Seno Jose

Stress Relaxation and Thermal Analysis of Hybrid Biofiber Reinforced Rubber Biocomposites

Natural rubber was reinforced using two hybrid biofibers namely sisal and oil palm. The stress relaxation characteristics of sisal/oil palm hybrid fiber reinforced natural rubber composites was analyzed with special reference to fiber loading and chemical modifications. It was seen that the rate of relaxation decreased with fiber content and was found to be maximum in gum compound. Chemical modification of the fiber surface was found to affect the degree of adhesion and thereby the nature of relaxation. The thermal stability of the composites was also investigated with reference to loading and chemical treatment. The kinetics of thermal degradation was also analyzed. Activation energy was calculated from two methods: the Horowitz and Metzger method and the Coats-Redfern method.

Development of hybrid composites for automotive applications: effect of addition of SEBS on the morphology, mechanical, viscoelastic, crystallization and thermal degradation properties of PP/PS–xGnP composites

In this article, we report on a simple and cost effective approach for the development of light-weight, super-tough and stiff material for automotive applications. Nanocomposites based on PP/PS blend and exfoliated graphene nanoplatelets (xGnP) were prepared with and without SEBS. Mechanical, crystallization and thermal degradation properties were determined and correlated with phase morphology. The addition of xGnP to PP/PS blend increased the tensile modulus at the expense of toughness. The presence of xGnP increased the enthalpy of crystallization and enthalpy of fusion of PP in the blends, without affecting segmental mobility and thermal stability. Addition of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) improved the toughness of PP/PS blends, but decreased the stiffness. The incorporation of xGnP into this ternary blend generated a super-tough material with improved stiffness and tensile elongation, suitable for automotive applications. It is observed that the presence of SEBS diminished the tendency of agglomeration of xGnP and their unfavorable interactions with thermoplastics, which in turn reduced the internal friction in the matrix.

Mechanical and dynamic mechanical properties of polyolefin blends: effect of blend ratio and copolymer monomer fraction on the compatibilisation efficiency of random copolymers

The mechanical and dynamic mechanical properties of isotactic polypropylene/high density polyethylene (PP/HDPE) blends, as a function of blend ratio and compatibiliser concentration were analysed. Ethylene propylene random copolymers (EPDM) with three different monomer fractions were used as compatibilisers. Compatibilisation improved the mechanical properties (except Young’s modulus) of the blends, considerably. The compatibiliser with 1:1 monomer fraction was found to be most efficient. A detailed discussion on the fundamental reasons responsible for the deterioration of properties in the absence of compatibilisers and the improvement of properties in the presence of compatibilisers was presented. The tensile strength of the uncompatibilised blends was theoretically modelled using Nielsen’s and Nicolais-Narkis models. The Young’s and storage moduli of uncompatibilised blends were compared with those predicted by various theoretical models. Attention was paid to correlate the mechanical properties of both compatibilised and uncompatibilised blends with their phase morphology.

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.

Phase morphology, mechanical, dynamic mechanical, crystallization, and thermal degradation properties of PP and PP/PS blends modified with SEBS elastomer

Binary and ternary blends comprised of polypropylene (PP), polystyrene (PS) and polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) were prepared. The effect of phase composition of minor components on the morphology, mechanical, viscoelastic, crystallization, and thermal degradation properties was studied. Binary blends exhibited inferior properties, typical of immiscible and incompatible multi-phase systems and showed matrix-droplet phase morphologies. Ternary blends, especially those with greater concentration of SEBS minor phase, exhibited interesting properties. Scanning electron micrographs of SEBS compatibilized PP/PS blends, did not show any PS particle pulling out of the PP matrix, indicating good compatibility of SEBS with PP/PS blends. Dynamic mechanical analysis also supported the heterogeneous phase structure of the blends. Thermogravimetry and differential scanning calorimetry showed that addition of PS and SEBS decreased the thermal stability of PP marginally, but shows slight variations in melting and crystallization behavior.