Impact of Long-Chain Branching on Polypropylene Nucleation and Crystallization over a Wide Temperature Range without the Influence of Shear

• DOI: 10.1021/acs.macromol.4c02256
• Publication Date: 2024-12-09T14:24:05Z
• Authors: Xinyan Chen; Ricardo Arpad Pér...; Pan Ma; Yilong Liao; Ying Zhao; Jin-Yong Dong; Xia Dong; Alejandro J. Müller; Dujin Wang
• Keywords: Branching (polymer chemistry); Supercooling; Polypropylene; Polarized light microscopy

Even though the crystallization of long-chain branched polypropylene (LCB-PP) has been widely studied, role branches within isotactic (iPP) under shear-free conditions and a comprehensive understanding its isothermal kinetics over wide temperature (Tc) range are still lacking. The samples in this work were prepared by solution casting to eliminate any possible shear effects. Then, impact LCB on behavior iPP with varying content (LCB) was investigated entire window range. Polarized light optical microscopy (PLOM) scanning electron (SEM) revealed that nucleation density increased branching content. Standard differential calorimetry (DSC) ultrafast chip (or FSC, fast calorimetry) showed overall rates had different dependence across (5–136 °C). Above 95 °C, only α-phase formed, an increasing rate In addition typical heterogeneous nucleation, LCBs provoke significant increase through homogeneous process triggered topological constraints segments linked branch point. These stabilize PP chain's helical structure facilitate self-assembly these neighboring chains into primary nuclei. Between 45 did not show specific trend, as there competition between diffusion. Below where supercooling high became dominant, similar for LCB-PP neat linear iPP. This deepens crystallization, providing critical insights both mechanisms polymers broader Tc