Analysis of structure and performance of thin⁃walled injection⁃molded polypropylene with high melt flow rate

doi:10.19491/j.issn.1001-9278.2021.12.005

Abstract

Abstract:

The melt crystallization properties， optical properties， molecular weight distribution， mechanical properties， capillary rheological properties， and thermal shrinkage properties of three types of thin-walled injection-molded polypropylenes were investigated. The results indicated that K1860 has the same properties with the commercial PP products， PP1 and PP2， and its molecular weight distribution was narrower than PP1 and PP2. The bending and tensile properties of the K1860 were better than those of PP1 and PP2. The K1860 can completely meet the requirements for the production of large thin?walled injection-molded products.

Key words: polypropylene, high melt flow rate, thin?wall, injection molding, thermal property, optical performance, mechanical property

CLC Number:

TQ325.1⁺5

BAO Lulu, LIU Yi, HAN Liwang, YANG Tingjie, MENG Xin, GUO Xiaodong, WANG Yong, GOU Rongheng, LI Guofeng, ZHANG Minghui. Analysis of structure and performance of thin⁃walled injection⁃molded polypropylene with high melt flow rate[J]. China Plastics, 2021, 35(12): 27-31.

Figures/Tables 9

Fig.1. Non?isothermal crystallization curves and secondary melting curves of three kinds of thin?walled injection PP materials

Fig.2. Isothermal crystallization curves of three kinds of thin?walled injection PP materials

Fig.3. Relative crystallinity vs time curves of three kinds of thin?walled injection PP materials

样品	熔融温度/ ℃	结晶热焓/ J·g^-1	结晶温度/ ℃	t_1/2/s
样品	熔融温度/ ℃	结晶热焓/ J·g^-1	结晶温度/ ℃	110 ℃	120 ℃
PP1	164.2	105.8	130.7	12.6	15.8
PP2	164.2	104.9	132.7	10.8	13.8
K1860	162.7	102.7	129.3	10.2	15.0

Tab.1. Crystallization properties of three kinds of thin?walled injection PP materials

样品	黄度	雾度/%	透光率/%
PP1	-6.3~-6.7	73.8	81.8
PP2	-1.4~-1.7	80.7	79.4
K1860	-1.4~-1.9	59.0	84.6

Tab.2. Optical performance of thin?walled injection PP materials

Fig.4. GPC curves of three kinds of thin?walled injection PP materials

样品

拉伸强度/

MPa

弯曲模量/

MPa

简支梁冲击强度/

kJ·m^-2

熔体流动速率/

g·（10 min）^-1

Tab.3. Mechanical properties of three kinds of thin?walled injection PP materials

Fig.5. Apparent viscosity vs shear rate curves of three kinds of thin?walled injection PP materials

样品	横向收缩率	纵向收缩率
PP1	1.16	1.26
PP2	1.27	1.37
K1860	1.23	1.36

Tab.4. Thermal shrinkage of three kinds of thin?walled injection PP materials

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