Effects Of Shear And Heat Treatment On Structure And Properties Of Impact Polypropylene Copolymer

Impact polypropylene copolymer(IPC)has been widely used in automotive industry,home appliances and other fields because of its special two-step synthesis process,which not only retains the high modulus of homo-polypropylene,but also has high impact toughness at room temperature and low temperature.IPC is a multi-phase and multi-component alloy in the reactor.The dispersed phase particles size,size distribution uniformity and phase structure of the dispersed phase in the condensed structure have a significant impact on the impact toughness of IPC products.In this paper,the effects of etching solvent,shear force and heat treatment on the phase structure and macro mechanical properties of automotive IPC products with significant differences in molecular weight of rubber phase were systematically studied by means of mechanical properties test,single solvent classification,viscosity average molecular weight test,FTIR,SEM,GPC,DSC,rotational rheology and other characterization methods.Guide users to select and use IPC raw materials.The main research contents and results of this paper are as follows:1)Under different etching conditions,two groups of IPC samples(IPC1,IPC2)with significant difference in molecular weight of rubber phase were etched.The results showd that the ethylene propylene random copolymers(EPR)and ethylene propylene block copolymers(EbP)which are used as dispersion phase were completely etched by etching IPC with n-heptane or n-octane at 23?,and only the single dispersed phase structure with independent pores could be observe d.When o-xylene was used as etching solvent or n-octane at 50? for 4 hours,four kinds of core-shell dispersed phase structures could be observed,which is of great significance to analyze the composition of IPC and the influence of condensed structure on its performance.2)It was found that the four phase structures of the dispersed phase did not disappear with the increase of shear times for the samples of IPC1 and IPC2.For IPC1 samples with small molecular weight of rubber phase,the size distribution of rubber phase was more uniform with the increase of shear times.Secondly,the small and uniform rubber phase dispersed in the material is beneficial to the impact resistance of IPC at room temperature,while the large-size rubber is beneficial to the impact resistance of IPC at low temperature.3)The samples of IPC1-2 and IPC2-2 obtained by the second shear of IPC1 and IPC2 were heat treated at different time and temperature.It was found that the chain migration rate was affected by the molecular weight of rubber phase,with the increase of heat treatment time(30 to 120 minutes),the largest rubber particle size of IPC1-2 sample increased from 4.8?m to 8.8?m,while the largest rubber particle size of IPC2-2 sample increased from 2.8?m to 5.6?m,which proved that the rubber agglomeration rate of IPC1-2 sample was higher than that of IPC2-2 sample.Secondly,heat treatment is conducive to improve the homogeneity of the multiphase system IPC products,so as to enhance the overall mechanical properties of the products.