Preparation and characterization of composites from starch with sugarcane bagasse nanofibres

This paper reports on the results of using unbleached sugar cane bagasse nanofibres (average diameter 26.5 nm; aspect ratio 247 assuming a dry fibre density of 1,500 kg/m3) to improve the physico-chemical properties of starch-based films. The addition of bagasse nanofibres (2.5 to 20 wt%) to modified potato starch (i.e. soluble starch) reduced the moisture uptake by up to 17 % at 58 % relative humidity. The film’s tensile strength and Young’s modulus increased by up to 100 % (3.1 to 6.2 MPa) and 300 % (66.3 to 198.3 MPa) respectively with 10 and 20 wt% fibre addition. However, the strain at yield dropped by 50 % for the film containing 10 wt% fibre. Models for composite materials were used to account for the strong interactions between the nanofibres and the starch matrix. The storage and loss moduli as well as the glass transition temperature (Tg) obtained from dynamic mechanical thermal analysis, were increased with the starch-nanofibre films indicating decreased starch chain mobility due to the interacting effect of the nanofibres. Evidence of the existence of strong interactions between the starch matrix and the nanofibres was revealed from detailed Fourier transform infra-red and scanning electron microscopic evaluation

Biodegradable nanocomposites based on poly(ester-urethane) and nanosized hydroxyapatite: Plastificant and reinforcement effects

The processing and characterization of biodegradable nanocomposites based on poly(ester-urethane) reinforced with different amounts (0.5, 1 and 3 wt %) of nanosized hydroxyapatite (nHA) are reported. The selected poly(ester-urethane) was synthesized starting from a tri-block copolymer based on poly(epsilon-caprolactone) (PCL) and poly(L-lactic acid) (PLLA). The nanocomposites were prepared by extrusion and by press molding. Several techniques were applied to investigate the properties of the nanocomposites. Electron microscopy revealed that the poly(ester-urethane) matrix is able to phase separate and that the addition of well-dispersed nanofillers modifies the dimension of the segregated phase. The thermal stability of the PU matrix, regulated by the PLLA block, decreased when low contents of nHA (0.5 and 1 wt %) were added, even if the thermal stability of the PCL-block was increased for each nHA amount. The good mechanical response of the nanocomposites confirmed the absence of agglomerates in the dispersion of the nanofillers in the polymeric matrix. The nHA presence also increased the surface hydrophilicity. Furthermore, rheology measurements, mechanical and thermal tests demonstrated the different behavior induced by the addition of nHA in different amounts. In fact, nHA acts as plasticizer at low concentrations (0.5, 1 wt %) and as reinforcement at a higher nHA amount (3 wt %). In vitro degradation tests were performed using a phosphate buffer solution. The results reported here are relevant for the development of nanocomposites based on a biodegradable and biocompatible polymeric matrix reinforced with small amounts of biocompatible nanofillers for different applications, especially in the biomedical field. (C) 2015 Elsevier Ltd. All rights reserved.We are indebted to the Spanish Ministry of Science and Innovation (MICINN) for their economic support of this research (MAT2013-48059-C2-1-R and MAT2014-55778-REDT) as well as the Regional Government of Madrid (S2013/MIT-2862). LP acknowledges also, the support of a JAEDoc grant from CSIC cofinanced by FSE. We thank the technical support of Prof. Juan Lopez Martinez from Universitat Politecnica de Valencia (Spain) for his assistance with water contact angle measurements, as well as Marco Rallini and Franco Dominici from the STM group of the University of Perugia for FE-SEM photographs and microextruder blending, respectively.Navarro-Baena, I.; Arrieta, MP.; Sonseca Olalla, A.; Torre, L.; López, D.; Giménez Torres, E.; Kenny, JM.... (2015). Biodegradable nanocomposites based on poly(ester-urethane) and nanosized hydroxyapatite: Plastificant and reinforcement effects. Polymer Degradation and Stability. 121:171-179. https://doi.org/10.1016/j.polymdegradstab.2015.09.002S17117912

High-Temperature Electronic Materials: Silicon Carbide and Diamond

The physical and chemical properties of wide-band-gap semiconductors make these materials an ideal wide bandgapsemiconductor choice for device fabrication for applications in many different areas, e.g. light emitters, high-temperature and high-power electronics, high-power microwave devices, micro-electromechanical system (MEM) technology, and substrates for semiconductor preparation. These semiconductors have micro-electromechanical system (MEMS) been recognized for several decades as being suitable for these applications, but until recently the low material quality has not allowed the fabrication of high-quality devices. In this material quality chapter, we review the wide-band-gap semiconductors, silicon carbide and diamond. Silicon carbide electronics is advancing from the research stage to commercial production. The commercial availability of single-crystal SiC substrates during the early 1990s gave rise to intense activity in the development of silicon carbide devices. The commercialization started with the release of blue light-emitting diode (LED). The recent release of high-power Schottky diodes was a further demonstration of the progress made towards defect-free SiC substrates. Diamond has superior physical and chemical properties. Silicon-carbide- and diamond-based diamondsilicon carbide (SiC) electronics are at different stages of development. The preparation of high-quality single-crystal substrates of wafer size has allowed recent significant progress in the fabrication of several types of devices, and the development has reached many important milestones. However, high-temperature studies are still scarce, and diamond-based electronics is still in its infancy