Shear-Induced Crystallization of Poly(butylene terephthalate): A Real-Time Small-Angle X-ray Scattering Study
2004; American Chemical Society; Volume: 37; Issue: 15 Linguagem: Inglês
10.1021/ma0496145
ISSN1520-5835
Autores Tópico(s)biodegradable polymer synthesis and properties
ResumoThe shear-induced crystallization behavior of poly(butylene terephthalate) (PBT) has been investigated by in-situ small-angle X-ray scattering at temperatures of 198, 203, and 208 °C as well as by ex-situ atomic force microscopy. Increasing the shear rate and/or the shear strain enhances the crystallization kinetics. The acceleration of the crystallization saturates with increasing shear rate. A pronounced effect of the shear field on the Avrami exponent is observed at 198 °C but not at 203 and 208 °C, even though at the latter temperatures the relative reduction of the crystallization time induced by the shear is twice the value at 198 °C. Compared to some other polymers like isotactic polypropylene, the shear field leads only to a weak orientation of the PBT crystals. The Avrami exponent and the orientation induced by the shear field are interpreted on the basis of a microshish model. Microshish structures are due to the breaking up of shear-induced row nuclei at high temperatures. Finally, the shear field is found to lead to a decrease of the long period.
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