Effect of Glue Spread on Bonding Strength, Delamination, and Wood Failure of Jabon Wood-Based Cross-Laminated Timber Using Cold-Setting Melamine-Based Adhesive

Abstract

Cross-laminated timber (CLT) has become a popular engineered wood product due to its innovative properties and rapid development, which involves the use of various wood species and adhesives. This study aimed to assess the effect of glue application on the bonding strength, delamination, and wood failure of CLT made from jabon wood and bonded with a cold-setting melamine-based adhesive at three different rates: 250, 280, and 300 g/m2. The adhesive was composed of melamine–formaldehyde (MF) by adding 5% citric acid, 3% polymeric 4,4-methylene diphenyl diisocyanate (pMDI), and 10% wheat flour. Adding these ingredients increased the adhesive viscosity and decreased the gelation time. The CLT samples, made using cold pressing in the melamine-based adhesive at a pressure of 1.0 MPa for 2 h, were evaluated as per the standard EN 16531:2021. The results revealed that a higher glue spread resulted in a greater bonding strength, lower delamination, and a higher wood failure. The glue spread was shown to have a more significant influence on wood failure compared with delamination and the bonding strength. The application of 300 g/m2 glue spread (MF-1) on the jabon CLT led to a product that met the standard requirements. The use of modified MF in cold-setting adhesive produced a potential product that could be a feasible option for future CLT production in terms of its lower heat energy consumption.

Surface Roughness, Dynamic Wettability, and Interphase of Modified Melamine Formaldehyde-Based Adhesives on Jabon Wood

“…The resulting mixture was then manually stirred for 1-2 min at 27 ± 2 • C, yielding a cold-setting melamine-based adhesive. According to a previously published study, the fundamental properties of the adhesives used in this study are shown in Table 1 [1]. The evaluation of wettability was performed through the measurement of the dynamic contact angle between the MF-based adhesives and the surface of Jabon wood.…”

“…The viscosity difference between the MF-0 and MF-I adhesives also exhibits an effect, alongside the initial contact angle and contact angle reduction ratio. The higher viscosity of MF-1 compared to MF-0 [1] hinders the absorption of the adhesive into the wood surface, resulting in a longer time required to reach the equilibrium contact angle. comparison to MF-0 (Table 1).…”

“…Adhesive quality is a critical component that must be meticulously evaluated during the production of laminated timber products [ 1 ]. In the manufacturing of wood products, surface preparation is a critical step preceding the gluing or finishing procedures [ 2 , 3 , 4 , 5 ].…”

“…Numerous adhesives can be used to fabricate laminated wood products such as urea formaldehyde (UF), phenol formaldehyde (PF), melamine formaldehyde (MF), melamine–urea formaldehyde (MUF), emulsion polymer isocyanate (EPI), and polyurethane [ 25 , 26 , 27 , 28 , 29 ]. Among them, MF adhesives are one type of adhesives ordinarily used to produce laminated wood products [ 1 , 26 , 27 , 29 ], such as cross-laminated timber (CLT), glued laminated timber (GLT), and laminated veneer lumber (LVL). Alongside PF adhesives [ 25 ], MF adhesives are extensively used in the production of semi-exterior- and exterior-grade wood-based panels [ 29 ].…”

“…Modifying formaldehyde-based adhesives is a remarkably effective strategy for increasing the economic advantages of these adhesives and preserving the environment [ 25 ]. A recent innovation concerning the modification of MF-based adhesives for CLT production from Jabon wood by means of cold-pressing application has been successfully developed [ 1 ]. Nevertheless, the specific attributes of the bonding mechanism between Jabon wood and MF-based adhesives have yet to be discovered.…”