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The glassy transition of the polyethylene terephthalate (PET) sampleswhich have been subjected to solvent induced crystallization (SINC) was investigated bymodulated differential scanning calorimetry (MDSC) and density measurement. The dif-ferential of heat capacity signal, d C_p/dT from MDSC, was used to monitor the SINCprocess. It reveals that the T_g temperature shifts to higher value with the advancement ofSINC. When the toluene-immersing time was longer (168h), the detection of T_g becomemore difficult, because some smaller peaks emerged at the lower temperatures and theseare explained as the movement of small segments in the amorphous region. These observedresults are due to the morphology and structure introduced by the SINC process. 相似文献
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ffects of the chain orientation in the global sense on the solvent induced crystallization (SINC),diffusion velocity of toluol into poly(ethylene terephtlialate)(PET)and crystallization morphology were:studied by using density measurement and SEM.It has been shown that the SINC and diffusion velocity of toluol into PET increase with increasing degree of chain orientation in global sense,and the chain orientatioll can be essentially remained during SINC. 相似文献
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<正> 在研究聚合物的结晶过程中,有时(如在同步辐射法、X-衍射法和红外法的测定中)须将试样两端固定,有时(如研究热处理过程中取向聚合物的尺寸和结构变化)须将试样处于松弛状态。因而研究两端固定或松弛状态对取向聚合物结晶速率和结构的影响引起了人们的兴趣。一些研究结果得出,与松弛状态结晶相比,试样两端固定态结晶使取向聚合物的结晶速率变慢,但有时也出现相反的结果。此外,在上述文献中所用的原始试样都已具有较高的结晶度。为了弄清这一问题,我们用密度、双折射和应力测量等方法对取向程度不同的非晶态PET膜进行了深入和系统的研究。结果表明,试样两端固定与否对结晶速率的影响与试样原始的取向程度有关。 相似文献
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The Crystallization of constrained and fre oriented amorphous PET films were studied by using density, birefringence and stress measurements. It has been shown that depending on the birefringence of original sample, the effect of fixing two ends of samples on the Crystallization rate shows different behavior. For amor hous PET film with high birefringence the Crystallization rate of constrained sample is faster. For oriented amorphous PET with very low birefringence the Crystallization rate of free sample is faster. 相似文献
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The physical aging behavior of atactic polystyrene (aPS) films achievedunder different drawing conditions has been studied by optical birefringence and modulatedifferential scanning calorimeter (m.d.s.c.). The results show that on annealing at specifictemperature below glass transition temperatue (T_g), the enthalpy relaxation (△H) and T_gdecrease with increasing of birefringence (△n). On the other hand, the effect of moleculardraw ratio (MDR) is confusing: △H and T_g decrease with increasing of MDR in the earlystage of aging, but the MDR's effect become unobvious with the development of aging.It may be concluded that the ordered domain generated by the drawing below or aboveglass transition temperature will affect the development of physical aging behavior. Theviewpoint of cohesional entanglement is used to account for the above observations. 相似文献
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