剪切速率对等规聚丙烯的结晶和形貌的影响

Influence of Shear on i-Polypropylene Crystallization and Morphology

利用同步辐射小角X射线散射、广角X射线衍射和差示扫描量热法研究了不同剪切速率下等规聚丙烯的结晶结构.结果表明,施加剪切会导致β晶生成,但基本不改变样品总结晶度.β晶含量随着剪切速率的提高先升高后降低,与α晶具有竞争关系.当剪切速率在10~32 s^(-1)之间时,α晶和β晶共存,并存在分属于两种晶型的两组长周期,其中较大的长周期属于β晶.

The shear-induced crystallization behavior of isotactic polypropylene （iPP） was investigated by synchrotron small angle X-ray scattering, wide angle X-ray diffraction and differential scanning calorimetry. The results showed that the β-crystallinity were found after shearing and the total crystallnity kept almost constant. The β-crystallinity increased with the shear rate up to 10 s^-1 and then decreased at higher shear rates indicating the existence of competing processes of developing α- and β-crystallinities. At the shear rates between 10 s^-1 and 32 s^-1 , two populations of long spacing were observed with the larger one attributed to the β-crystallinity.