【摘要】 以矩形聚丙烯(PP)/乙烯-辛烯共聚物(POE)共混制品为例,研究了注射成型工艺参数对结晶度的影响规律。通过扫描电子显微镜(SEM)得到POE分散相含量,结合差示扫描量热仪(DSC)获得PP基体的绝对结晶度。实验结果表明,通常表层的结晶度最低,例外的是在最高注射速率条件下,表层内0.2 mm处结晶度最小;随保压压力增大结晶度减小;高的熔体温度会使剪切形成的晶核前驱(precursor)被重新融化,取向松弛,弱化充填中剪切诱导作用,造成结晶度减小;高的注射速率提高了充填结束后型腔内熔体温度,对结晶度的影响类似提高熔体温度;在低熔体温度和低注射速率条件下成型可获得高的结晶度。更多还原

【Abstract】 This study is concern with the effect of processing conditions on depth distribution of crystallinity of PP in injection molded isotactic polypropylene(PP) /ethylene-octane copolymer(POE) blends with fixed mass ratio(75/25).POE content was calculated from scanning electron microscope(SEM) pictures,then depth distribution of absolute crystallinity of PP was calculated by enthalpy of fusion measured through differential scanning calorimetry(DSC).The results indicate that the crystallinity of outmost skin is 7%~10% lower than of other area.But in the most speed injection rate condition,the lowest crystallinity is located in the layer of 0.2 mm beneath skin.The crystallinity decreases with increasing holding pressure,injection rate and melt temperature.Higher melt temperature will make shear induced precursor remelt and chain orientation relaxed faster,in turn lower crystallinity.Increasing injection rate higher melt temperature after filled,and get similar effect on crystallinity as increasing melt temperature.Higher crystallinity can be got by lower melt temperature and slower injection rate.更多还原