Crosslinking of polypropylene–polyethylene blends by peroxide and the effect of pentaerythritol tetrallyl ether

Abstract

SynopsisCrosslinking of polypropylene-polyethylene (PP-PE) blends involving 10, 20, 30, 40, 50, 60, 70, 80, and 90% of PP with dicumylperoxide (DCP) or tert-butyl perbenzoate (TBPB) and in the presence of coagent pentaerythritol tetrallyl ether (PETA) was investigated at 180°C. It was found that at lower concentrations of peroxide alone (e.g., 2.5% of DCP) only PE component is crosslinked in all compositions of PP-PE blends. In the crosslinking of PP-PE 50 : 50 with 4% of TBPB, insoluble gel was obtained, which contained 13% PP and 87% PE. If 2% PETA was also used, the portion of PP in gel increased to 39%; the total yield of gel in PP-PE blend increased from 50 to 70%. The lower crosslinking efficiency of coagent PETA in the PP-PE blends compared with PP alone is associated with better solubility of the coagent in the PE phase in contrast to the PP phase. The coagent does not particularly raise the crosslinking efficiency of peroxide in PE, but increases it in the PP phase. A remarkable decrease in melting temperature and temperature of crystallization of both polymer components depending on peroxide concentration was found by calorimetric measurements.

Comparison of rheological behavior of branched polypropylene prepared by chemical modification and electron beam irradiation under air and N2

“…Comparing these results with the results obtained for copolymer shows that the presence of low amounts of ethylene in polypropylene structure can reduce the b-chain scission reaction during chemical modification. Similar results were also reported by Graebling et al (1997) and Borsig et al (1989) in which presence of PE limited the extent of PP degradation during a polypropylene free radical modification process and helped build a branched/ crosslinked structure.…”

Long chain branching on linear polypropylene by solid state reactions

“…Scheme 1 depicts a generally accepted mechanism for the reactions, based on the available information in the literature [10][11][12][13][14][15]. Primary radicals formed by the decomposition of the peroxide (2) react with iPP (1) to yield macro-radicals (3).…”

“…The curves of all the samples that have been modified in the presence of FS (#12, 13,14,17) show much lower values for d than the curve for iPP, indicating higher elasticity at the same frequencies. As the amount of FS increases, the curve starts to show a deflection and then a local plateau at around 10 rad/s.…”

Structure and Properties of Reactive Extruded Ethylene-block-co-Polypropylene: Influence of Dicumyl Peroxide and Divinylbenzene

“…Much work has been done on highly crosslinked PP or related polyblends by using polyfunctional monomer or coagents in glass ampules or a batch mixer. [11,12,19,20] Using a reactive extrusion technique, Tzoganakis et al [1] prepared pentaerythritol triacrylate (PETA)/isotactic polypropylene/peroxide mixtures and studied the formation of the branched/crosslinked structure and the transformation of crystalline structure. Except for noting the melt strength, they did not examine the influence of structure transformation on the fracture behavior of modified polymers.…”