Softening/melting step

Similarly to non-reactive blends, Scott and Sundararaj showed that the major reduction of the particle size of reactive blends, e.g., polyamide/polystyrene and polypropylene/ polystyrene prepared in batch mixer or in twin-screw extruder, occurred during the softening/melting step of the blend components with, however, a clear influence of the chemical reaction at the interface [63, 46]. 

When the reactive groups X were carbamates, the interfacial reaction was controlled by the carbamate thermolysis into primary amine, which was the rate determining step. The interfacial reaction was then occurring essentially after the softening/melting of the blend components, i.e. in the melt state as shown in Fig. 4.3(b). Phase dispersion was then... 

The crystalline hexamine salt may be isolated and recrystallized at this step. It softens at 120° and melts with decomposition at 150°. 

Equimolecular proportions of theophylline and 2-amino-2-methyl-l-propanol are dissolved in water and the water is evaporated until crystallization is almost complete. The crystals are filtered off and dried. The product has a melting point of 254-256°C, softening at 245°C. It has a water solubility of about 55%. It may be compounded in the form of tablets, for oral administration, or may be prepared in solution for distribution in ampoules. For the manufacture of solutions for packaging in ampoules, it is more convenient to simply dissolve the theophylline and the butanolamine in water, without going through the intermediate step of separating the crystalline salt. 

Doi and Edwards (1978a, 1979) explained this strain softening using an extension of the tube model of de Gennes. Suppose that the melt is subjected to a step strain and... 

The iron-on patch was a big step forward in repairing clothing. The hot-melt adhesive used on it must adhere well to the fabric initially and through repeated laundering or dry cleaning, must not soften in the clothes drier, must not be damaged by repeated flexing in use, and must be appli-... 

A crystalline solid will melt when heated, and this change of state is known as a first-order transition, It is accompanied by step changes in volume and heat content as well as the obvious change from a solid to a liquid, Softening point is the temperature at which a somewhat arbitrary stress condition results in a predefined reduction in modulus. 

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