Effect of particle size, coupling agent and DDGS additions on Paulownia wood polypropylene composites

Studies aimed at improving the tensile, flexural, impact, thermal, and physical characteristics of wood–plastic composites composed of Paulownia wood flour derived from 36-month-old trees blended with polypropylene were conducted. Composites of 25% and 40% w/w of Paulownia wood were produced by twin-screw compounding and injection molding. Composites containing 0–10% by weight of maleated polypropylene were evaluated and an optimum maleated polypropylene concentration determined, i.e., 5%. The particle size distribution of Paulownia wood filler is shown to have an effect on the tensile and flexural properties of the composites. Novel combination composites of dried distiller’s grain with solubles mixed with Paulownia wood (up to 40% w/w) were produced and their properties evaluated. Depending on the composite tested, soaking composites for 872 h alters mechanical properties and causes weight gain

Tensile and impact properties of three-component PP/wood/elastomer composites

Polypropylene (PP) was reinforced with wood flour and impact modified with elastomers to increase stiffness and impact resistance simultaneously. Elastomer content changed in four (0, 5, 10 and 20 wt%), while that of wood content in seven steps, the latter from 0 to 60 wt% in 10 wt% steps. Structure and adhesion were controlled by the addition of functionalized (maleated) polymers. Composites were homogenized in a twin-screw extruder and then injection molded to tensile bars. Fracture resistance was characterized by standard and instrumented impact tests. The results showed that the components are dispersed independently of each other even when a functionalized elastomer is used for impact modification, at least under the conditions of this study. Impact resistance does not change much as a function of wood content in PP/wood composites, but decreases drastically from the very high level of the PP/elastomer blend to almost the same value obtained without impact modifier in the three-component materials. Increasing stiffness and fiber related local deformation processes led to small fracture toughness at large wood content. Micromechanical deformation processes depend mainly on the strength of PP/wood interaction; debonding and pull-out take place at poor adhesion, while fiber fracture dominates when adhesion is strong. Composites with sufficiently large impact resistance cannot be prepared in the usual range of wood contents (50–60 wt%)

Methacrylic Acid Based Polymer Networks with a High Content of Unfunctionalized Nanosilica: Particle Distribution, Swelling, and Rheological Properties

The poor stability and tendency to agglomerate of unfunctionalized nano-SiO2 in the presence of ionic species presents a challenge for preparing poly(methacrylic acid)/nano-SiO2 nanocomposite (NC) hydrogels with desired strength and swelling capability. We proposed a facile and eco-friendly method for the preparation of PMAA/SiO2 NC hydrogels using unfunctionalized silica nanoparticles (NPs) in the form of a suspension. SEM and TEM analyses showed that the NP distribution in the polymer matrix highly depended on the particle concentration. At lower concentrations (up to 13.9 wt %), the NPs were uniformly dispersed as single nanoparticles. With an increase in NP concentration, homogeneously dispersed nanoscale aggregates were formed, while a further increase in the silica concentration led to the formation of homogeneous structures consisting of mutually interacting nanosilica particles coated with PMAA. Swelling experiments confirmed that the silica NPs behaved as adhesive fillers that interacted with PMAA chains, causing the formation of a thin polymer layer strongly adsorbed at the particle interface. The thicknesses of the adsorbed polymer layer, as well as the swelling kinetic parameters, were strongly influenced by nanoparticle size and concentration. Combining nanosilica and PMAA in the form of a soft hydrogel network provided stabilization of the NPs and ensured better mechanical properties of the obtained NC hydrogels compared to pure polymer matrix. The optimal loadings, necessary to ensure the most improved dynamical-mechanical properties, were found in the case of the formation of homogeneously dispersed, nanosized silica aggregates in a PMAA matrix