Nitroxide‐mediated controlled degradation of polypropylene

Abstract

Nitroxide-Mediated Controlled Degradation of PolypropyleneControlled-rheology polypropylene resins (CRPP) have been produced industrially for years using reactive extrusion processes employing peroxides as free radical initiators. The molecular weight characteristics of CRPP materials can be tailor-made depending on the final application in a very efficient and economic manner.A PP-based nitroxide (NOR) with the trade name Irgatec CR76 has been recently developed by CIBA Chemicals, as a source of radicals and it is currently being evaluated for the production of CRPP. NORs are well-known as powerful stabilizers to protect plastics from the negative influence of light and heat, and easy in handling during processing. Preliminary experimental results exhibit a qualitative difference between Irgatec CR76 and other commonly used peroxides.The purpose of this research work is to evaluate this new material as a potential replacement of commonly used peroxides in the production of CRPP. CRPP will be produced by reactive processing using varying amounts of Irgatec CR76 and the rheological properties of the materials produced will be investigated. By comparing results with Irgatec CR76 to those from other typical initiators, the effectiveness of Irgatec CR76 as an initiator will also be assessed.

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

“…First of all, the effect of the thermolysis of L101 on the polyethylene backbone was studied through linear viscoelastic measurements which allow to monitor even slightly modification of the PE macromolecular architecture after a cross-linking reaction [23,41]. Since peroxide thermolysis is a relatively slow first-order decomposition that controls the rate of subsequent radical reactions [42], cross-linking rates are, therefore, fastest in the early stages.…”

A UV‐initiated reactive extrusion process for production of controlled‐rheology polypropylene

“…These publications describe experimental and modeling studies that highlight the effects of processing conditions on the molecular weight, rheological, and thermal properties of CRPPs [1–22]. Although peroxides have dominated as free radical initiators for CRPP production, nitroxide free radical generators have been recently introduced [23, 24], and their performance has been briefly compared with routinely used difunctional initiators [25]. In addition, the use of a tetrafunctional peroxide initiator has been explored for the production of CRPP [26].…”

Sulfonated polyetheretherketone/polypropylene polymer blends for the production of photoactive materials

“…The decrease in viscosity could be explained by the degradation behavior of SPEEK at elevated temperatures and the following chain scission reactions in the material caused by the decomposition products of SPEEK, such as the acid groups mentioned in the TGA paragraph. A similar degradation has been seen when adding compatibilizating maleic anhydride to PP and peroxides or nitroxyl radical generators to PP for rheology control.…”