连续自成核退火技术在抗冲共聚聚丙烯微观结构表征中的应用OA

Impact copolymer polypropylene(ICP)possesses a complex multiphase architecture consisting of a polypropylene(PP)matrix,an ethylene propylene rubber(EPR)dispersed phase,and an ethylene-propylene copolymer component.Conventional characterization methods for such heterogeneous systems require cumbersome pre-separation of individual components.Successive self-nucleation and annealing(SSA)is a thermal fractionation technique based on DSC that enables the effective fractionation of polymer chains during crystallization without physical separation of the constituents.Despite its established utility in characterizing polyolefins such as polyethylene and PP,the direct application of SSA to unfractionated ICP remains rarely reported.In this study,SSA,DSC,GPC,and POM were employed to investigate the PP chain segments within six commercial ICP grades.Three key parameters derived from SSA,i.e.,the melting enthalpy after SSA thermal fractionation(ΔHm SSA),the height of the first melting peak(H1),and the ideal self-nucleation temperature(Ts ideal),were systematically examined in relation to material properties.The results reveal that ICP-A,ICP-C,ICP-D,and ICP-F exhibit a broad Domain Ⅱa region,accompanied by considerable nucleation site density during the early stage of crystallization,suggesting the presence of nucleating agents in these grades.Negative correlations of ΔHm SSA with both ethylene content and EPR content are observed,with a stronger correlation coefficient for the latter,confirming the diluting effect of the rubbery phase on the crystallizability of the PP matrix.ICP-D shows the most pronounced increase in ΔHm SSA,indicative of a higher population of folded-chain segments within its structure.ICP-C exhibits an abnormally high H1,which implies a concentrated distribution of PP chain segments.ICP-E,despite attaining a high ΔHm SSA of 119.8 J/g,displays a flexural modulus of only 1 200 MPa,a discrepancy attributed to the absence of nucleating agents in this sample.Furthermore,a positive linear relationship is established between the Ts ideal and Mw of PP(R2=0.892),demonstrating that higher molecular weight chains possess enhanced ability to retain ordered structures at elevated temperatures.These results demonstrate that SSA enables direct microstructural characterization of PP chain segments within ICP without pre-separation.