Study On The Processing Behavior Of Random Impact Copolymer Polypropylene PBE

Random impact copolymerized PP combines the excellent properties of random copolymerized PP and impact copolymerized PP.A certain amount of butene is copolymerized in the continuous phase of impact copolymerized PP.The butene is used to adjust the relationship in the refractive index of the rubber phase to reduce haze,a new material with both transparency and impact toughness can be obtained.In order to put this material into production and use it in various fields,the processability research of this material is very important.Because of the differences in composition and structure,the processing properties of existing types of PP cannot be used to guide the production and application of random impact copolymerized PP.Therefore,systematic research is necessary and its processing properties are prepared for further applications.In this dissertation,we take the random impact copolymerization PP(PBE)which is produced independently by PetroChina Lanzhou Chemical Research Center as the research material,and systematically studied the effects of rheological parameters and crystallization properties of PBE on processing methods and process parameters.We used the cross test to optimize the processing technology,and find that the obtained results provide important guidance for the processing and application of random impact copolymerized PP materials with similar melt figures.We summerized the conclusions as follows:(1)Firstly,the effects of temperature and shear rate changes on the processing rheological properties of PBE were studied using a capillary rheometer,and through the experimental comparison of ethylene-propylene random copolymer PP(RPE)and propylene random copolymer PP(RPB).It shows that PBE is a typical pseudoplastic fluid,and the processing methods of other PP materials are also applicable to PBE.At the same time,the"cut sensitivity"of PBE was the highest,and the rheological properties of temperature and shear rate PBE were the most important.The unstable flow occurred when the PBE was extruded at a temperature of 160°C,indicating that the processing temperature of PBE was higher than 160°C.The melt strength of PBE was significantly lower than that of RPB and RPE,and the maximum variation with temperature indicated that injection molding was the most suitable processing method for PBE.At a certain shear rate,PBE has the smallest extrusion expansion ratio and the best dimensional stability.(2)Then the non-isothermal crystallization kinetics of PBE RPE and RPB were studied by DSC.The effects of crystallization rate and activation energy on the crystallization performance of PBE were investigated.The results show that PBE contains chain segment with small molecular weight,which can dilute polymer chain,so the crystallization peak temperature of PBE is the lowest.By analyzing the semi-crystallization time and non-isothermal crystallization kinetics model,the crystallization rate o f three samples is RPB>PBE>RPE,and showed that the introduction of a branch chain in the polymer molecular chain can accelerate the crystallization rate of the polymer.The wide molecular weight distribution of PBE increases the movement ability of the molecular chain,resulting in the lowest crystal activation energy.(3)Eventually,different nucleating agents were added to improve the rheological properties and crystallization properties of PBE,and the samples with JHC755 were compared with those with the best comprehensive properties.The effects of injection molding process parameters on the four properties of bending modulus tensile strength impact strength and haze were studied by orthogonal experiment,and the injection molding process conditions with better comprehensive properties were obtained:the melt temperature is 200°C,the injection pressure is 20kg/cm~2,the injection rate is 20%,the holding pressure is 60 kg/cm~2,the dwell time is30 s,the cooling time is 30 s,and the mold temperature is 40°C,and the product molded under this condition had a bending strength of 9 71.36 MPa,an impact strength of 7.3863 KJ/m~2,a tensile strength of 26.83 MPa and a haze is 11.3%.