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The goal of this study was to fibrillate cellulose from micro to nano scale and evaluate how these microfibers and nanofibrils affected the mechanical and thermal properties of thermoplastic polyurethane. The source of cellulosic material was hard wood cellulose fibers and the fibrillation was done with a high pressure homogenizer. The composite materials were prepared using compression moulding, by stacking the cellulose fiber mats between polyurethane films. The results showed that both microfibers and nanofibrils reinforced the polyurethane and provided better heat stability. The addition of 16.5 wt% of cellulose nanofibrils to PU increased the strength nearly 500% and the stiffness by 3000%. These results are very promising in terms of obtaining fibrils with a novel processing method and by improving the mechanical and thermal properties of polyurethane. This is expected to expand the application areas of polyurethanes.

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Sandwich composites with a polyurethane foam (PUF) core have become a versatile set of materials with applications ranging from basic construction elements to advanced engineering materials. This diverse range of applications has provided these sandwich materials with a distinctive position in today's engineering world. This review focuses on the broad research that has been carried out on PUF core‐based sandwich composites over the years—especially in the last decade. Thorough details have been presented focusing on basic PUF core sandwich structures, advanced PUF core sandwich composites with different kinds of reinforcements and complex structures such as hybrid sandwich panels. All the research presented here has been categorized carefully, such as the types of materials used in various studies, the types of reinforcements and testing techniques used, including mechanical, electrical, dynamic, thermal and acoustic methods etc. Comparisons have also been made based on similar materials, similar testing procedures and similar application areas. Research areas have been highlighted by giving a deep insight into the most promising research, manufacturing techniques and improvement procedures. Major consumption areas and application sectors for PUF core sandwich composites have also been discussed in this review. Finally, conclusions have been made based on the results found from a literature investigation.

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Blends of polyacrylonitrile (PAN) and lignin were prepared with three different lignin types by solution blending and solution casting. Among three types of lignin, one type was chosen and different blend concentrations were prepared and casted. The casted blend films were characterized chemically with fourier transform infrared spectroscopy (FTIR), and thermally with thermogravimetric analysis (TGA). The mechanical properties of the blends were measured using dynamic mechanical analysis (DMA). FTIR analysis shows an excellent interaction of PAN and lignin. The interaction of the lignins and PAN was confirmed by TGA analysis. The DMA results reveal that the lignin enhance the mechanical properties of PAN at room temperature and elevated temperatures. The blend structure and morphology were observed using scanning electron microscopy (SEM). SEM images show that excellent polymer blends were prepared. The results show that it is possible to develop a new precursor material with a blend of lignin and PAN. These studies show that the side product of paper and cellulosic bioethanol industries, namely, lignin can be used for new application areas.

Recyclability of the bioplastic polyhydroxybutyrate‐co‐valerate (PHBV) was studied with multiple melt processing (five cycles), with their performances evaluated. A batch of PHBV was processed with a twin screw extrusion followed by injection molding. This operation was repeated five times and samples were collected from each cycle for characterization. For each cycle, the mechanical properties were characterized with tensile, flexural, and impact testing, along with dynamic mechanical analysis. The results showed that the mechanical properties are maintained for four cycles; but in the fifth cycle, there was slight decrease in the properties. Gel permeation chromatography studies revealed that the molecular weight of the polymer does not decrease drastically; however, a drop was observed after third, fourth, and fifth cycle (8.7% decrease after third cycle, 13.5% decrease after fourth cycle, and 16.6% decrease after fifth cycle). The differential scanning calorimeter showed that the glass transition and melting temperatures did not change upon reprocessing, but the degree of crystallinity was reduced as a consequence of melt processing. The thermal gravimetric analysis showed that the onset value of thermal decomposition decreased very slightly. It was observed by Fourier transform infrared spectroscopy that the chemical structure of PHBV was maintained without any side chain reaction during processing. Scanning electron microscopy studies from the fractured surfaces of Cycles 1 and 5 confirmed that the uniformity of PHBV surfaces was maintained after five cycles, coinciding with the mechanical tests. The density measurements revealed that there was no change in the density of PHBV. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

In this study, the impact strength and elongation properties of a bacterial biopolymer, polyhydroxyutyrate-co-valerate (PHBV) co-polymer were improved with different functionalized vegetable oils, and nano structured Polyhedral Oligomeric Silsesquioxane (POSS). PHBV was blended with functionalized oils, epoxidized linseed oil, epoxidized soybean oil, and epoxy soyate using twin screw melt processing, and samples for testing were prepared by injection molding. PHBV was also blended with POSS and blend of PHBV with and without epoxy soyate were also prepared. The materials were characterized by impact strength testing, tensile testing, dynamic mechanical analysis, differential scanning calorimetry, and scanning electron microscopy studies. The studies showed that the impact strength was improved 92% with the epoxy soyate, which is a chemically modified version of epoxidized soybean oils by reaction with alcohols. The impact strength was further improved (120%) compared to neat PHBV synergistically with the addition of POSS to PHBV-epoxy soyate blend. With the addition of POSS to the PHBV-epoxy soyate system, elongation was improved 105%. It was also observed that with the addition of functionalized oils and POSS, the melting temperature of the PHBV was reduced more than 10°C which is very important for the processing of PHBV.