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Ethylene Vinyl Alcohol (ethylene + vinyl_alcohol)
Selected AbstractsEffect of Pasteurization, High-Pressure Processing, and Retorting on the Barrier Properties of Nylon 6, Nylon 6/Ethylene Vinyl Alcohol, and Nylon 6/Nanocomposites FilmsJOURNAL OF FOOD SCIENCE, Issue 1 2009L. Halim ABSTRACT:, This study determined the impact of pasteurization, high-pressure processing (HPP), and retorting on the barrier properties of nylon 6 (N6), nylon 6/ethylene vinyl alcohol (N6/EVOH), and nylon 6/nanocomposite (N6/nano) materials. The pasteurized and high-pressure treated films were coextruded with low-density polyethylene (PE) as the heat-sealing layer. The retorted films were coextruded with polypropylene (PP). Oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the samples were measured after pasteurization (75 °C for 30 min), HPP (800 MPa for 10 min at 70 °C), and retorting (121 °C for 30 min) treatments. These were compared with the thermal characteristics and morphologies of the samples using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Results showed that OTR of N6 and N6/Nano increased after HPP (16.9% and 39.7%), pasteurization (13.3% and 75.9%), and retorting (63.3% and 112.6%), respectively. For N6/EVOH, a decrease in OTR after HPP (53.9%) and pasteurization (44.5%) was observed. The HPP treatment increased the WVTR of N6 (21.0%), N6/EVOH (48.9%), and N6/Nano (21.2%). The WVTR of N6, N6/EVOH, and N6/Nano increased by 96.7%, 43.8%, and 40.7%, respectively, after pasteurization. The DSC analyses showed that the enthalpy and percent crystallinity increased (2.3% to 6.5%) in the N6/Nano when compared with the N6 material after each treatment. Retorting caused a decrease (3.5%) in the percent crystallinity of the polypropylene material. HPP did not cause major morphological changes to the samples. Results of the barrier studies were influenced by the crystallinity changes in the materials as seen in the XRD diffractograms. [source] Towards Thermoconductive, Electrically Insulating Polymeric Composites with Boron Nitride Nanotubes as FillersADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Chunyi Zhi Abstract Ultilizing boron nitride nanotubes (BNNTs) as fillers, composites are fabricated with poly(methyl methacrylate), polystyrene, poly(vinyl butyral), or poly(ethylene vinyl alcohol) as the matrix and their thermal, electrical, and mechanical properties are evaluated. More than 20-fold thermal conductivity improvement in BNNT-containing polymers is obtained, and such composites maintain good electrical insulation. The coefficient of thermal expansion (CTE) of the BNNT-loaded polymers is dramatically reduced because of interactions between the polymer chains and the nanotubes. Moreover, the composites possess good mechanical properties, as revealed by Vickers microhardness tests. This detailed study indicates that BNNTs are very promising nanofillers for polymeric composites, allowing the simultaneous achievement of high thermal conductivity, low CTE, and high electrical resistance, as required for novel and efficient heat-releasing materials. [source] An In Vivo Study of the Host Response to Starch-Based Polymers and Composites Subcutaneously Implanted in RatsMACROMOLECULAR BIOSCIENCE, Issue 8 2005Alexandra P. Marques Abstract Summary: Implant failure is one of the major concerns in the biomaterials field. Several factors have been related to the fail but in general these biomaterials do not exhibit comparable physical, chemical or biological properties to natural tissues and ultimately, these devices can lead to chronic inflammation and foreign-body reactions. Starch-based biodegradable materials and composites have shown promising properties for a wide range of biomedical applications as well as a reduced capacity to elicit a strong reaction from immune system cells in vitro. In this work, blends of corn starch with ethylene vinyl alcohol (SEVA-C), cellulose acetate (SCA) and polycaprolactone (SPCL), as well as hydroxyapatite (HA) reinforced starch-based composites, were investigated in vivo. The aim of the work was to assess the host response evoked for starch-based biomaterials, identifying the presence of key cell types. The tissues surrounding the implant were harvested together with the material and processed histologically for evaluation using immunohistochemistry. At implant retrieval there was no cellular exudate around the implants and no macroscopic signs of an inflammatory reaction in any of the animals. The histological analysis of the sectioned interface tissue after immunohistochemical staining using ED1, ED2, CD54, MHC class II and ,/, antibodies showed positively stained cells for all antibodies, except for ,/, for all the implantation periods, where it was different for the various polymers and for the period of implantation. SPCL and SCA composites were the materials that stimulated the greatest cellular tissue responses, but generally biodegradable starch-based materials did not induce a severe reaction for the studied implantation times, which contrasts with other types of degradable polymeric biomaterials. [source] Injection molded composites of short Alfa fibers and biodegradable blendsPOLYMER COMPOSITES, Issue 4 2006I. Ammar Fully biodegradable composites made from two polymer blend matrices (SEVA-C: starch and a copolymer of ethylene vinyl alcohol; and SCA: starch and cellulose acetate) and short Alfa fibers were developed and processed by conventional injection molding into standard tensile specimens. For each kind of matrix, the influence of the reinforcement load was evaluated, using fiber amounts from 0 to 30% (wt/wt). An optimization study was carried out for the composite SEVA-C with 10% Alfa fiber. The obtained results establish that the produced biodegradable composites present a significant improvement in stiffness for both matrices. Improvements in the tensile strength were observed only for the Alfa fiber reinforced SEVA-C. However, for both matrices, the reinforcement causes a significant loss in the material ductility. Results from design of experiments (Hadamard plans) were used to explain the influence of the injection molding conditions on the mechanical behavior of the obtained composites, mainly on the stiffness values. POLYM. COMPOS., 27:341,348, 2006. © 2006 Society of Plastics Engineers [source] Influence of high-pressure processing on selected polymeric materials and on the migration of a pressure-transmitting fluidPACKAGING TECHNOLOGY AND SCIENCE, Issue 5 2002A. Schauwecker Abstract This study investigated the migration of 1,2-propanediol (PG) through selected food packaging films exposed to high-pressure processing (HPP). Pouches made from these materials were filled with 95% ethanol as a food-simulating liquid. These packages were then processed using a pilot-scale high-pressure food processor at 400, 600 and 827,MPa and 30, 50 and 75°C for 10,min. Controls were processed at similar temperatures and times, but at atmospheric pressure. To investigate any structural changes to these films during HPP, water was used as the food simulant at temperatures of 30, 75, 85, 90 and 95°C and at pressures of 200, 400, 690 and 827,MPa. No detectable PG migration into the polyester/nylon/aluminium (Al) polypropylene (PP) meal-ready-to eat (MRE)-type pouches was observed. PG migration into the nylon/ethylene vinyl alcohol (EVOH)/PE (EVOH) pouches was similar at 30, 50 and 75°C after 10,min under atmospheric pressure. However, PG migration into the EVOH pouches significantly decreased when treated with high pressure at 30, 50 and 75°C. At 75 and 50°C, the PG migration was significantly higher than the amounts detected at 30°C. Visible signs of delamination between the polypropylene (PP) and aluminum (Al) layers were observed in the MRE pouches processed at ,200,MPa and 90°C for 10,min. This delamination appeared to occur between the PP and Al layers. The differential scanning calorimetric analyses and Fourier transform infrared (FTIR) spectra were similar for the high-pressure treated pouches when compared to their respective controls. This indicated that there were no HPP-induced molecular changes to the treated pouches. Results from this study should be useful to HPP users for predicting PG migration trends and in deciding the selection of appropriate packaging materials for use under similar processing conditions. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||