STRUCTURE AND PROPERTIES OF IMPACT COPOLYMER POLYPROPYLENE - II - PHASE-STRUCTURE AND CRYSTALLINE MORPHOLOGY

In this work, an impact copolymer polypropylene (ICPP) was separated i nto 4 fractions, A, B, C, and D. The phase structure, thermal behavior , and crystalline morphology of the ICPP and its 4 fractions were stud ied thoroughly using scanning electron microscopy (SEM). Dynamic mecha nical analysis (DMA), differential scanning calorimetry (DSC), and pol arized light microscopy (PLM). Results of SEM and DMA show that ethyle ne-propylene rubber (EPR) and part of the ethylene-propylene segmented copolymer disperse as toughening particles in the ICPP. The size and size distribution of these particles are determined by chain structure of the fractions of ICPP. From fraction A to fraction D, the morpholo gy changes from noncrystalline to semicrystalline gradually, as shown by DSC. DSC results also indicate that thermal behavior of the ICPP ag rees greatly with its chain structure. PLM demonstrates that it is dif ficult for the ICPP to grow perfect spherulites, that is, partially, b ecause the matrix of ICPP, fraction D, has defects in its macromolecul ar chain. Another cause is that there is a good compatible structure i n the ICPP and so the noncrystalline component (including all fraction s) hinders the growth of the spherulite. (C) 1999 John Wiley & Sons, I nc.