Study On Effects Of Nucleating Agents And Processing Condition On Polypropylene Modification

In this paper, nucleating agents including NX8000K, HPN-68L, Millad 3988, dispersing agents TAS-2A, halogen-absorber DHT-4A and antioxidants including 1010 and 168 were added to isotactic polypropylene(iPP) and random copolymer polypropylene(PPR) via melt blending method to modify iPP and PPR. The crystallization properties and crystal morphologies of samples prepared with different additive contents and prepared under different processing conditions were studied exploiting differential scanning calorimeter(DSC) and polarizing optical microscopy(POM), respectively. Their optical, mechanical and thermal properties were also tested to explore the effect of each additive on polypropylene(PP) modification, which leads to the optimum dosage of additives and processing temperature.Nucleating agent NX8000K was selected to modify iPP (1102K), the results show that NX8000K has significant nucleating effects on iPP with a nucleation efficiency as high as 74.6%, and obvious improvements were observed on transparency, strength and thermal properties, but no significant improvement in toughness was observed. A optimum dosage of 0.6 phr was determined. Since additives were essential in PP modification, effects of DHT-4A, TAS-2A and m(1010):m(168) on iPP modification were investigated on basis of optimum NX8000K dosage, optimum dosage of each additive was determined as follows, DHT-4A:0.04 phr, TAS-2A:0.2 phr, m(1010):m(168)=1.0:1.6. Nucleating agent HPN-68L was also selected to modify iPP(140), and the results show that HPN-68L has very significant nucleating effect on iPP. Transparency, stiffness and heat resistance of iPP were improved with the addition of HPN-68L, and its dosage was optimized as 0.08 phr.Nucleating agents NX8000K and HPN-68Lwere formulated to modify iPP (140), the results show that a ratio of (0.35/0.05) phr can reduce haze and increase transparency of iPP. Strength, modulus and thermal properties were also improved, meanwhile, notched impact strength were increased by 26.7% compared with neat iPP. Formulated nucleating agents NX8000K and HPN-68L show synergetic effect in iPP modification, which results in improved comprehensive properties of iPP.Processing temperature has pronounced influence on PP modification. Four processing temperatures were used in this work to investigate the effects of nucleating agent Millad 3988 and NX8000K on PPR (R503) modification, respectively. The results show that suitable processing temperatures for Millad 3988 and NX8000K in PPR modification were 250℃ and 240℃, respectively. The tensile properties of resulting nucleated PPR increases, but accompanied by slightly decrease in toughness and heat resistance and results in satisfying overall properties of PPR.