Cure Characteristics and Mechanical Properties of Maleic Anhydride Grafted Reclaimed Rubber/ Styrene Butadiene Rubber Blends

Blends of styrene butadiene rubber (SBR) with maleic anhydride grafted whole tire reclaim (MA-g-WTR) have been prepared and the cure and mechanical properties have been studied with respect to the reclaim content. The grafting was carried out in the presence of dicumylperoxide (DCP) in a Brabender Plasticorder at 150'C. The presence of anhydride group on the WTR was confirmed by infrared spectrometry (IR) study. The properties were compared with those of the blends containing unmodified WTR. Though the cure time was marginally higher, the mechanical properties of the blends containing grafted WTR were better than that of the unmodified blends.

Effect of Silane Coupling Agent on Cure Characteristics and Mechanical Properties of Nitrile Rubber/Reclaimed Rubber Blend

Blends of nitrile rubber and reclaimed rubber containing different levels of a coupling agent, Si 69 (bis(3- triethoxysilyl propyl)(tetrasulphide) were prepared and the cure characteristic's and mechanical properties were studied. Optimum loading of Si-69 was found to be a function of blend ratio. 3 phi- of Si 69 in a 70:30. Blend was found to be the optimum combination with respect to the mechanical properties. The rate and state of cure were also affected bv the conp/ing agent. Tensile strength, tear strength and abrasion resistance were improved in the presence of coupling agent. While the state of cure improved, the cure rate and scorch time decreased with increasing silane content. Ageing studies showed that the blends containing the coupling agent were inferior to the unmodified blends.

Effect of Silane Coupling Agent on Cure Characteristics and Mechanical Properties of Chloroprene Rubber/Reclaimed Rubber Blend

Chloroprene rubber was blended with whole tire reclaimed rubber (WTR) in presence of different levels of a coupling agent Si69 [bis- (3-(triethoxysilyl)propy1)tetrasuIfide] and the cure characteristics and mechanical properties were studied. The rate and state of cure were also affected by the coupling agent. While the cure time was increased, the cure rate and scorch time were decreased with increasing silane content. Tensile strength, tear strength, and abrasion resistance were improved in the presence of coupling agent. Compression set and resilience were adversely affected in presence of silane-coupling agent.Aging studies showed that the blends containing the coupling agent were inferior to the unmodified blends.

Studies - on Maleic Anhydride Grafted Reclaimed Rubber/Acrylonitrile Butadiene Rubber Blends

Blends of Acrylonitrile rubber with Maleic anhydride grafted Whole Tyre Reclaim WTR (MA-g-WTR) have been prepared and the cure and mechanical properties have been studied with respect to reclaim content. Control compounds containing unmodified WTR were also prepared for comparison. Grafting was confirmed by IR studies. Blends containing grafted WTR showed higher minimum torque and (max-min) torque. They also showed longer cure time, scorch time and lower cure rate. Grafting of the WTR with maleic anhydride also resulted in the improved tensile strength, abrasion resistance, compression set and resilience. However, the heat build up under dynamic loading was marginally higher for the blends containing grafted reclaimed rubber.

Acrylonitrile-Butadiene Rubber/ Reclaimed Rubber-Nylon Fiber Composite

The effect of diphenylmethane diisocyanate (MDI) -polyethyleneglycol (PEG) resin on the cure characteristics and mechanical properties of nitrile rubber/whole tyre eclaim-short nylon fiber composite-was studied. At a constant loading of 5 phr, the resin composition was varied. The minimum torque .,id (maximum - minimum) torque increased with isocyanate concentration. Scorch time and cure time showed a reduction on introduction of bonding agent. Properties like tensile strength, tear strength, and abrasion resistance increased with increase in MDI/PEG ratio, and these properties are higher in the longitudinal direction of fiber orientation. Compression set increased with isocyanate concentration and the resilience remain unchanged.

Cure Characteristics and Mechanical Properties of Short Nylon Fiber Reinforced Acrylonitrile Butadiene Rubber/Reclaimed Rubber Blends

Cure characteristics and mechanical properties of short nylon fiber reinforced acrylonitrile butadiene rubber-reclaimed rubber composites were studied. Minimum torque, (maximum-minimum) torque and cure rate increased with fiber concentration. Scorch time and cure time decreased by the addition of fibers. Properties like tensile strength, tear strength, elongation at break, abrasion loss and heat build up were studied in both orientations of fibers. Tensile and tear properties were enhanced by the addition of fibers and were higher in the longitudinal direction. Heat build up increased with fiber concentration and were higher in the longitudinal direction. Abrasion resistance was improved in presence of short fibers and was higher in the longitudinal direction. Resilience increased on the introduction of fibers. Compression set was higher for blends.

Studies on Acrylonitrile Butadiene Rubber/Reclaimed Rubber Blends

Cure characteristics and mechanical properties of acrylonitrile butadiene rubber/reclaimed rubber blends were studied. Minimum torque, (ma)dmum -minimum) torque, scorch time, cure time and cure rate decreased in presence of reclaimed rul3ber. Tensile strength, elongation at break and compression set increased'with increase in reclaim content. Resilience and abrasion resistance decreased with reclaim loading. Heat build up was higher for the blends. The ageing resistance of the blends was inferior to that of the gum compound.

STYRENE BUTADIENE RUBBER/RECLAIMED RUBBER BLENDS

Cure characteristics and mechanical properties of styrene butadiene rubber reclaimed rubber blends were studied. The blends showed improved processability, as indicated by the minimum torque values. Cure characteristics like minimum torque, (maximum-minimum) torque, cure time and cure rate decreased in the presence of reclaimed rubber. Tensile strength, tear strength, elongation at break were higher for blends. Resilience decreased with reclaim content. Compression set and abrasion loss were higher in the blends.

Studies on short nylon fiber - reclaimed rubber/elastomer composites

The thesis deals with the development of short nylon fiber-reclaimed rubber/elastomer composites. Three rubbers viz, natural rubber, acrylonitrile butadiene rubber and styrene butadiene rubber were selected and were partially replaced with reclaimed rubber. The blend ratio was optimized with respect to cure characteristics and mechanical properties. Reclaimed rubber replaced 40 parts of NR and SBR and 20 parts of NBR without much affecting the properties. These blends were then reinforced with short nylon fibers. The mechanical properties of the composites were studied in detail. In all the cases the tensile strength, tear strength and the abrasion resistance increased with increase in fiber content. In the case of NRlreclaimed rubber blends, the tensile strength-fiberloading relationship was non-linear where as in the case of NBRlreclaimed rubber blends and SBRlreclaimed rubber blends the tensile strength-fiber loading relationship was linear. All the composites showed anisotropy in mechanical properties. The effect of bonding system on the composite properties was also studied with respect to cure characteristics and mechanical properties. For this, a 20 phr fiber loaded reclaimed rubber/elastomer composites were selected and the effect of MDI/PEG resin system was studied. The resin used was 5 phr and the resin ratios used were 0.67: I, 1:1, 1.5:1 and 2:1. The bonding system improved the tensile strength, tear strength and abrasion resistance. The best results are with SBRlreclaimed rubber-short nylon fiber composites. The optimized resin ratio was 1:1 MDI/PEG for all the composites.

Evaluation of reclaimed rubber in bituminous pavements /

"June 1995."

Science and technology of rubber reclamation with special attention to NR-based waste latex products

A comprehensive overview of reclamation of cured rubber with special emphasis on latex reclamation is depicted in this paper. The latex industry has expanded over the years to meet the world demands for gloves, condoms, latex thread, etc. Due to the strict specifications for the products and the unstable nature of the latex as high as 15% of the final latex products are rejected. As waste latex rubber (WLR) represents a source of high-quality rubber hydrocarbon, it is a potential candidate for generating reclaimed rubber of superior quality. The role of the different components in the reclamation recipe is explained and the reaction mechanism and chemistry during reclamation are discussed in detail. Different types of reclaiming processes are described with special reference to processes, which selectively cleave the cross links in the vulcanized rubber. The state-of-the-art techniques of reclamation with special attention on latex treatment are reviewed. An overview of the latest development concerning the fundamental studies in the field of rubber recycling by means of low-molecular weight compounds is described. A mathematical model description of main-chain and crosslink scission during devulcanization of a rubber vulcanizate is also given.

Studies on the Utilisation of Rubber Reclaim in Elastomers

The thesis describes utilisation of reclaimed rubber, Whole Tyre Reclaim (WTR) produced from bio non- degradable solid pollutant scrap and used tyres. In this study an attempt has made to optimize the substitution of virgin rubber with WTR in both natural and synthetic rubber compounds without seriously compromising the important mechanical properties. The WTR is used as potent source of rubber hydrocarbon and carbon black filler. Apart from natural rubber (NR), Butadiene rubber (BR), Styrene butadiene rubber (SBR), Acrylonitrile butadiene rubber (NBR) and Chloroprene rubber (CR) were selected for study, being the most widely used general purpose and specialty rubbers. The compatibility problem was addressed by functionalisation of WTR with maleic anhydride and by using a coupling agent Si69.The blends were systematically evaluated with respect to various mechanical properties. The thermogravimetric analyses were also carried out to evaluate the thermal stability of the blends.Mechanical properties of the blends were property and matrix dependant. Presence of reinforcing carbon black filler and curatives in the reclaimed rubber improved the mechanical properties with the exception of some of the elastic properties like heat build up, resilience, compression set. When WTR was blended with natural rubber and synthetic rubbers, as the concentration of the low molecular weight, depolymerised WfR was increased above 46-weight percent, the properties deteriorates.When WTR was blended with crystallizing rubbers such as natural rubber and chloroprene rubber, properties like tensile strength, ultimate elongation were decreased in presence of WTR. Where as in the case of blends of WTR with non-crystallizing rubbers reinforcement effect was more prominent.The effect of functionalisation and coupling agent was studied in three matrices having different levels of polarity(NBR, CR and SBR).The grafting of maleic anhydride on to WTR definitely improved the properties of its blends with NBR, CR and SBR, the effect being prominent in Chloroprene rubber.Improvement in properties of these blends could also achieved by using a coupling agent Si69. With this there is apparent plasticizing effect at higher loading of the coupling agent. The optimum concentration of Si69 was 1 phr for improved properties, though the improvements are not as significant as in the case of maleic anhydride grafting.Thermal stability of the blend was increased by using silane-coupling agent.

Effect of Diphenyldisulfides with Different Substituents on the Reclamation of NR Based Latex Products

The latex industry has expanded over the years to meet the world demands for gloves, condoms, latex thread etc. Because of the strict specifications for the products and the unstable nature of the latex, as high as 15%, of the final latex products are rejected. Since waste latex rubber (WLR) represents a source of high quality rubber hydrocarbon, it is a potential candidate for generating reclaimed rubber of superior quality. Two types of WLR with different amounts of polysulfidic bridges are used in these experiments, which are reclaimed with variation of the concentration of the reclaiming agents, the reclamation temperature and time, Di phenyldisultide, 2-aminophenyldisulfide and 2,2'-dibenzamidodiphenyldisulfide (DBADPDS) are used as reclaiming agents, and the effect of diphenyldisulfides (DPDS) with different substituents, on the reclamation efficiency of WLR is investigated. A kinetic study of the reclamation reaction with the three reclaiming agents is done. The reaction rates and activation energies are calculated and compared with literature values. The comparative study of the three different reclaiming agents shows that (DBADPDS) is able to break the crosslinks at temperature levels 20'C below the temperature levels normally used with DPDS. Another advantage of this reclaiming agent is the reduced smell during the reclamation process and of the final reclaims, one of the most important shortcomings of other disulfides used for this purpose.

Production of latex reclaim and its utilisation in polymer blends

The overall objective of the present study was to develop a novel and economic reclaiming process that does not adversely affect the quality of rubber and to investigate methods of utilising the reclaim. Since waste latex products represent a potential source of high quality rubber hydrocarbon, it was decided to develop a process based on such latex wastes. The study revealed that latex reclaim could replace raw natural rubber upto about 50 per cent of its weight without any serious deterioration in mechanical properties.

Covulcanization of elastomer blends with special reference to NR/EPDM blends

Attempts have been made to attain satisfactory network structures in each of the phases of a rubber blend by minimising the cure rate imbalance by employing methods such as grafting of accelerators to the slow curing rubber, chemically bonding the crosslinking agents to the rubber in which it has lower solubility, functionalisation of the slow curing rubber, masterbatching of the curing agents to the slow curing rubber etc. Functionalisation of the slow curing constituents of NR/IIR and NR/EIPDM blends is tried using novel reagents as the first part of this study. However, the crux of the present study is a more direct approach to attaining a covulcanized state in NR/IIR and NR/EPDM blends: Precuring the slow curing rubber (IIR or EPDM) to a low level when it can still blend with NR and then to ck) the final curing after blending with NR. TNM3 precuring is also likely to minimise the viscosity mismatch. Since a low level of resmmal crosslink density is likely to be present lJ1 reclaimed rubbers, blending heat resistant reclaimed rubber such as butyl reclaim with NR may also have the same effect of precuring IIR, and then blending with NR. Hence use of IIR reclaim for developing blends with NR is also proposed to be investigated in this study