Segmented elastomers elastomer

Trade name Manufacturer Hard segment Elastomer segment Notes... 

Speckhard T.A. and Cooper S.L., Ultimate tensile properties of segmented pol3furethane elastomers Factors leading to reduced properties for pol3mrethane based on nonpolar soft segments. Rubber Chem. TechnoL, 59, 405, 1986. 

Step polymerization is used to synthesize multiblock copolymeric elastomers (referred to as segmented elastomers). An example is the polyester-polyurethane system produced by the reaction of a diisocyanate with a mixture of macro diol and smallsized diol (Eq. 14). The macro diol (usually referred to as a... 

Seymour, R.W., G.M. Estes, and S.L. Cooper. Infrared Studies of Segmented Polyurethane Elastomers. I. Hydrogen Bonding. Macromolecules 3 5 (1970) 579-583. 

A powerful technique for the study of orientation and dynamics in viscoelastic media is line shape analysis in deuteron NMR spectroscopy [1]. For example, the average orientation of chain segments in elastomer networks upon macroscopic strain can be determined by this technique [22-31]. For a non-deformed rubber, a single resonance line in the deuterium NMR spectrum is observed [26] while the spectrum splits into a well-defined doublet structure under uniaxial deformation. It was shown that the usual network constraint on the end-to-end vector determines the deuterium line shape under deformation, while the interchain (excluded volume) interactions lead to splitting [26-31]. Deuterium NMR is thus able to monitor the average segmental orientation due to the crosslinks and mean field separately [31]. 

Yilgor I, Yilgor E, Eberle J, Steckle W Jr, Johnson BC, Tyagi D, Wilkes GL, McGrath JE (1983) Novel segmented elastomers from amino alkyl-terminated dimethylsiloxane oligomers Polymer Preprints 24(1) 167... 

The first group are the semicrystalline homopolymers, while a second group would include a diverse collection of block polymers, blends, and segmented elastomers. The latter systems were emphasized at a symposium on "Multicomponent Polymer Systems organized as part of the 175th National Meeting of the American Chemical Society in Anaheim, March 13-17, 1978. 

Segmented thermoplastic elastomers exhibit structural heterogeneity on the molecular, the domain, and in some cases on a larger scale involving periodic or spherulitic texture. Each level of structural organization is studied by specific methods. Molecular sequence distributions can be studied by chemical methods, such as NMR or IR spectroscopy. 

Comparative studies are presented that demonstrate that homopolyurethane and segmented copolyurethane elastomers and plastics and rubber-modified polyurethane glasses with properties similar to counterparts formed from oil-... 

The segmented polyamide elastomers are synthesized from MDI (4,4 -diisocyanato-diphenylmethane) and dicarboxylic acids and a carboxylic acid terminated aliphatic polyester, polycarbonate or polyether prepolymer with an average molecular weight of M = 500-5000. The dicarboxylic acids used as hard segment extenders are adipic and azelaic acid. Also, poly(ester amide) alloys are obtained using nylon-6,6 or polyesters (PEA/PBT). 

Several studies have been published in recent years on the properties of RIM polyurethanes and polyurethane-ureas (1-7). Unlike most studies, however, we have restricted our attention to simplified linear systems in order to establish the effect of reaction rates and mold temperatures on the phase separation and molecular weight of segmented polyurethane elastomers produced by RIM(6). 

Figure 2. General method for synthesizing segmented polyester elastomers. HORQH is a mixture of a long-chain diol and a short-chain diol.

SEGMENTED POLYURETHANE ELASTOMERS SCHEME OF THE CHAIN STRUCTURE ... 

Figure 5. Scheme of primary chain structure of segmented polyurethane elastomers and chain segment organization. 

Styrene-based thermoplastic elastomers (see Chapter 4) are sensitive to oxidation since they contain unsaturated soft segments. These elastomers are manufactured by solution polymerization process in aliphatic hydrocarbons. In order to prevent autoxidation during the finishing steps (stripping, drying), which manifests itself by a rise in melt flow index and discoloration of the raw polymer, antioxidant is added to the polymer solution before finishing. Hence the antioxidant has to be soluble in the polymerization solvent. 

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