Search

Simultaneous interpenetrating networks (IPNs) comprising of polymethylsilsesquioxane (PMSQ) and phenolic resole (PF) systems at various PMSQ to PF ratios (0–75% w/w PF) which formed the matrix resin for 60% w/w short silica fibre reinforced composites (SR-PMSQ-PF) are subjected to a controlled heating regime in argon atmosphere at 1500 °C to investigate the microstructure and phase evolution based on IPN composition. This study aims at giving an insight into thermal, mechanical and chemical stability of silicone-phenolic IPN composites, particularly for high temperature thermal protection applications as in aerospace. The morphology and microstructure of the pyrolysed composites are well characterized using Raman and FTIR spectroscopy, XRD and SEM-EDS and based on this a mechanism for microstructure evolution is proposed. It is inferred that the pyrolysis of SR-PMSQ-PF composites results exclusively in the formation of cristobalite silica. In addition to that, the formation of SiC is also facilitated particularly in nano dimension with increase in phenolic content, by carbothermal reduction of silica derived from PMSQ and silica fibre predominantly through solid-vapour phase reaction along the (111) crystalline plane. The systematic evaluation of microstructure and morphology of pyrolysed SR-PMSQ-PF IPN composites is useful to define specific thermal protection applications for these composites.

Extensive and excessive use of organic pesticides poses a serious threat to the environment. The degradation products of most organic pesticides are far more toxic than the parent compound. The toxic effect of common pesticides, their degradation mechanisms, and common detection techniques are evaluated here. A literature survey shows that a detailed discussion on this relationship is extremely relevant in the current scenario.

Workplace noise is hazardous to worker safety and health. Noise can not only cause hearing impairment but also act as a causal factor for stress and raise the systolic blood pressure.There are many methods available and being used in industries at present to reduce acoustic emissions from various equipment. The process of reducing sound emissions from equipment is called acoustic quieting. The method of using piezoelectric material to reduce transmitted sound from equipment rather than damping structural vibration can be applied where it is difficult to damp structural vibrations completely. If piezoelectric materials are attached to vibrating machine parts,withthe supply of suitable voltages, they counter-vibrate which helps in damping structural vibration. Previous studies conducted using simulations with the help of ANSYS software showed noise reductions of up to20 decibels. This paper presentsan effective technique for tuning the frequencies of vibrations of the piezoelectric material with the source vibrations for the reduction of noise. It can help in cancelling the original vibrations which ultimately lead to the reduction in transmitted noise levels. Experiments reveal that a reduction of 9 decibels innoise level is possible by using a filtercontrol circuit.

The influence of epoxidation level of natural rubber (i.e., ENR25, ENR50) on the dielectric and oxygen gas barrier properties of thermally reduced graphene oxide (GR) and graphite (GT) (with 2%·w/w) filled nanocomposites are investigated here. GR, GT filled epoxidized natural rubber (ENR) nanocomposites were fabricated by mechanical mixing using environment friendly two-roll mill mixing method. Raman spectroscopy and Fourier transform infrared spectroscopy studies were carried out to investigate the extent of chemical interactions between GR and ENR. Morphological studies were done using transmission electron microscopy to evaluate the distribution of GR and GT in the ENR. The improved gas barrier and dielectric properties of GT-ENR and GR–ENR composites synthesized by a novel green ecofriendly method is correlated with the chemical interactions among GT, GR, and ENR. POLYM. ENG. SCI., 55:2439–2447, 2015. © 2015 Society of Plastics Engineers

The effect of processing conditions on the morphology of polymer blends is a topic of tremendous practical interest especially for thermoset–thermoplastic blends. The effect of blend ratio and the nature of the flow field (shear flow vs. elongation flow) on the morphology is followed here using blends of diglycidyl ether of bisphenol A (DGEBA)-poly(trimethylene terephthalate) (PTT). Morphology of the blends prepared by the conventional melt mixing technique is compared with that prepared by using an elongation mixer (RMX device invented by Muller et al.). The blends prepared by the elongation mixer showed excellent transparency and higher storage modulus at room temperature than the conventional mixer. In the case of samples prepared by the RMX device Tg of the epoxy phase has been shifted to lower temperatures indicating a molecular level mixing between PTT and DGEBA. However the conventional melt mixed samples showed only a marginal shift in Tg to low temperatures indicating that the system is not as miscible as that prepared by the RMX device. The use of RMX device for thermoset–thermoplastic blends is novel and no work has been reported in this relation. The properties of the blends were strongly affected by the composition and the crystallization of the semicrystalline PTT phase. POLYM. ENG. SCI., 55:1679–1688, 2015. © 2014 Society of Plastics Engineers

The influence of chemical interaction between poly(epsilon-caprolactone) (PCL) and Cloisite 10A on rheology, water permeability and antibacterial properties were subjected to detailed investigation. Mats of PCL with varying amounts of Cloisite 10A were prepared by electrospinning technique. The hydrogen bonding interaction between PCL and the organic modifier present in Cloisite 10A encourages the exfoliation/intercalation of Cloisite 10A resulting in a strong immobilized polymeric zone which was confirmed by small angle oscillatory shear experiments (SAOS). Unimpeded permeation of water through a PCL-Cloisite 10A porous nanocomposites scaffold was confirmed by different diffusion models. This strong immobilized zone or percolated network formation, aids in the elution of the organic modifier present in the nanoclay, which leads to the rupture of the cell wall of the bacteria. The antibacterial properties were tested using Gram positive bacteria and compared with the results obtained for Gram negative bacteria to test the use of our nanocomposites for wound healing applications.

Vascular malformations are rare congenital vascular anomalies composed of inappropriately connected vasculature. They are usually present at birth, are progressive, infiltrative and require intervention. Vascular malformations need to be differentiated from haemangiomas which are congenital vascular neoplasms. We present a case of vascular malformation in a 6-year old child who presented with a progressive swelling in the neck and was treated by surgical excision. This case is being presented because of its peculiar clinical presentation.

Millimeter-wave wireless communication is an uprising technology. Millimeter-wave has large bandwidth and short wavelength. Eventhough it is advantageous, it gets easily blocked by obstacles. As a result, effective communication does not take place. Relays are used widely to solve this problem. Unmanned Autonomous Vehicles (UAV), such as drones, allows the mobile relays in real applications. It is difficult for relay to find its position quickly and accurately. Here, a method AutoRelay specialized for mmwave communication have been reviewed. In AutoRelay, the link qualities of mmwave beams are sampled while moving. Based on real-time sampling, UAV adjusts its path to reach the optimal location by using compressive sensing theory which increases accuracy and saves time.