Jayamol George

Effects of environment on the properties of low-density polyethylene composites reinforced with pineapple-leaf fibre

Abstract The influence of water environment on the sorption characteristics of low-density polyethylene composites reinforced with short pineapple-leaf fibers (PALF/LDPE) has been studied by immersion in distilled water at 28, 50 and 70°C. The effects of fiber loading, temperature and chemical treatment on the sorption behavior are also evaluated. Water uptake is found to increase with fiber loading owing to the increased cellulose content. Weight change profiles for the composites at high temperature indicated that the diffusion is close to Fickian. All of the treated composites showed lower uptake than the unmodified composites. Parameters like diffusion, sorption and permeability coefficients were determined and activation energies were calculated. The thermodynamic constants such as entropy, enthalpy and first-order kinetic rate constant have been evaluated. A correlation between theoretical and experimental sorption results was evaluated. The effect of water uptake on uniaxial tensile properties has also been studied. Mechanical properties decreased after exposure to water, depending on time of immersion, fiber loading and chemical treatment. Finally, studies were carried out on the flexural properties of PALF/LDPE composites exposed to ultraviolet radiation.

Thermogravimetric and dynamic mechanical thermal analysis of pineapple fibre reinforced polyethylene composites

The thermal behaviour of pineapple leaf fibre (PALF) reinforced polyethylene composites was studied by thermogravimetric and dynamic mechanical thermal analysis. Fibre treatment was carried out using isocyanate, silane and peroxide to improve the interfacial adhesion between fibre and matrix. The effects of fibre loading and surface modification on the thermal properties were evaluated. It was found that at high temperature PALF degrades before the polyethylene matrix. The storage modulus increased with increase of fibre loading and decreased with increase of temperature. The treated fibre composites impart better properties compared to untreated system. Tan δ showed a distinct peak at low temperature ascribed to the glass transition temperature of polyethylene but no peak was observed for PALF fibre. The relative damping increased with fibre loading. Cole-Cole analysis was made to understand the phase behaviour of the composite samples.

Melt rheological behaviour of short pineapple fibre reinforced low density polyethylene composites

Abstract The melt theological behaviour of short pineapple fibre reinforced low density polyethylene composite has been studied using a capillary rheometer. The influence of fibre loading, fibre length, and fibre treatment on the theology of composites was investigated. Studies were carried out in the temperature range of 125 to 145°C and shear rate of 016.4 to 5468 s−1. The melt viscosity was found to be increased with fibre loading. Various chemical treatments were made to improve fibre—matrix interfacial adhesion. Treatments based on poly(methylene)—poly(phenyl)isocyanate (PMPPIC), silane and peroxide increased the viscosity of the system due to high fibre—matrix interfacial interaction. Viscosity of the system decreased with increase of temperature. However, in peroxide treated composites viscosity is increased due to the crosslinking of composite at higher temperature. The fibre breakage during extrusion was analysed using optical microscopy. The morphology of the extrudates has been studied by optical and scanning electron microscopies. Master curves were generated using modified viscosity and shear rate functions that contain melt flow index as a parameter.

Improved interactions in chemically modified pineapple leaf fiber reinforced polyethylene composites

Mechanical properties of pineapple leaf fiber reinforced low density polyethylene composites have been studied with special reference to the effects of interface modifications. Various chemical treatments using reagents such as NaOH, PMPPIC, silane and peroxide were carried out to improve the interfacial bonding. Both infrared spectroscopy and SEM were used to characterize the interface and the modified fiber surface. It has been found that the treatments improved the mechanical properties significantly. However, the effect varied according to the nature of the treatments. SEM studies on the fracture surfaces revealed the extent of fiber-matrix adhesion. It has been observed that the PMPPIC treatment reduced the hydrophilicity of the fiber and thereby enhanced the mechanical properties of the composites. The addition of a small quantity of peroxide and silane increased the mechanical properties considerably. The action of peroxide is associated with the peroxide-induced grafting of polyethylene on the fib...

Effect of fiber surface treatments on the fiber–matrix interaction in banana fiber reinforced polyester composites

Cellulosic fibers have been used as cost-cutting fillers in plastic industry. Among the various factors, the final performance of the composite materials depends to a large extent on the adhesion between the polymer matrix and the reinforcement and therefore on the quality of the interface. To achieve optimum performance of the end product, sufficient interaction between the matrix resin and the cellulosic material is desired. This is often achieved by surface modification of the resin or the filler. Banana fiber, the cellulosic fibers obtained from the pseudo-stem of banana plant (Musa sepientum) is a bast fiber with relatively good mechanical properties. The fiber surface was modified chemically to bring about improved interfacial interaction between the fiber and the polyester matrix. Various silanes and alkali were used to modify the fiber surface. Modified surfaces were characterized by SEM and FTIR. The polarity parameters of the chemically modified fibers were investigated using the solvatochromic technique. The results were further confirmed by electrokinetic measurements. Chemical modification was found to have a profound effect on the fiber–matrix interactions. The improved fiber–matrix interaction is evident from the enhanced tensile and flexural properties. The lower impact properties of the treated composites compared to the untreated composites further point to the improved fiber–matrix adhesion. In order to know more about the fiber–matrix adhesion, fractured surfaces of the failed composites where further investigated by SEM. Of the various chemical treatments, simple alkali treatment with NaOH of 1% concentration was found to be the most effective. The fiber–matrix interactions were found to be dependent on the polarity of the modified fiber surface.

Influence of short pineapple fiber on the viscoelastic properties of low-density polyethylene

Abstract Viscoelastic properties of low-density polyethylene reinforced with short pineapple fibers, extracted from pineapple leaves, have been studied as a function of temperature at different fiber orientations. It was found that longitudinally oriented fiber composites show the maximum value of storage modulus. The effects of fiber loading and fiber length on the viscoelastic properties have been assessed.