Composite Flooring Quality of Combined Wood Species Using Adhesive from Merbau Wood Extract

Abstract

Polyphenol chemical components extracted from merbau (Intsia spp.) wood exhibit a strong affinity for resorcinol and formaldehyde in alkaline conditions, forming a copolymer that could serve as an adhesive. A liquid extract of merbau wood (M) was allowed to copolymerize with resorcinol (R) and formaldehyde (F) under alkaline conditions, with an M:R:F weight ratio of 100:5:10. The course of the reaction and potential mechanisms of copolymerization were scrutinized using Fourier transform infrared spectroscopy, X-ray diffraction, and differential thermal analysis. The adhesive was used to manufacture three-ply composite flooring consisting of a back layer of rubberwood (Hevea brasiliensis), a core layer from sengon (Paraserianthes falcataria) wood, and a face layer with one of seven wood species, namely, sengon, sungkai (Peronema canescens), mangium (Acacia mangium), rubberwood, mahogany (Swietenia spp.), kempas (Koompassia malaccensis), and merbau. The adhesive was spread on the face and back layers of 170 g/m2 single glue line, which was followed by pressing at 11 kg/cm2 for 3 hours at room temperature. After conditioning for 10 days, the resulting composite flooring was examined to assess its physical and mechanical properties, shear strength, and formaldehyde emission. Results revealed that the bioadhesive exhibited crystallinity of 23.32 percent and a melting glass transition of 115.31°C. IV-meter intrinsic viscosity tools were used to determine the product's molecular weight of 49,658. Physical–mechanical properties and shear quality of the composite flooring were similar to products that use synthetic phenolic adhesive and belong to the exterior quality type with E0 or F**** types of low formaldehyde emission.

Characterization of Merbau Extractives as a Potential Wood-Impregnating Material

“…The results of the UV-visible analysis in this study are presented in Fig. 1 Figure 1 shows that the liquid extract of merbau wood (λ=279 nm) consisted of conjugated or aromatic systems, similar to standard resorcinol (which was used as the reference), which had a wavelength (λ) of 274 nm. In previous work (Santoso et al 2014), similar spectra were found for different instruments of UV-vis spectroscopy. For example, the wavelength for merbau extractives (ME) was 279.5 nm, and the value was 273.5 for analytical resorcinol.…”

“…The wavelength difference between ME and standard resorcinol is acceptable because ME is a crude extract, not a pure substance. The previous study also revealed the crystallinity degree of ME at 20.86%, and its melting or glass transition temperature at 111 °C (Santoso et al 2014). All identifications indicated that ME consisted mostly of phenolic compounds, especially 1,3-benzenediolresorcin, commonly called resorcinol.…”

“…The table shows that extraction using organic solvents composed of 80% ethanol (polarity index 5.2) and 60% ethyl acetate (polarity index 4.4) resulted in much higher yields (12.45% and 12.56%, respectively) than that of hot water (polarity index 9.0), which gave a yield of 1.10%. The higher ethanol and ethyl acetate solvent yields can be explained by the fact that the polar and non-polar solvents dissolving more compounds, including tannins and other polyphenols, color pigments, volatile compounds, fat, resin, wax, gum, and starch (Santoso et al 2014). The density and viscosity of the extract from both solvents are also higher than that of hot water.…”

“…Tohmura (1998) showed that the addition of merbau extractives slightly increased the gelatinous rate of the phenolic resin. Santoso et al (2014) used liquid of merbau extract to form wood adhesives, utilizing a formaldehyde reaction. Applying the bio-adhesive to three-layer flooring caused the composite flooring's performance to be similar to flooring produced with synthetic phenolic adhesives, which are classified as exterior quality products with low formaldehyde emissions.…”

Properties of Laminated Composite Panels Made from Fast-Growing Species Glued with Mangium Tannin Adhesive

“…These adhesives are expensive and contain high levels of formaldehyde, and their availability will steadily decrease with time (Santoso et al 2014). Bio-adhesives that use renewable materials can substitute for synthetic adhesives in laminated composite manufacture.…”