Thermoplastic elastomers, prepared by melt blending of natural rubber (NR) and isotactic polypropylene (PP) through a dynamic vulcanization technique, were developed during the later 1970s. However, they have certain drawbacks due to thermal degradation and higher molecular weight of NR. In the study reported here, NR was masticated to different levels prior its addition to isotactic polypropylene to improve the flow properties and to reduce the incompatibility resulting from molecular weight mismatch of NR/PP thermoplastic blends. Mixing energy curves of uncrosslinked blends and those of dynamically vulcanized blends crosslinked using different cure systems were compared. The mixing energy curves of blends containing NR of different molecular weight (M n ) and two grades of PP (injection and film grades) were also compared. Technological and processing properties of the dynamically vulcanized (sulphur and peroxide cure systems) and unvul-canized blends were compared with those of the samples containing unmasticated NR. The results indicated that a number average molecular weight in the range 4 ϫ 10 5 for NR increased the procoessability without significantly affecting the technological properties of NR/PP thermoplastic blends. Among the three cure systems studied Luperox 101 and dicumyl peroxide gave better technological properties than the sulphur-cured samples. Two antioxidants, viz. quinoline (TDQ) and imidazole (MBI) type, were tried in NR/PP blends. It was found that TDQ imparts better aging resistance compared to MBI. The improvement in processability due to the reduction in molecular weight of natural rubber by mastication is more noticeable in the case of peroxide vulcanized blends compared to sulphur vulcanized samples.

Dichlorocarbene-modified styrene-butadiene rubber (SBR) prepared by the alkaline hydrolysis of chloroform using cetyltrimethylammonium bromide as a phase-transfer agent resulted in a product that showed good mechanical properties, excellent flame resistance, solvent resistance, and good thermal stability. The activation energy for this chemical reaction calculated from the time-temperature data on the chemical reaction by the measurement of the percentage of chlorine indicated that the reaction proceeded according to first-order kinetics. The molecular weight of the polymers, determined by gel permeation chromatography, showed that chemical modification was accompanied by an increase in molecular weight. The chemical modification was characterized by proton NMR, FTIR studies, thermogravimetric analysis, and flammability measurement. Proton NMR and FTIR studies revealed the attachment of chlorine through cyclopropyl rings to the double bond of butadiene.

ABSTRACT:The application of rubber seed oil (RSO) and epoxidized RSO (ERSO) as a plasticizer in acrylonitrile butadiene rubber (NBR) was studied using RSO and ERSO with different levels of epoxidation. The results indicated that ERSO could be used as a less leachable and low volatility plasticizer for NBR. The use of ERSO in NBR gave better abrasion resistance whereas the tensile strength and tear strength were comparable to those vulcanizates that contained dioctyl phthalate as a plasticizer.

Natural rubber (NR) usage is wide‐spread from pencil erasers to aero tyres. Carbon black and silica are the most common reinforcing fillers in the rubber industries. Carbon black enhances the mechanical properties, while silica reduces the rolling resistance and enhances the wet grip characteristics. However, the dispersion of polar silica fillers in the nonpolar hydrocarbon rubbers like natural rubber is a serious issue to be resolved. In recent years, cardanol, an agricultural by‐product of the cashew industry is already established as a multifunctional additive in the rubber. The present study focuses on dispersion of silica filler in natural rubber grafted with cardanol (CGNR) and determination of its technical properties. The optimum cure time reduces and the cure rate increases for the CGNR vulcanizates as compared to that of the NR vulcanizates at all loadings of silica varying from 30 to 60 phr. The interaction between the phenolic moiety of cardanol and the siloxane as well as silanol functional groups present on the silica surface enhances the rubber–filler interaction which leads to better reinforcement. The crosslink density and bound rubber content are found to be higher for the silica reinforced CGNR vulcanizates. The physico‐mechanical properties of the silica reinforced CGNR vulcanizates are superior to those of the NR vulcanizates. The CGNR vulcanizates show lower compression set and lower abrasion loss. The dynamic‐mechanical properties exhibit less Payne effect for silica reinforced CGNR vulcanizates as compared to the NR vulcanizates. The transmission electron photomicrographs show uniform dispersion of silica filler in the CGNR matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43057.

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Rubber seed oil (RSO) and epoxidised rubber seed oil (ERSO) were used as secondary plasticiser cum heat stabiliser in polyvinyl chloride (PVC). High temperature mixing studies, dynamic mechanical analysis, hot air aging tests and colour stability tests indicated that ERSO could be used as a less volatile secondary plasticiser and heat stabiliser for PVC in combination with dioctyl phthalate (DOP). The tensile properties of the compound containing 50 : 10 DOP/ ERSO were found to be comparable to that containing 60 parts of DOP per 100 parts PVC.

Flow behavior of latices is industrially important for the manufacturing of various latex goods. Rheology of latices having fillers can assist in the understanding and quantification of the matrix-filler interaction. The impact of layered silicates such as sodium bentonite and sodium fluorohectorite on the rheological behavior of natural rubber, carboxylated styrene butadiene rubber latices, and their blends was analyzed with special reference to shear rate, temperature, and filler loading. The layered silicatesreinforced latex samples were characterized by X-ray diffraction technique to analyze the extent of intercalation and exfoliation. In the presence of layered silicates, latex systems exhibited enhancement in viscosity due to the network formation. Because of the breaking of networks at higher temperature, the viscosity of all systems decreased with increase in temperature. Layered silicates-reinforced latex systems showed pseudoplastic flow behavior and possesses enhanced zero shear viscosity and yield stress.

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