Elastomers Thermal stability

Total composition operating range was found to be wide enough from -90 to 350 °C. At a similar degree of crosslinking of the composite samples of the elastomers, thermal stabilization increases according to basic siloxane chain fhunewoik in the series M2 MF MPh Ph2, where M2... 

The behavior of these polymers was studied and reported by Tobol sky and coworkers (17-18). They concluded that S1B2 had better high temperature properties than a polydimethylsiloxane based elastomer. Thermal stability decreased as the distance between car-boranyl units was increased with dimethyl siloxane (QMS) units. In... 

Plasma processing technologies ate used for surface treatments and coatings for plastics, elastomers, glasses, metals, ceramics, etc. Such treatments provide better wear characteristics, thermal stability, color, controlled electrical properties, lubricity, abrasion resistance, barrier properties, adhesion promotion, wettability, blood compatibility, and controlled light transmissivity. 

Phenolics Elastomers Powder, solutions Excellent thermal stability to over 300 F generally, and over 400 F in special formulations. Broad choice of resins. May be cast or compression, transfer, or injection molded. Precision potentiometers, RF connectors, heating panels. 

W. A. Romanchick, J. E. Sohn, and J. F. Geibel Synthesis, Morphology, and Thermal Stability of Elastomer-Modified Epoxy Resin, in ACS Symposium Series 221 — Epoxy Resin Chemistry II, R. S. Bauer (ed.), American Chemical Society, Washington DC, 1982, pp. 85-118. 

Elastomers containing fluorine, also called fluorelastomers. These combine the good physical properties of organic elastomers with the thermal stability of inorganic materials. Trade names are Viton, Fluorel, Kel-F and Technoflon. 

Polyphosphazene-based PEMs are potentially attractive materials for both hydrogen/air and direct methanol fuel cells because of their reported chemical and thermal stability and due to the ease of chemically attaching various side chains for ion exchange sites and polymer cross-linking onto the — P=N— polymer backbone. Polyphosphazenes were explored originally for use as elastomers and later as solvent-free solid polymer electrolytes in lithium batteries, and subsequently for proton exchange membranes. 

These products find use in specialty applications requiring better thermal stability than available in the sulfur vulcanized elastomers. Other processes are also used to crosslink polydiene rubbers (Secs. 9-2c and 9-2d). 

MDI- or NDI-based PUs usually have better mechanical properties than PUs obtained from aliphatic polyisocyanates. The effect of various diisocyanates on the thermal stability of their PU elastomers is given below for a polycap-rolactone (mol. wt. 2000)/diisocyanate/BDO type elastomer of molar ratio 1 2.6 1 and synthesized using the prepolymer technique. 

Fluorocarbon elastomers represent the largest group of fluoroelastomers. They have carbon-to-carbon linkages in the polymer backbone and a varied amount of fluorine in the molecule. In general, they may consist of several types of monomers poly-vinylidene fluoride (VDF), hexafluoropropylene (HFP), trifluorochloroethylene (CTFE), polytetrafluoroethylene (TFE), perfluoromethylvinyl ether (PMVE), ethylene or propylene.212 Other types may contain other comonomers, e.g., 1,2,3,3,3-pentafluropropylene instead of HFP.213 Fluorocarbon elastomers exhibit good chemical and thermal stability and good resistance to oxidation. 

We recently synthesise a new polymer (see exp. part) containing significant amounts of tetra-methyl piperidine groups. Such a polymer is a very efficient polymeric thermal stabilizer for elastomer however, when present in low content in the polymer matrix its IR detection is not easy because of the low absorption coefficients of all its functional groups. 

The high-molecular-weight perfluoropolyethers obtained in the first step have excellent thermal stability (TGA initial decomposition >370°C) and chemical resistance and are true fluorocarbon elastomers that are, in contrast to polytetrafluoroethylene, flexible. Other methods for the synthesis of perfluoropolyethers and functionalized perfluoropolyethers are under development in our laboratories. 

The description of the physical properties of fluoroelastomers is necessarily less precise than that of fluoroplastics because of the major effect of adding curatives and fillers to achieve useful cross-linked materials of a given hardness and specific mechanical properties Generally, two parameters are varied increasing cross-link density increases modulus and decreases elongation, and raising filler levels increases hardness and decreases solvent swell because of the decreased volume fraction of the elastomer In addition to these two major vanables, the major determinants of vulcanizate behavior are the chemical and thermal stabilities of its cross-links The selection of elastomer, of course, places limits on the overall resistance to fluids and chemicals and on its service temperature range... 

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