Non-Negligible Effect of Additives in the Application of Successive Self-Nucleation and Annealing Fractionation for Microstructure Characterization of Matrix Resin in Additive-Containing Samples

Successive self-nucleation and annealing (SSA) is a convenient and versatile thermal fractionation technique that has been extensively used to characterize the chain microstructure of semicrystalline polymers. In practical applications, commercial products containing various additives are frequently tested by SSA to analyze the resin structure. In this case, whether the presence of additives affects the SSA result of matrix resin is worth considering. In this work, four additives including two nucleating agents (β-NA and α-NA), a lubricant, and an acid scavenger were purposefully added into the same polypropylene random copolymer (PPR) matrix resin, and SSA fractionation results of PPR with and without these additives were comparatively studied. It was found that SSA results of PPR containing diverse additives and pristine PPR are different. The results of small-angle X-ray scattering monitoring of the melting process of the “standard” crystal proved that additives altered the thermal stability of the ordered structure in the polymer upon heating. It is the variation in thermal stability that led to the change in the ideal self-nucleation temperature determined by the self-nucleation experiment, which is a crucial reason why different additives affected the SSA results of the same matrix resin. This work reminds that in the practical application of SSA to characterize the chain microstructure of the resin matrix for samples containing additives, the influence of additives cannot be ignored.