC)) per valutare l’effetto della reticolazione sulla stabilità termica della matrice di PVA e per valutare la capacità di rigonfiamento degli idrogel. Da un punto di vista morfologico (tramite calorimetria a scansione differenziale (DSC)) per valutare la mesostruttura delle matrici sintetizzate. Da un punto di vista reologico (mediante analisi reologica (AR)) per determinare se le proprietà viscoelastiche dei materiali sono confrontabili con quelle del nucleo polposo spinale. Infine, sono stati effettuati test citotossicologici e di proliferazione cellulare secondo le norme internazionali vigenti (ISO/FDIS 10993-5 Biological evaluation of medical device) per valutarne la citotossicità e la citocompatibilità dei materiali sintetizzati. Dai risultati ottenuti il materiale che meglio mima le caratteristiche del NP è il campione 5.0%, con proprietà di idratazione e meccaniche in linea con quelle del NP. Pertanto, il campione 5.0% può essere considerato un valido candidato per la realizzazione di impianti biomedici per la cura delle degenerazioni spinali12. Il lavoro svolto alla ricerca di materiali biomimetici per la cura delle lesioni meniscali è stato affrontato proponendo due tipologie di idrogel differenti, a base di PVA, per la sostituzione/rigenerazione del menisco a seconda della tipologia di lesione subita. Per casi in cui il paziente sia stato sottoposto a menischectomia totale in seguito ad una grave frattura del menisco, è stato proposto un idrogel di PVA, reticolato mediante STMP con un rapporto PVA:STMP 1:0.25, sottoposto a tre reticolazioni consecutive allo scopo di incrementarne le proprietà meccaniche fino al raggiungimento di valori paragonabili a quelli del menisco (c.a. 120 kPa). Tale idrogel è quindi inteso come sostituto permanente13. Per i casi in cui le lesioni del menisco siano di minor entità, è stato proposto uno scaffold cellulare, costituito da un idrogel misto a base di PVA e Gomma-Xantano (XG), reticolati contemporaneamente mediante STMP, come sostituto temporaneo in grado di indurre e favorire la rigenerazione del tessuto meniscale. La XG è stata scelta poichè in grado di favorire e supportare l'adesione, la proliferazione e la differenziazione cellulare14. La ricerca del miglior sostituto ha coinvolto la sintesi di tre campioni con differenti contenuti % p/v di XG-PVA (60-40; 30-70; 15-85). Una volta sintetizzate, entrambe le tipologie di materiali sono state sottoposte a caratterizzazione chimica, fisica e meccanica. Inoltre, i materiali sono stati sottoposti a test di citotossicità in vitro per valutarne l’idoneità come sostituti meniscali temporanei e/o permanenti. Nel caso dei sostituti a lungo termine il campione 3R PVA-H 0.25 può essere considerato come un potenziale sostituto biomimetico del menisco. Da un punto di vista di rilassamento degli sforzi, esso è, infatti, in grado di dissipare istantaneamente la deformazione applicata, toccando mediamente una riduzione percentuale > dell’95% dopo 1 secondo allo stesso modo del tessuto cartilagineo umano15 e possiede valori di G' paragonabili a quelli del menisco13. Mentre nel caso degli scaffold cellulari il materiale che si comporta maggiormente come materiale biomimetico è il campione XG15 con caratteristiche, in termini di idratazione e proprietà meccaniche, idonee alla colonizzazione cellulare. Pertanto, il campione XG15 risulta un potenziale candidato per la realizzazione di impianti biomedici per la cura delle lesioni meniscali e viene abilitato alla successiva fase di valutazione della citotossicità in vitro secondo le norme ISO/FDIS 10993-5.
All human tissues are mainly made by fibrous networks (collagens and elastin) deeply interpenetrated by an amorphous polysaccharide matrix of proteoglycans and non-collagenous glycoproteins, forming an insoluble solid permeated by a ionic fluid, which is the extracellular matrix (ECM)1, in which there is also a cellular component which supplies nutrients for all the tissue components. The macroscopic properties of the tissue are determined by the peculiar composition and assemblage of the fibrillary components and of the matrix. The hierarchical structure of the tissues at a dimensional level [molecular scale (1-100 nm), ultramolecular scale (0.1-100 μm) and tissue scale (0.1-100 mm)] acquire a significant role in the determination of the physical and physiological features. The ECM, as a consequence of the specialization of the tissue, is able to meet expectations for the specific functions required, such as the mechanical resistance in the tendons and ligaments, the extreme hardness through calcification in bones and teeth, the glomerular filtration rate, the adherence to basal membranes, etc., so to be responsible for the mechanical support functions of elasticity, cellular anchoring, the determination of cell orientation and the exchange of molecules and fluids in human tissues. The different functions, thanks to their specific roles, allow us to distinguish the tissues at a micro and macro level, so to divide them easily in two categories: soft tissues (muscles, heart, nerves, tendons, ligaments, cartilage, skin, crystalline lens, etc.) and hard tissues (mainly bones and teeth). On the basis of the nature and the structure of the ECM, hydrogels seemed to be the best choice for the simulation of the chemical-physical features. Hydrogels are renowned for their hydrophilic reticulum, which inflate in water or in biological fluids, absorbing a high percentage of liquids, although remains insoluble. Moreover, they are excellent biomimetic materials for the capability of modulating their structural, morphologic and mechanical features on the basis of the specific need, by varying their composition and their grade of reticulation (such as for hydrogels with a polyvinyl alcohol basis2-4). Therefore, hydrogels were ideal candidates for tissue engineering and for regenerative medicine. The aim of the PhD research was the synthesis and characterization of bio composite materials with a hydrogel matrix to be used as tissue replacement. During this study, some of the most invalidating and high cost articular pathologies have been taken into consideration; among these:  Osteoarthritis (OA) of the knee cartilage, degenerative illness, which leads to the friction between the bones, with consequent atherosclerosis formations, eburnation of the bones, bone cists, synovitis, effusion and swelling of the knee and in large scale stiffness and pain which compromise the regular walking functions5.  The degeneration of the intervertebral disc (IDD), featured by a clear drop in cellular liveliness, a reduction of the water content and the consequent nourishment supply, a gradual substitution of the core with a fibrocartilage tissue and the formation of cracks and fractures in the external fibroses annul, which may lead to a structural fail of the IVD, causing also serious spine disorders, another invalidating syndrome6.  Meniscus injuries subject to wear, caused by demanding work, or by trauma or stress, especially for athletes. This last case is very common and it is characterized by pain and a period of impediment, with short or medium term prognosis or with the total block of the articulation. As a result, surgery includes a permanent change in the amount of load and stress on the articular cartilage, which often causes a premature onset of OA7. In order to face inconveniences produced by OA, a biomimetic material was projected and synthesized, so to use it as a substitute of the tibia cartilage. This material was the PVA hydrogel, reticulated chemically through STMP (both materials are notoriously atoxic and used as food additives)3,8. To determine the best conditions, five hydrogel samples with different molar ratios PVA:STMP (1:0.1; 1:0.25; 1:0.5; 1:1; 1:2)were synthetized and valued. While monitoring the effect of the variation of the parameters such as, pH (11, 12, 13), the concentration of the reticulated solution (10%/20% p/v), the reaction time (24, 48, 72 o 96 ore) and the different modalities of solution agitation (mechanical and magnetic), the desiccation methodology (through Lyophilisation (_L) or through heater (_E) 60°C) evaluating the results on the base of the reaction feedback, the solidity and continuity of the materials’ structure.The synthetized materials were later chemically characterized through an IR spectrometry, mass spectrometry of secondary ions (ToF-SIMS), colorimetric test and element analysis (AE), in order to determine the quality and quantity of the reticulum. From a physical point of view, the materials were characterizedthanks to the thermogravimetric analysis(TGA) and the evaluation of the water content (WC), it was possible to value if the entrance of the reticulum changed the thermic stability of the PVA matrix and, moreover, the inflatement capability of the hydrogel. Then, the material was characterized morphologically, through scanning electron microscope (SEM) and differential scanning calorimeter (DSC)to analyse respectively the micro and the meso-structure. Finally, a rheological and mechanical characterization was made, thanks to a rheological analysis and a dynamo mechanical analysis(DMA) to determine if the viscoelastic properties of the materials are comparable to those of the tibia cartilage tissue. In conclusion, degradation and cytotoxic tests were made, following international procedures (ISO/FDIS 10993-5 e 10993-13 Biological evaluation of medical device), to evaluate the chemicalstability and the cytocompatibility of the synthetizedmaterials. From the analysis made on the sample PVA-H 0.5_E,it is possible to identify similar characteristics to the cartilage of the tibial plafond, in terms of hydration, stability, mechanical properties, and cytotoxicity and, therefore, it may be used in the realization of biomedical implants for the osteoarthritis therapy9,10. In order to face one of the most serious spinal disorders, the herniation of the intervertebral disc, in which a leak of material of the nucleus pulposus (NP) touches the nervous structures of the spine and causes intense pain, it was possible to propose a PVA hydrogel, synthetized chemically through STMP and enriched by PVP. The PVP is a highly hydrophilic polymer, which interacts through hydrogen bonds with the PVA chains11, and has allowed to decrease the degree of reticulation, producing a matrix with similar mechanical properties to the NP, and, at the same time, it has increased the water content of the samples, reaching the measures of the tissue that is being replaced.To determine the best conditions, three hydrogels were synthetized with the same molar ratioPVA:STMP (1:0.5), but with growing contents of PVP % p/v (1%, 2.5% e 5% p/v). The materials were later characterized through a chemical analysis, by IR spectrometry and colorimetric tests to determine the quality and quantity of the reticulum and to appraise if the introduction of PVP produced disturbing effects in the hydrogel’s matrix. More tests were made, by a physical viewpoint, thanks to thermogravimetric analysis(TGA) and evaluation of the water content(WC) to estimate the inflatement capacities of the hydrogels.Morphological tests, through differential scanning calorimeter (DSC) were made to determine the mesostructure. Rheological analyses (AR) were made to determine if the viscoelastic properties of the materials were comparable with those of the spinal nucleus pulposus, and finally cytotoxic tests were made, following international procedures (ISO/FDIS 10993-5 e 10993-13 Biological evaluation of medical device), to evaluate the chemical stability and the cytocompatibility of the synthetized materials. In conclusion, from the results obtained in this study, the best material which mimes best the NP features is the 5.0% sample, with hydration and mechanical properties similar to the NP. Therefore, the 5.0% sample may be considered an excellent possibility for the realization of biomedical implants for the therapy of spinal degenerations12. The research of biomimetic materials for the therapy of meniscal injuries was made by proposing two different samples of PVA based hydrogels for the substitution of regeneration of the meniscus, depending on the type of lesion: For those cases in which the patient had undergone Meniscectomy for a serious fracture, a PVA hydrogel reticulum obtained through STMP with ratioPVA:STMP 1:0.25, after three reticulations with the aim of incrementing the mechanical properties, so to reach similar features to those of the meniscus (approximately120 kPa) was proposed as a possible substitute13.For those cases in which the meniscal lesions were of a minor entity, a cellular scaffold was proposed. This scaffold was made by a hydrogel mix of PVA and Xanthan Gum, reticulated simultaneously through STMP for the regeneration of the meniscal tissue14. The research of the best substitute involved the synthesis of three samples with different content % p/v di XG-PVA (60-40; 30-70; 15-85).Once synthetized, both typologies of materials were cross-examined by a chemical, physical and mechanical characterization. Moreover, the materials undergone citotoxicological tests in vitro to evaluate the suitability for temporary or permanent meniscal substitutes. In the case of long-term substitutes, the sample 3R PVA-H 0.25 may be considered as a potential biomimetic substitute of the meniscus. To what may concern the stress relaxation tests, it is capable of instant dissipation of the deformation performed, by touching a decrease percentage > than 95% after 1 second, similarly to the human cartilage tissue15and with the same G value13.In the case of celluar scaffolds, the sample with improved skils such as biomimetic material is XG15.X15posses good properties in terms of hydration, mechanical properties apt for cellular colonization.Therefore, the sample XG15 is a potential candidate for the realization of biomedical implants for the therapy of meniscal lesions and it is qualified for the following evaluation fase of citotoxicology in vitro, in accordance with the law ISO/FDIS 10993-5.

La tecnología de la electrohilatura, mediante la que se obtienen filamentos de polímero utilizando una fuerza electrostática, a partir de la disolución de polímero cargado eléctricamente, se ha convertido en los últimos años en la tecnología más popular para la obtención de velos de nanofibras, habiéndose desarrollado dispositivos capaces de obtener de forma contínua y a escala industrial dichos velos, para ser utilizados en aplicaciones tan diversas como son la filtración, defensa y seguridad, electrónica y medicina, entre otras. Estos materiales catalogados estructuralmente de nanométricos, se caracterizan por ser materiales contínuos, porosos y de gran relación superficie/volumen, al estar conformados por un enmarañado homogéneo de fibras de diámetros nanométricos. Desde el punto de vista de la absorción acústica, estos materiales presentan un fuerte potencial como elementos resonadores a bajas frecuencias y absorbentes acústicos convencionales, capaces de actuar en todo el rango de frecuencias de interés para la acústica arquitectónica. En este trabajo se pretende optimizar el proceso de obtención de los velos de nanofibras de alcohol de polivinilo, (PVA) sobre substratos textiles de polipropileno no tejido, haciendo uso de la tecnología de la electrohilatura, para posteriormente ser caracterizados acústicamente, con el fin de conocer la capacidad de mejora que aportan a los absorbentes acústicos convencionales base-textil, en edificación y en la industria de la automoción y aeroespacial, teniendo en cuenta que la contribución en peso y espesor al conjunto resulta despreciable. Para todo ello, será necesario el uso de técnicas instrumentales que permitan analizar las propiedades superficiales del substrato colector del velo de nanofibras, como la medición de los ángulos de contacto o la medición de la conductividad eléctrica superficial. También será necesaria una serie de técnicas instrumentales que permitan caracterizar la disolución percursora de los velos de
Blanes Company, M. (2011). Obtención de velos de nanofibras de alcohol de polivinilo (PVA) sobre substratos textiles, con aplicaciones como absorbentes acústicos [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/11401
Palancia

Orientadores: William Dias Belangero, Vanessa Petrilli Bavaresco
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas
Made available in DSpace on 2018-08-19T13:54:42Z (GMT). No. of bitstreams: 1 Batista_NilzaAlzira_M.pdf: 2999795 bytes, checksum: 62c4ef5808533e1bb33930f97cede278 (MD5) Previous issue date: 2011
Resumo: Hidrogel de álcool de polivinil (PVA) foi utilizado como potencial reparador de defeitos osteocondrais da cartilagem articular. A citotoxicidade in vitro foi avaliada com células Vero e células-tronco mesenquimais da medula óssea de ratos Wistar-Kyoto. Para análise in vivo, os implantes foram colocados em defeitos produzidos nos joelhos de ratos Wistar. Após tempos de seguimento de 0, 3, 6, 12 e 24 semanas, as amostras foram analisadas por microscopia óptica convencional, ensaio mecânico de fluência à indentação, espectrometria de fluorescência raio X e microscopia eletrônica de varredura. Os resultados in vitro motraram que o hidrogel de PVA não afetou a atividade metabólica de ambas as células estudadas, nem tampouco a diferenciação osteogênica das células mesenquimais. Atividade da enzima fosfatase alcalina e formação de matriz mineralizada foram identificadas. O PVA implantado não apresentou sinais de desgastes ou qualquer mudança de aspecto quando comparado com o dia do implante. A interface do implante/tecido mostrou a formação e manutenção de tecido conjuntivo denso e osso recém-formado em todos os grupos estudados. Foi observado um aumento no módulo de fluência e concentração de cálcio e fósforo no PVA longo do tempo. O desempenho do higrogel de PVA irradiados e acetalizadas foi considerado satisfatório para a aplicação proposta
Abstract: Irradiated and acetalized polyvinyl alcohol (PVA) hydrogel was investigated as a potential material for osteochondral defect repair in articular cartilage. The in vitro cytotoxicity of the material was evaluated with Vero cells and mesenchymal stem cells from bone marrow of Wistar-Kyoto rats. For in vivo analyses, plugs of the material were implanted into defects produced in the knees of male Wistar rats-WH. After follow-up times of 0, 3, 6, 12 and 24 weeks, the samples were analyzed by conventional optical and scanning electron microscopy, X-ray fluorescence spectrometry and submitted to mechanical testing of creep indentation. The in vitro results suggest that the PVA hydrogel did not affect the viability and morphology of any of the cell types studied. The hydrogel affected neither the metabolic activity of both studied cells nor the osteogenic differentiation of the mesenchymal cells. Activity of alkaline phosphatase and mineralized organic matrix formation could be identified. The implanted plugs showed no sign of wear or aspect change. The interface plug/tissue exhibited dense connective tissue and newly formed bone in all groups. It was observed an increase in the creep modulus and in the concentration of calcium and phosphorus in the PVA over time. The performance of the irradiated and acetalized PVA was considered satisfactory for the proposed application
Mestrado
Fisiopatologia Cirúrgica
Mestre em Ciências

Focal chondral defects impair considerably patients’ quality of life and may predispose for osteoarthritis. The strong association between age and increasing incidence of osteoarthritis marks it as an age related disease. However, osteoarthritis can be also consequence of other concomitant disorders; among these, the hereditary disease haemophilia stands out. The articular problems of patients with haemophilia begin still in infancy, when minor injuries result in recurrent hemarthroses that may predispose for haemophilic arthropathy. The lack of efficient modalities of treatment has prompted research into tissue engineering, whose basic approach depends upon the interaction between cells, scaffolds and signalling factors to create in vitro a biological tissue construct to implant in vivo, mimicking the tissue of interest. Engineering cartilage is no exception to this approach. Such tissue engineering strategies are still adopted in orthopaedic surgical practice, providing for autologous chondrocytes implants with or without a supporting matrix in order to promote cartilage regeneration. Conversely, in patients with haemophilia, current available strategy can only slow the progression of joint damage, without recovery of tissue integrity. The aim of this work was twofold. At first, a novel supporting structure to treat focal articular defects was manufactured and characterized. Then, the feasibility of using haemophilic chondrocytes for autologous cartilage tissue engineering was considered. By a controlled chemical oxidation, 1% or 2% hydroxyls of the synthetic polymer polyvinyl alcohol (PVA) backbone were oxidized to carbonyls. Oxidation was verified by 2,4-dinitrophenylhydrazine assay and covalent binding with lysozyme. After physical cross-linking of polymeric solutions, 1% and 2% oxidized PVA scaffolds were evaluated and compared to neat PVA scaffolds. Scanning Electron Microscopy (SEM) micrographs showed oxidation to affect hydrogel surface continuity. Moreover, increasing carbonyls content, physical and biodegradation properties were modulated. In particular, mechanical properties, hydrodynamic radius of particles, thermal characteristics, and crystallinity degree of PVA hydrogels decreased with oxidation rate. Conversely, swelling behavior and protein release were enhanced, suggesting oxidized PVA potentiality as protein delivery system. Most important, biocompatibility and biodegradability of PVA scaffolds increased along with oxidation. After 12-week in vivo implantation, hydrogels did not elicit severe inflammatory reactions. Nevertheless, a little limphomonocytic infiltration by CD3+ and F4/80+ cells suggested a role for inflammatory populations in implant reabsorption. Afterwards, non-haemophilic and haemophilic chondrocytes were isolated and cultured. After a morphological evaluation through optical microscopy, cells were compared for the expression of specific mRNAs (COL2A1, COL9A3, COMP; ACAN; SOX9) by RT-PCR and specific surface markers (CD44; CD49c; CD49e; CD49f; CD151; CD26; CD73) by flow cytometry. RT-PCR results confirmed the expression of target genes and any immunophenotypic difference was observed despite haemophilic chondrocytes were exposed to blood in vivo which is one of the major responsible of cytotoxicity. Flow-cytometry showed that both subcultures consisted of CD44+/CD49c+/CD49e+/CD151+/CD73+/CD49f-/CD26- cells. High expression of adhesion molecules (e.g. CD44, CD49c, CD49e) involved in cell-cell or cell-matrix interactions, revealed high chondrogenic capacity. As it is well known PVA inability in sustaining cell adhesion, a bio-hybrid composite scaffold was than obtained combining the biomechanical properties of 1% oxidized PVA with an alternative matrix source that is decellularized Wharton’s jelly (W’s J). The hydrogel itself and the more specific decellularized articular cartilage (AC) matrix, combined with 1% oxidized PVA, were used as controls. Both cell populations behaviour was evaluated after seeding cells on scaffolds. According to SEM micrographs and Thiazolyl Blue Tetrazolium Blue proliferation assay, W’s J matrix showed a singular attitude in sustaining adhesion and proliferation of both cell populations. Our results highlighted oxidized PVA as a smart biomaterial useful for manufacturing scaffolds with customizable mechanical behaviour, protein-loading ability and biodegradability. Moreover, this study contributes to the definition of haemophilic chondrocytes phenotype, providing new potential markers to characterize them. Our preliminary evidences support the chance of using haemophilic chondrocytes for autologous implant in haemophilic patients. W’s J/oxidized 1% PVA may be considered as an innovative and easily available scaffold for cartilage restoration both in haemophilic and non-haemophilic patients.
I difetti condrali focali compromettono significativamente la qualità della vita dei pazienti predisponendo all'osteoartrite. Eziologicamente sussiste una forte associazione tra l'età del paziente e l’incidenza di osteoartrite, consentendo di identificarla come una malattia legata all’invecchiamento. L’osteoartrite tuttavia può essere anche conseguenza di patologie concomitanti; tra queste l’emofilia, coagulopatia ereditaria. I problemi articolari nei pazienti emofilici esordiscono già nell’infanzia, quando danni minori possono esitare in emartri ricorrenti predisponendo all’artropatia emofilica. L’assenza di trattamenti soddisfacenti per efficacia ha spinto la ricerca nell’ambito dell’ingegneria tissutale, il cui approccio di base si fonda sull’interazione tra cellule, scaffolds e fattori di crescita. L’obiettivo è di creare in vitro costrutti biologici funzionali, capaci di mimare il tessuto d’interesse dopo impianto. Alcune strategie di ingegneria tissutale sono già adottate in chirurgia ortopedica. Esse prevedono l’impianto di condrociti autologhi come tali o supportati da matrici al fine di promuovere la rigenerazione e quindi l’integrità del tessuto compromesso. Di esse tuttavia i pazienti emofilici non possono beneficiare, disponendo ad oggi di approcci volti a rallentare solamente la progressione del danno senza favorirne il recupero. Lo scopo di questo lavoro di Tesi è stato duplice. Dapprima è stato realizzato e caratterizzato un nuovo scaffold funzionale al recupero del danno cartilagineo focale. Successivamente, è stata valutata la possibilità di utilizzare i condrociti del paziente emofilico nella prospettiva di un impianto autologo. Mediante una reazione chimica di ossidazione, l’1% o il 2% dei gruppi ossidrilici presenti sul backbone del polimero sintetico polyvinyl alcohol (PVA) sono stati ossidati a gruppi carbonilici. L’avvenuta ossidazione è stata verificata mediante saggio con 2,4-dinitrofenilidrazina e binding covalente di lisozima. A seguito di cross-linking fisico delle soluzioni polimeriche, scaffolds in PVA ossidato all’1% ed al 2% sono stati quindi valutati e confrontati con scaffolds in PVA non ossidato. La microscopia elettronica a scansione ha rivelato come l’impiego di soluzioni polimeriche ossidate influenzi la continuità superficiale degli idrogeli risultanti. Inoltre, aumentando il contenuto in carbonili, anche le proprietà fisiche e di biodegradazione risultano modulate. In particolare, la meccanicità degli scaffolds, il raggio idrodinamico delle particelle, le proprietà termiche ed il grado di cristallinità degli idrogeli di PVA diminuiscono all’aumentare del grado di ossidazione. Diversamente, il rigonfiamento ed il rilascio proteico aumentano, suggerendo potenzialità di protein-delivery system. Anche le caratteristiche di biocompatibilità e biodegradazione sono state considerate. Dopo 12 settimane di impianto sottocutaneo in vivo, gli idrogeli non hanno provocato gravi reazioni infiammatorie. Tuttavia, una limitata infiltrazione linfomonocitaria da parte di cellule CD3+ e F4/80+ ha suggerito un ruolo delle popolazioni infiammatorie nel riassorbimento dell’impianto: all’aumento del grado di ossidazione è stato riscontrato un incremento del tasso di degradazione degli scaffolds. I condrociti da paziente emofilico e non emofilico sono stati quindi isolati e messi in coltura. Dopo valutazione morfologica mediante microscopia ottica, le cellule sono state comparate per l’espressione di specifici mRNA (COL2A1; COL9A3; COMP; ACAN; SOX9) attraverso RT-PCR; e per l’espressione di marker di superficie caratteristici (CD44; CD49c; CD49e; CD49f; CD151; CD26; CD73) attraverso analisi di citofluorimetria. I risultati di RT-PCR hanno confermato l’espressione dei geni target; inoltre differenze immunofenotipiche non sono state osservate tra i tipi cellulari sebbene i condrociti da paziente emofilico fossero stati esposti in vivo al sangue, tra i maggiori responsabili di citotossicità. La citofluorimetria ha mostrato dunque che entrambe le popolazioni presentavano cellule con immunofenotipo CD44+/CD49c+/CD49e+/CD151+/CD73+/CD49f-/CD26-. L’elevata espressione di molecole di adesione (e.g. CD44, CD49c, CD49e) coinvolte in interazioni cellula-cellula o cellula-matrice, ha suggerito un alto potenziale condrogenico. Essendo nota l’inadeguatezza del PVA nel promuovere l’adesione cellulare, è stato realizzato uno scaffold bio-ibrido composito combinando le proprietà meccaniche del PVA ossidato all’1% con una matrice extracellulare decellularizzata non tessuto specifica: la gelatina di Wharton. L’idrogel tal quale e la più specifica matrice da cartilagine articolare decellularizzata, combinata con il PVA ossidato all’1%, sono stati usati come controllo. Il comportamento di entrambe le popolazioni cellulari è stata valutata dopo semina sugli scaffolds. Immagini di microscopia elettronica a scansione ed il saggio di proliferazione con Thiazolyl Blue Tetrazolium Blue hanno mostrato come la matrice da W’s J sostenga in modo singolare l’adesione e la proliferazione di entrambe le popolazioni cellulari. I risultati di questo lavoro di Tesi hanno consentito di identificare nel PVA ossidato un biomateriale intelligente per la realizzazione di scaffolds con proprietà meccaniche, di protein-loading, e di biodegradazione modulabili. Inoltre, questo studio ha contribuito a definire il fenotipo dei condrociti da paziente emofilico, provvedendo a fornire nuovi potenziali marker per caratterizzarli e suggerendo la possibilità di impianto autologo. Lo scaffold composito W’J/ PVA ossidato 1% potrebbe infine essere considerato come una struttura innovativa per il recupero del danno cartilagineo sia in pazienti affetti da osteoartrite idiopatica che secondaria.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Neste trabalho foram obtidos e caracterizados filmes de polivinil álcool (PVAl) puro e híbrido polivinil álcool/sulfeto de cádmio (PVAl/CdS). A síntese foi realizada usando o método “hidrotérmico in situ”. O híbrido é composto pela matriz orgânica o PVAl e a outra fase inorgânica é o CdS. As amostras foram obtidas na forma de filmes pelo método “casting” a partir de soluções de PVAl/CdS sintetizadas, as quais possuem concentrações de (0.05 %); (0.1 %); (0.2 %); (0.4 %) e (0.7 %) em peso de CdS. A morfologia e as propriedades ópticas, térmicas e elétricas do filme de PVAl e do híbrido PVAl/CdS foram caracterizadas pelas técnicas de Difração de Raios –X (DRX), Espectroscopia na Região do Ultravioleta-visível (UV-vis), Calorimetria Diferencial Exploratória (DSC) e Espectroscopia de Impedância. A análise de DRX utilizando o software composto por um banco de dados de cristalografia indicou a formação de nanopartículas de CdS que possuem estrutura hexagonal. Através de cálculos usando a equação de Scherrer obteve-se o tamanho das nanopartículas que variaram entre (70 e 113 nm). As medidas de UV-vis também confirmaram que as partículas possuem diferentes tamanhos. A presença das nanopartículas é indicada por um pequeno deslocamento da banda de absorção característica do material em determinado comprimento como o CdS “bulk” (490 nanômetro (nm)). O deslocamento desta banda, característica para comprimento de onda menor (de 490 para 485 nm) indica que os tamanhos das partículas são suficientemente pequenos para produzir o chamado efeito quântico. A análise térmica de DSC indicou o comportamento térmico e a influência das partículas CdS sobre os tipos de transformações básicas do polímero como a temperatura de transição vítrea (Tg), temperatura de fusão (Tm), temperatura...
In this work were obtained and characterized films of pure polyvinyl alcohol (PVAl) and hybrid PVAl/CdS. The synthesis was performed using the “hydrothermal in situ” method. The hybrid is composed by one organic part, called matrix polyvinyl alcohol (PVAl) and an inorganic phase, cadmium sulfide (CdS). The samples were obtained as films by the casting method from PVAl/CdS solutions with (0.05 %); (0.1 %); (0.2 %); (0.4 %) and (0.7 %) concentration of CdS. The morphology, optical properties, thermal properties and electrical properties of pure PVAl film and hybrid PVAl/CdS were characterized by techniques such as X-ray diffraction (XRD) spectroscopy in the ultraviolet-visible (UV-vis), Differential Scanning Calorimetry (DSC) and impedance spectroscopy. The analysis of XRD using programs with crystallography data stored shows the formation of CdS nanoparticles which have hexagonal structure. Through calculation using the Scherrer equation, the sizes of the nanoparticles were obtained in a gap between (70 and 113 nm). The measurements of UV-vis also showed that the particles have different sizes and that the CdS particles have dimensions in nanometric scale. The presence of nanoparticles is indicated by a small shift of the absorption band of the material characteristic as in the CdS bulk, (490 nm). When such characteristic band shift occurs to shorten wavelength from (490 to 485 nm), it indicates that the particle size decreased due to quantum effects. It is confirmed by the XRD technique. The thermal analysis of DSC studied the thermal behavior and the influence of CdS particles on the types of transformations as the basic polymer glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc). The external factor that most affect the T m and Tg is the presence of plasticizers. It could be noted when intentionally added the CdS... (Complete abstract click electronic access below)

Memoria para optar al título de Ingeniera Civil Mecánica
El presente trabajo es un estudio de carácter exploratorio sobre el tema de materiales compuestos de alcohol polivinílico y diferentes nanopartículas. El objetivo es estudiar la influencia del tipo, tamaño y morfología de nanopartículas sobre las propiedades mecánicas de PVA reforzada con ellas. El alcohol polivinílico es un polímero no tóxico para el ser humano, esta característica hace que sea interesante de estudiar en aplicaciones como transporte de fármacos y revestimiento de heridas. En estos casos los materiales compuestos nanopartículas pueden actuar como agentes transportadores de los fármacos y la matriz de PVA actúa aglomerando estas nanopartículas. Además tienen amplias aplicaciones como membranas. El estudio mecánico de este tipo de materiales es relevante a la hora de la fabricación en masa. En este caso se observa que los materiales tienen propiedades similares al PVA con respecto al módulo de Young y al esfuerzo de fluencia y no así con respecto a la deformación. La síntesis de las nanopartículas puede ser controlada mediante el pH y la temperatura. En este caso se utilizan cantidades similares de NaOH y temperatura de 80°C para todas las nanopartículas. El análisis mediante TEM muestra que estas condiciones de síntesis no son las ideales para la mayoría de las nanopartículas. En la síntesis de las nanopartículas y nanocompuestos con ferritas es necesario disminuir la temperatura de 80°C a 30-40°C y controlar cuidadosamente el pH de la solución en 9.5 u 11 para obtener partículas de menor tamaño con desviaciones estándar más acotadas. El impacto de la morfología y tamaño en las propiedades mecánicas no es del todo claro. Sí se observa una tendencia general a mejorar el módulo de Young y el esfuerzo de fluencia con la adición de nanopartículas, sin embargo, existen excepciones como la muestra de CuO/CoFe2O4 en la que disminuye E y el esfuerzo de fluencia. El incremento de E ocurre porque las nanopartículas tienden a generar enlaces secundarios entre las cadenas de polímeros, generando un efecto de reticulación, dándole mayor rigidez al sistema. El cambio en el esfuerzo de fluencia depende más de la interacción entre nanopartículas y matriz que de los enlaces. Depende de si la matriz tiene un contacto uniforme con las nanopartículas, de si las nanopartículas se aglomeran y de la morfología de las mismas nanopartículas. Estas características no pueden ser estudiadas con los resultados obtenidos en este estudio. El estudio puede ser continuado de distintas maneras. En primera instancia se puede orientar a caracterizar un tipo de material separando las nanopartículas según tamaño. Se puede estudiar el área superificial para buscar una correlación entre este valor y las propiedades mecánicas. Además, como el PVA es un material viscoelástico se sugiere hacer otras pruebas de estabilidad térmica y de dinámica de las piezas.

Memoria para optar al título de Ingeniero Civil
El siguiente trabajo presenta un estudio del comportamiento de hormigones tradicionales al ser reforzados con microfibras de polivinilo de alcohol. Específicamente, este analiza cambios en propiedades mecánicas de este material como lo son su resistencia y su ductilidad. Esto último, sin dejar de lado la posibilidad de estudiar otros fenómenos que se pudieran observar a lo largo de la investigación. Esta investigación consiste tanto en experimentación en laboratorio como en análisis mediante el uso de software computacional. La primera parte mencionada contempla la elaboración de tandas de probetas cilíndricas de hormigón con y sin fibra. Diferentes cantidades de fibra son utilizadas en distintas mezclas buscando contrastar resultados con mezclas sin fibra. De igual manera, las proporciones agua/cemento y áridos/cemento y el tamaño máximo de árido en cada set de probetas son diferentes con el fin de obtener un espectro mayor de resultados y de esta forma poder realizar un análisis más completo. Existe un primer grupo de probetas que se elabora para llevar a cabo ensayos preliminares a modo de prueba y obtener algún tipo de tendencia general. Un segundo grupo para ajustar dosificaciones y un último grupo, mucho más amplio en cantidad que el primero, el cual es necesario para efectuar un estudio más complejo y global del comportamiento del hormigón tradicional reforzado con microfibras de PVA. De las probetas finales, cuyas variables más características son: la cantidad de fibra y el tamaño máximo de árido (0%, 1% y 2% de fibra y tamaños de árido de 0.3 mm, 4.75 mm y 9.5 mm), se obtiene que a compresión la resistencia siempre es mayor (entre 5% y casi 400% veces) sin microfibra que con microfibra, mientras que la deformación última, en casos con PVA puede llegar a ser hasta 8 veces mayor. De esta etapa, sin embargo, no es posible obtener resultados claros a tracción. Por otro lado, con lo que respecta a la parte computacional, diferentes softwares se utilizan como herramienta para procesar la información obtenida en el campo experimental. Además, se realizan parametrizaciones que representen las curvas obtenidas y así obtener fórmulas generales. Dichas modelaciones, provenientes de combinar modelos ya ampliamente conocidos con regresión de datos experimentales, son utilizadas en un análisis de tipo Pushover en el programa SAP2000 con el fin de tener una idea general del comportamiento estructural del hormigón fibroreforzado. Para efectos prácticos, el análisis es llevado a cabo en una torre de 10 pisos de muros con confinamiento de borde. De esto último y empleando las mismas cantidades de fibra e iguales tamaños máximos de árido que en las probetas finales, se puede constatar que para todos los casos, previo a los 0.6 metros de desplazamiento de techo, la carga requerida es siempre mayor en hormigones sin PVA alcanzando a ser esta, en casos extremos como aquellos con árido de 9.5 milímetros, hasta 1.2 veces mayor.

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Removing microcontaminants from effluents is a challenge today, because of its high cost and low efficiency, especially in the treatment of effluents containing heavy metals. An alternative that has emerged is the use of biodegradable nanocomposites, which exhibit good removal and recovery performances, in addition to its low cost. With this in mind, the present study aimed to develop and characterize a nanocomposite based on hydroxyapatite (HAP), polyurethane (PU) and polyvinyl alcohol (PVA) for removing heavy metals. Thus, the research was conducted in several steps: i)- Physico-chemical and microbiological hospital effluent characterization; ii)- Production of hydroxyapatite by aqueous precipitation technique, and their characterization; iii)- Production of the nanocomposite in which the hydroxyapatite was added to the polyurethane prepolymers and then the polyvinyl alcohol/hydroxyapatite film was produced; iv)- Polyvinyl composite without film PU/HAp was also produced in the proportions of 20 and 40% HAp; v)- The composites was characterized by the techniques of XRD, FTIR, SEM / EDS, BET, Zeta Potential and TGA; vi)- The sisal and coconut fibres were washed and dried for comparative tests of adsorption; vii)- Adsorption tests for evaluating the removal of heavy metals (nickel and cadmium). Initial screening adsorption capacity (HAp; PU/HAp - 20 and 40%; PU / HAp / PVA), kinetic studies of adsorption of Cd (II) by HAp; multifactorial design analysis (factorial design) for identifying the most important variables in the adsorption of Cd (II) by composite PU/HAp. Also comparative analysis of adsorption of Cd and Ni by composite PU/HAp were conducted, as well as comparative tests of adsorption of Cd (coconut fibre) and Ni (sisal fibre). It was possible to verify that the composite PU/HAp 40% showed better effectiveness for the removal of Cd (II) and Ni (II), above 80%, equivalent to the lignocellulosic fibre used and HAp produced. As main conclusion, it can be referred that the composite PU/HAp 40% is an effective adsorvent to wastewater treatment for heavy metal removal, with low cost and high efficiency
A remo??o de microcontaminantes, em especial no tratamento de efluentes contendo metais pesados, ? um desafio na atualidade, em decorr?ncia de seu elevado custo e baixa efici?ncia. Uma tecnologia que vem surgindo como promissora ? a aplica??o de nanocomp?sitos biodegrad?veis, a qual apresenta uma efici?ncia favor?vel de remo??o e recupera??o deste microcontaminante, al?m de seu baixo custo. Neste ?mbito, o presente estudo objetivou desenvolver e caracterizar um nanocomp?sito ? base de hidroxiapatita (HAP), poliuretano (PU) e ?lcool povinil?co (PVA) para remo??o de metais pesados. A investiga??o foi desenvolvida em v?rias etapas: i)- caracteriza??o f?sico-qu?mica e microbiol?gica de efluentes hospitalares, como potencial caso de estudo; ii)- produ??o de hidroxiapatita por meio da t?cnica de precipita??o aquosa, e respectiva caracteriza??o; iii)- produ??o de nanocomp?sito com revestimento, no qual a hidroxiapatita (HAp) foi adicionada aos pr?-pol?meros de poliuretano, e a pel?cula de ?lcool poliv?nilico e hidroxiapatita foi produzida e aderida ao comp?sito; iv)- produ??o de comp?sito n?o-peliculado PU/HAp nas propor??es a 20 e 40% de HAp; v)- caracteriza??o do comp?sito pelas t?cnicas de DRX, FTIR, MEV/EDS, BET, Potencial Zeta e TGA; vi)- tratamento f?sico-qu?mico da fibra de sisal e coco, como potenciais bioadsorventes de baixo custo utilizados em estudos comparativos; vii)- testes de adsor??o de metais pesados (n?quel e c?dmio). Neste ?mbito, foi realizada uma triagem inicial de capacidade de adsor??o da HAp, PU/HAp 20 e 40% e PU/HAp/PVA, envolvendo estudos cin?ticos de adsor??o de Cd (II). De modo a identificar as vari?veis mais importantes na adsor??o de Cd (II) pelo comp?sito PU/HAp, foi tamb?m considerado o desenho de experi?ncias (factorial design). Adicionalmente, este adsorvente (PU/HAp) foi tamb?m testado como adsorvente de Cd e Ni. Finalmente, foram realizados testes de adsor??o de Cd em fibras de coco, e de Ni em fibras de sisal. O estudo realizado permitiu concluir que o comp?sito PU/HAp 40% apresentou elevada efici?ncia na remo??o de Cd (II) e Ni (II), superiores a 80%, sendo equivalente ?s fibras lignocelul?sicas utilizadas e ? HAp produzida. Como principal conclus?o deste estudo, destaca-se o fato de que estes materiais podem ser utilizados no tratamento de efluentes para remo??o de metais pesados, dado que apresentam baixo e custo e elevada efici?ncia
2020-01-01

Le PVA est un polymère non inflammable, non toxique et biodégradable. Malheureusement, sa réaction principale de synthèse produit un haut débit de résidu qui à niveau du monde devient plusieurs millions de tonnes annuelles. Le résidu est un mélange azéotropique du méthanol et acétate de méthyle, étant l'acétate de méthyle au tour des 80 % en poids. Le méthanol est un réactif utilisé dans la synthèse du PVA et par la réaction de l'acétate de méthyle avec constituants qui sont donneurs de groupes alcool, on peut enrichir en méthanol la courant résiduelle. L'utilisation de l'éthanol comme réactif semble la meilleure alternative parce que sa réaction avec l'acétate de méthyle produise méthanol et acétate d'éthyle. Le méthanol peut être recyclé pour synthétiser plus de PVA et l'acétate d'éthyle est un solvant organique commercialisable.
Le mélange du produit de la transesterification de l'acétate de méthyle avec l'éthanol a quatre azeotropes : acétate de méthyle / méthanol ; acétate d'éthyle / éthanol ; acétate de méthyle / éthanol et acétate d'éthyle / méthanol. Les deux derniers réagissent entre eux et disparaîtrent quand on utilise la distillation réactive. La constante d'équilibre chimique de la transesterification avec éthanol n'est pas très favorable vers la formation des produits (K=0,63) mais par la combinaison de la distillation et la réaction dans le même appareil, on évite la limitation de l'avancement de la réaction due à la constante d'équilibre. A fur et mesure que la réaction génère plus de produits, ils sont enlevés du milieu réactif par la distillation et la réaction est favorisée de nouveau pour fournir plus de produits. Cet exemple semble une situation typique pour appliquer la distillation réactive, mais il y a la particularité que les deux azeotropes qui ne réagissent, restent et ne permettent pas d'avoir les produits purs dans une seule colonne. Un procédé original qui combine la réaction et un système de changement de pression, nous permet de surpasser les azeotropes réactifs et non réactifs en même temps et en utilisant seulement deux colonnes.
Une méthodologie à complexité croissante est utilisée pour caractériser le système proposé qui se compose de : l'analyse infini/infini, la synthèse par un calcul plateau à plateau qui part du plateau d'alimentation en direction aux extrêmes de colonne et la conception qui utilise une fonction coût basée en les proportionnalités par rapport aux variables disponibles de l'analyse et la synthèse.
Dans l'étape d'analyse on étudie la faisabilité des séparations proposées et les paramètres des courants externes des colonnes et leur interrelation par moyen des bilans de matière qui englobent les unités. Dans l'étape de synthèse, on étudie les paramètres internes de chaque colonne, en particulier nous avons déterminé l'influence du reflux sur le nombre de plateaux sous les hypothèses simplificatrices de McCabe-Thiele. Dans l'étape de conception, on évalue les paramètres externes et internes ensembles sous les considérations économiques afin de trouver les valeurs optimales. Cette étape est plutôt utile pour l'étude de la pression laquelle influence toutes les autres variables du système.
D'autres aspects développés dans la thèse sont l'étude des données expérimentaux des équilibres liquide-vapeur du système, la comparaison de l'alternative proposée avec les autres alternatives, estimation des conditions optimales d'opération et la vérification des résultats est obtenue par simulation rigoureuse avec ProSim Plus.

MOTS CLEFS: distillation réactive, équilibres liquide-vapeur, analyse, synthèse, conception, alcool de polyvinyle (PVA), acétate de méthyle, système de changement de pression réactif.
The PVA is a non flammable, non toxic and biodegradable polymer but its synthesis reaction generates methyl acetate which is collected as a residue at its azeotropic composition with one of the reactants: the methanol. Several millions tons of residue are collected each year around the world. The residue contains around 80 % weight in methyl acetate but it can be enriched in methanol by reaction with alcohol donors. The ethanol seems the best alternative because its reaction with the methyl acetate produces methanol and ethyl acetate which is a commercial solvent.
The obtained mixture by methyl acetate transesterification with ethanol contains four azeotropes. The components of two of the azeotropes reacts each other and overcomes the azeotrope in a reactive distillation. The reactive distillation is also able to overcome the limitations produced by the small equilibrium constant value. This is the typical situation to use the reactive distillation but there are two non reactive azeotropes remaining. An original process which combines the reaction and a pressure swing distillation is able to overcome the reactive and non reactive azeotropes at the same time with only two columns.
The next fast to rigorous methodology is used: infinite/infinite analysis, stage by stage calculation from the feed to the column boundaries at the synthesis and a cost function based on proportionalities on the variables calculated previously at the conception.
The feasibility and the characterization of the streams outside the columns is performed at the analysis; the characterization of the parameters inside each column is performed at the synthesis, the reflux influence on the number of stages is the main goal of the synthesis; the parameters with an influence on the overall process like the pressure are evaluated under economical considerations at the conception.
It is proposed to fix the recycle stream flow rate and control the product purities with the first column bottoms flow rate. There is a degrees of freedom corresponding to the methyl acetate trapped inside the system which can not be manipulated at steady state.

KEYWORDS: reactive distillation, VLE, analysis, synthesis, conception, PVA, reactive pressure swing.

Le PVA est un polymère non inflammable, non toxique et biodégradable. Sa réaction principale de synthèse produit un important débit de résidu. Le résidu est un mélange azéotropique du méthanol et acétate de méthyle. Le méthanol est un actif utilisé dans la synthèse du PVA et par la réaction de l'acétate de méthyle avec un alcool, on peut enrichir en méthanol le courant résiduel. Un procédé original, qui combine la distillation réactive et un système de changement de pression, nous permet de revaloriser le résidu en utilisant seulement deux colonnes pour produire du méthanol et de l'acétate d'éthyle. Une méthodologie à complexité croissante est utilisée
The PVA is non inflammable, non toxic and biodegradable polymer. Its main reaction of synthesis produces a high flow rate of residue. The residue is an azeotropic mixture of methanol and methyl acetate. The methanol is a raw material for the synthesis of PVA and by reaction of the methyl acetate with alcohol it is possible to produce methanol and an other acetate. An original process combining the reaction inside a pressure swing system allows the residue revalorization with only two column. A fast to rigorous methodology is used. We determine experimentally the vapor liquid equilibria, compare the alternatives and verify the results by rigorous simulation with ProSim Plus

La adición de fibras en compuestos a base de cemento portland es una práctica común para la prevención de la formación de grietas y para incrementan la resistencia a la flexión. En esta investigación, se estudiaran los compuestos fibro-reforzados (CFR) con fibras de polivinilo alcohol (PVA), reforzadas con nanofibras de carbono (NFC) o nanotubos de carbono (NTC). Los especímenes fabricados fueron ensayados a la resistencia a la flexión y a la conductividad eléctrica en agua o en solución con NaCl. Los resultados demostraron una dependencia de los especímenes al tipo de solución a la cual fueron expuestos. Se demostró que la sensitivdad a la deformación y a la solución de NaCl puede ser incrementada por la adición de los NTC. Los resultados en el incremento de la conductividad con los compuestos de NTC pueden ser escalables para las aplicaciones de monitoreo no-destructivo en estructuras de concreto que requieran una mejora integral bajo las cargas aplicadas y estabilidad en ambientes deletéreos.DOI: http://dx.doi.org/10.4995/HAC2018.2018.6473