Butyl vulcanized rubber, performance

Puskas, J.E., Kumar, B., Ebied, A., and Lamperd, B. Novel Butyl Composites for Less-Lethal Ammunition. Papei 126, ACS Rubber Division, 164th Technical Meeting, October 14—17, Cleveland, OH, 2003. Puskas, J.E., Kumar, B., Ebied, A., and Lamperd, B. Comparison of the Performance of Vulcanized Rubbers and Elastomer/TPE Composites for Specialty Applications. Proceedings of the Polymer Processing Society, 2004. 

Now dynamically vulcanized rubber-plastic blends are poised to enter the realm of automobile tires. A TPV comprising a PA thermoplastic phase with isobutylene-co-p-methylstyrene (BIMSM) rubber can be used as an innerliner, outperforming either historical butyl rubber or the more classical halobutyl and its blend with natural rubber. These and future developments are targeting down-gauging of the barrier film thickness to simultaneously reduce both tire weight and reduced air permeation. A five-to-tenfold reduction in the latter is claimed to be feasible along with improved tire performance (Tsou 2007). 

Thermoplastic vulcanizates (TPVs) are composed of a vulcanized rabber component, such as EPDM, nitrile rubber, and butyl rubber in a thermoplastic olelinic matrix. TPVs have a continuous thermoplastic phase and a discontinuous vulcanized rubber phase. The most common TPV polymer systan is PP/EPDM rubber however, a number of other polymer systems have been commercially developed. These include PP/NBR, PP/butyl and PP/halobutyl, PP/NR, and PP/EVA/EPDM. Producers include Advanced Elastomers Systems (Santoprene, Geolast, and Trefsin). The highly rubberlike properties of TPV have enabled than to perform as engineered thermoplastic rubbers. In numerous application areas they have directly replaced premium-performance thermoset rubber compounds. Prominent among these are dananding automotive applications, electrical insulation and connectors, compression seals, appliance parts, medical devices, and food and beverage contact applications. 

The prevulcanization of natural rubber in latex form has also been a subject of much investigation. The cross-linking mechanism is not yet fully understood, but the water apparently plays a major role in it. Irradiation results in the cross-linking of the rubber molecules and in coarsening of the latex particles. A process of cross-linking of natural rubber latex has been developed to the point that it can be used for an industrial-scale application. The irradiation is performed in aqueous media by electron beam without a prorad (sensitizer) at a dose of 200 kGy (20 Mrad) or in the presence of n-butyl acrylate at considerably lower doses, typically 15 kGy. The cross-linked film exhibits physical properties comparable to those obtained from sulfur cured (vulcanized) film. As an alternative, the addition of a variety of chloroal-kanes makes it possible to achieve a maximum tensile strength with radiation doses of less than 5 Mrad (50 kGy). ... 

A process of cross-linking of natural rubber latex has been developed to where it should be soon ready for an industrial-scale process.149 The irradiation is performed in aqueous media by electron beam without a prorad ( sensitizer ) at a dose of 200 kGy (20 Mrad) or, in the presence of n-butyl acrylate at considerably lower doses, typically 15 kGy. The cross-linked film exhibits physical properties comparable to those obtained from sulfur-cured (vulcanized) film. 

Vulcanization of regular butyl rubber can be performed either by the classical sulfur-ZnO-accelerator method, by phenolic resin cure with... 

Reactivity with Tetrazoles. Reactive tetrazoles were used for the synthesis of rubbers having an appreciable ageing protection [237]. 2-(Subst.)phenyl -5-(3,5-di-tert-butyl-4-hydroxyphenyl)tetrazole (181) can be compounded without thermolysis with BR or IR. At vulcanization temperatures, 181 is thermolysed and reactive nitrileimine 182 undergoes 1,3-dipolar addition to C = C double bonds. 183 is formed with yields from 70 to 85%, depending on the character of R in 181 (the activity series R = CH3 < H < Cl). Mechanistic model experiments were performed with 181 (R = Cl) and styrene, the latter was isued as a model instead of IR [237]. l-(3-Chloro-phenyl) -3-(3,5-di-/ert-butyl-4-hydroxyphenyl)-5-phenyl-2-pyridazoline was isolated in 44% yield and medhanism of the attachement of 183 to IR was thus confirmed. 

Polyisobutylenes (PIB) have the inertness of paraffinic hydrocarbons and cannot be cured or vulcanized using standard rubber technology. On a molecular weight basis they bracket the butyl polymers, are compatible with them, and can function in a manner similar to butyl in adhesive and sealant compositions that will not be cured. Contributions to finished composition performance are strongly influenced by PIB molecular weight. 

High performance elastomeric butyl tapes are available for large window lite glazing in high-rise structures and for windshield sealing. These usually contain crosslinked butyl elastomers (20-40%) plus poly butenes, resinous tackifiers, and reinforcing fillers such as carbon black and platy talc. Chlorobutyl rubber compositions are available for faster and more thorough vulcanization. 

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