Elastomers, structure characterization

Chattopadhyay S., Chaki T.K., and Bhowmick A.K., New thermoplastic elastomers from poly(ethyle-neoctene) (engage), poly(ethylene-vinyl acetate) and low-density polyethylene by electron beam technology structural characterization and mechanical properties. Rubber Chem. TechnoL, 74, 815, 2001. Roy Choudhury N. and Dutta N.K., Thermoplastic elastomeric natural rubber-polypropylene blends with reference to interaction between the components. Advances in Polymer Blends and Alloys Technology, Vol. 5 (K. Finlayson, ed.), Technomic Publishers, Pensylvania, 1994, 161. 

The characterization of the physical and chemical changes that occur in montmorillonite/PDMS nanocomposite elastomers as they are thermally aged is reported. Broadband Dielectric Spectroscopy (BDS) was used to track changes in the physical interaction between the polymer and clay associated with increases in non-oxidative thermal stability (as determined by TGA). The evolution of volatile siloxane species from the elastomers was characterized with Thermal Volatilization Analysis (TVA). Results suggest that the improved thermal stability and the increases in polymer/clay association are a result of significant re-structuring of the polymer network. 

Structure Characterization in the Science and Technology of Elastomers 119 TABLE II Solution Mscosity Definitions (i) = soinfion viscosity ffo = solvent viscosity)... 

Structure Characterization in the Science and Technology of Elastomers 125 Homopolymers... 

This systematic study, carried out throughout the 1980s, constituted a very thorough approach to both the synthetic aspects, with their corollary structural characterization, and a whole set of physical and technological properties. Elastomers as well as rigid polymers were prepared and their possible applications carefully examined on the basis of the specific performances determined for each one. Further additions to the basic investigation included the use... 

The possession of these unique properties can, in part, be explained by the way the polyurethane elastomer structure differs from that of conventional elastomers. An elastomer is usually described as a material characterized by the property of high elasticity. This means it has the ability to stretch to a great extent under load and to recover almost completely when the load is released. This property of elasticity is a result of a particular molecular structure, the general features of which are exhibited by all elastomers, although there are many variations in detail. In simple terms this structure consists of long linear flexible molecular chains which are joined together at intervals by crosslinks which may be in the form of... 

The most typical adhesive solvents are those based on elastomers, compounds characterized by the fact that they have a strong natural adhesiveness, especially in respect of themselves (the phenomenon of self-adhesion, the instantaneous adhesion of two films of glue after almost total evaporation of the solvent, is the basis for the composition of the contact glues especially neoprene-based (Fletcher 1971)). The basic chemical composition of neoprene synthetic rubber is polychloroprene (O Fig. 14.6). The polymer structure can be modified by copolymerizing chloroprene with, for example, 2,3-dichloro-1,3-butadiene to yield a family of materials with a broad range of chemical and physical properties. 

Dielectric spectroscopy was shown to be a powerful technique when dealing with molecular dynamics in thermoplastic elastomers. The combination of dielectric measurements over broad frequency and temperature ranges with a precise structural characterization opens up new possibilities of studying the structure-dynamic relationships in block copolymers (see also Chapter 14). 

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