No abstract

RESUMENEl objetivo del presente estudio fue observar la morfología y caracterizar las propiedades mecánicas de materiales compuestos de madera y plásticos reciclados espumados. Se mezcló polietileno de alta densidad reciclado con fibra de madera de Pinus radiata D.Don (pino radiata) de 60 mesh. Las concentraciones de fibra fueron de 15 y 25% en peso, el polímero se espumó con un agente químico ACA (azodicarbonamida) y se utilizó anhídrido maleico MAPE (Epolene E-20) como agente de acoplamiento. Los compuestos se obtuvieron usando un proceso de extrusión en un equipo doble tornillo. Los resultados demostraron que el agente acoplamiento tuvo un efecto positivo sobre la adherencia del polímero reciclado y la fibra de madera. La densidad de los compuestos disminuyó con el agente espumante y las propiedades mecánicas de dureza, impacto, módulo de elasticidad en flexión y tracción fueron superiores para los compuestos no espumados. Se concluyó que al aumentar la concentración de fibra aumentaron las propiedades mecánicas de los compuestos a excepción de la tenacidad que al incorporar el agente espumante disminuyó ligeramente. Palabras claves:Materiales compuestos madera-plástico, polietileno reciclado, azodicarbonamida, propiedades mecánicas, pino radiata. ABSTRACTThe objective of the present study was to observe the morphology and characterize the mechanical properties of wood plastic composite foams. Recycled high density polyethylene was mixed with Pinus radiata D. Don (radiata pine) wood fiber of 60 mesh. The fiber concentrations were 15 and 25% by weight. The compounds were foamed with a chemical agent ACA (azodicabonamide) and MAPE (Epolene E-20) was used as a coupling agent. The composites were obtained by twinscrew extrusion. The results showed that the coupling agent had a positive effect on the adhesion of the recycled polymer and wood fiber. The density of the compounds decreased with blowing agent and the mechanical properties of hardness, impact, modulus of elasticity in bending and tension were higher for unfoamed composites. It was concluded that increasing the concentration of fiber increases the mechanical properties with the exception of impact resistance of the compounds that by incorporating the blowing agent decreased slightly.

Funding informationNatural Sciences and Engineering Research Council of Canada; Fonds de recherche du Québec -Nature et technologies Polydimethylsiloxane (PDMS)/iron oxide magnetic nanoparticle (NP) composites with tailored mechanical properties are prepared for use in magnetically actuated soft devices based on their controlled deformation by the application of an external magnetic field. This investigation reports the synthesis and functionalization of iron oxide NPs, the preparation of the PDMS/NP composites, the evaluation of NP dispersion using scanning electron microscopy (SEM) and optical microscopy, and the mechanical characterization of the composite films. Characterization includes rheological measurements as well as stress-strain curves to obtain the Young modulus and elongation at break. SEM is used to probe individual NP dispersion, whereas optical microscopy provides rapid access to quantitative information about the size and distribution of particle aggregates. Results for nonfunctionalized (nf), oleic acid (OA)coated, and stearic acid (SA)-coated iron oxide NPs and their blends are presented.PDMS elastomers containing both OA-and SA-coated iron oxide NPs are found to have very low Young moduli with substantially higher resistance to failure than neat PDMS. For example, a formulation containing 2.5 wt% OA-coated NPs and 2.5 wt% SA-coated iron oxide NPs has a modulus of 0.15 MPa (compared with 0.24 MPa for neat PDMS), while it can withstand an elongation of about 1.5 times its initial length compared with only 0.3 times for neat PDMS. As a comparison, the modulus of the most commonly used commercial PDMS elastomer (Sylgard 184) is an order of magnitude higher than that of the composites prepared here, whereas maximum elongation is similar for the two. The formulations developed in this work could be used in applications where high deformability is required with limited magnetic field strength and/or NP loading. K E Y W O R D S iron oxide, mechanical properties, polydimethylsiloxane, surface treatment

The effect of physical aging of the partially miscible blend of polycarbonate: polystyrene (PC:PS) at temperatures near the glass transition temperature (T g ) of the PS was studied as a function of time. For this purpose, blends of PC and PS with different ratios were elaborated and characterized using SEM, FTIR, DSC, and DMA techniques. The results indicated the presence of weak interaction upon blending with a maximum of interaction for the 50:50 blend. The effect of physical aging on the latter was then investigated via DMA, DSC, and NMR analyses. The DMA results showed that both phases were sensitive to aging. The effect was found to be strongly dependent on both the temperature and time. The aging of PC:PS blend was also found to trap stress during the process which induced an instability in the viscoelastic behavior. The latter was found to be associated with a phase-separation morphology of the blend and influenced by its composition. The NMR analysis also showed a pronounced distortion of the conformation combined with increasing molecular motion. These effects were found to be important for aging below the PS's T g .