Mining waste and coconut fibers as an eco-friendly reinforcement for the production of concrete blocks

Using mineral and agro-industrial wastes associated with the cement matrix can add value and guarantee suitable properties for reinforced composites. This research aimed to evaluate the effect of the incorporation of quartzite and coconut fibers on masonry blocks' physical, mechanical, and thermal properties. Quartzite was evaluated replacing 0%, 25%, 50%, 75%, and 100% of the sand, whereas the coconut fibers were added in a proportion of 2.5% of the volume of gravel. Quartzite residues were analyzed regarding their granulometry, chemical composition, and pozzolanicity. The block initial formulation (control) was: 8.2% cement, 45.9% sand, and 45.9% gravel. The cement was cured at room temperature for 28 days. Subsequently, the blocks were subjected to the characterization of physical, mechanical, and thermal properties. Coconut fibers presented a low percentage of extractives, with a low inhibition index (1.93%), reducing their effect on cement hardening. The increase in the content of quartzite incorporated provided a reduction in bulk density and an increase in porosity (from 11.7 to 16.0%) and water absorption after 24 h (from 7.0 to 8.5%). The compressive strength was reduced from 50% with the insertion of the quartzite. The quartzite and coconut fibers reduced the concrete's thermal conductivity, providing essential reflections for the performance of the blocks in terms of thermal comfort in built environments. Further, incorporating these materials provided the potential to obtain blocks with characteristics of resistance and offering possible thermal comfort, besides contributing as an option for a destination for these mineral and agro-industrial wastes.

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.

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.

Copaiba oil and vegetal tannin as functionalizing agents for açai nanofibril films: valorization of forest wastes from Amazonia

The applicability of cellulose nanofibrils (CNFs) has received attention due to their attractive properties. This study proposes the functionalization of açai CNFs with copaiba oil and vegetal tannins to produce films with potential for packaging. Bio-based films were evaluated by vapor permeability, colorimetry, and mechanical strength. CNFs were produced by mechanical fibrillation, from suspensions of bleached açai fibers and commercial eucalipytus pulp. Moreover, copaiba oil and vegetal tannin were added to the CNFs to produce films/nanopapers by casting from both suspensions with concentrations of 1% (based on CNF dry mass). The bulk densities of the eucalyptus CNF films were higher (1.126-1.171 g cm^-3) compared to the açai CNF ones. Films from eucalyptus and açai pulps containing copaiba oil and tannins presented higher Tonset and Tmax, respectively (312 and 370 °C). Films with açaí CNFs functionalized with copaiba oil and tannin showed the lowest permeability value (370 g day^-1 m^-2). Films produced with eucalyptus pulp, and eucalyptus pulp functionalized with copaiba oil highlighted by superior mechanical strength, achieving 133.8 and 121.4 MPa, respectively. The evaluation of colorimetry showed a greater tendency to yellowing for açai films, especially those functionalized with vegetal tannins. Besides the low cost, functionalized vegetal-based nanomaterials could have attractive properties, with potential for application as some kind of packaging, for transporting basic products, such as breads, flours, or products with low moisture content, enabling efficient utilization of forest wastes.

Bio-based films/nanopapers from lignocellulosic wastes for production of added-value micro-/nanomaterials

The growing demand for products with lower environmental impact and the extensive applicability of cellulose nanofibrils (CNFs) have received attention due to their attractive properties. In this study, bio-based films/nanopapers were produced with CNFs from banana tree pseudostem (BTPT) wastes and Eucalyptus kraft cellulose (EKC) and were evaluated by their properties, such as mechanical strength, biodegradability, and light transmittance. The CNFs were produced by mechanical fibrillation (after 20 and 40 passages) from suspensions of BTPT (alkaline pre-treated) and EKC. Films/nanopapers were produced by casting from both suspensions with concentrations of 2% (based in dry mass of CNF). The BTPT films/nanopapers showed greater mechanical properties, with Young's modulus and tensile strength around 2.42 GPa and 51 MPa (after 40 passages), respectively. On the other hand, the EKC samples showed lower disintegration in water after 24 h and biodegradability. The increase in the number of fibrillation cycles produced more transparent films/nanopapers and caused a significant reduction of water absorption for both raw materials. The permeability was similar for the films/nanopapers from BTPT and EKC. This study indicated that attractive mechanical properties and biodegradability, besides low cost, could be achieved by bio-based nanomaterials, with potential for being applied as emulsifying agents and special membranes, enabling more efficient utilization of agricultural wastes.

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.

Potential destination of Brazilian cocoa agro-industrial wastes for production of materials with high added value

This research proposed to investigate a possible destination for the cocoa waste as component in the core layer of Medium Density Particleboards (MDPs) and to evaluate the effect of the waste insertion on the physical-mechanical properties of the panel. The core layers of the MDPs were composed by different percentages of cocoa wastes (0, 25, 50, 75 and 100%) in combination with pine wood. The targeted density of the panels was pre-established in 0.7 g cm^-3, bonded with urea-formaldehyde. The cocoa waste showed higher extractives content (34.8%) when compared with the pine wood (4.0%). The inclusion of the waste did not cause a significant difference in the moisture and bulk density of the panels; however, there was an increase in water absorption 24 h (71-105%) and thickness swelling 24 h (13-35%). Despite the values of the mechanical properties decreased in general, in low percentages, the cocoa waste does not prevent the use of the MDPs as furniture for internal environments. The results show that the cocoa waste has potential for being applied as raw material in the core layer of the MDP, in percentages up to 21%. The lignocellulosic wastes are promising alternatives for the achievement of the required current context of the sustainability and should be highlighted with research focused on their management for the development of added value materials.

Preparation of Cellulose Nanofibrils from Bamboo Pulp by Mechanical Defibrillation for Their Applications in Biodegradable Composites

There is a growing interest in cellulose nanofibrils from renewable sources for various industrial applications. However, there is a lack of information on cellulose arising from bamboo pulps. Nanofibrils from refined bamboo pulps, including bleached, unbleached, and unrefined/unbleached, were obtained by mechanical defibrillation for use in biodegradable composites. The influence of industrial processes, such as pulping and refining of unbleached pulps, as well as of alkali pretreatments and bleaching of refined pulps, on the chemical composition of the samples was analyzed. Morphological, structural, thermal, optical and viscometric properties were investigated as a function of the number of passages of refined/bleached suspensions through a defibrillator. For the unbleached suspensions, the effects of refining and bleaching on the properties of nanofibrils were evaluated, fixing the number of passages through the defibrillator. Microscopic studies demonstrated that nanoscale cellulose fibers were obtained from both pulps, with a higher yield for the refined/bleached and refined/unbleached pulp, at the expense of the unbleached/unrefined pulps. The study showed that, in addition to the effectiveness of the pre-treatments, there was an increase in the production efficiency of nanofibrils, as well as in the transparency of the bleached suspensions, while viscosity, thermal stability and crystallinity had reduced levels as the number of passages through the defibrillator increased, showing a gradual improvement in the transition from the micro- to the nano-scale. The present study contributed to the different methods that are available for the production of bamboo cellulose nanofibrils, which can be used in the production of biodegradable composites for various applications.

CARACTERÍSTICAS DAS DIMENSÕES DAS FIBRAS E ANÁLISE DO ÂNGULO MICROFIBRILAR DE Toona ciliata CULTIVADA EM DIFERENTES LOCALIDADES

O presente trabalho teve como objetivos determinar as dimensões das fibras e avaliar o ângulo microfibrilar da madeira de cedro australiano aos 4 anos de idade, no sentido axial base–topo, proveniente dos municípios de Cana Verde, Campo Belo e Santo Antônio do Amparo, localizados na região do sul de Minas Gerais. A partir da altura comercial de cada árvore, foi retirada uma tábua com 5 m de comprimento, da qual foram retiradas amostras em três posições: base, 50 e 100%. Os elementos anatômicos foram mensurados por meio de análise de imagens. Conclui-se que a correlação do AMF com a parede e lume das fibras foi positiva, sendo negativa apenas a interação AMF com o comprimento das fibras em Cana Verde. Em Santo Antônio do Amparo a correlação foi baixa. Não houve um padrão definido da variação no ângulo microfibrilar com as dimensões das fibras no sentido axial por município. As dimensões das fibras apresentaram características semelhantes às do eucalipto. Estudos complementares são necessários para um melhor direcionamento do uso da espécie.Palavras-chave: Dimensões das fibras; ângulo microfibrilar; Toona ciliata. AbstractFibers dimensions characteristics and microfibril angle analisys of Toona ciliata cultivated at different places. The objective of this work was to determine the fibers dimensions and to evaluate the microfibril angle of the wood of Australian cedar with 4 years of age, in the axial direction base–top, proceeding from the municipal districts of the Cana Verde, Campo Belo and Santo Antonio do Amparo, located in the region of the South of Minas Gerais. From the commercial height of each tree, a board with 5 m of length was removed, from this board it was taken samples in three positions: base, 50 and 100%. The anatomical elements were measured through image analysis. Concluded that: the correlation of the AMF with the wall and fire of fibers dimensions was positive and negative only interaction AMF with the fiber length in municipal districts of Cana Verde and in Santo Antonio do Amparo, was low. Top for municipal district did not have a definite standard of variation in the microfibril angle with the fibers dimensions in the axial direction from municipal district. The fibers dimensions presented similar characteristics of the eucalipto. Complementary studies are necessary for one better aiming of the use of the species.Keywords: Fiber dimensions; microfibril angle; Toona ciliata.