The Influence of Thermal Processing on the Adhesion Bonding Strength of Cross-Laminated Timber
Abstract
Further investigation is needed on the adhesion bond characteristics of temperature-sensitive wood (TMW) under diverse production conditions, despite its increasing use as an exterior laminating medium in cross-laminated timber (CLT). This investigation aimed to improve joint-glue performance by refining production methods for integrated TMW CLT. This was accomplished by assessing the influence of five distinct construction tensions on the binding strength of one-component urethane (1C-PUR) in CLT panels constructed from TMW and unaltered yellow pigment (YP): 0.21, 0.50, 0.70, 1.03, and 1.40 MPa. This study aimed to achieve the three main objectives: firstly, to identify the ideal atmospheric pressure for the large-scale production of TMW-CLT; secondly, to employ academic microscopy to evaluate bondline depth and kinetic parameters of adhesive penetration; and thirdly, to analyze the effects of atmospheric pressure on shear resistance and wood rejection percentages (WFP). A control panel constructed entirely of untreated wood was contrasted with a hybrid screen that included TMW and unaltered YP lamellae.The shear strengths of the unaltered control samples were about 1.5 to 2.0 times greater than those of the TMW samples at pressures between 0.70 and 1.40 MPa. Regarding failure mechanisms, TMW mostly failed within the wooden foundation (yielding 90-100% WFP), whereas raw, untreated wood showed a broader spectrum of WFP ranging from 60-95%, depending on the pressure assessments. Although achieving 100% WFP at temperatures between 0.48 and 1.40 MPa, TMW’s shear resistance unexpectedly decreased as stress increased. This suggests that substantial clamping pressures might lead to structural impairment or minute cell wall fractures that remain undetectable by optical microscopy to In contrast, the unchanged YP exhibited a distinct relationship between elevated pressure and enhanced shear strength. Furthermore, across the pressure range of 0.70 to 1.40 MPa, the unaltered substrate absorbed 5.4 to 5.6 times more glue than the TMW, indicating deeper penetration. Microscopic analysis revealed that total penetration increased in direct correlation with rising pressure, while bonding line thickness declined as pressure intensified. It is important to note that effective penetration consistently rose, despite the deceleration of maximum penetration rise under heightened conditions. The findings indicate that a clamping pressure of 0.70 MPa is optimal for the commercial manufacturing of TMW-CLT, as it ensures adhesive penetration stability and maintains maximum shear strength.
Reference
Tiancheng Wang. (2026). The Influence of Thermal Processing on the Adhesion Bonding Strength of Cross-Laminated Timber. Elsevier BV. https://doi.org/10.2139/ssrn.7552825
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