Elastomeric point

A slightly higher temperature than the haze point, where there is a marked increase in strength and elongation which could readily be noticed by simple manual stressing, he defined as the elastomeric point. ... 

Six transition points in all were defined by Greenhoe which, with rising temperatures, were fluid point dry point gel point haze point elastomeric point and fusion point. 

Exxon products appear to release via a unique mechanism. Like other polymer-coated technologies, the penetration of water iato the granule is purely by diffusion. However, as water enters the particle, an osmotic pressure is created as the fertilizer is solubilized. This pressure causes an expansion of the elastomeric coating and the particle swells to many times its original diameter. As the particle swells, the coating becomes increasingly thinner to the point where it caimot contain the internal pressure and the nutrient is released. 

When compared to the early models that describe the adhesion of elastomers in the presence of interfacial chains, the central findings of this work, namely, observations b and d above, were quite surprising. In his recent work, de Gennes [102] pointed out that when a surface tethered chain diffuses into an elastomeric... 

The mechanical and thermal behaviors depend partly on the degree of crystallinity. For example, highly disordered (dominantly amorphous) polymers make good elastomeric materials, while highly crystalline polymers, such as polyamides, have the rigidity needed for fibers. Crystallinity of polymers correlates with their melting points. 

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.)... 

When a thermoplastic polyurethane elastomer is heated above the melting point of its hard blocks, the chains can flow and the polymer can be molded to a new shape. When the polymer cools, new hard blocks form, recreating the physical crosslinks. We take advantage of these properties to mold elastomeric items that do not need to be cured like conventional rubbers. Scrap moldings, sprues, etc. can be recycled directly back to the extruder, which increases the efficiency of this process. In contrast, chemically crosslinked elastomers, which are thermosetting polymers, cannot be reprocessed after they have been cured. 

Melt-processable polymer blend or copolymer in which a continuous elastomeric phase domain is reinforced by dispersed hard (glassy or crystalline) phase domains that act as junction points over a limited range of temperature, or... 

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