丙乙无规共聚聚丙烯正压成型杯的雾度与结构的关系

研究了丙乙无规共聚聚丙烯正压成型杯制品的结构演变及其对雾度的影响。结果表明:丙乙无规共聚聚丙烯流延片经过正压成型,内部结构发生了显著变化,晶体经过重新排列组合,分子链方向和片晶组的法线方向从无规分布到沿着施加压力方向取向;流延片外表面存在缺陷,经过正压成型其表面三维结构也发生变化,外表面的凹坑被拉大且变浅,内表面出现起伏和取向条纹结构,外表面存在很多凹坑,对光的散射作用强于内表面,导致外表面雾度高于内表面雾度;内部凝聚态结构从片晶无规分布演变成取向纤维晶结构,使内部雾度降低;流延片表面结构存在缺陷,在正压成型过程中并不会被消除,是影响制品雾度的关键因素。

Impact of structure on haze of deep draw drink cup of propylene/ethylene random copolymer

The structural evolution of deep draw drink cup of propylene/ethylene random copolymer and its effect on haze were investigated.The results indicate that the internal structure of propylene/ethylene random copolymer changes drastically during positive pressure thermal-forming process,namely,the molecular chains and the normal direction of crystal lamellae are arranged along the press direction from original random distribution state.The three-dimensional structure of the surface also changes during positive pressure thermal-forming process due to the defects on the outer surface of casting plate.The pits on the outer surface of the cup are enlarged and shallower.Undulating and oriented striped structures appear on the inner surface.The light scattering effect of the outer surface is stronger than that of the inner surface thanks to the pits on the outer surface,which is the cause of the higher haze of outer surface than that of inner surface.The internal haze is reduced since the internal lamellar structure evolves from random distribution into an oriented fiber structure.It is found that defective surface of the cast plate affects the haze of deep draw drink cup,which will not be eliminated during the thermal-forming.