Impact on thermomechanical behaviour of a maleic anhydride grafted ABS on ABS/PC multi-layered blends

The significant increase of Waste Electric and Electronic Equipment (WEEE) has led to an important research in upgrading recycled engineering plastics by means of a blending technique. In particular, there is an interest in studying the properties of ABS/PC blends, the two most important components of WEEE, at ABS rich compositions, according to the generation ratio of waste [1]. Since ABS and PC are immiscible, the final properties depend to a large extent on the flow-induced morphology [2]. In order to better control the final blend morphology of injection molded samples, we propose a two-step approach: the first step consists in producing pellets with multilayered structure, using a multilayer coextrusion device. During the second subsequent step, the pellets are injection molded, with temperature conditions chosen to minimize the deformation of the created structures. The effect of a compatibilizer, namely, an ABS grafted with maleic anhydride (ABS-g-MA) [3] on the thermomechanical properties and morphology has been investigated

Modeling of the rheological properties of multinanolayer films in the presence of compatibilized interphase

heological behavior of nanolayered films of polyethylene/polyamide 6 (PE/PA6) compatibilized in situ during the coextrusion process has been studied at a temperature between the melting temperatures of PE and PA6. Thanks to the high number of interfaces, a drastic increase in dynamic moduli has been measured when increasing the interphase volume fraction in the films, and a solid-like behavior for the interphase was identified. Different models are compared to capture the complex viscosity of nanolayered films as a function of angular frequency. A model considering interphase and bulk viscosities and a single fitting parameter, namely, the thickness over which the viscosity decreases linearly from the interphase to the bulk one, captures the complex viscosity of all samples. This thickness is comparable to the PE layer thickness up to values about 1 μm before a significant bulk region has to be added to capture the behavior for thicker layers. This suggests that the melt rheology is impacted by the presence of a nanometric interphase over very large (micronic) length scales

Amorphous rigidification and cooperativity drop in semi−crystalline plasticized polylactide

Plasticization of amorphous polylactide shifts the glass transition and extends its temperature range of crystallization to lower temperatures. In this work, we focus on how low−temperature crystallization impacts the mobility of the amorphous phase. Plasticizer accumulates in the amorphous phase because it is excluded from the growing crystal. The formation of rigid amorphous fraction is favored by the low crystallization temperature. It reaches values up to 50% in plasticized polylactide. The increase in the content of rigid amorphous fraction coincides with both the increase of free volume quantified by positron annihilation lifetime spectroscopy, and the decrease in the cooperativity length obtained from the temperature fluctuation approach. The drop of cooperativity is interpreted in terms of mobility gradient due to the amorphous rigidification

How reproducible are methods to measure the dynamic viscoelastic properties of poroelastic media?

There is a considerable number of research publications on the acoustical properties of porous media with an elastic frame. A simple search through the Web of Science™ (last accessed 21 March 2018) suggests that there are at least 819 publications which deal with the acoustics of poroelastic media. A majority of these researches require accurate knowledge of the elastic properties over a broad frequency range. However, the accuracy of the measurement of the dynamic elastic properties of poroelastic media has been a contentious issue. The novelty of this paper is that it studies the reproducibility of some popular experimental methods which are used routinely to measure the key elastic properties such as the dynamic Young's modulus, loss factor and Poisson ratio of poroelastic media. In this paper, fourteen independent sets of laboratory measurements were performed on specimens of the same porous materials. The results from these measurements suggest that the reproducibility of this type of experimental method is poor. This work can be helpful to suggest improvements which can be developed to harmonize the way the elastic properties of poroelastic media are measured worldwide

Élaboration et propriétés des composites polypropylène recyclé/fibres de bambou

Cette étude présente des résultats obtenus sur l’élaboration de composites à base de polypropylène recyclé renforcé par des fibres végétales (fibres de bambou), fabriqués à l’aide d’une extrudeuse double vis modulaire pour produire un composite sous forme de granulés transformables. L’effet de la teneur en fibres de bambou, du compatibilisant et des méthodes de traitement chimique de la surface des fibres sur les propriétés mécaniques et rhéologiques du composite a été étudié. Nous avons montré que le traitement avec la soude enlève les impuretés et augmente la rugosité de surface des fibres, ce qui entraîne une meilleure adhésion des fibres dans la matrice polymère. Les composites fibres de bambou acétylées/polypropylène recyclé présentent de meilleures propriétés mécaniques, dues au greffage de groupes acétyles sur la surface des fibres et donc à l’amélioration de la compatibilité entre les fibres de bambou et la matrice polymère. Les propriétés rhéologiques des composites à différents taux de fibres de bambou et pour différentes méthodes de traitement de surface sont également analysées. Les facteurs prédominants qui influencent les propriétés des composites sont identifiés

Surface modification of polypropylene by radiation grafting of hydrophilic monomers: physicochemical properties

1 - ArticleThe surface of polypropylene was modified by the post-irradiation grafting of acrylic acid (AAc), N,N-dimethylacrylamide (DMA) and mixtures of AAc (DMA) and a quaternary ammonium salt (QAS). The polypropylene sheets were activated by electron beam radiation before the grafting reaction. The degree of grafting was determined by weighing and the surface hydrophilicity was measured by measuring the water contact angles. The presence of oxygen and nitrogen was demonstrated by XPS. The surface charge and the isoelectric point were determined by the streaming potential method. The grafting of DMA, like that of AAc, depended on monomer availability, but the monomer did not permeate into the polypropylene bulk. For the same surface hydrophilicity, depending on the nature of the monomer or comonomer grafted, it is possible to modulate the physicochemical characteristics which determine the phenomena governing adhesion, and probably to adapt them to a given application

Barrier properties of confined polylactide

Barrier properties of confined polylactide. Matbim 2017 - 4th international meeting on Material/Bioproduct Interactio