Indose Aravind

Studies on Tensile and Flexural Properties of Short Banana/Glass Hybrid Fiber Reinforced Polystyrene Composites

The interest in natural fiber-reinforced polymer composites is growing rapidly due to its high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost, and low density. The development of composite materials based on the reinforcement of two or more fiber types in a single matrix, which leads to the production of hybrid composites. In the field of technical utilization of plant fibers, banana fiber-reinforced composites represent one of the most important areas. The influence of fiber content, fiber loading, and hybrid effect on the mechanical properties such as tensile strength, Youngs modulus, elongation at break, and flexural properties of the composites, was evaluated. The volume fraction of glass fiber based on total fiber content increases all the mechanical properties, except elongation at break. The tensile and flexural properties of composites are observed to have improved as the fiber loading (vol%) increases. On the other hand, lack of good interfacial adhesion and poor resistance to moisture absorption make the use of natural fiber-reinforced composites less attractive. Modification of the banana fiber improves the optimum fiber-matrix properties. Hybrid effect was calculated using additive rule of hybrid mixtures. The comparison of theoretical and experimental values of tensile properties was determined using a number of models. All the models except parallel show good agreement with the experimental results.

A study on reaction-induced miscibility of poly(trimethylene terephthalate)/polycarbonate blends.

The effect of annealing on the miscibility and phase behavior of Sorona {poly(trimethylene terephthalate), PTT} and bisphenol A polycarbonate (PC) blends was examined. These blends exhibited heterogeneous phase-separated morphology and two well-spaced glass transition temperatures (Tgs) indicating immiscibility. The Sorona/PC blends were thermally annealed at 260 degrees C for different times to induce various extents of transreactions between the two polymers. After annealing at high temperature the original two Tgs of blends were found to merge into one single Tg, exhibiting a homogeneous morphology. It is interesting to note that upon extended annealing the original semicrystalline morphology transformed into an amorphous nature. This is attributed to chemical transreactions between the PTT and PC chain segments as evidenced with FTIR, DSC, DMA, 1H NMR, and WAXS measurements. A new characteristic aryl C-O-C vibration band present at 1070 cm(-1) in the FTIR spectra of the annealed blends indicated the formation of an aromatic polyester structure due to the transreactions between PTT and PC. The sequence structures of the produced copolyesters were determined by a NMR triad analysis, which showed that the randomness increased with time of heating. WAXS analysis confirmed that the PTT/PC blends completely lost their crystallinity when annealed at 260 degrees C for a period of 120 min or longer, indicating the formation of fully random copolyesters. A random copolymer formed as a result of the transreactions between PTT and PC serves as a compatibilizer at the beginning, and upon extended annealing this became the main species of the system which is finally transformed to a homogeneous and amorphous phase.

Phase Morphology Development in Uncompatibilized and Reactively Compatibilized Nylon‐6/Ethylene Propylene Rubber (EPR) Blends: Effect of Mixer Type on Morphology

Abstract The evolution of phase morphology in uncompatibilized and reactively compatibilized nylon‐6/ethylene propylene rubber (EPR) blends has been investigated by scanning electron microscopy with special reference to the effect of mixer type and size. Three types of mixing instruments were used for the melt preparation of the blends. These include the Haake Rheocord mixer, the DSM twin‐screw mini extruder, and the industrial Werner Pfleiderer twin‐screw extruder (ZSK‐25). In the reactively compatibilized blends, EPR‐g‐maleic anhydride (MA) has been used as the compatibilizer precursor. The MA group of the EPR reacts with the amino group of nylon forming a graft copolymer at the interface, which decreases the interfacial tension and suppresses the coalescence. In the case of uncompatibilized blends the final morphology is developed within 3–4 min of the mixing time in the DSM twin‐screw mini extruder. The size of the dispersed phase in the uncompatibilized blends, as obtained in the Werner Pfleiderer twin‐screw extruder and the DSM mini extruder, was found to be smaller than that obtained in the Haake Rheocord mixer on account of elongational flow occurring in the twin‐screw extruder. In the case of the Werner Pfleiderer twin screw extruder, sampling was done at various points in order to understand the evolution of the phase morphology along the axis of the extruder. It has been found that the final morphology of the uncompatibilized blends in the Werner Pfleiderer extruder is controlled by the geometry of the die at the exit. In the case of reactively compatibilized blends, the morphology development in the DSM twin‐screw mini extruder was so fast that the final morphology developed within 30 sec of mixing. This occurs because since the compatibilizer formed as a result of the reaction remains located at the blend interface, coalescence is substantially suppressed, and thereby the blend system rapidly attains a stable morphology. Finally the size of the dispersed phase and morphology development in reactively compatibilized blends in the three mixers were carefully studied and compared.

Rheology of multiphase polymer blends with and without reactive compatibiliser: evaluation of interfacial tension using theoretical predictions

The phase morphology and rheology of polyamide 12/polypropylene (PA12/PP) blends have been studied. Effects of blend ratio and reactive compatibilisation on the rheological properties of compatibilised and uncompatibilised blends were analysed. The viscosity ratio between the polymers was found to be sensitive to frequency. The complex viscosity and dynamic modulus increased with increase in the amount of compatibiliser, up to critical micelle concentration. The interfacial tension between the polymers was calculated from the storage modulus of the blends using Palierne and Choi-Schowalter models. It was found that the rheological properties of both compatibilised and uncompatibilised blends are intimately related to their phase morphology.

Blends of nylon 6/66 and acrylonitrile-butadiene rubber : Effects of blend ratio and dynamic vulcanization on morphology and properties

The morphology and mechanical properties of nylon (copolyamide 6/66)/ acrylonitrile-butadiene rubber (NBR) blends have been studied with special reference to the effect of blend ratio and crosslinking systems. Morphological investigations of the blends using scanning and transmission electron microscopies show that a uniform and finer dispersion of the elastomer phase is achieved by dynamic crosslinking. The effects of various crosslinking systems such as sulphur and dicumyl peroxide on the morphology and mechanical properties of these blends were analysed. Morphological stability of the blends upon annealing has been investigated and the mechanical properties of the blends have been discussed. Attempts have been made to correlate the morphology with the mechanical properties of the dynamically vulcanized blends. The stability of the blend morphology during annealing has been examined.