Effect of ion modification on viscoelasticity of broad molecular weight distribution polypropylene
PP4 was obtained through treating polypropylene with a wide molecular weight distribution(BMWDPP)PP1 using an ion modifier.The molecular structures and rheological properties of PP1 and PP4 were investigated by gel per-meability chromatography(GPC),plate rotational rheology,stretch rheology,and melt strength tests.The PP degrada-tion induced by free radicals reduced the molecular weight and polydispersity of BMWDPP.There was no real long branch chain structure generated due to the"long-like branched chain"effect of the ionic interaction between the metal salts on the PP chain segment.PP4 exhibits a stretch hardening phenomenon.The large molecular weight components could weaken the molecular entanglement,whereas the small molecular weight components could enhance the plasticiz-ing effect due to the degradation of PP4.This makes its viscoelasticity lower than that of PP1.The influence of stretch strain hardening on the enhancement of melt strength is stronger than the effect of molecular weight reduction on the weakening of melt strength.Therefore,the melt strength of PP4 is higher than that of PP1 at different temperatures.This indicated that the PP was featured with linear large molecular chains at low temperature and long branched chains at high temperature.
broad molecular weight distribution polypropyleneion modificationviscoelasticitystretch hardeningmelt strength
国家科技期刊平台
NSTL
万方数据
维普
