Rheometer Evidences for the Co-Curing Effect of a Bismaleimide in Conjunction with the Accelerated Sulfur on Natural Rubber/Chloroprene Rubber Blends

Abstract

The rheometer curing curves of neat natural rubber (NR) and neat chloroprene rubber (CR) with maleide F (MF) exhibit considerable crosslinking torque at 180 °C. This indicates that MF can crosslink both these rubbers via Alder-ene reactions. Based on this knowledge, MF has been introduced as a co-crosslinking agent for a 50/50 blend of NR and CR in conjunction with accelerated sulfur. The delta (Δ) torque obtained from the curing curves of a blend with the addition of 1 phr MF was around 62% higher than those without MF. As the content of MF increased to 3 phr, the Δ torque was further raised to 236%. Moreover, the mechanical properties, particularly the tensile strength of the blend with the addition of 1 phr MF in conjunction with the accelerated sulfur, was around 201% higher than the blend without MF. The overall tensile properties of the blends cured with MF were almost retained even after ageing the samples at 70 °C for 72 h. This significant improvement in the curing torque and the tensile properties of the blends indicates that MF can co-crosslink between NR and CR via the Diels–Alder reaction.

The Use of Copper Oxides as Cross-Linking Substances for Chloroprene Rubber and Study of the Vulcanizates Properties. Part I

“…In elastomer technology, metal oxides are used to cross-link materials containing atoms belonging to the halogen group in their main chains. This rubber group includes chloroprene rubber [ 4 , 5 , 6 , 7 , 8 ], chlorosulfonated polyethylene [ 9 ] and halogenobutyl rubbers: chlorobutyl [ 10 , 11 , 12 ] and bromobutyl [ 12 , 13 ]. For cross-linking of these materials, a mixture of two oxides is used: zinc oxide [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] and magnesium oxide [ 4 , 6 , 7 , 8 , 9 , 11 , 13 , 14 , 16 , 17 , 18 ].…”

“…This rubber group includes chloroprene rubber [ 4 , 5 , 6 , 7 , 8 ], chlorosulfonated polyethylene [ 9 ] and halogenobutyl rubbers: chlorobutyl [ 10 , 11 , 12 ] and bromobutyl [ 12 , 13 ]. For cross-linking of these materials, a mixture of two oxides is used: zinc oxide [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] and magnesium oxide [ 4 , 6 , 7 , 8 , 9 , 11 , 13 , 14 , 16 , 17 , 18 ]. Zinc oxide is a compound in the form of white hexagonal crystals.…”

“…Magnesium oxide is in the form of a white, finely divided powder. Cross-linking of rubber containing halogen atoms occurs as a result of the reaction of this atom with zinc oxide, resulting in the formation of a Lewis acid (e.g., zinc chloride) [ 5 , 6 , 7 , 10 , 15 ]., whereas magnesium oxide is an acceptor of the formed hydrogen chloride [ 15 ]. Additionally, ZnO and MgO can be used for the cross-linking of carboxylated acrylonitrile-butadiene rubber [ 16 , 17 , 18 ].…”

Identifying the Co-Curing Effect of an Accelerated-Sulfur/Bismaleimide Combination on Natural Rubber/Halogenated Rubber Blends Using a Rubber Process Analyzer

“…The natural rubber (standard Vietnamese rubber with a Mooney viscosity ML ( the curing behavior of neat NR with CV system and the curing behaviors of BIIR with metal oxides were also reported. To check the validity of the cur and the mechanism proposed in reference [18], a specially designed testing employed in this study with the help of a rubber process analyzer (RPA).…”

“…In our previous article, the co-curing effect of a combination of conventional accelerated sulfur (CV) and a bismaleimid on a 50/50 blend of NR/CR was reported based on a moving die rheometer (MDR-3000, Mon Tech, Buchen, Germany). Mainly based on this rheometer cure data, a mechanism responsible for the co-curing effect of the CV/bismalimide on the NR/CR blend has been proposed [18]. In the present work, the curing behavior of a 50/50 blend of NR with another grade of CR and a 50/50 blend of NR with another halogenated rubber was investigated; BIIR was again investigated in the presence of a combination of CV/bismaleimide using the same MDR.…”