Elastomeric, characteristics

Copolymerization of ethylene and styrene by the INSITE technology from Dow generates a new family of ethylene-styrene interpolymers. Polymers with up to 50-wt% styrene are semicrystalline. The stress-strain behavior of the low-crystallinity polymers at ambient temperature exhibits elastomeric characteristics with low initial modulus, a gradual increase in the slope of the stress-strain curve at the higher strain and the fast instantaneous recovery [67], Similarly, ethylene-butylene copolymers may also be prepared. 

FIGURE 5.7 Phase separation in styrene-butadiene-styrene (SBS) triblock copolymer. The isolated spherical styrene domains form the hard phase, which act both as intermolecular tie points and filler. The continuous butadiene imparts the elastomeric characteristics to this polymer. MW = molecular weight. (From Grady, B.P. and Cooper, S.L., Science and Technology of Rubber, Mark, J.E., Erman, B., and Eirich, F.R. (eds.). Academic Press, San Diego, CA, 1994. With permission.)... 

An unfortunate characteristic of early zinc polycarboxylate cements was the early development of elastomeric characteristics- cobwebbing -in the cement pastes as they aged, thus shortening working time (McLean, 1972). Improvements in cement formulation, the addition of stannous fluoride to the oxide powder (Foster Dovey, 1974, 1976) and modifications in the polyacid have eliminated this defect. However, the cements have to be mixed at quite a low powder/liquid ratio, 1 -5 1 0 by mass, when used for luting. 

A typical synthetic route to the incorporation of pendent carboranyl units into a polymer chain is shown in scheme 3. Poly(o-carboranyl-organo-siloxane)s have been successfully prepared through hydrolysis of dimethyldichlorosilane in the presence of carboranedichloromethylsilane. The polymer has some of the elastomeric characteristics of the parent poly(siloxane) however, the thermal-oxidative cleavage of the o-carboranyl pendent group is reported to occurat lower temperatures than that for the thermooxidative cleavage of Si—O and Si—C bonds.10 Thermal studies have... 

Small amounts of comonomers (typically less than 6%) are often added to improve specific performance characteristics in cases where homopolymer is deficient. A higher level of comonomer than that (for example, HFP) would yield a product with elastomeric characteristics.58... 

As occurs in natural rubber, only the 1,4-cis isomer exhibits elastomeric characteristics. The most important synthetic diene rubbers are polychlor-oprene (neoprene) and rubbers derived from butadiene such as styrene-butadiene and acrylonitrile-butadiene copolymers. 

FIGURE 13.8 Schematic illustration of phase separation in a thermoplastic elastomer based on a styrenic triblock copolymer such as SBS. The isolated spherical domains containing the polystyrene end blocks form the hard phase, which acts as both intermolecular tie point ("physical crosslinks ) and filler. The continuous phase from the polybutadiene midblock imparts the elastomeric characteristics to this polymer. 

I. 14) which is about two-fold less than equivalent size nylon (Dermalon)-and PP (Surgilene)-based monofilament sutures. The elastomeric characteristic of polybutester block copolymer also renders Novafil less susceptible to package memory than PP and nylon-based monofilament sutures. 

During the 1930s the styrene monomer was obtained and used first in copolymers with elastomeric characteristics [7]. In 1938 several tonnes of polystyrene (PS) were obtained [9]. 

Stretching the matrix represents another method of aligning CNTs or CNFs. This is limited to polymers that present elastomeric characteristics. The change in orientation on stretching can be reversible (i.e., equilibrium) with the orientational order parameter becoming null after the imposed strain is removed (Ahire et al. 2008). 

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