Anil K. Bhowmick

Effect of chain length of amine and nature and loading of clay on styrene-butadiene rubber-clay nanocomposites

Abstract Polymer nanocomposite is one of the highly discussed research topics in recent time. In this paper, we have reported the preparation and the properties of different nanoclays based on sodium montmorillonite, bentonite and potassium montmorillonite and organic amines of varying chain lengths, and Styrene Butadiene Rubber (SBR)-clay nanocomposites. The clays and the rubber nanocomposites have been characterized with the help of Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). X-ray results suggest that the intergallery distance is increased by incorporation of various amines. There is a great improvement in mechanical properties like tensile strength, elongation at break, modulus, work to break, and hysteresis on incorporation of nanoclay in SBR. TEM photographs show exfoliation of the clays in rubber to 5–10 nm range. The X-ray diffraction peak o...

Thermal ageing, degradation and swelling of acrylate rubber, fluororubber and their blends containing polyfunctional acrylates

Abstract The thermal ageing and degradation behaviour of acrylate rubber (ACM) fluoroelastomer (FKM), and blends of ACM and FKM containing polyfunctional acrylates were studied in air and nitrogen atmospheres. The blends were also subjected to swelling in different solvents. Thermogravimetric analysis of the blends containing polyfunctional acrylate indicated higher thermal stability of the blends by shifting initiation of degradation to higher temperature. The ageing and degradation of FKM-containing blends resulted in elimination of hydrogen fluoride and formation of some lower molecular weight components. Polyacrylates with higher functionality showed multi-step degradation. Higher levels of polyacrylate in the blend resulted in an additional step of degradation compared to polyacrylate. Swelling studies indicated higher swelling resistance of ACM and FKM containing polyacrylate in solvents having different solubility parameters. Maximum swelling of the blends was observed with the solvents having solubility parameter values comparable to that of blends i.e. in the range of 9–10 MPa 1/2 . The swelling index of the blends decreased with increasing level of polyfunctional acrylates. Higher functionality of polyfunctional acrylates decreased the swelling index.

Polyaniline–Carbon Nanofiber Composite by a Chemical Grafting Approach and Its Supercapacitor Application

Unlike conventional routes by van der Waals forces, a facile and novel approach using covalent bonding is established in the present work to synthesize polyaniline (PANI)-grafted carbon nanofiber (CNF) composites as promising supercapacitors. For this purpose, toluenediisocyanate was initially functionalized to carboxylated CNF via amidation followed by reaction with excess aniline to form a urea derivative and residual aniline, which was subsequently polymerized and grafted with a urea derivative. Amidation of CNF (TCNF) and, consequently, the grafting of PANI on TCNF were verified by IR, Raman, 1H NMR, X-ray photoelectron, and UV-visible spectroscopic methods, X-ray diffraction, and thermogravimetric analysis. Morphological analysis revealed uniform distribution of PANI on the surface of TCNF, indicating strong interaction between them. Electrochemical tests of the composite containing 6 wt % TCNF demonstrated efficient capacitance of ∼557 F g(-1) with a capacity retention of 86% of its initial capacitance even after 2000 charge-discharge cycles at a current density of 0.3 A g(-1), suggesting its superiority compared to the materials formed by van der Waals forces. The remarkably enhanced electrochemical performance showed the importance of the phenyl-substituted amide linkage in the development of a π-conjugated structure, which facilitated charge transfer and, consequently, made it attractive for efficient supercapacitors.

Influence of electron beam irradiation on the mechanical properties and crosslinking of fluorocarbon elastomer

Abstract The influence of electron beam irradiation on the mechanical and dynamic mechanical properties, gel fraction and crosslink density of terpolymeric fluorocarbon rubber has been investigated in this paper. An attempt has been made to correlate the structure of the irradiated rubber with the properties. With increase in radiation dose, an increase in degree of crosslinking results which leads to increase in modulus and Tg with a corresponding decrease in elongation at break, set and tan δ . The effect of multifunctional monomer is realized only at relatively higher level of trimethylolpropane triacrylate (TMPTA), where improvement in strength and failure properties is observed. The dynamic storage modulus at 50°C is higher and loss tangent becomes lower. Among the various polyfunctional monomers tripropyleneglycol diacrylate (TPGDA), trimethylolpropane triacrylate (TMPTA) and tetramethylolmethane tetracrylate (TMMT), the mechanical properties and the degree of crosslinking are lowest for systems based on TPGDA. MgO used in the formulation leads to the improvement in mechanical properties. Increase in the crosslink density is in line with reduced loss tangent and increased storage modulus for the MgO filled rubber vulcanizate.

Thermoplastic elastomeric blends of nylon-6/acrylate rubber: Influence of interaction on mechanical and dynamic mechanical thermal properties

Abstract Nylon-6 and acrylate rubber (ACM) were melt blended in a Brabender Plasticorder at 220 °C and 40 rpm rotor speed. The reactive nature of the blend is reflected in the mixing torque behavior of the blends at different compositions. The solubility characteristics of the blends in formic acid solution gives an approximate idea of the amount of nylon-6 grafted onto ACM and vice-versa. A reaction mechanism is proposed based on the well known epoxy—amine and epoxy—acid reactions and is confirmed by infrared spectroscopic studies of the blends. The influence of interaction between the two polymers on the mechanical and the dynamic mechanical properties of the blends is analyzed in detail, and the results are interpreted on the basis of the formation of nylon—ACM graft copolymer at the interfaces. The dynamic mechanical thermal analysis (DMTA) reveals a two phase morphological structure, indicating incompatibility of the blend components. The grafting reaction results in dramatic increase in both the sto...

Thermal degradation studies of electron beam cured ethylene-vinyl acetate copolymer

The thermal degradation of pure ethylene-vinyl acetate copolymer (EVA, 12% vinyl acetate) and electron beam radiation-cured EVA, cured in the presence of a small amount of sensitizer, has been studied by non-isothermal thermogravimetry and infrared spectroscopy. These studies suggest that radiation-cured EVA is more thermally stable than pure EVA.

Quantitative estimation of filler distribution in immiscible rubber blends by mechanical damping studies

Abstract The peak value of tan δ at the glass-transition temperature (Tg) in the plot of tan δ versus temperature is lowered on addition of filler to a rubber. This relative lowering of tan δ at Tg can be used to estimate the filler distribution in an immiscible rubber blend. In the present investigation, distribution of silica filler and carbon black was studied in blends of natural rubber (NR) and epoxidized natural rubber (ENR). It was observed that silica migrated preferentially to the ENR phase. The magnitude of the distribution depends on filler loading and the epoxy content of ENR. The amount of carbon black migrated to the NR phase is higher than that of silica at a similar loading in blends of NR and ENR.

Effect of electron beam irradiation on the properties of crosslinked rubbers

Abstract Influence of electron beam (EB) irradiation on the mechanical and dynamic mechanical properties of crosslinked fluorocarbon (FKM) rubber, natural rubber (NR), ethylene propylene diene monomer (EPDM) rubber and nitrile rubber (NBR) has been investigated. The modulus, gel fraction, glass transition temperature (Tg) and storage modulus increased, while the elongation at the break and the loss tangent (tan δ)Tg decreased. FKM and NBR vulcanizates have been shown to have EB radiation resistance up to 1500 kGy.

Effect of the Microstructure of a Hyperbranched Polymer and Nanoclay Loading on the Morphology and Properties of Novel Polyurethane Nanocomposites

Novel polyurethane nanocomposites based on toluene diisocyanate, poly(propylene glycol), various hyperbranched polymers (HBPs), and layered silicate were synthesized with the aim of determining the effect of the layered silicate loading and the functionality of HBP on the structure and properties of polyurethane nanocomposites. The microstructure of the nanocomposites was investigated by X-ray diffraction analysis and high-resolution transmission electron microscopy. It was found that exfoliated morphology and good dispersion were obtained up to 8 phr clay loading for all of the nanocomposites. approximately 100% increment in tensile strength, approximately 2-fold increase in the lap shear strength, approximately 200% increment in the peel strength, and 120% increment in the storage modulus along with a dramatic improvement in thermal stability were observed with the addition of 8 phr clay, over the pristine polyurethane. The higher the level of functionality of the HBP, the higher is the property enhancement. These properties were correlated with the state of dispersion of the clay platelets in the polyurethane matrix, the structure of the matrix, and clay-polymer interaction.

Studies on thermal degradation of short melamine fibre reinforced EPDM, maleated EPDM and nitrile rubber composites

This paper reports the results of studies on the thermal and ablative properties of the vulcanizates based on EPDM, maleated EPDM and nitrile rubber reinforced with melamine fibre, one of the recent generation high performance fibres. The thermogravimetric studies of the composites show that the presence of melamine fibre in the vulcanizates reduces the rate of decomposition and the effect is pronounced in the presence of the dry bonding system consisting of resorcinol, hexamethylene tetramine and silica. The first degradation step of the vulcanizate is controlled by the fibre, whereas the fibre as well as the matrix contributes to the second degradation step. An increase in fibre loading decreases the rate of degradation and weight loss in the second degradation step. The rate of decomposition of NBR vulcanizates is lower than those based on EPDM and maleated EPDM rubbers. The activation energy of decomposition of the vulcanizates is increased, if fibre is properly adhered to the matrix in the presence of the dry bonding system. The crosslinking system also affects the activation energy of decomposition, especially for the second degradation step. Melamine fibre causes significant reduction in the thermal erosion rate of the vulcanizates. The fibre filled composites, in the presence of the dry bonding system, display a lower thermal erosion rate compared to those containing no dry bonding system, showing that proper adhesion between the fibre and the matrix is important to achieve improved ablative properties. Among the three matrices, the vulcanizates based on nitrile rubber display the lowest thermal erosion rate.