How does the type of adhesive affect the delamination behavior of cross laminated wood under radiant heat

Research Background and Objective

Heat Induced Delamination (HID) is a phenomenon in engineering wood products: before the carbonization front advances to the bonding line interface, the bonded wood layers may have already undergone debonding. For engineering wooden components widely used in the fields of architecture and home decoration, this early layering will directly affect the load-bearing and fire resistance performance of the components. A study published in Fire and Materials correlated the thermal degradation behavior of two 1-c polyurethane adhesives at the microscale with the thermal water mechanical behavior of cross laminated wood (CLT) tensile shear lap samples at the mesoscale, attempting to clarify the relationship between adhesive type and thermally induced delamination.

Experimental design and evaluation indicators

The performance indicators studied include failure mode, failure time, and bonding line temperature at the time of failure.

. The variable settings cover three aspects: adhesive type (standard adhesive Loctite HB S, and an improved high-temperature performance adhesive Loctite HB X), initial moisture content, and severity of heat exposure. At the micro level, differential scanning calorimetry (DSC) and dynamic thermo mechanical analysis (DTMA) were used to characterize the thermal degradation behavior of adhesives, and correlation analysis was conducted with the mechanical response of mesoscale samples.

Main results

The results showed that both types of adhesives exhibited thermally induced delamination.

. The temperature at the time of failure is affected by changes in heat flux intensity and initial moisture content. The study also established a corresponding relationship between the thermal degradation characteristics revealed by microscopic analysis and the results of mesoscale experiments. The above results indicate that even with adhesives with improved high-temperature performance, delamination cannot be completely avoided under the action of radiation heat flow. Both thermal exposure conditions and moisture content are important factors affecting the failure temperature.

Significance for polymer additives and building materials industry

From a material perspective, this study suggests that the heat resistance performance of adhesives used in engineering wood structures needs to be evaluated in the context of actual heat exposure conditions and moisture content fluctuations, rather than solely based on a single high-temperature performance indicator.

. For building and home decoration material systems, similar weather resistance and thermal aging concepts are also applicable to other polymer building materials that are exposed to heat, light, and moisture environments for a long time. For example, PVC profiles need to rely on weather resistant and stable systems to delay aging in outdoor applications, where the combination of antioxidants and light stabilizers directly affects the color and mechanical retention of the product under long-term light and temperature cycling; When designing the formula for waterproof and architectural coatings, sealants, and other materials, it is also necessary to comprehensively consider the synergistic effects of thermal oxidative aging and photoaging. The combination of micro thermal analysis and mesoscale mechanical testing provided by this study has methodological reference value for evaluating the heat resistance behavior of adhesive and sealing systems in the field of building materials.

Research Information

Source:Fire and Materials, paper title “Influence of Adhesive Type on Heat Induced Delamination in Tension Loaded Shear Lap Cross Laminated Timber Samples Exposed to Radiant Heat Flux”, DOI: 10.1002/fam.70041.

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Information source:Influence of Adhesive Type on Heat Induced Delamination in Tension Loaded Shear Lap Cross‐Laminated Timber Samples Exposed to Radiant Heat Flux， Organized by Herun Chemical.