Crosslinking and scission in radical‐promoted functionalization of polyethylene

Abstract

SYNOPSISWe reported earlier on grafting hexafluoroisopropanol groups onto polyethylene through the reaction of polyethylene with hexafluoroacetone and di-t-butyl peroxide. The modified polyethylene was partially crosslinked. In this work, we adapted the Charlesby-Pinner Equation to estimate the ratio of chain scission to crosslinking in the reaction.

Effect of nitroxyl-based radicals on the melt radical grafting of maleic anhydride onto polyethylene in presence of a peroxide

“…high temperature and low monomer concentration, the kinetic chain length for homopolymerization is much lower than in typical vinyl polymerizations and degrees of polymerization are relatively low [25]. Grafting, branching, cross-linking and degradation set boundaries of the desired grafting reaction and their extent of grafting depends on the type of polymer and nature/type of chemicals used [26]. Primary and secondary radicals are reported to give more easily the coupling reaction than the tertiary ones which instead undergo b-scission reactions or disproportionation reactions.…”

Control of Degradation Reactions during Radical Functionalization of Polypropylene in the Melt

“…7 Free radical initiators give rise, in the bulk and at the high-temperature necessary for good rheology, to scission, grafting, branching, and crosslinking reactions. 8 The polymer degradation through β-scission reactions 4,9 predominates over the other reactions in the case of isotactic polypropylene (iPP). Probably hydrogen abstraction from PP backbone proceeds preferably at the level of the tertiary carbon atom, even though the abstraction from secondary carbon atoms or from methyl groups is possible as well.…”

Microstructural Evolution in Linear Low Density Polyethylene During Peroxide Modification: A Monte Carlo Simulation Study

“…The range of microstructural variations the specific modification method may generate is essential to correlate the evolving micro‐scale architecture to processing conditions . The main chemical modification mechanisms proposed are as follows (Scheme ):…”

“…Polyolefinic specialty polymers are produced by modifying the molecular weight [either a reduction in the average molecular weight and polydispersity in the case of controlled rheology polypropylene (PP), or a build‐up of molecular weight in the case of polyethylene (PE)] or by grafting functional groups onto the polymer backbone. The grafting process can be accompanied by other changes in the structure and properties of the basic polymer . Organic peroxides have become increasingly important as initiators of free‐radical degradation mechanisms in PE in order to modify the polymer structure and modulate its properties .…”

“…The grafting process can be accompanied by other changes in the structure and properties of the basic polymer. [1,2] Organic peroxides have become increasingly important as initiators of free-radical degradation mechanisms in PE in order to modify the polymer structure and modulate its properties. [3] One of the most popular peroxides, dicumyl peroxide (DCP), is very effective in introducing long-chain branches in linear PEs, and at low concentrations, it favorably alters MWD.…”