Rani Joseph

Swelling behaviour of isora/natural rubber composites in oils used in automobiles

Natural rubber/isora fibre composites were cured at various temperatures. The solvent swelling characteristics of natural rubber composites containing both untreated and alkali treated fibres were investigated in aromatic and aliphatic solvents like toluene, andn-hexane. The diffusion experiments were conducted by the sorption gravimetric method. The restrictions on elastomer swelling exerted by isora fibre as well as the anisotropy of swelling of the composite have been confirmed by this study. Composite cured at 100°C shows the lowest percentage swelling. The uptake of aromatic solvent is higher than that of aliphatic solvent for the composites cured at all temperatures. The effect of fibre loading on the swelling behaviour of the composite was also investigated in oils like petrol, diesel, lubricating oil etc. The % swelling index and swelling coefficient of the composite were found to decrease with increase in fibre loading. This is due to the increased hindrance exerted by the fibres at higher fibre loadings and also due to the good fibre-rubber interactions. Maximum uptake of solvent was observed with petrol followed by diesel and then lubricating oil. The presence of bonding agent in the composites restrict the swelling considerably due to the strong interfacial adhesion. At a fixed fibre loading, the alkali treated fibre composite showed lower percentage swelling compared to the untreated one.

Rubber seed oil: A multipurpose additive in NR and SBR compounds

Rubber seed oil was used as a multipurpose ingredient in natural rubber (NR) and styrene butadiene rubber (SBR) compounds. The study shows that the oil, when substituted for conventional plasticiser, imparts excellent mechanical properties to NR and SBR vulcanizates. Further, it also improves aging resistance, reduces cure time, increases abrasion resistance and flex resistance, and reduces blooming.

Studies on epoxidised rubber seed oil as secondary plasticiser/stabiliser for polyvinyl chloride

Abstract 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.

Studies on Conductive Silicone Rubber Compounds

The electrical conductivity of silicone rubber vulcanizates containing carbon blacks [e.g., acetylene black, lamp black, and ISAF (N-234) black] were investigated. The change in electrical conductivity with varying amounts of carbon blacks and the temperature dependence was measured. The mechanical properties like tensile strength, tear strength, elongation at break, hardness, etc., of the vulcanizates were determined. A comparative study of the electrical conductivity of the composites revealed that the electrical conductivity of the composites made with acetylene black was higher than that of the composites made of other blacks.

Natural Rubber-Carbon Nanotube Composites through Latex Compounding

Natural rubber (NR)-based nanocomposites have been prepared with single-walled carbon nanotubes (SWNTs) through a latex stage mixing method. SWNTs were dispersed in water through ultrasonication and stabilized by the subsequent addition of a surfactant. The stabilized aqueous dispersion of SWNTs was mixed with NR latex and the effect of nanofiller on the flow properties of NR latex was investigated. Casting the compounded latex followed by curing gave good quality composite films with significantly improved mechanical properties. For example, the tensile strength and modulus of the composite film containing 2.0 phr (parts per hundred parts of rubber) SWNTs were, respectively, 56% and 63% higher in relation to pure NR. Electrical percolation threshold concentration of SWNTs in the NR matrix was found to be 1.5 phr. Thermogravimetric analysis indicated that the thermal stability of NR remains unaffected by the presence of SWNTs at low concentrations.

Studies on polyisobutylene bound paraphenylene diamine antioxidant in natural rubber

Abstract Paraphenylene diamine was chemically attached to low molecular weight chlorinated polyisobutylene.The polymer bound paraphenylene diamine was characterised by VPO, 1 H NMR, IR and TGA. The efficiency and permanence of the polymer bound paraphenylene diamine was compared with conventional amine type antioxidant in natural rubber vulcanizates. The vulcanizates showed improved ageing resistance and ozone resistance in comparison to vulcanizates containing conventional antioxidant. The presence of liquid, polymer-bound paraphenylene diamine reduces the amount of plasticiser required for compounding.

Fabrication and characterization of methylene-blue-doped polyvinyl alcohol-polyacrylic acid blend for holographic recording

A methylene-blue-sensitized polymer blend of polyvinyl alcohol and polyacrylic acid is fabricated and tested for holographic recording. It was found to have good characteristics such as high sensitivity, storage stability, ease of fabrication, and environmental stability. Optimization of the ratio of polyvinyl alcohol/polyacrylic acid, the sensitizer concentration, pH, energy, diffraction efficiency measurements, etc., have been done. pH is found to have a great influence on the recovery of the dye in this matrix. The results of experimental investigations into the properties of this new material are reported.

PET-SWNT Nanocomposite Fibers through Melt Spinning

Poly(ethylene terephthalate)-single-walled carbon nanotube (PET-SWNT) nanocomposite fibers have been prepared through melt spinning and drawing. While acting as effective nucleating agents for PET melt crystallization, SWNTs also provide significant reinforcement to PET fibers. For example, the tenacity and initial modulus of the composite fiber with 1 wt% SWNTs were, respectively, 1.8 times and 3.2 times higher as compared to those of the pristine PET fiber prepared under identical conditions. When the draw ratio was increased, tenacity and modulus of the fibers increased, indicating that drawing induced orientation of the polymer molecules and SWNTs. Thermal stability of the fibers was not significantly affected by the presence of SWNTs at low concentrations.

New oligomer-bound antioxidants for improved flex crack resistance and ozone resistance

Abstract New oligomer-bound antioxidants have been prepared by condensation reaction. The efficiency and permanence of these oligomer-bound paraphenylene diamines as antioxidants has been compared with conventional amine type antioxidants in NR, SBR, IIR and NBR and in elastomer blends like NR/BR and NR/SBR. The oligomer-bound antioxidants are found to impart improved ozone, flex resistance and mechanical properties to the vulcanizates of NR, SBR, IIR and NBR and to blends of NR/BR and NR/SBR in comparison with those containing conventional antioxidants.

Silver-doped photopolymer media for holographic recording

Incorporation of silver ions into a dye-sensitized poly(vinyl alcohol)/acrylamide photopolymer is observed to give better performance compared to other metal-ion-doped photopolymer holographic recording media. Plane-wave transmission gratings were recorded in the photopolymer films using a He-Ne laser, and various holographic parameters were optimized so as to explore maximum potential of the material for various holographic applications. Silver-doped films showed good energy sensitivity, and gratings recorded in optimized film exhibited a diffraction efficiency of more than 75%. The potential of the material for holographic data storage applications is also studied using peristrophic multiplexing.