Parameters affecting the grafting reaction and side reactions involved in the free‐radical melt grafting of maleic anhydride onto high‐density polyethylene

Abstract

The parameters affecting the grafting reaction and side reactions in free-radical melt grafting of maleic anhydride (MA) onto high-density polyethylene with the aid of 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane peroxide(DTBPH) have been studied using an internal mixer. MA grafting degree of the maleated samples was measured with titrometry and FTIR spectroscopy methods. The extent of chain-branching/crosslinking side reactions was evaluated with gel content and MFI determination. The flow behavior and melt viscoelastic properties of the samples were measured using a rheometric mechanical spectrometer. DTBPH and MA concentrations, reaction temperature, rotor speed, the type and concentration of coagents were among the studied parameters. The results show that MA and DTBPH concentration has a major role on the grafting reaction, chain-branching/crosslinking side reactions and also the grafts microstructure in the final product. The reaction temperature has a complex effect on the maleation reaction. Increasing the rotor speed causes an increase in MA grafting degree of the samples and reduces the competitive side reactions. By using Gaylord additives, gel formation reduces at the expense of a dramatic decrease in the grafting degree. MA grafting degree is increased by the use of comonomers in the reaction and this is accompanied with a decrease in crosslinking side reaction when the vinyl type styrene comonomer is used. The results of processing torque in combination with the measurements of the melt viscoelastic property and gel content of the samples provide a great insight into understanding the gel formation mechanism.

Rice husk ash – A valuable reinforcement for high density polyethylene

“…The spectrum of the compatibilized composite shows a peak at 1740 cm À1 assignable to symmetric stretching of C@O group present in ester moieties. The C@O group present in the anhydride ring will show absorbance at a different wave number 1830 cm À1 [36] which is not noticeable in the spectrum. This indicates that the functional groups of MA-g-HDPE react with the hydroxyl groups of RHA (Scheme 1) leading to covalent bonding and esterification reactions [37].…”

Graft copolymerization of maleic anhydride onto low‐molecular‐weight polyisobutylene through solvothermal method

“…5. Side reactions 30 are shown in Scheme 6 include cross-link reaction, homopolymerization of MAH, intra molecular radical transferring, chain transferring to solvents and so on.…”

“…The formation of macro radicals-addition of the radical to the double bond of the chain. 29,30 According to different end groups, there are several kinds of macromolecular radicals shown in the following as I-HÁ (in Scheme 3). 3.…”

In Commodity Plastics

“…Increasing the rotor speed enhanced the degree of grafting while lowering the extent of competitive side reactions. The use of styrene as a comonomer decreased crosslinking side reactions and increased the degree of grafting [11] .…”