Poly crystallized from glassy state

Geil PH, Hsu CC (1984) Crystallization of polypropylene and poly(vinylidene fluoride) from the glassy state. J. Phys. Soc., 412... 

Since PHB is a polyester it might have been expected that it could be drawn and oriented into fibres quite easily using similar techniques to those developed for poly (ethylene terephthalate). This is not the case. PET is normally melt-spun into a fibre which is then quenched and wound up as an amorphous, glassy material.In a separate stage it is then drawn over a hot pin at a temperature above its 7 and crystallized in this oriented state to produce the familiar strong polyester fibres. This type of stress-induced crystallization from the quenched amorphous state does not seem to be possible with PHB. Indeed, the application of strain to a supercooled PHB melt can inhibit recrystallization rather than promote it. 

Figure 7.20 DSC curves for poly(p-phenylene sulfide) (PPS) fibers [19]. 1, Heating curve of as-spun fiber 2, cooling curve 3, heating curve of the sample cooled from the molten state at 20 "C min 4, heating curve of the sample quenched from a temperature between the glass transition temperature and the cold crystallization temperature . 3, heating curve of the. sample cooled from the glassy state...

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