Tuning Melt Strength and Processability of Polyolefins by Addition of a Functionalized Additive Designed via the TEMPO-Driven Thiol-ene Reaction

• Published in: Industrial & engineering chemistry research Vol. 60; no. 28; pp. 10155 - 10166
• Main Authors: Jaisingh, Aanchal, Kapur, Gurpreet Singh, Nebhani, Leena
• Format: Journal Article
• Language: English
• Published: American Chemical Society 21.07.2021
• Subjects: Materials and Interfaces
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.1c01190

Thiol-ene chemistry with TEMPO as an initiator has been utilized to synthesize a first-generation dendrimer having eight peripheral hydroxyl groups. Long chain branched impact copolymer polypropylene (ICP) and linear low-density polyethylene (LLDPE) were prepared by a postreactor modification process by a melt-grafting dendrimer onto a polyolefin chain using peroxide and maleic anhydride as a co-agent. Long chain branching in ICP controlled the chain scission initiated by peroxide by increasing entanglement, while for LLDPE, it controlled the excessive crosslinking because of peroxide. Neat and modified ICP and LLDPE samples were analyzed by FT-IR, TGA, DSC, HT-GPC, MFI, and parallel-plate rheometry as well as for their melt strength. The presence of long chain branching was mainly confirmed by time–temperature superposition (TTS) analysis obtained using a parallel-plate rheometer. In comparison to neat polymers, modified ICP and LLDPE samples showed higher values of Arrhenius flow activation energy. In the case of ICP, higher processability was observed for a dendrimer-grafted sample, while modified LLDPE samples exhibited higher melt strength as compared to neat polymers. Van Gurp–Palmen plots showed a decrease in phase angle as a function of angular frequency for modified ICP and LLDPE samples, which also confirmed their thermorheological complex behavior.