Synthesis of s‐triazine‐based hyperbranched polyurethane for novel carbon‐nanotube‐dispersed nanocomposites

s‐Triazine‐based hyperbranched polyurethanes (HBPUs) with different hard segments were synthesized by A₂ + B₃ approach. Various kinds of multiwalled carbon nanotube (MWNT) nanocomposites with HBPU were prepared to investigate an impact of hyperbranched polymer on dispersion of MWNTs in the polymer matrix and the resulting properties of nanocomposites. Synthesized HBPUs were characterized using FTIR and NMR measurements. The highly branched structures were found very effective in enhancing the pristine MWNT dispersion in the polymer matrix. As a result, the MWNT‐reinforced HBPU nanocomposites showed a steep increase in the yield stress and modulus and enhanced shape memory effect with an increase of hard segment and MWNT loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Natural weather,soil burial and sea water ageing of low‐density polyethylene: Effect of starch/linear low‐density polyethylene masterbatch

Degradation of the blends of low‐density polyethylene (LDPE) with a starch‐based additive namely, polystarch N was studied under various environmental conditions such as natural weather, soil and sea water in Saudi Arabia. Stress–strain properties and thermal behavior were investigated for the LDPE and LDPE/polystarch N blend having 40% (w/w) of polystarch N. Environmental ageing resulted in the reduction of percentage of elongation and crystallinity for the blend. Rheological studies and scanning electron microscope photomicrographs of the polymer samples retrieved after ageing showed that addition of polystarch N enhanced the degradation of LDPE. This is ascribed to high extent of chain scission and leaching out of starch present in polystarch N, which was corroborated by the results of morphology and Fourier transform infrared spectroscopy analyses. In the case of underground soil ageing, microbes present in the soil consume the starch in the blend, thus accelerating the degradation process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Chemical Resistance,Mechanical and Physical Properties of Biofibers-Based Polymer Composites

A study on physical and chemical properties along with mechanical characterization of Hibiscus Sabdariffa fiber-reinforced Phenol–Formaldehyde resin matrix based polymer composites have been reported. Effect of fiber dimension on mechanical properties was evaluated. The interfacial bonding between Hibiscus Sabdariffa fiber and polymer matrix has been found to affect the properties of polymer matrix. It has been observed that particle reinforced polymer composites exhibit better mechanical properties as compared to short and long fiber reinforced polymeric composites. These composites were further subjected to evaluation of morphological, thermal, physical (swelling and moisture absorption) and chemical properties.     

Mechanical,Thermal and Morphological Properties of Grewia Optiva Fiber/Polymer Matrix Composites

This work is concerned with the evaluation of properties of compression molded Grewia Optiva fiber reinforced Resorcinol-Formaldehyde (RF) matrix-based polymer composites. Reinforcing of the RF resin with Grewia Optiva fiber was done in the form of particle size (200 micron). Present work reveals that mechanical properties such as: tensile strength, compressive strength, flexural strength and wear resistance of the RF matrix have been found to increase up to 30% fibre loading (in terms of weight) and then decreases for higher loading. Morphological and thermal studies of the matrix, fibre and particle reinforced (P-Rnf) green composites have also been studied.     

Rapid Synthesis of MMA Grafted Pine Needles Using Microwave Radiation

Cellulose-graft-poly (methylacrylate) copolymers were prepared by microwave assisted free radical polymerization to develop an efficient rapid way to alter the surface properties of the cellulosic fibers. The effect of microwave radiation doses, ratio of monomer, solvent and initiator concentrations were determined to get the highest percentage of grafting. The graft copolymers were characterized by FTIR and SEM studies. The results clearly demonstrate that graft polymerization successfully occurred onto the cellulose backbone. The cellulose-graft-poly (methylacrylate) copolymers have been found to be more water- and moisture-resistant as well as also revealing enhanced chemical and thermal resistance.     

Catalytic activity of a reusable polymer‐anchored nickel(II)–phenanthroline complex on the oxidation of various organic substrates

A polymer‐anchored nickel(II)–phenanthroline complex [polyNi(II)–phen] was synthesized and used effectively as a reusable catalyst in various oxidation reactions in the presence of tert‐butylhydroperoxide as an oxidant in acetonitrile medium. The catalyst was characterized with elemental analysis, atomic absorption spectrometry (AAS), thermogravimetric analysis, scanning electron microscopy, and spectrometric methods such as diffuse reflectance spectroscopy, ultraviolet–visible spectroscopy, and Fourier transform infrared spectroscopy. The study of the effects of the time, temperature, oxidant, catalyst concentration, molar ratio of substrate to oxidant, and solvent in the oxidation of styrene individually gave the optimized reaction conditions. Under optimized conditions, the catalyst exhibited good conversions for the oxidation reactions of various olefins, alkanes, aromatic alcohols, and thioethers. The catalyst was easily recovered by simple filtration and reused for more than five times with consistent catalytic activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphine promotes autonomic learning.

Morphine (0.01-10 mg/kg) promoted rapid autonomic learning of discriminative, Pavlovian conditioned heart rate decelerations to tone signals in male and female rabbits, and the higher doses (1-10 mg/kg) promoted decelerative heart rate orienting reflexes to novel tones. Morphine does dependently reduced heart rate acceleration to signaled shock but had no effect on heart rate acceleration to unsignaled shock. Morphine did not impair retention of cardiac conditioned reflexes, and its U-shaped dose effect, increasing conditioned heart rate discrimination early in training, reappeared in extinction. The authors propose that morphine promotes autonomic learning of preparatory, compensatory reflexes to signaled stressors that reduce their stressful effects. This action may mimic the normal, adaptive function of an endogenous messenger released by the Pavlovian contingency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of expandable graphite on the properties of intumescent flame‐retardant polyurethane foam

Water‐blown rigid polyurethane foam (PUF) with two different particle sizes (180 and 300 μm) of expandable graphite (EG) as a flame‐retardant additive were prepared, and the effects on the mechanical, morphological, water absorption, thermal conductivity, thermal, and flame‐retardant properties were studied. In this investigation, EG content was varied from 5 to 50 php by weight. The mechanical properties of PUF decreased with increasing EG loading in both cases. The water absorption of the PUF increased with an increase in the EG loading mainly because of the collapse of foam cells, as evidenced from the scanning electron microscopy pictures. The thermal conductivity of the EG‐filled PUF showed that the insulation properties decreased with EG loading. The flame‐retardant properties (limiting oxygen index and char yield measurement) of the PUF improved with increasing EG loading. PUF filled with the higher particle size EG showed better mechanical properties and fire‐retardant properties than the PUF filled with the lower particle size EG. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Fabrication and characterization of <Emphasis Type="Italic">S. cilliare</Emphasis> fibre reinforced polymer composites

In the recent times, there has been an ever-increasing interest in green composite materials for its applications in the field of industries, aerospace, sports, household etc and in many other fields. In this paper, fabrication of Saccharum cilliare fibre reinforced green polymer composites using resorcinol formaldehyde (RF) as a novel matrix has been reported. A systematic approach for processing of polymer is presented. Effect of fibre loading on mechanical properties like flexural, tensile, compressive and wear resistances has also been determined. Reinforcing of the RF resin with Saccharum cilliare (SC) fibre was done in the form of particle size (200 micron). Present work reveals that mechanical properties of the RF resin have been found to increase up to 30% fibre loading and then decreases. Morphological and thermal studies of the resin, fibre and particle reinforced (P-Rnf) green composites have also been studied.