M. T. Ramesan

Role of dichlorocarbene modified styrene butadiene rubber in compatibilisation of styrene butadiene rubber and chloroprene rubber blends

Abstract A study was conducted on the use of dichlorocarbene modified styrene butadiene rubber (DCSBR) for the compatibilisation of blends of styrene butadiene rubber (SBR) and chloroprene rubber (CR). Stress–strain behaviour, mechanical properties, and low temperature transitions of the blends were examined in order to elucidate the efficiency of the compatibiliser. It was found that effective compatibilisation was achieved when chlorine content of DCSBR was 25% and its dosage was 5 phr (parts per hundred rubber). Thermal analysis by DSC showed that an appreciable extent of molecular level miscibility has been achieved in SBR/CR blends by using DCSBR as a compatibiliser. The formation of interfacial crosslinks in the presence of DCSBR is evident from the cure characteristics and stress–strain isotherms. An increase in tensile strength, tear strength, resilience and hardness and a decrease in compression set was observed when the chlorine content and dosage of the compatibiliser increased from 15% to 25% and 5 phr, respectively. Compatibilised blends showed enhanced mechanical properties in the presence of reinforcing fillers such as HAF carbon black and precipitated silica.

Utilization of coconut shell powder as a novel filler in natural rubber

This work focuses on the use of coconut shell powder as filler in natural rubber. Coconut, one of the food crops in the world, generates large amounts of waste material namely coconut shell. Modified and unmodified coconut shell powder–natural rubber composites with varying particle size and dosages were prepared by an open mill-mixing technique. The processing characteristics and the curing behavior of the composites were determined by Monsanto Rheometer. The technological performance was done by analyzing the tensile strength, tear strength and hardness of the vulcanizates. The swelling studies were carried out to observe the crosslink density and the reinforcement ability of the filler on natural rubber. The observed variation in mechanical properties has been supported by the fractography of the composites obtained by scanning electron microscopy. The results of the study show that the coconut shell powder is most effective filler in natural rubber at 10 parts per hundred loading. Reinforcement ability of modified coconut shell powder is more when compared to unmodified coconut shell powder, therefore modified coconut shell powder–natural rubber composites show better physicomechanical properties. Incorporation of coconut shell powder into natural rubber matrix enhances the thermal properties of the natural rubber—coconut shell powder composites.

Transport studies of peanut shell powder reinforced natural rubber composites in chlorinated solvents

Composites of Natural rubber (NR) Peanut shell powder (PSP) were prepared and their morphology, transport behavior at different temperatures in chlorinated solvent were studied. The PSP used in compounding the natural rubber was processed in two particle sizes. The effect of modification by alkali treatment of PSP on polymer properties was also investigated. The computed solvent properties were discussed in terms of PSP content, particle size, nature of solvent, and temperature. All the NR-PSP composites were found to decrease with the uptake of chlorinated solvents than NR, but the effect was more significant in the case of alkali treated PSP composites. Furthermore, the uptake of solvent decreased with increase in penetrant size; being the highest for dichloromethane, and the lowest for carbon tetrachloride. Activation energy was found to be maximum for highest in dichloromethane at the filler contents investigated. The thermodynamic parameters of the sorption process were also evaluated. The results showed that PSP filler acts as functional additives capable of manipulating and tailoring the transport of chlorinated solvents through elastomeric membranes even at concentrations as low as 10 parts per hundred (phr). The relationship between the transport behaviour and the morphology of the system was also examined.

Investigations on the addition of styrene butadiene rubber in natural rubber and dichlorocarbene modified styrene butadiene rubber blends

This paper focuses on the use of styrene butadiene rubber (SBR) as a viscosity modifier in novel blends of natural rubber (NR) and dichlorocarbene modified styrene butadiene rubber (DCSBR). The processing characteristics, vulcanisation kinetics, stress-strain behaviour, mechanical properties and low temperature transition of the blends have been examined in order to analyse the influence of SBR in the blends. The change in cross-link density values from stress strain behaviour and equilibrium swelling data has been correlated with the technological properties of the blends. The excellent mechanical properties and the increased cross-link density in blends in the presence of 5—10 phr of styrene butadiene rubber reveals the viscosity modifying action of SBR in NR/DCSBR blends. The variation in viscosities of these blends with the addition of SBR is reflected in the DSC thermograms. The resulting blends show very high resistance to thermal ageing as compared to those without SBR.

Biodegradation behaviour of natural rubber composites reinforced with natural resource fillers – monitoring by soil burial test

Biodegradation studies of natural rubber composites reinforced with natural resource fillers like peanut shell powder and coconut shell powder of 10 and 40 parts per hundred part of rubber (phr) filler loadings were carried out under soil burial conditions for three/six months. The extent of biodegradation of natural rubber and natural rubber composites were evaluated through tensile strength and hardness measurements. It was observed that the durability of the composites was greatly dependent on chemical treatment, filler particle size and filler content. The stability of composites decreased with increase in filler content. Composites containing chemically treated fillers were found to be more resistant to soil erosion. But composites containing larger sized fillers were found to be less resistant to soil erosion. Surface morphology of the composites was determined using scanning electron microscopy to evaluate the degradation of the samples. The results indicate that the tensile strength and hardness were decreased after soil burial testing due to the possible biological attack by microbes onto the samples.

Synthesis and electrical conductivity studies of metal chloro and nitroxide group containing styrene butadiene rubber

The introduction of different functional group in SBR was done by a simple reaction between sodium nitrite and mercuric chloride in the presence of phase transfer catalyst. The attachment of chlorine and NO2 functional group in the double bond of the butadiene was monitored by FTIR and UV spectroscopy. The structure and morphology of chloro nitro SBR was studied by SEM and XRD. Flame retardency studies revealed that the chemical modification imparts better flame resistance to chemically modified SBR. AC conductivity and dielectric properties of chloro- nitro SBR was higher than that of SBR and conductivity increases with the level of chemical modification.

Preparation and characterization of zinc sulphide nanocomposites based on acrylonitrile butadiene rubber

Rubber composite based on acrylonitrile butadiene rubber (NBR) reinforced with nano zinc sulphide (ZnS) have been prepared via vulcanization process and characterized by several techniques. Processing characteristics such as scorch time, optimum cure time decreases with increase in concentration of nano filler in acrylonitrile butadiene rubber. Mechanical properties such as tensile and tear strength increases with increase in concentration of nano filler up to 7 phr of loading thereafter the value decreases, whereas hardness, and flame resistance increases with the dosage of fillers. These enhanced properties are due to the homogenous dispersion of nano fillers in NBR matrix, which is evidenced from the structure that evaluated using X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Transport properties of coconut shell powder (CSP)-reinforced natural rubber composites in aromatic solvents

The solvent swelling characteristics of natural rubber composites containing both untreated and alkali-treated coconut shell powder (CSP) were investigated in three, aromatic organic solvents (benzene, toluene, and xylene) by conventional weight-gain experiments. The effects of fiber loading, chemical treatment, and filler particle size on solvent sorption were analyzed. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient have been calculated in terms of CSP content, particle size, nature of solvent, and temperature. All the NR–CSP composites were found to decrease with the uptake of aromatic solvents than NR, but the effect was more significant in the case of alkali-treated CSP composites. The estimated Arrhenius activation energy (ED) for the processes of sorption, diffusion, and permeation were discussed. The thermodynamic parameters of the sorption process were also evaluated. The mode of transport in all cases was evaluated.

Development, characterization and conductivity studies of chlorinated EPDM

Halogenation of EPDM has been carried out by passing chlorine gas by a simple and inexpensive chemical method. Chlorinated EPDM was characterized by FTIR and UV spectroscopy, SEM, TGA, DSC and AC conductivity measurements. FTIR and UV spectra revealed the attachment of chlorine to double bond of EPDM. SEM images showed the coarsen morphology arising from polar nature of the resulting polymer. TGA and DSC analysis indicated that the chlorination on EPDM affected the basic decomposition pattern and glass transition temperature of synthesized polymer. Conductivity of halogenated polymer was significantly increased with increase in chlorine content and also with increase in frequency.

Compatibilization of SBR/NBR Blends Using Chemically Modified Styrene Butadiene Rubber

Abstract The effect of dichlorocarbene modified styrene butadiene rubber (DCSBR) as a compatibilizer in blends of acrylonitrile butadiene rubber and styrene butadiene rubber (SBR/NBR) has been studied. The cure characteristics, physical properties, crosslink density, FTIR studies and low temperature transitions of the blends were determined as a function of chlorine content of DCSBR. Compatibilizing efficiency depended on the chlorine content of DCSBR and composition of blend constituents. Effective compatibilization was achieved when chlorine content of compatibilizer was 25% and SBR content of blend was either 50% or lower. FTIR studies, glass transition behavior measured by DSC and DMA showed that an appreciable extent of molecular level miscibility has been achieved in SBR/NBR blends by using DCSBR as a compatibilizer. Improvement in mechanical properties such as tensile strength, tear strength, resilience, hardness and compression set were achieved both when DCSBR was added and chlorine content of DCSBR increased up to 25%. The resistance of the vulcanizate towards air and oil aging improved with compatibilization. The change in technological properties correlated with crosslink density of the blends assessed from swelling studies and stress-strain data.