Research On Preparation Of High Fluidity Polypropylene By Degradation

In this paper,the di-tert-butyl peroxide(DTBP),2,5-dimethyl-2,5-bis(tert-butyl-peroxy)hexane(DHBP),2,5-dimethyl-2,5-bis(tert-butyl-peroxy)-3-hexyne(DYBP)were selected as thermal decomposition initiator for the degradation of polypropylene to prepare high fluidity polypropylene.The effects of processing temperature,initiator type,and initiator content on the properties of polypropylene were investigated.The effect of processing temperature on the fluidity of polypropylene with different initiators was investigated.The results showed that the degradation process of polypropylene was basically completed when the processing temperature was over at 220 ~oC.The effect of initiator DTBP contents on the properties of polypropylene was investigated.The results showed that the melt flow rate(MFR)of polypropylene increased slightly with the increment of initiator DTBP contents.The notched impact strength,tensile strength and elongation at break decreased gradually with the increment of DTBP contents.When the DTBP content exceeded a certain value,the elongation at break decreased greatly.With increasing initiator DTBP contents,the crystallization temperature of polypropylene increased slightly,the crystallinity changed little,and the melting peak of polypropylene changed gradually from unseparated two endotherms to be resolved into two.With increasing initiator DTBP contents,the initial degradation of polypropylene shifted to lower temperature.And the temperature corresponding to the maximum degradation rate was not significant.The complex viscosity of polypropylene at different frequencies decreased gradually with the increment of DTBP contents.The effective degradation of polypropylene was not obvious using DTBP as initiator.The effect of initiator DHBP contents on the properties of polypropylene was investigated.The results showed that the MFR of polypropylene increased rapidly with the increment of initiator DHBP contents.And the fluidity of polypropylene was enhanced significantly.With the increment of initiator DHBP contents,the mechanical properties of polypropylene decreased.And the elongation at break of polypropylene decreased rapidly at a lower content of DHBP,showing brittle fracture.With the increment of DHBP contents,the change law of thermal behavior,thermal stability and complex viscosity of polypropylene were similar to those of DTBP-degraded polypropylene.When DHBP content reached a certain value,the complex viscosity of polypropylene remained almost constant with frequency.Using DHBP as initiator,the degradation effect of polypropylene was obviously better than that of DTBP.The effect of initiator DYBP contents on the properties of polypropylene was investigated.The results showed that the MFR of polypropylene increased rapidly with increasing DYBP contents.The effect of the DYBP content on the properties of polypropylene was similar to that of DHBP.And the degradation effect was more obvious when the content was the same.The degradation effect of DYBP as initiator on the polypropylene was better.