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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.

The epoxy resins are widely used in nuclear and aerospace industries. The certain properties of epoxy resins as well as the resistance to radiation can be improved by the incorporation of different fillers. This study examines the effect of electron beam irradiation on the thermal and mechanical properties of the epoxy composites filled with aluminum nanoparticles at percentage of 0.35 wt%. The epoxy composites were exposed to the irradiation doses of 30, 100 and 300 kGy using electron beam generated by the linear electron accelerator ELU-4. The effects of the doses on thermal and mechanical properties of the aluminum based epoxy composites were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The results revealed that the studied epoxy composites showed good radiation resistance. The thermal and mechanical properties of the aluminum based epoxy composites increased with increasing the irradiation dose up to 100 kGy and decreased with further increasing the dose.

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

In this work, we investigate the morphological and mechanical properties of blends of diglycidyl ether of bisphenol-A (DGEBA) and epoxidized polystyrene–polybutadiene star block copolymer (epST3) using diamino-diphenyl sulphone (DDS) as a hardener. The epoxidation of the star block copolymer was performed using meta-chloroperoxybenzoic acid (m-CPBA). Chemical modification of the copolymer was characterized by Fourier transform infrared (FTIR) spectroscopy while the morphology of the blends was analyzed by microscopic techniques. The mechanical behavior of the blends was analyzed by recording microindentation as well as impact tests. It has been demonstrated that the completely macrophase-separated morphology of the blends could be dispersed into the structures comprising co-continuous networks of the block copolymer phase and the epoxy resin leading to an increment in impact strength. At the same time, the hardness and stiffness of the blends, as shown by the indentation microhardness and indentation modulus, was maintained to a pretty high level.

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.

We investigated the dynamics of phase separation in a bisphenol A diglycidyl ether (BADGE)-poly(trimethylene terephthalate) (PTT) blend in this study, along with its effects on the long-term mechanical properties of the blend. BADGE-PTT blends with 4,4′-diaminodiphenyl sulfone were prepared by a conventional melt-mixing technique followed by curing at 180 °C for 4 h. PTT is a rapidly crystallizing polymer because of its unique stereochemistry. The crystalline fraction of PTT is incompatible with BADGE, whereas the amorphous fractions are miscible. Similarly, the blend of BADGE and PTT represented a system with a strong dynamic asymmetry. We examined the effect of the curing (crosslinking) of BADGE in the system discussed previously, with a special emphasis on the viscoelastic properties and long-term mechanical properties because they are extremely important in tuning these materials for various high-performance applications in the aerospace industry. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45059.