No abstract

Compared to other fibrous materials, plant fibers can act as a reinforcement in plastics due to their relatively high strength and rigidity, low cost, low density, biodegradability, and renewability. In this context, this study examines the effect of the particle size and content of white oak wood flour (Quercus laeta Liemb), obtained from its branches, on the properties of commercial polypropylene. In Mexico, wood from the branches of Quercus laeta Liemb is barely utilized despite its abundance and viability. The main objective of this study is to demonstrate that this waste material can be exploited to prepare useful materials, in this case composites with competitive properties. Tensile and flexural tests, as well as impact strength and melt flow index were evaluated. In addition, density and water absorption capacity were also tested. Results showed that the water absorption increased with the incorporation of wood particles. Mechanical properties were strongly influenced by particle content. A reduction in elongation and strength was observed, while Young’s modulus and flexural modulus increased with the incorporation of wood particles. Impact strength increased with particle size and particle content.

The effects of size and concentration of wood particles on the properties of composites, obtained by extrusion, were evaluated based on polystyrene and wood particles from Eucalyptus globulus Labill. Woodplastic ratios were 10:90, 30:70, and 50:50 (weight / weight), and wood particles were retained in 40, 50, 65, and 100-mesh sieves. The density, flow index, water absorption, and the mechanical properties were evaluated. Scanning electron microscopy revealed poor adhesion between the wood particles and the polystyrene. The size and content of wood particles were found to have a strong influence on the mechanical properties of the composite. The introduction of the wood particles induced a reduction of the Young's modulus, ultimate strength and deflection, as well as an increment in the elongation at break. The impact resistance also increased with the size and concentration of the wood particles. Furthermore, with increasing content of wood particles, the value of the melt flow index decreased and the water absorption rose. .

Nanocrystalline cellulose (NCC) was prepared from Agave tequilana Weber blue variety via acid hydrolysis. The NCC was used in forming acrylic acid/acrylamide hydrogels (AA/AM), (80/20 w/w), crosslinked with N-N-methylene bisacrylamide (MBA) at addition levels of 1, 2, 4, and 8 wt% of the monomeric phase. The NCC was dosed at 0.1, 0.5, and 1.0 wt%. Two synthesis routes were used. In the first route, polymerization was performed immediately after mixing the components. In the second route, the mixture of the components was kept at 2 °C ± 1 °C for 24 h before the polymerization (thermal treatment). All the hydrogels were characterized by nuclear magnetic resonance (NMR), water absorption tests, scanning electron microscope (SEM) analysis, and rheology tests. The NCC particles had a diameter of approximately 75 nm. The hydrogels that were subjected to the thermal treatment reached the equilibrium after approximately 72 h. The un-treated hydrogels reached the equilibrium after approximately 58 h. The thermally treated samples had a lower swelling degree and the swelling degree decreased as the crosslinking degree and the NCC concentration increased. The swelling kinetics followed the Schott´s pseudo-second-order.

In this work, a photo-polymerization route was used to obtain potassium acrylate-co-acrylamide hydrogels with enhanced mechanical properties, well-defined microstructures in the dry state, and unique meso- and macrostructures in the hydrated state. The properties of the hydrogels depended on the concentration of the crosslinking agent. Mechanical properties, swelling capacity, and morphology were analyzed, showing a well-defined transition at a critical concentration of the crosslinker. In terms of morphology, shape-evolving surface patterns appeared at different scales during swelling. These surface structures had a noticeable influence on the mechanical properties. Hydrogels with structures exhibited better mechanical properties compared to unstructured hydrogels. The critical crosslinking concentration reported in this work (using glycerol diacrylate) is a reference point for the future preparation of multistructured acrylic hydrogel with enhanced properties.