Search results for "plastics"
showing 10 items of 2724 documents
Effect of CTBN rubber inclusions on the curing kinetic of DGEBA–DGEBF epoxy resin
2003
Abstract The curing kinetics of an epoxy resin matrix, based on diglycil ether of bisphenol A and F (DGEBA–DGEBF), associated with an anhydride hardener, at different carboxyl-terminated copolymer of butadiene and acrylonitrile liquid rubber (CTBN) concentration (0–10 phr) are studied using a differential scanning calorimetry (DSC) and a stress-controlled rheometer in isothermal and dynamic conditions. The aim of this work is to correlate the presence of the rubber phase with the transition phenomena that occur during the curing process. The CTBN rubber induces a catalytic effect on the polymerization of the pure resin clearly observed by a significant enhancement of the curing rate. Calori…
Hepatocyte-targeted fluorescent nanoparticles based on a polyaspartamide for potential theranostic applications
2015
Abstract Here, the synthesis of a galactosylated amphiphilic copolymer bearing rhodamine (RhB) moieties and its use for the preparation of polymeric fluorescent nanoparticles for potential applications in therapy and diagnosis are described. To do this, firstly, a fluorescent derivative of α,β-poly( N -2-hydroxyethyl)- d , l -aspartamide (PHEA) was synthesized by chemical reaction with RhB, and with polylactic acid (PLA), to obtain PHEA-RhB-PLA. Then, the derivatization of PHEA-RhB-PLA with GAL-PEG-NH 2 allows obtaining PHEA-RhB-PLA-PEG-GAL copolymer, with derivatization degrees in -PLA and -PEG-GAL equal to 1.9 mol% and 4.5 mol%, respectively. Starting from this copolymer, liver-targeted f…
Investigation on the Properties and on the Photo-Oxidation Behaviour of Polypropylene/Fumed Silica Nanocomposites
2021
This work investigates the effects of very small amounts of fumed silica on the morphology and on the rheological and mechanical behaviour of polypropylene nanocomposites and on their photo-oxidation behaviour. Polypropylene nanocomposites were prepared using a twin-screw corotating extruder with 0, 1 and 2 wt/wt% of SiO2. Morphological, mechanical, thermomechanical and rheological properties were examined. It was found that the viscosity of the matrix is reduced by the presence of the silica nanoparticles, suggesting a poor adhesion between the two phases and probably some lubricating effect. On the contrary, the mechanical and, in particular, the thermomechanical properties of the matrix …
Monitoring molecular dynamics of bacterial cellulose composites reinforced with graphene oxide by carboxymethyl cellulose addition
2017
[EN] Broadband Dielectric Relaxation Spectroscopy was performed to study the molecular dynamics of dried Bacterial Cellulose/Carboxymethyl Cellulose-Graphene Oxide (BC/CMC-GO) composites as a function of the concentration of CMC in the culture media. At low temperature the dielectric spectra are dominated by a dipolar process labelled as a beta -relaxation, whereas electrode polarization and the contribution of dc-conductivity dominate the spectra at high temperatures and low frequency. The CMC concentration affects the morphological structure of cellulose and subsequently alters its physical properties. X-ray diffractometry measurements show that increasing the concentration of CMC promote…
Effect of Moisture Content on the Processing and Mechanical Properties of a Biodegradable Polyester
2021
This work is focused on the influence of moisture content on the processing and mechanical properties of a biodegradable polyester used for applications in injection molding. The pellets of the biodegradable polyester were exposed under different relative humidity conditions at a constant temperature before being compression molded. The compression-molded specimens were again placed under the above conditions before the mechanical testing. With all these samples, it is possible to determine the effect of moisture content on the processing and mechanical properties separately, as well as the combined effect of moisture content on the mechanical properties. The results obtained showed that th…
Reversible Modulation of Elasticity in Fluoroazobenzene-Containing Hydrogels Using Green and Blue Light.
2017
Hydrogels are soft materials that have found multiple applications in biomedicine and represent a good platform for the introduction of molecular switches and synthetic machines into macromolecular networks. Tuning their mechanical properties reversibly with light is appealing for a variety of advanced applications and has been demonstrated in the past; however, their activation typically requires the use of UV light, which displays several drawbacks related to its damaging character and limited penetration in tissues and materials. This study circumvents this limitation by introducing all-visible ortho-fluoroazobenzene switches into a hydrophilic network, which, as a result, can be activat…
Recycling of a Biodegradable Polymer Blend
2020
Mechanical recycling is one of the possible ways to enhance the value of postconsumer plastic materials. However, the final performance of the recycled material will strongly depend on the quality of the selection made on the recycled product and on the degradation of the properties. In this context, the present study examines the effect of reprocessing for five successive extrusion cycles on the rheological, mechanical and thermal properties of a poly(butylene adipate-co-terephthalate) (PBAT)-based blend on samples reprocessed in both dry and wet conditions. The results showed that when the sample was processed after drying, degradation of the material was less than when it was processed i…
Methyl cellulose-based edible films and coatings I. Effect of plasticizer content on water and 1-octen-3-ol sorption and transport
1995
Edible films were prepared from methyl cellulose with various concentrations of poly(ethylene glycol) 400 (PEG400) used as a plasticizer. Water vapour and 1-octen-3-ol (an aroma compound) were selected as hydrophilic and hydrophobic volatile penetrants respectively. Their solubility and permeability through methyl cellulose-based edible films were studied using gas chromatography methods. Whatever penetrant was used, the flux increased with the PEG400 content. Transfer behaviour, i.e., the order of increased magnitude of the transfer rate, strongly depends on the nature of the volatile compound. However, water sorption only depends on the PEG400 content whereas the aroma compound sorption i…
Inherently fluorescent polyaniline nanoparticles in a dynamic landscape
2012
Abstract In this paper we report for the first time on the emissive behavior of two polyaniline (PANI) nanoparticle systems produced via oxidative chemical polymerization in the presence of either poly(vinyl alcohol) (PVA) or chitosan as polymeric stabilizers in water. The emission from PANI nanoparticles is irreversibly quenched by an increase of pH of the suspending medium from acid to neutral (chitosan–PANI) or alkaline (PVA–PANI). Conversely, PANI nanorods synthesized in the same conditions of the above, but in presence of poly(N-vinyl pyrrolidone), is not emissive at any pH. The role of the polymeric surfactant as a soft template is key in controlling the morphology and the properties …
Degradation of polymer blends: A brief review
2017
Abstract The usefulness of any material, including polymer blends, depends on its degradability and durability. The blend composition can significantly affect the degradative behavior of a polymer blend and can differ from the degradation routes of the pure components since the interactions among different species in the blends during degradation, and among the degradation products, can occur. These reactions can lead either to an acceleration of the degradation rate or to a stabilizing effect in comparison with the pure components. Thus, the additive rule cannot be often applied in case of degradation of polymer blends and, therefore, it is difficult to predict the degradative behavior of …