Kinetics of, free radical modification of polyolefins in extruders – chain scission, crosslinking and grafting

Abstract

Free radical reactions, carried out in polymer melts, have become a popular method of chemically modifying polyolefins. The elementary free-radical reactions which are relevant in the chemical modification of polyolefins at high temperatures in extruders, such as chain transfer to polymer via primary and polymer radicals, /3-scission, double bond addition and bimolecular termination, affect chain scission, long chain branching, crosslinking and grafting. This brief review will discuss some of the work focused on the kinetics and mathematical modelling of these reactions. ~ ~~Les reactions de radicaux libres, effectutes dans les mklanges de polymtres, sont devenues des methodes rkpandues pour modifier chimiquement les pol yolkfines. Les reactions de radicaux libres ClCmentaires qui sont importantes dans la modification chimique des polyolkfines a des tempkratures Clevees dans les extrudeuses, telles que le transfert de chaine vers le polymtre via des radicaux primaires et de polymtres, la /3-scission, I'addition des doubles liens et la terminaison bimoliculaire, influent sur la scission de chaine, le branchement de chaines longues, la rkticulation et le greffage. Nous examinerons brievement certains des travaux portant en particulier sur la modelisation cinetique et mathkmatique de ces reactions.

Maleic anhydride-grafted polypropylene: FTIR study of a model polymer grafted by ene-reaction

“…Chains are first cleaved as presented in Scheme 1. By this way, unsaturated bonds are almost exclusively located at the ends of chains [11][12][13]. Appearances of bands at 888 cm K1 (assigned to vinylidene) and at 1648 cm K1 (assigned to double bonds stretching) are observed by FTIR after chainscission as reported, respectively, in Fig.…”

“…-On the other hand, the PP macroradicals are reported as first leading to chain scissions (bscission) [11][12][13]. The secondary C-radical generated by b-scission may then form an adduct with MA [3,14,15].…”

Mathematical Modeling of the Grafting of Maleic Anhydride Onto Poly(propylene): Model Considering a Heterogeneous Medium

“…This model was based on the general mechanism for chemical modification of polyolefins presented by Hamielec et al [23,24] . Differently from the work of Zhu et al, [3] this kinetic scheme does not distinguish between H abstraction from secondary and tertiary carbons of the PP chain, a simplification that does not significantly affect the evaluations of the MWD and the grafting degree.…”

Kinetic Modeling of Semi‐Interpenetrating Polymer Network (SIPN) Process ‐ A Comprehensive Study on the Case of Polyethylene/Polystyrene Semi‐I IPN

“…First, the gelation point is always a point of discontinuity for kinetic analyses (modeling). [36] The gel point is determined by the widely known Charlesby-Pinner equation which is valid only when the initial MWD is the most probable one. However, the Charlesby-Pinner equation is frequently used for distributions where it is not applicable.…”