S. N. Maiti

Mechanical properties of silver-powder-filled polypropylene composites

Mechanical properties, such as tensile and flexural properties, as well as impact behavior of silver-powder-filled isotactic polypropylene composites were investigated in the composite composition range of 0–5.6 vol% of Ag. Tensile modulus, strength, and elongation at break decreased with incorporation of silver and an increase in silver concentration. Analysis of tensile strength data indicated the introduction of stress concentration and discontinuity in the structure upon addition of Ag particles. Izod impact strength decreased sharply on addition of 0.43 vol % of Ag particles, beyond which the value decreased marginally. Both flexural modulus and strength increased with filler content due to an increase in rigidity. Surface treatment of filler marginally improved mechanical properties.

Effects of Crystallinity of PP and Flexibility of SEBS-g-MA Copolymer on the Mechanical Properties of PP/SEBS-g-MA Blends

Mechanical properties of polypropylene and SEBS-g-MA copolymer blends up to volume fraction 0.5 of SEBS-g-MA are evaluated. Tensile properties and impact strength are described and correlated with theoretical models. Crystallinity on which strength properties depend decreases with increasing concentrations of SEBS-g-MA copolymer. Tensile modulus and strength decreased but tensile elongation and impact strength enhanced. Morphological studies show good dispersion of SEBS-g-MA in polypropylene with a weak level of interaction between the phases.

Effects of crystallinity of polypropylene (PP) on the mechanical properties of PP/styrene-ethylene-butylene-styrene-g-maleic anhydride (SEBS-g-MA)/teak wood flour (TWF) composites

Tensile and impact properties of PP/SEBS-g-MA/WF composites up to wood flour volume fraction 0.31 are evaluated. Tensile modulus and strength increased while elongation-at-break and Izod impact strength decreased with increase in volume fraction of the filler (Φf). The crystallinity of PP enhanced with Φf. The tensile properties were compared with predictive theories. SEM studies indicated formation of stress concentration points around WF particles with only limited extent of adhesion which led to large decrease in elongation-at-break and Izod impact strength of PP.

Dynamic rheological studies and applicability of time–temperature superposition principle for PA12/SEBS-g-MA blends

The viscoelastic behaviour of PA12/SEBS-g-MA blends was studied. Time sweep, amplitude sweep, and frequency sweep tests were analysed by the use of parallel-plate rheometer. Time sweep test shows time-independent viscoelastic behaviour of the polymer and blends during the entire duration of test. The critical shear strain was higher for PA12 as compared to that of SEBS-g-MA and the blends in amplitude sweep test. However, the plateau modulus was higher for SEBS-g-MA as compared to PA12. The complex viscosity, dynamic storage, and loss moduli of PA12 increased with the addition of SEBS-g-MA as a consequence of phase interaction between them. The influence of phase morphology of blend composition on their rheological properties was also examined. The blend showed a transformation from liquid-like to solid-like behaviour. The decrease in viscosity for PA12 and blends was observed with increasing temperature. The van Gurp plots was successfully used to validate time–temperature superposition principle (TTS) for PA12, SEBS-g-MA and blend compositions. PA12 holds TTS with a horizontal shift factor that fits Arrhenius equation. Whereas TTS fails for SEBS-g-MA and the blends studied because of different temperature-sensitive response and microstructural changes of melt during shear application.

Influence of microstructure and flexibility of maleated styrene-b-(ethylene-co-butylene)-b-styrene rubber on the mechanical properties of polyamide 12

AbstractThe present investigation deals with the mechanical and morphological properties of binary polyamide 12/maleic anhydride-grafted styrene-b-(ethylene-co-butylene)-b-styrene rubber (PA12/SEBS-g-MA) blends at varying dispersed phase (SEBS-g-MA) concentrations. Tensile behavior, impact strength and crystallinity of these blend systems were evaluated. Influence of microstructure, dispersed phase particle size, and ligament thickness on the impact toughness of the blend was studied. DSC data indicated an increase in crystallinity of PA12 in the blends. Tensile modulus and strength decreased while impact strength and elongation-at-break increased with the elastomer concentration. The enhanced properties were supported by interphase adhesion between the grafted maleic groups of rubber with polar moiety of polyamide 12. Analysis of the tensile data employing simple theoretical models showed the variation of stress concentration effect with blend composition.

Crystallization of Polypropylene in PP/PDMS/Nano-SiO2 Ternary Composite

Effect of dispersion morphology, resulting from different mixing sequences used in making ternary composite polypropylene (PP)/poly(dimethylsiloxane) (PDMS)/nano SiO2, on the crystallization of PP phase is studied. Mixing sequence is found to have significant effect on the dispersion morphology of the ternary composite, which in turn affected the crystallization of the PP matrix of the ternary composite. Crystallization behaviour of PP, studied by the differential scanning calorimetry, is discussed for the effect of different dispersion morphologies on overall crystallization process rate, nucleation rate, crystal size distribution and crystallinity.

Effect of Teak Wood Flour on Melt Rheological Behaviour of High Density Polyethylene

The melt rheological studies on HDPE/TWF (teak wood flour) composites were studied at (volume fraction) Φf = 0.00−0.32 and at 180°C, 190°C and 200°C. Viscosity of HDPE/TWF composites increases with Φf while decreases with increase in temperature. Addition of coupling agent, maleic anhydride grafted HDPE (HDPE-g-MAH) enhances viscosity as compared to the corresponding HDPE/TWF. This was attributed to increase in interaction between TWF and HDPE by HDPE-g-MAH which in turn stiffens the system. The power law coefficient, n, decreases with increase in Φf and increase in temperature and lower for HDPE/TWF/HDPE-g-MAH composites as compared to HDPE/TWF composites. The consistency index increases with increase in Φf and were higher for HDPE/TWF/HDPE-g-MAH.

Non-isothermal crystallization kinetics and thermal behaviour of PA12/SEBS-g-MA blends

The thermal behaviour and crystallization kinetics of PA12/SEBS-g-MA blends were investigated under non-isothermal and isothermal conditions using thermogravimetric analysis and differential scanning calorimetry, respectively. The macrokinetic model given by Avrami was used to analyse both the nonisothermal and isothermal crystallization kinetics of the blends. The value of the Avrami exponent during non-isothermal crystallization predicted that pure PA12 and PA12/SEBS-g-MA blends show spherulitic growth with random nucleation of crystal structures as the n-values lie between 3 and 4. The slight nucleating effect of SEBS-g-MA was showed by nucleating activity calculated by the Dobreva and Gutzowa method.

Flexible non-metallic electro-conductive textiles

ABSTRACT This issue of Textile Progress reviews research carried out on electrically conducting polymers, fibres and fabrics prepared by in situ chemical, electrochemical and vapour-phase polymerisation. It provides information about various inherently conducting polymers prepared from aniline, pyrrole, thiophene and their derivatives that are often used to prepare flexible non-metallic electro-conductive textiles. Several methods for the characterisation of electro-conductive fabrics are included, namely scanning electron microscopy, X-ray diffraction, elemental disruptive X-ray analysis and Fourier transmission infrared spectroscopy. The role of the polymerisation process in determining the electrical properties of electro-conductive textiles is examined. The review highlights applications of flexible non-metallic conductive textiles in electro-magnetic shielding materials, heating pads, sensors and actuators.

Effect of Thermoplastic Elastomer on Melt Rheological and Fracture Behaviour of Poly(Lactic Acid)

ABSTRACT Poly(lactic acid) (PLA) was melt blended with thermoplastic elastomer, maleic anhydride grafted poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS-g-MA) copolymer with varied concentration (10–40 wt%) using twin screw extruder. Dynamic rheological behavior of PLA/SEBS-g-MA blends investigated a transition from liquid-like behavior to solid-like behavior in the composition range of 10–20 wt% of SEBS-g-MA. The capillary rheometer analysis showed enhanced shear viscosity with increase in SEBS-g-MA content. At 10 wt% of SEBS-g-MA, a maximum in the non-essential work of fracture was observed which reflects resistance to crack propagation. Scanning electron microscopy revealed a transition in deformation mechanisms from voids, to fibrillation and cavitation. GRAPHICAL ABSTRACT