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New chemistry for preparing polypropylene (PP) thermosets is described, wherein radical degradation suffered during conventional peroxide treatment is overcome using a nitroxyl additive that bears a polymerizable functional group. A small amount of 4-vinylbenzoic-2,2,6,6-tetramethylpiperidin-N-oxyl (VBTEMPO) is used to trap peroxide-derived, alkyl radical intermediates during the early stages of the...
Delayed onset formulations for the peroxide-initiated crosslinking of a range of commodity polymers are described. 4-Acryloyloxy-2,2,6,6,-tetramethylpiperidin-N-oxyl (AOTEMPO) is effective for controlling the crosslinking dynamics and yields of linear low density polyethylene (LLDPE), poly(ethylene-co-vinyl acetate) (EVA), poly(ethylene-co-propylene) (EPR), and poly(ethylene-co-propylene-co-ethylidenenorbornadiene)...
Strategies employing 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl (AOTEMPO) to control the onset, rate and yield of polyolefin cross-linking are demonstrated and discussed in terms of underlying reaction mechanisms. Rheological studies of a wide range of dicumyl peroxide (DCP) + AOTEMPO formulations confirm that linear low density polyethylene (LLDPE) cross-linking can be delayed precisely and...
New imidazolium bromide ionomers are prepared by halide displacement from brominated poly(isobutylene-co-isoprene) (BIIR) with a variety of imidazole-based nucleophiles. N-alkylation of butylimidazole (BuIm) by the allylic halide functionality within BIIR provides stable imidazolium bromide functionality in high yields. Characterization of the resulting thermoformable ionomer by dilute solution viscosity...
The dynamics of halide displacement from brominated poly(isobutylene-co-isoprene)(BIIR) by carboxylate nucleophiles are detailed and discussed in terms of a general reaction mechanism. The exomethylene allylic bromide isomer within BIIR is shown to undergo simultaneous S N 2 alkylation of Bu 4 Nacetate and S N 2′ rearrangement with Bu 4 NBr. The latter generates a Z-BrMe...
The thermolysis of 2,3-dimethyl-2,3-diphenylbutane (bicumene) at temperatures ranging from 220 to 310°C is used to initiate the radical-mediated graft addition of vinyltriethoxysilane (VTEOS) to polyethylene. Model hydrocarbon studies indicate that the cumyl radicals generated by the slow decomposition of bicumene are capable of direct hydrogen atom abstraction at levels that are sufficient to sustain...
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