The use of cellulosic fibers in composites is advantageous compared to inorganic materials, because they present lower density, abrasiveness and cost, besides the renewable origin. This study aimed to evaluate the influence of wood pulp obtained by the chemical (bleached and unbleached) and mechanical process, and wood-flour of Pinus taeda as reinforcement in low density polyethylene (LDPE) matrix. The composites were extruded and the specimens molded by compression. The samples were characterized by thermal analysis, density, mechanical properties and scanning electron microscopy (SEM). The incorporation of the wood pulps and the wood flour in the matrix improved the composites mechanical properties and reduced the rate of material degradation. All fibers types acted as nucleating agents because the composites had better mechanical properties than pure LDPE. There was influence of the studied parameters on tensile and flexural strength and the interactions were significant. In general, the highest values of strength and stiffness were obtained with the use of thermo-mechanical process pulp as reinforcement and the lowest values with the use of unbleached chemical process pulp. micrographs analysis showed that the coupling agent was effective for compatibilizing the wood fibers with the LDPE in the composites. It was possible to produce composite materials with good physical and mechanical properties and improved thermal stability by experimental model.

The objective was to evaluate the production process of polymer-fiber composites, by means of pressing, using low density polyethylene (LDPE) reinforced with wood flour in two granulometries and coconut fibers. The physical and mechanical properties of the molds produced were evaluated. In the process, it was used as a LDPE matrix in a virgin and recycled mixture reinforced with “thick” pine wood flour obtained in forestry industries in the city of Irati-PR, “fine” pine wood flour and coconut fiber provided by Inbrasfarma Ltda. The LDPE was mixed with each reinforcement, together with a coupling agent (Polybond 3009), and the mixtures were then processed using a twin screw extruder. The mixture was molded by compression, resulting in a series of pressed specimens, which were subjected to tensile, bending and hardness tests. The evaluation of the results showed that the addition of wood reinforcement to plastic, in general, increased the mechanical properties of the composite while the coconut fiber reinforcement was favorable only to flexion. There were significant differences in the properties of the composites due to the studied compositions.

The growing demand for polymeric materials makes them significant in both industry and the environment, and the task of making them sustainable is becoming increasingly challenging. Cellulose presents an opportunity to minimize the effect of non-degradable materials. Cellulose nanofiber (CNF) is part of a class of cellulose fibers with superior performance due to its high strength and stiffness combined with low weight and biodegradability. This work aimed to produce composites using Low Density Polyethylene (LDPE) as matrix and CNF from Pinus sp. (Pinus) and Eucalyptus sp. (Eucalyptus) as reinforcement. The CNF were obtained by mechanical defibrillation of the cellulose, subsequently the water was removed by centrifugation to then produce a master with CNF and LDPE using a thermokinetic homogenizer. The master was milled and blended with LDPE to obtain booster concentrations of 1, 2 and 3 percent by weight (wt. %). To characterize the composite, tensile and flexural tests, thermal and rheological analysis were performed. As a result, an increase of between 3 and 4% in the crystallinity of the composite was evidenced with the addition of Pinus CNF and a reduction of 2 to 3% in the crystallinity index with the addition of Eucalyptus CNF. Thermal stability increased for all compositions. For mechanical properties, increasing the CNF content increased the stiffness and tensile strength. In general, it was found that the process is an effective alternative to produce composites of LDPE with cellulose nanofibers.