Vulcanization with maleimides

Abstract

SynopsisSeries of mono-and bismaleimides were evaluated as curing agents to determine the effect of structure on crosslinking ability. The activity of N-phenylmaleimide derivatives (monomaleimides) as crosslinking agents is highly dependent upon the substituent on the phenyl group. The activity of bismaleimides is likewise affected by the nature of the moiety connecting the maleimide rings. Isomaleimides and itaconimides are less effective curatives. Initiators for the maleimide cures include peroxides and sulfur accelerators of the thiazole type. Saturated and unsaturated hydrocarbon rubbers, except those containing a high percentage of isobutylene units, are vulcanized by a maleimide-initiator system. One of the attractive features of a maleimide curing system is that the physical properties of the cured rubbers are independent of curing temperature. Further, these vulcanizates have the good aging characteristics typical of nonsulfur-cured vulcanizates. In contrast to sulfur vulcanization, the maleimide curing systems do not markedly affect the ability of elastomers to crystallize when stretched.Therefore, the Ta test cannot be used to assess the state of cure of maleimide-natural rubber vulcanizates. Maleimides containing an appropriate second functional group can be used as self-accelerating curing agents or as adhesives.

The Influence of Electron Beam Irradiation Dose and Polyfunctional Monomers Concentrations on the Physico-mechanical Characteristics of the EPDM/HPDE Blends

“…Generally speaking, there are two factors which affect the functionality of polyfunctional monomers in the polymer: one is the unsaturation of polyfunctional monomers and the other is the solubility of polyfunctional monomers in the polymer [10]. The polyfunctional monomers are coagents and can participate in a number of radical reaction mechanisms, including grafting and radical addition [11][12][13][14].…”

“…În general, existã doi factori care afecteazã funcþionalitatea monomerilor polifuncþionali în polimer: unul este nesaturarea monomerilor polifuncþionali, iar celãlalt este solubilitatea acestora în polimer [10]. Monomerii polifuncþionali sunt coagenþi ºi pot participa într-o serie de mecanisme de reacþii radicalice, inclusiv grefare ºi adiþie radicali [11][12][13][14].…”

The Effect of HVA-2 Addition on the Properties of PP–EPDM–NR Ternary Blends

“…These indicate that blends with HVA-2 show better heat resistance than the blends without HVA-2. According to Tawney et al [17] a maleimide curing system not only gives heat-stable vulcanized but also acts as vulcanizate, which are less susceptible to oxygen attack. The sulfur cross-link makes hydrogen atoms on the carbon backbone attached to the sulfur more susceptible to oxidation.…”

“…They have a desirable versatility in their ability to cross-link polymers of widely differing types such as unsaturated hydrocarbon polymers (NR), PE, HDPE, PP, amino-containing polymers, and urethane polymer [13,14]. In these blends, cross-linking reactions are generally proceeded under intensive melt blending conditions to give fine particles of cross-linked elastomers in thermoplastic matrix and the process involved is known as dynamic cross-linking [17].…”

“…HVA-2 is capable of reacting with the polymer radicals formed by the chain scission during blending [16,[18][19][20]. Tawney et al [17] have found that substituted maleimide produce vulcanizates which generally have better heat or air aging properties than the corresponding sulfur-cured stocks.…”