Literatura académica sobre el tema "Room temperature vulcanization"

The degree of vulcanization of latex compound was determined by capillary viscometer with controlled temperature to study effect of time and temperature on vulcanization process. The standard equilibrium swelling test was also conducted to assess the degree of vulcanization. A latex compound for medical glove was investigated. The latex viscosity was observed to increase over time at above room temperature condition. On the other hand, the viscosity fluctuated around mean value at room temperature. This is partly consistent with the swell ratio measurement which complete vulcanization was observed at curing temperature of 60 °C.

In this study, in situ aluminum matrix composites were synthesized through pyrolysis of high temperature vulcanization silicone in commercially pure aluminum melt. For this purpose, 1 to 4 wt% of high temperature vulcanization silicone was added to a vortex of molten aluminum at 750℃ and the resulting slurries were cast in steel dies. Microstructure, hardness, and tensile properties of the as-cast samples were examined at ambient and high temperatures. The results revealed the in situ formation and distribution of reinforcement particles in the matrix. Energy-dispersive X-ray analysis indicated that the formed reinforcement particles consisted of O and Si elements. This confirms the in situ reinforcement formation by pyrolysis of high temperature vulcanization silicone in the melt. The size of the in situ formed particles was mostly in the range of 200–2000 nm. It was shown that the composites synthesized by the addition of 4 wt% high temperature vulcanization had the highest mechanical properties both at ambient and high temperatures. Room temperature hardness, tensile strength, and yield strength of this sample were increased by about 50%, 23%, and 19% compared to the monolithic sample, respectively.

Abstract The mechanism of the accelerated sulfur vulcanization of rubber was studied by the use of 2,3-dimethyl-2-butene (C6H12, TME) as a simple, low-molecular model alkene. Treatment of TME with a mixture of ZnO, S8 and the classical accelerator TMTD at temperatures above 100°C yields a mixture of addition products ((C6H11—Sn—C6H11) ). In the temperature range of 50 up to 100 °C only intermediate products, C6H11—Sn—S(S)CN(CH3)2 are obtained. Room temperature vulcanization is feasible using highly reactive accelerators, such as xanthate derivatives. These derivatives result in formation of the crosslink precursors which are converted to the actual crosslink in the presence of zinc dithiocarbamates. The addition of (secondary) amines enhances the solubility of the dithiocarbamates, and therefore the reactivity of the xanthate/zinc dithiocarbamate combination.

The main objective of this study was to investigate the effect of the pre-vulcanization temperature on mechanical and rheological properties of starch filled natural rubber (NR) latex films. The 10 phr filler loading of starch was added into the latex prior to the pre-vulcanization process at 60°C to 140°C. The dipped films were cured in the oven at 100°C for 20 minutes and cooled at room temperature for 24 hours before stripping. The rheological properties of NR latex compounds were studied based on the viscosity measurement. The tensile and tear tests of starch filled NR latex films were also carried out. The results indicated that the rheological properties of the latex compounds showed shear thickening behavior where viscosity was increased with the increase in shear rate and pre-vulcanization temperature proportionally. The pre-vulcanization temperature at 80°C showed the optimum mechanical properties of starch filled NR latex films.

Abstract HXNBR (Hydrogenated Carboxylated Nitrile Rubber) has very good heat ageing resistance and oil resistance. A novel accelerator system is designed to bring about the vulcanization of HXNBR at room temperature. The room temperature cured samples showed good mechanical properties equivalent to those of high (150 °C) temperature cured samples. Natural rubber vulcanizates are highly prone to oxidative and ozone degradation. The oil resistance of natural rubber vulcanizates is also very low. The oil resistance, ozone and oxidative degradation resistance of natural rubber vulcanizates are considerably improved by placing a thin coating of HXNBR over it.

The polyacrylonitrile short fibers/ room temperature vulcanizing silicone rubber (PAN/RTV silicone) composites were prepared by mechanical mixing method and vulcanization at room temperature for 7 days as internal insulator. The effects of the content of fiber on the mechanical and ablative performances for the composites were investigated. The results show that with increasing content of PAN fiber filled, the tensile strength increases, the break elongation decreases, and the ablation rate(Rt) of PAN/silicone composites decreases rapidly at first, then increases. When PAN fiber content is 10phr, the ablation rate(Rt) is 0.06mm/s.

Les élastomères silicones sont couramment utilisés dans l’industrie pour des applications nécessitant des joints d’étanchéité dotés de bonnes performances mécaniques ainsi que de bonnes résistances chimique et thermique. Le vieillissement thermique des silicones est cependant rarement étudié à des températures inférieures à 100-120 °C. Les travaux de thèse visent à étudier le vieillissement thermique à températures modérées de joints élastomères réticulés à température ambiante. L’application industrielle sous-jacente à la thèse met en œuvre des joints minces de silicone injectés et réticulés dans des structures confinées. La température d’utilisation, proche de l’ambiante, et les durées de vie des joints visées impliquent une méthodologie d’étude basée sur l’accélération du vieillissement dans une gamme de température comprise entre 30 °C et 70 °C pour des durées allant jusqu’à 600 jours. Des échantillons sandwiches représentatifs de l’application industrielle, dans lesquels le joint est confiné entre deux substrats, ont été conçus et fabriqués à l’aide d’un moule d’injection spécialement réalisé pour ces travaux de thèse. Un confinement total est également appliqué pour suivre l’impact de ce dernier sur le mécanisme de vieillissement du joint. L’impact du vieillissement thermique est étudié par un ensemble de caractérisations mécaniques et physico-chimiques. L’épaisseur du joint au sein de l’application est inférieure à 1 mm. L’étude du comportement mécanique en surface du joint a nécessité le développement original de la méthode d’indentation instrumentée sur des élastomères chargés. Le développement des méthodes d’essais et d’analyse prend en compte la rugosité de surface et la faible rigidité du matériau pour détecter au mieux le point de contact. Un bon accord a été établi entre les modules élastiques mesurés par traction et par indentation instrumentée. Les comportements dissipatifs cycliques caractérisés aux deux échelles montrent des tendances similaires. Le matériau vierge, un PDMS chargé, présente une distribution homogène et aléatoire de particules de SiO2 et de CaCO3. En outre, le réseau 3D est homogène chimiquement et constitué de chaînes courtes sans liaisons covalentes avec les particules. Une faible fraction de chaînes n’est cependant pas réticulée au réseau. Le comportement mécanique hyper-élastique et dissipatif a été caractérisé par des essais de traction monotone à rupture, de relaxation par paliers, cycliques et par indentation instrumentée. Il a été noté que le comportement mécanique dissipatif vient majoritairement de l’effet Mullins. Le vieillissement à l’air conduit à une dégradation et une rigidification des surfaces, une perte de masse et de volume importante, une fragilisation et une rigidification à l’échelle macroscopique. Les modules élastiques d’indentation au cœur des plaques coulées restent constants. La spectroscopie infrarouge révèle une quantité de particules plus importante en surface des échantillons. Le mécanisme proposé est ainsi basé sur l’évaporation d’espèces chimiques non liées au réseau, pouvant présenter plusieurs cinétiques. L’ensemble des caractérisations a été appliqué aux échantillons vieillis en confinement et montre l’absence d’évolutions notables des propriétés mécaniques et physico-chimiques au niveau des surfaces protégées. L’évaporation des espèces chimiques observée à l’air libre est alors bloquée
Silicone elastomers are frequently used in industry for their low manufacturing cost as seals, with good mechanical properties as well as increased chemical and thermal resistance. However, the thermal ageing of silicone seals is rarely performed at temperatures lower than 100-120 °C. Research work performed during this PhD aims at studying the thermal ageing of RTV (room temperature vulcanized) elastomer seals under moderate ageing temperatures. The industrial application is designed with thin injected silicone seals and vulcanised in confined structures at room-temperature. Targeted lifespans involve developing a methodology based on accelerated ageing in a temperature range between 30°C and 70°C for 10 to 600 days. Industrial representative multi-layered samples, inside which the seal in injected, were designed and manufactured using specifically designed injection moulded for the research works. A total confinement has also been applied to monitor its impact on the ageing mechanism of the seal.The impact of thermal ageing is monitored using several mechanical and physical-chemical characterisations. The thickness of the seal inside the application is smaller than 1mm. The mechanical study performed on the surface of the seal needed a unique development of instrumented indentation method for filled elastomers behaving hyper-elastically. Measurement and analysis method takes into account the surface roughness as well as the low stiffness of the material to better detect the contact point. A good agreement was established between the elastic moduli measured by tensile tests and instrumented indentation. Dissipative cyclic mechanical behaviours reveal similar trends at both scales. The virgin material, a filled PDMS-RTV, has an homogeneous and random distribution of SiO2 and CaCO3 fillers. Moreover, the 3D network is chemically homogeneous and made of short chains without covalent bonds with fillers. A small fraction of chains is however not cross-linked to the network. The hyperelastic and dissipative mechanical behaviour was characterised through monotonic failure tensile tests, multi-steps relaxation tests, cyclic tests and instrumented indentation tests. It was found that the dissipative mechanical behaviour mainly comes from the Mullins effect. The open to air thermal ageing leads to a degradation and stiffening of the surfaces, high mass and volume loss, an embrittlement and a stiffening at the macroscopic scale. The elastic indentation moduli at the core of the samples remain constant. Infrared spectroscopy reveals a higher fraction of fillers on the sample surface. Thus, the proposed ageing mechanism is based on the evaporation of chemical species which are not cross-linked to the network. This mechanism can present several kinetics. All the characterisations were applied to the confined thermally aged samples and the results showed no remarkable evolutions of the mechanical nor physical-chemical properties on the protected surfaces. Thus, the evaporation of the chemical species noticed for the open to air ageing is blocked

The paper presents the behavior of some samples based on nitrile rubber reinforced with inorganic and organic type of filler, respectively, to composting. The organic filler used was obtained as waste in the leather and footwear industry. Before use, the waste was ground and then functionalized with potassium oleate in order to improve compatibility with the polymer matrix. The samples of rubber mixtures were obtained on a Brabender mixer, the vulcanization agents were added on a laboratory roller, and the vulcanization of the samples was performed in a hydraulic laboratory press, at 165°C, with a pressing force of 300 kN. The aerobic composting test was performed at laboratory scale, using solid, standardized and homogeneous synthetic waste. After a thermophilic incubation period of 42 days (at 58°C), followed by a period of mesophilic incubation (at the room temperature) of 42 of days, a decrease of some physico-mechanical properties was noticed (hardness, 100% modulus, tensile strength), of the gel fraction, and of the crosslinking densities, the largest decrease of these characteristics being observed in the sample with the highest content of organic filler. The results obtained may indicate that the biodegradation of the rubber samples is favored by the organic fillers.

This paper describes preliminary methodology and characterization of the vulcanized nitrile butadiene rubber (NBR) samples submitted to swelling and mechanical testing. Nitrile rubber was used to study swelling processes of swelling packer sealing element. Five different compositions for a rubber vulcanization were used trying to build the best possible combination of components applying different concentrations of each component. Both swelling and mechanical testing were done at the room temperature. Rubber samples swelling was performed in oil acquired from one of Croatian oil fields. The other part of the testing sequence refers to tensile stress-strain tests to the point of break performed on dumbbell samples. Tensile testing was rendered on non-swollen rubber samples using a tensile testing apparatus. From the obtained results it can be seen that swelling process of the nitrile rubber strongly depends on cross-link density.