Abstract
Butyl rubber (isobutylene–isoprene–rubber, IIR) was functionalized in solution with a nitroxide moiety taking advantage of the unsaturations present in the isoprene units of IIR, and was further grafted with maleic anhydride (MA) or styrene–MA (SMA) to produce IIR-g-MA and IIR-g-SMA. In one of the functionalization techniques used, the molecular structure of the IIR was preserved as the chain-breaking reactions are prevented from occurring. The resulting graft copolymers were tested as compatiblizers/impact modifiers blended with Nylon-6, and one of them was preliminarily tested as a coupling agent in the preparation of nanocomposites of IIR and an organo-clay. Blends of PA-6/IIR-g-MA exhibited a significant increase in impact resistance at increasing loads of the modified IIR, as well as a good rubber particle dispersion in the polyamide matrix. On the other hand, the performance of IIR-g-SMA as an impact modifier of PA, or as a coupling agent in the preparation of rubber-organoclay nanocomposites, is marginal.
Highlights
Grafted and functionalized polymers are very attractive materials from both the scientific and the industrial points of view due to their potential applications as compatibilizers [1], adhesives [2], surfactants, etc
IIR functionalized with 4-hydroxy-tetramethyl piperidine 1-oxyl (TEMPO) moieties along its backbone was produced using two initiator addition procedures and scales
The procedure employed for nitroxide functionalization of butyl rubber using the unsaturations present in the isoprene units of IIR proved to be effective in spite of the relatively low content of isoprene in IIR
Summary
Grafted and functionalized polymers are very attractive materials from both the scientific and the industrial points of view due to their potential applications as compatibilizers [1], adhesives [2], surfactants, etc. In this work a procedure that we have developed for controlled functionalization and grafting with MA and styrene–MA using nitroxide chemistry (more details below) is applied to butyl rubber, or IIR. This is a more challenging system than others previously studied by us due to the fact that the unsaturations present in IIR are only a small percentage (less than 2% molar) of the rubber chain and Polymers 2017, 9, 63; doi:10.3390/polym9020063 www.mdpi.com/journal/polymers. Butyl rubber (IIR) is the copolymer of isobutylene and a small amount of isoprene, which is commercially produced by cationic polymerization It was first commercialized in the early 1940s; its main attributes are excellent gas barrier and good flex properties, resulting from low levels of unsaturated units between long polyisobutylene segments [6]. An ethylenically unsaturated compound (maleic anhydride, among others) is added
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