ON THE PHASE-STRUCTURE OF BLENDS OF POLYCARBONATE WITH POLY(ACRYLONITRILE-BUTADIENE-STYRENE)

Polycarbonate (PC) and poly(acrylonitrile-butadiene-styrene) (ABS) was co-extruded at different weight ratios by a single screw extruder. In order to obtain a finer blend, two times extrusion was carried out. In this case, a ''network'' structure with two-continuous phases was observed for the blends with two compositions of PC/ABS, being 80/20 and 70/30. It is found that the blends with these two compositions just have maximum values on the curves of notched Izod impact strength, flexural modulus and flexural strength vs. composition, respectively. This was never observed in previous publications.

The ageing behaviour of hydrogenated nitrile butadiene rubber/nanoclay nanocomposites in various mediums

Hydrogenated nitrile butadiene rubber (HNBR) nanocomposites were prepared using commercially available organoclays (Cloisite 15A). The main focus of the current investigation is to study the influence of the organoclay reinforced in HNBR after subjecting it to long-term oxidative ageing and immersion studies. All the different nanoclay nanocomposites were air aged for a period of 168 h and at 150°C. The changes in the mechanical properties such as tensile strength and elongation at break have been compared with respect to the control sample. For immersion tests, three different liquid mediums were considered for this current investigation. All the samples were immersed in different mediums for a period of 168 h at 150°C. The changes in the swelling index and the mechanical properties have been reported with respect to the control sample. After reinforcing nanoclays into HNBR there was good resistance to swelling in all the three different liquid mediums in comparison to control sample. Tensile testing was performed on the immersed nanocomposites to evaluate the mechanical behaviour after immersion studies. A probable mechanism behind the improved performance has been suggested. © The Author(s) 2012.

The Utilization of Waste Latex Products in Styrene-Butadiene Rubber

Waste latex products are converted to a processabto material by a novel economical process developed in our laboratory , It contains rubber hydrocarbon of very high quality and Is lightly cross -linked. Styrene-butadlene rubber is mixed with latex reclaim In different proportions . The mechanical properties are found to be improved up to 60 percent replacement of styrene-butadlene rubber by latex reclaim . The curing of styrene-butadiene rubber Is found to be accelerated by the addition of latex reclaim. The processablllty study shows that the blends can be processed similar to SBRINR blends.

Starved Feeding for Improving the Mechanical Properties of Styrene-Butadiene Rubber Vulcanizates

Gum and filled compounds of styrene-butadiene rubber are extruded through a laboratory extruder by varying the feeding rase at different temperatures and screw speed (rpm). The extruded compounds are vulcanized up4o their optimum cure times and the mechanical properties of the vulcanizates are determined. From the properties data obtained it Is concluded that there is a specific feeding rate wit in the starved fed region, which results In maximum Improved mechanical properties . The enhancement In properties is found to be due to better thermal and shear homogeneity.

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.

Rheological Characteristics of Short Nylon -6 Fiber Reinforced Styrene Butadiene Rubber Containing Epoxy Resin as Bonding Agent

The rheological characteristics of short Nylon-6 fiber-reinforced Styrene Butadiene rubber (SBR) in the presence of epoxy resin-based bonding agent were studied with respect to the effect of shear rate, fiber concentration , and temperature on shear viscosity and die swell using a capillary rheonzeter. All the composites containing bonding agent showed a pseudoplastic nature, which decreased with increasing temperature. Shear viscosity was increased in the presence of fibers. The temperature sensitivity of the SBR matrices was reduced on introduction of fibers. The temperature sensitivity of the melts was found to be lower at higher shear rates. Die swell was reduced in the presence of fibers. Relative viscosity of the composites increased with shear rate. In the presence of epoxy resin bonding agent the temperature sensitivity of the mixes increased. Die swell was larger in the presence of bonding agent.

Rheology of Short Nylon -6 Fiber Reinforced Styrene-Butadiene Rubber

The rheological characteristics of short Nylon-6 fiber reinforced styrene butadiene rubber (SBR) were studied using a capillary rheometer. The study was done with respect to the effect of shear rate, fiber concentration, and temperature on shear viscosity and die swell. All the melts showed pseudoplastic nature, which decreased with increasing temperature. Shear viscosity increased in the presence of fibers. Introduction of fiber reduces the temperature sensitivity of the rubber matrix. A reduction in die swell was found in presence of fibers.

Thermal Degradation of Short Nylon -6 Fiber-Reinforced Styrene Butadiene Rubber Composite

The thermal properties of short Nylon-6 fiber-reinforced Styrene butadiene rubber (SBR) composites were studied by Thermogravimetric Analysis (TGA). The effect of epoxy-based bonding agent on thermal degradation of the gum and the composites was also studied. The thermal stability of the SBR was enhanced in the presence of Nylon-6 fibers and the stability of the composites increased in the presence of bonding agent. The epoxy resin did not significantly change the thermal stability of SBR gum vulcanizate. Results of kinetic studies showed that the degradation of SBR and the short nylon fiber-reinforced composites with and without bonding agents followed first-order kinetics.

Effect of Urethane Based Bonding Agent on the Cure Characteristics and Mechanical Properties of Styrene Butadiene Rubber - Whole Tyre Reclaim - Short Nylon Fiber Composite

The cure characteristics and mechanical properties of short nylon fiber- styrene /whole tyre reclaim (SBR/WTR) composites with and without an interfacial bonding agent based on 4,4 diphenyl methane diisocyanate and polyethylene glycol (MDI/PEG) have been studied. An 80:40 blend of SBR/ WTR reinforced with 20 phr of short nylon fiber has been selected and the MDI/ PEG ratio has been changed from 0.67:1 to 2:1. The minimum and maximum torques increased with isocyanate concentration. The scorch time and cure time showed an initial reduction. The cure rate showed an initial improvement. Tensile strength, tear strength and abrasion resistance increased with MDI/PEG ratio, these values were higher in longitudinal direction. Resilience and compression set increased with isocyanate concentration.

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.

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.

NMR study of styrene-butadiene rubber (SBR) and TiO2 nanocomposites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nanocomposites of Styrene-Butadiene Rubber and Synthetic Anatase Obtained by a Colloidal Route and Their Photooxidation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)