The manufacture of forest products with high physical and mechanical properties contribute to the development of the forest industry in obtaining more resistant products with potential in the construction sector. In this context, to contribute to the study of reconstituted panels this article discusses the manufacture of panels reinforced with recycled thermoplastics (WPC), which had as raw material sawdust of Pinus caribaea and as recycled thermoplastics polyethylene terephthalate, low-density polyethylene and polypropylene. The panels were obtained by extrusion and developed in four treatments with different proportions of raw material. Thickness swelling rates of the manufactured WPC were evaluated by immersing them in water at room temperature and monitoring thickness changes for several weeks. A swelling model developed by Saeed Kazemi Najafi was used to study the thickness swelling process of WPC. The WPC were characterized by thickness swelling, apparent density, static blending, longitudinal compression and tensile strength. The treatment with 50% sawdust and blend of all thermoplastics (T5) showed a tendency to reduce the thickness swelling because it absorbs 0.28% of water and maintains the balance of water absorption in 16.2% the apparent density was 1206 kgm-3. For the mechanical properties, the static blending, longitudinal compression and tensile strength are around 24.6, 142.4 and 32.8 MPa, respectively. These characteristics make a treatment the best response. Hence, is suggested this board be used for structural applications, such as interior or exterior walls, since the water absorption index is low and high mechanical properties allow being more resistant.

Pinus forests are the second most planted in Brazil and the wood obtained from them is mainly used as structural elements in the civil construction sector. The Brazilian standard that deals with calculations of wooden structures projects recommends the use of wood in the range of 10% to 20% of moisture content. Thus, this study aimed to present an investigation about the influence of moisture content on the static modulus of elasticity (MOEst) of wooden beams by transverse vibration tests. The MOEst was evaluated by static bending tests and transverse vibration tests for various moisture content. The transverse vibration test was performed in a free condition using an accelerometer and an impulse hammer, and the dynamic modulus of elasticity (MOEd) was determined from the frequency of the first bending vibration mode. A total of 20 wooden beams were obtained from freshly cut Pinus spp. logs with initial high moisture content were used, with nominal dimensions of 5 cm × 10 cm × 200 cm (thickness × width × length). It was observed that the MOEd is also affected by moisture content according to the non-linear regression model. There were significant changes in the dynamic modulus of elasticity (MOEd) for the moisture contents (M) below 25% (near the fiber saturation point - FSP).

This research aims to evaluate the physico-mechanical properties of wood-plastic composites produced with recycled polyethylene terephthalate, high-density polyethylene, low-density polyethylene and polypropylene, and sawdust from the following species: Pinus caribaea, Pinus cubensis, Cedrela odorata, Talipariti elatum and Eucalyptus sp. Composites were obtained by extrusion with dimension of 1,000 × 250 × 16 mm (length × width × thickness), through six treatments. The following physico-mechanical properties were evaluated: density, moisture content, water absorption and thickness swelling, compression, static bending and traction. Treatment 6 obtained the best results, with 1,060 kg m-3 density, 5.23% moisture content, 0.32% water absorption, and 0.18% thickness swelling. Compressive strength was 138.10 MPa, static bending 18.53 MPa, and traction 29.4 MPa. The technology developed has prospects for large-scale production.