Ester functionalization of polypropylene via controlled decomposition of benzoyl peroxide during solid-state shear pulverization

Mirian F. Diop, John M. Torkelson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

Polypropylene (PP) is a nonpolar polyolefin that is sometimes functionalized with polar molecules to allow for reactive compatibilization and improve interfacial adhesion. Functionalized PP is conventionally synthesized by melt extrusion at elevated temperature (T) (≥∼180 C) with a radical initiator and polar monomer, e.g., maleic anhydride. A drawback to high T functionalization is that β-scission, which leads to cleavage of C-C backbone bonds, is significant and results in major molecular weight (MW) reduction and property degradation. We present a novel method of functionalizing PP using benzoyl peroxide (BPO) alone by a process called solid-state shear pulverization (SSSP), resulting in ester functional groups (benzoates) grafted at high yield onto PP. Ester functionalized PP (PP-g-ES) is synthesized with limited MW reduction because SSSP is done at sufficiently low T to suppress β-scission. Characterization before and after grafting at 0.18 mol % (0.46 wt %) graft level indicates that functionalization (and subsequent purification) is accompanied by only one chain scission event per 12 400 PP repeat units, resulting in 17% and 36% reductions in number-average MW and weight-average MW, respectively. Benzoate grafting levels are tuned from 0.08 to 0.41 mol % (0.22 to 1.14 wt %) by varying the BPO feed level. In addition to limited MW reduction, PP-g-ES exhibits modified interfacial properties, the ability to undergo transesterification reactions consistent with reactive compatibilization, and little to no loss of physical and mechanical properties relative to neat PP.

Original languageEnglish (US)
Pages (from-to)7834-7844
Number of pages11
JournalMacromolecules
Volume46
Issue number19
DOIs
StatePublished - Oct 8 2013

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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