Rubber crystallization rate

A different case has also been explored by Martuscelli [1984] for PA-6 blended with an EPR-rubber. As shown in Figure 3.40, the PA-6/EPR blend decreased (faster overall crystallization rate) as the content of the rubbery phase increased, especially at lower concentrations of the EPR phase. 

Processing of these thermoplastic rubbers is quite straightforward. The high crystallization rates of the hard segments facilitate injection molding, while the low viscosity at low shear rates facilitates a low shear process, such as rotational molding. 

Desmocoll 176, 400 and 420 are primarily linear thermoplastic polyurethane elastomer resins of medium, medium-high and high crystallization rates, respectively. They are supplied as small, light brown, talc-covered, pieces. The polymers have a density of 1 2-1-23 g cm . This density, and their stabilization by the hydrolysis stabilizer Staboxal PCD, imply that they are poly(ester-urethanes). They show outstanding adhesion to numerous materials including plastics, rubber, leather, fabrics, wood, metals, etc. 

Choi WJ, Kim SC (2(X)4) Effects of talc orientation and non-isothermal crystallization rate on crystal orientation of polypropylene in injection-molded polypropyloie/ethylene-propylene rubber/talc blends. Polymer 45 2393-2401... 

Fig. 9.6 Plot of the crystallization rate of natural rubber over an extended temperature range. The rate plotted is the reciprocal of the time requested for one-half the total volume change. (From Wood and Bekkedahl (19))...

An interesting observation associated with crystallization under uniaxial deformation is the marked enhancement of the crystallization rate at constant tempera-tures.(43,44,55,56) For example, the crystallization rate constant of natural rubber increases by six to nine orders of magnitude with extension ratio at constant temper-atures.(43) This enhancement is also reflected in the crystallization half-time, which also increases by several orders of magnitude.(44,46,47,55,56) This enhancement of crystallization rate is not limited to rubber-like polymers. It is also observed in poly(pentenamer) (50) and in poly(ethylene terephthalate) (47 9,57,57a) when crystallized under uniaxial deformation. The change in rate can be attributed in part... 

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