Effect of surface treatment on the technological properties of coconut fiber-reinforced plant polyurethane composites

Polymeric composites reinforced with plant fibers have numerous advantages, such as low cost, high raw material availability and good physical, mechanical and thermal properties. Thus, in recent years, they have been studied as thermal insulation substitutes for synthetic polymers in buildings. The aim of this study was to evaluate the technological properties of castor oil-based polyurethane composites reinforced with coconut fibers treated with hot water, alkaline solutions of NaOH and Ca(OH)₂ and corona discharge and without surface treatment as materials for the thermal insulation of buildings. The composites were produced by the hand lay-up method followed by compression; 10% by weight coconut fibers were used to replace the synthetic polymer. Specimens were produced, and physical, mechanical, thermal and microstructural tests were performed. The results showed that the polymer had a thermal conductivity of 0.016 W/(mK), while the composites produced with fibers treated with NaOH had a thermal conductivity of 0.028 W/(mK); therefore, these polymers are considered insulating materials (k = 0.01 to 1.0 W/(mK)). Thus, the composites produced with coconut fibers can be considered as lighter, less expensive and environmentally friendly alternatives to synthetic polymers.

Cardanol-based adhesive with reduced formaldehyde emission to produce particleboards with waste from bean crops

Free formaldehyde is a carcinogen whose emission reduction in particleboard has been studied recently to mitigate this environmental and human health problem. One alternative to reduce the emission of formaldehyde in particleboards is by using adhesives produced from natural sources. Cardanol-formaldehyde is an environmentally friendly adhesive made with cashew nut liquid, a byproduct from the cashew chain. This work aimed to produce particleboard using cardanol-formaldehyde in place of urea. In addition, different proportions of bean straw wastes were used to replace pine wood. The combination of eco-friendly adhesive and lignocellulosic waste particles could result in a product that meets market demands while being environmentally nonaggressive. Cardanol-formaldehyde promoted a higher modulus of elasticity (MOE) (1172 MPa) and modulus of rupture (MOR) (4.39 MPa) about panels glued with urea-formaldehyde, which presented a MOE of 764 MPa and MOR of 2.45 MPa. Furthermore, the cardanol-formaldehyde adhesive promoted a 93% reduction in formaldehyde emission, with a reduction from 16.76 to 1.09 mg/100 g oven-dry board for particleboards produced with cardanol-formaldehyde, indicating potential as an adhesive in the particleboard industry.

Eco-friendly particleboard production from coconut waste valorization

Reusing agro-industrial waste does not only help to mitigate environmental impact but also enables valorization through the development of new products. The aim is to enhance the physical and mechanical properties of particleboard panels produced with Eucalyptus wood and different proportions of waste products-coconut fiber (Cocos nucifera L.). Physical properties (density, water absorption, and thickness swelling) and mechanical properties (static bending and internal bond resistance) were assessed, and panels reinforced with coconut fiber showed the best qualities with higher density, greater dimensional stability, and less water absorption. Static bending resistance and internal bond resistance also increased significantly. This demonstrated the potential of achieving compatible characteristics for civil construction and furniture production through the inclusion of waste material. The impact of this research is obtained from the utilization of an important agro-industrial residue in the manufacture of permanent composites.

Substitution of urea-formaldehyde by renewable phenolic compound for environmentally appropriate production of particleboards

In recent years, research has been conducted in search of alternative adhesives that are less harmful to human health and the environment. Cardanol derived from cashew nut shell liquid (CNSL) has attracted considerable attention due to its chemical and specific characteristics (antioxidant activity, flame resistance, and hydrophobicity). In this sense, this study aimed to evaluate the quality of particleboards using cardanol instead of urea-formaldehyde (UF) adhesive. Different percentages of cardanol were used (0, 20, 40, 60 and 80%) in which its physicochemical properties were evaluated. The panels were produced with particles of Pinus oocarpa and nominal density of 0.75 g/cm³, their physical and mechanical properties were evaluated, wood-adhesive interface evaluation with scanning electron microscopy (SEM), and the combustibility test. It is concluded that the maximum replacement of UF by cardanol is 5%, since, in this situation, the mentioned properties reach the established norms for the commercialization of the boards.

Influence of wood species and adhesive type on the performance of multilaminated plywood

The quality of plywood depends on factors such as the forest species and the adhesive used in their production, and understanding the interferences of these factors in the final properties of the plywood is of fundamental importance. The study aimed to develop multilayer plywood with two forest species and two types of adhesive and to evaluate the influences of these factors (forest species and adhesive) on the physical and mechanical properties of the plywood. The panels were produced with wood veneers of parica and pine with two types of adhesives, urea-formaldehyde and phenol-formaldehyde, with a weight of 150 g.m². Then, each set was pressed for 10 min under a specific pressure of 0.98 MPa at a temperature of 150 °C. Three panels were produced for each type of veneer and adhesive, totaling four treatments. The plywood was evaluated for physical properties (moisture content, bulk density, and water absorption) and mechanical properties (parallel and perpendicular static bending strength and shear strength). The results showed that the forest species had a greater influence on physical and mechanical properties, with the best results being observed for plywood produced with pine and PF adhesive. The specific mass of the panels should be considered as it positively influenced the mechanical properties and negatively impacted water absorption. The PCA was used to reduce the dimensionality of the data from 9 dependent variables to 2 main components, explaining 76.70% of the total variance of the data. The multivariate analyzes of the differentiated independent factors showed that both the species and the adhesive affected as properties of the plywood and both independent variables must be taken into account in the production of the plywood. It is concluded that the porosity and specific mass of the paricá veneers contributed to a greater penetration of the adhesives, resulting in lower physical and mechanical properties than the pine veneers. However, in general, it is concluded that the plywoods produced can be used for internal and external applications. However, it is not indicated for structural purposes as it did not meet the requirements of the NBR 31.000.001/2:2001.

Sustainable valorization of recycled low-density polyethylene and cocoa biomass for composite production

The development of products from wastes such as plastic and lignocellulosic materials brings great advantages from the economic and sustainable point of view. The use of waste, previously destined for disposal, enables the changes in production patterns, and prevents major environmental problems. This research investigated the inclusion of different contents of cocoa almond husk on the properties of composites with recycled low-density polyethylene (LDPE) matrix. The composites were produced by extrusion process with proportions: 0%, 10%, 20%, 30%, and 40% of cocoa waste reinforcement in the polymer matrix. The density of the composites decreased (from 0.81 to 0.61 g/cm3) with the addition of the lignocellulosic waste in the matrix. The hygroscopicity was increased, however, at considerably low levels (0.17 to 2.68 %). There was a decrease in composite strength and elongation, becoming the material more rigid. The use of the cocoa waste for composites production is feasible to use since it can be adapted to the required application and still incorporate additives requested for specific purposes. This research demonstrated that is possible the combination of recycled low-density polyethylene and lignocellulosic wastes for the production of materials with high added value.