Abstract
Tannins from Myrcia splendens from the Amazon rainforest were used for the first time in the formulation of a urea-tannin-formaldehyde (UTF) resin. The objective was to evaluate the effect of different tannin proportions on the glue line performance in Pinus sp. woods, glued with UTF adhesive. The tannins were extracted in a water bath, using 1500 mL of water and 100g of dry bark (liquor/bark 15:1), with addition of 3% Na2SO3, at a temperature of 70 °C for three hours. The adhesives formulations were based on the gradual replacement of mass of the urea-formaldehyde (UF) adhesive by tannin powder, totalizing four compositions and one control treatment. UTF adhesives were evaluated for their physicochemical properties, shear bond strength (wet and dry) and wood failure. The addition of M. splendens tannins to the urea formaldehyde adhesive promoted an increase in glue line strength. The proportion of 5.0% of tannins proved to be ideal in the formulation of the UTF adhesive, considering all the parameters evaluated. Thus, this study proves the potential use of Amazonian tannins from Myrcia splendens in the partial composition of more sustainable UTF adhesives.
Highlights
Wood-based panels are produced from the reconstitution of wood fibers, particles or veneers with formaldehydebased resins, under specific heat and pressure conditions
Commercial resins have some disadvantages related to price fluctuations, formaldehyde emission and environmental pollution (Shirmohammadli et al, 2018), this is because, when formulated, they depend on non-renewable petrochemical resources (Li et al, 2020), as for the release of formaldehyde to the environment, it can occur during and after the production of wood panels (Ferreira et al, 2019)
3.1 Adhesive properties The solids content (TS) is the fraction of the adhesive that polymerizes after pressing the wood
Summary
Wood-based panels are produced from the reconstitution of wood fibers, particles or veneers with formaldehydebased resins, under specific heat and pressure conditions These products are targeted for non-structural and structural uses, such as furniture, common housewares, cabinets, frames, doors, floors, "I" beams, and trusses (Santos et al, 2020; Ang et al, 2019). Constant inhalation of formaldehyde can cause damage to the respiratory and nervous system, eyes, and even lead to cancer and leukemia (Tang et al, 2011) These issues have encouraged the use of alternative chemicals to replace all or part of the petrochemical components of synthetic resins (Jia et al, 2020), especially if the change promotes reduced formaldehyde emissions and improves the adhesive's performance in this regard (Zhao et al, 2018)
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