Surface modification of low density polyethylene (LDPE) film by low pressure O2 plasma treatment

In this work, low pressure glow discharge O₂ plasma has been used to increase wettability in a LDPE film in order to improve adhesion properties and make it useful for technical applications. Surface energy values have been estimated using contact angle measurements for different exposure times and different test liquids. In addition, plasma-treated samples have been subjected to an aging process to determine the durability of the plasma treatment. Characterization of the surface changes due to the plasma treatment has been carried out by means of Fourier transformed infrared spectroscopy (FTIR) to determine the presence of polar species such as carbonyl, carboxyl and hydroxyl groups. In addition to this, atomic force microscopy (AFM) analysis has been used to evaluate changes in surface morphology and roughness. Furthermore, and considering the semicrystalline nature of the LDPE film, a calorimetric study using differential scanning calorimetry (DSC) has been carried out to determine changes in crystallinity and degradation temperatures induced by the plasma treatment. The results show that low pressure O₂ plasma improves wettability in LDPE films and no significant changes can be observed at longer exposure times. Nevertheless, we can observe that short exposure times to low pressure O₂ plasma promote the formation of some polar species on the exposed surface and longer exposure times cause slight abrasion on LDPE films as observed by the little increase in surface roughness.     

Kinetic analysis of thermal degradation of recycled polycarbonate/acrylonitrile-butadiene-styrene mixtures from waste electric and electronic equipment

The study of properties in waste polymeric materials is important for a further recycling and eventual reuse. The determination of thermal properties of PC-ABS mixtures obtained from waste electric and electronic equipment (WEEE) by using thermogravimetric analysis (TGA) has been carried out in this work. Kinetic parameters, such as apparent activation energies, have been calculated by using the autocatalytic model, which has shown a good correlation with experimental data. A good agreement between calculated and experimental results was observed for PC-based mixtures. This is an indication that the addition of a high amount of ABS permits the creation of a network formed by elastomeric domains which leads to a general increase in heterogeneity of the mixture.     

Improvement of Impact Strength of Polylactide Blends with a Thermoplastic Elastomer Compatibilized with Biobased Maleinized Linseed Oil for Applications in Rigid Packaging

This research work reports the potential of maleinized linseed oil (MLO) as biobased compatibilizer in polylactide (PLA) and a thermoplastic elastomer, namely, polystyrene-b-(ethylene-ran-butylene)-b-styrene (SEBS) blends (PLA/SEBS), with improved impact strength for the packaging industry. The effects of MLO are compared with a conventional polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene-graft-maleic anhydride terpolymer (SEBS-g-MA) since it is widely used in these blends. Uncompatibilized and compatibilized PLA/SEBS blends can be manufactured by extrusion and then shaped into standard samples for further characterization by mechanical, thermal, morphological, dynamical-mechanical, wetting and colour standard tests. The obtained results indicate that the uncompatibilized PLA/SEBS blend containing 20 wt.% SEBS gives improved toughness (4.8 kJ/m²) compared to neat PLA (1.3 kJ/m²). Nevertheless, the same blend compatibilized with MLO leads to an increase in impact strength up to 6.1 kJ/m², thus giving evidence of the potential of MLO to compete with other petroleum-derived compatibilizers to obtain tough PLA formulations. MLO also provides increased ductile properties, since neat PLA is a brittle polymer with an elongation at break of 7.4%, while its blend with 20 wt.% SEBS and MLO as compatibilizer offers an elongation at break of 50.2%, much higher than that provided by typical SEBS-g-MA compatibilizer (10.1%). MLO provides a slight decrease (about 3 °C lower) in the glass transition temperature (T_g) of the PLA-rich phase, thus showing some plasticization effects. Although MLO addition leads to some yellowing due to its intrinsic yellow colour, this can contribute to serving as a UV light barrier with interesting applications in the packaging industry. Therefore, MLO represents a cost-effective and sustainable solution to the use of conventional petroleum-derived compatibilizers.     

Improvement of thermal inertia of styrene–ethylene/butylene–styrene (SEBS) polymers by addition of microencapsulated phase change materials (PCMs)

In this work, microencapsulated phase change materials (PCMs) with a melting temperature of 52 °C have been used to improve thermal inertia phenomena on an elastomeric matrix of styrene–ethylene/butylene–styrene (SEBS) material. The amount of PCMs has varied in the 1–10 wt.% and these materials have been processed by conventional injection molding without PCM degradation. Mechanical characterization of SEBS–PCM compounds has been carried out and the obtained results show good maintenance of both resistant and ductile properties for PCM amounts comprised in the 1–5 wt.% range. Scanning electron microscopy (SEM) analysis has revealed good wetting properties of PCM microcapsules with the SEBS matrix which is a key factor to obtain good mechanical performance. The effect of PCM addition on thermal inertia has been evaluated by active infrared thermography (IRT), showing a remarkable effect on thermal regulation of SEBS in the temperature range close to the melting point of the PCM (52 °C). This thermoregulation effect is more accurate as the PCM content increases. Also, cooling curves have been constructed in order to quantify the thermal inertia effect in a cooling process.     

Thermal expansivity and degradation properties of PLA/HA and PLA/βTCP in vitro conditioned composites

Journal of Thermal Analysis and Calorimetry - The objective of this study was to investigate the thermal expansivities and degradation properties for several in vitro conditioned biodegradable...     

Optimization of the curing conditions of PVC plastisols based on the use of an epoxidized fatty acid ester plasticizer

The use of an epoxidized fatty acid ester (EFAE) as a natural-based plasticizer for plasticized PVC (P-PVC) has been evaluated in this work. The effect of the curing conditions has been studied by following several test techniques such as mechanical properties, thermal behavior, color changes, solvent migration and microstructure. Different curing processes at isothermal conditions (ranging from 160 °C to 220 °C) have been carried at curing times in the 6–16 min range. The optimum mechanical response (tensile strength values in the 9–10 MPa range and elongation at break close to 250%) is obtained for plastisols cured at 200 and 220 °C for 12 and 8 min curing times, respectively. These curing conditions also offer the lowest migration in n-hexane (lower than 11%) which is indicative of plasticizer total absorption. Furthermore, the use of these curing conditions does not lead to thermal degradation as confirmed by color measurements.     

Predictive Models of Ethylene-Vinyl Acetate (EVA) Copolymers with Powdered Zn Fillers

Metallic Zn filler was used to increase the electrical properties of ethylene-vinyl acetate copolymer (EVA). Other properties were also modified such as mechanical and thermal behavior. It is possible to predict the behaviour of EVA-Zn system by using different models.     

Enhancement of wettability in low density polyethylene films using low pressure glow discharge N2 plasma

Low pressure glow discharge nitrogen plasma has been used to improve wettability in a low density polyethylene (LDPE) film for technical applications. The plasma treatment was carried out at a power of 300 W for different exposure times in the 1–20 min range. Wettability changes were analyzed using contact angle measurements. In addition to this, plasma‐treated samples were subjected to an aging process to determine the durability of the plasma treatment. X‐ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy were used for surface characterization. The nitrogen plasma treatment considerably reduced contact angle values thus indicating an increase in surface wettability. The spectroscopic study showed presence of oxygen‐based species on the plasma‐treated samples, which are mainly generated after the plasma treatment as a consequence of air exposure. These polar species contribute to improve surface functionalization, but this is almost lost during aging due to the hydrophobic recovery process. Microscopic studies revealed that also small changes in surface roughness occurred during the plasma treatment but these are very low compared to surface activation. The results confirmed that low pressure nitrogen can be considered as an environmentally efficient process to improve wettability in low density polyethylene films. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2390–2399, 2007     

Recycling of ABS and PC from electrical and electronic waste. Effect of miscibility and previous degradation on final performance of industrial blends

The aim of this work, within the framework of polymer recycling, is to upgrade waste from electrical and electronic equipment. Blends of the two major residues were prepared via a melt blending process. These are ABS consisting of a SAN thermoplastic matrix with a dispersed elastomeric (polybutadiene rubber) component and polycarbonate (PC). The effect of partial miscibility and previous degradation levels was investigated. Mechanical characterization of ABS/PC systems was carried out to determine the optimum composition range. Previous degradation levels of the two wastes were investigated by FTIR and little degradation was found on ABS due to the presence of a polybutadiene rubber which is more sensitive to thermo-oxidative processes but no significant degradation was found on PC. Differential scanning calorimetry (DSC) tests demonstrated certain miscibility between the two components by identifying two glass transition temperatures. This partial miscibility, together with the small degradation of the elastomeric component, contributes to a low interaction promoting a decrease on mechanical performance. Scanning electron micrographs (SEM) showed the system morphology and certain lack of adherence along SAN/polybutadiene interface related to degradation of polybutadiene spheres which act as stress concentrators. The use of the equivalent box model (EBM) allowed to quantify the interaction level by determining an interaction/adherence parameter “A”, which turned to be lower than 1 and corroborated the lack of interaction.     

Closed inflationary universe with tachyonic field

In this article we study closed inflationary universe models by using a tachyonic field theory. We determine and characterize the existence of a universe which has Ω>1 and which describes a period of inflation. We find that the considered models are less restrictive compared to the standard ones with a scalar field. We use recent astronomical observations to constrain the parameters appearing in the model. The results obtained are compared to those found in the standard scalar field inflationary universes. PACS 98.80.Bp; 98.80.Cq