非线性大应变振荡剪切流场中PP结晶行为的傅立叶转变流变学研究  

FOURIER-TRANSFORM RHEOLOGY STUDIES ON THE CRYSTALLIZATION OF ISOTACTIC POLYPROPYLENE IN NON-LINEAR LARGE STRAIN OSCILLATION SHEAR FIELDS

作　　者：于逢源[1] 张洪斌[1] 

机构地区：[1]上海交通大学化学化工学院高分子科学与工程系流变学研究所,上海200240

出　　处：《高分子学报》2010年第3期372-376,共5页Acta Polymerica Sinica

基　　金：国家自然科学基金(基金号10590355);上海市领先学科项目(项目号B202)资助

摘　　要：通过对等规聚丙烯(iPP)过冷熔体施加不同应变的正弦振荡剪切场,研究了大应变振荡剪切流场作用下,等温iPP的流动诱导结晶过程.研究结果表明,施加大应变振荡剪切流场可以明显加速iPP的结晶动力学,且施加的应变越大可以促使iPP结晶动力学加速现象越明显.通过对iPP熔体的应力波形进行傅立叶变换分析发现,由于结晶会引起熔体内部非线性行为改变,傅里叶变化峰值的3倍基频峰值I3与基频峰值I1之比I3/I1可以敏感反映iPP的流动诱导结晶过程.当流变仪施加的应变幅度从10%提高到30%时,I3/I1比值发生突跃的时间则从2500 s迅速减小为600 s.The isothermal flow induced crystallization （FIC） of isotactic polypropylene （iPP） under large amplitude oscillation shear fields was studied by rotational rheometer. The sinusoidal-strain dynamic shear flow of different amplitudes was performed on the undercooling iPP melts. Experimental results showed that, in comparison with the case for a small amplitude oscillation, the storage modulus of the melt would increase within a short period when a large amplitude oscillation was performed on the melts. This fact is attributed to that the large amplitude oscillation shear field is able to accelerate the crystallization kinetics of iPP significantly. Moreover, the larger strain performed on the melts would inevitably result in a more prominent acceleration of the iPP’s crystallization kinetics. Thus the rapid rise of the crystallinity of the melt directly gives rise to a more evident change of storage modulus. The Fourier transformation method was employed to analysis the stress waveform during the crystallization of iPP melts under large amplitude oscillation shear. It was found that the transition change of the ratio （I3/I1） of the peak value at triple-fundamental frequency I3 to the peak value at fundamental frequency I1 was sensitive in characterizing the FIC process of iPP melts when the change of the non-linear mechanical property occurred in the melt during crystallization. In addition, at a crystallization temperature of 140℃, the onset time corresponding to the abrupt increase in I3/I1, a little longer than the time when the storage modulus increased remarkably, decreased from 2500 s to 600 s as the amplitude of strain increased from 10% to 30%.

关 键 词：聚丙烯 等温结晶 傅立叶变换 流变学 结晶动力学 

分 类 号：O632.12[理学—高分子化学]