MELT MEMORY EFFECTS IN POLYMER CRYSTALLIZATION

Polymer melts submitted to local shear flow fields, as well as isotrop ic solid samples, were treated in the melt at different temperatures a nd for various duration of time. The effects of thermal history on kin etics and morphological characteristics of subsequent isothermal cryst allization was investigated. Results suggest that subcritical pseudocr ystalline aggregates, behaving as predetermined athermal nuclei when t emperature is brought below melting point, can survive in the melt for long time. Their concentration decays exponentially with a single cha racteristic relaxation time. For all investigated polymers, temperatur e dependence of relaxation times can be fitted by an Arrhenius law wit h high apparent activation energy. Experiments performed with narrow m olecular weight fractions of poly(ethylene oxide) suggest that relaxat ion times relevant to destruction of oriented nucleation precursors ar e proportional to M-1.5.