The demand for debondable adhesives is becoming more urgent, as countries begin implementing policies to enforce circularity and recyclability. Specifically in the construction industry, the switch from carbon pool-depleting materials to carbon pool-replenishing materials demonstrates the importance of circularity for the high-demand wood species used to produce engineered wood products. To this end, a dual chemical and physical debonding adhesive was prepared with the intent to debond solid wood specimens. The one-pot synthesis of a poly(urethane urea) (PUU) adhesive was prepared with a thermoresponsive furan maleimide (FM) Diels–Alder adduct capable of dissociating at temperatures above 90 °C coupled with thermally expanding microspheres (MS). First, PUU polymer films containing only FM bonds and a second control adhesive with a butyl spacer replacing the thermoresponsive FM bond were prepared and characterized. Next, simple single wooden lap specimens were prepared by using the PUU adhesives to investigate bonding and debonding via a lap shear test. Adhesives containing only FM bonds or MS were tested to investigate the effect of a chemical versus physical debonding mechanism on the bond strength of the glued specimens. Next, the combination of FM bonds and MS was incorporated to combine chemical and physical debonding mechanisms, respectively, which resulted in the most drastic reduction in tensile shear strength of the glued specimens by 71%.

中文翻译：

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聚（聚氨酯脲）热固性粘合剂的按需化学和物理脱粘，促进工程木制品的回收


随着各国开始实施加强循环和可回收性的政策，对可脱粘粘合剂的需求变得更加紧迫。特别是在建筑行业，从消耗碳库的材料到补充碳库的材料的转变表明了循环性对于用于生产工程木制品的高需求木材品种的重要性。为此，制备了化学和物理双重脱粘粘合剂，以脱粘实木样本。采用能够在高于 90 °C 的温度下解离的热响应性呋喃马来酰亚胺 (FM) Diels-Alder 加合物与热膨胀微球 (MS) 结合，一锅法合成了聚（聚氨酯脲）(PUU) 粘合剂。首先，制备并表征了仅包含 FM 键和带有丁基间隔基的第二控制粘合剂的 PUU 聚合物薄膜，该粘合剂取代了热响应 FM 键。接下来，使用 PUU 粘合剂制备简单的单木搭接样本，通过搭接剪切测试研究粘合和脱粘。对仅包含 FM 键或 MS 的粘合剂进行了测试，以研究化学脱粘机制与物理脱粘机制对胶合样品粘合强度的影响。接下来，将 FM 粘合和 MS 结合起来，分别结合化学和物理脱粘机制，导致胶合样品的拉伸剪切强度大幅降低 71%。