Abstract Tailored crystalline and amorphous powdered polylactic acid (PLA) bio-renewable green polymers were studied for their use as adhesive for the joining of 2 and 3-ply veneers to produce and test plywood panels for strength, substrate failure and water soak resistance properties per ANSI/HPVA standards. For 3-ply construction Douglas Fir (DF) was used for the core whereas, Southern Pine (SP) veneer was used for the faces per sponsor specifications. It was found that heat or ionizing radiation tailored crystalline and amorphous type PLA-based adhesive resin formulations can both offer adequate strength as measured by the attained shear stress [ranging through ~3.4 MPa (500 psi)], and degree of substrate failure (50–90%) for a range of adhesive loadings ranging from 85 g/m2 to 300 g/m2. Highest shear strength values approaching 500 psi were obtained with emulsion spray based application using amorphous PLA in the 125–250 μm range. For 2-ply samples prepared with either crystalline or amorphous PLA adhesive, both offered satisfactory strength and soak resistance. Successful dry shear strength and 3-cycle soak water resistance under standard conditions were possible to achieve with amorphous PLA formulation for both 2-ply and 3-ply plywood samples. 3-ply tests with panels using crystalline form PLA adhesive formulation did not meet 3-cycle resistance metrics even with 300 g/m2 adhesive loading; although, 1-cycle soak resistance was possible. The superior performance of the amorphous formulation is deemed to arise out of improved wetting and substrate penetration due to its x10 higher melt index and x3 lower relative viscosity as compared with the crystalline form polymer adhesive. Plywood samples prepared with PLA formulations (as yet without cross-linking or strength tailoring), did not survive boiling water testing metrics as would be required of Type I (exterior grade) plywood. However, the research results indicate that ANSI/HVPA metrics for Type II (interior grade) plywood are attainable using the as-formulated amorphous form PLA based adhesive and the associated application methods described in the paper.

中文翻译：

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使用结晶/无定形 PLA 聚合物粘合剂的胶合板木基复合材料

摘要 研究了定制的结晶和无定形粉末状聚乳酸 (PLA) 生物可再生绿色聚合物作为粘合剂用于连接 2 层和 3 层单板，以生产和测试胶合板面板的强度、基材失效和耐水浸泡性能。 ANSI/HPVA 标准。对于 3 层建筑，花旗松 (DF) 用于核心，而南方松 (SP) 单板用于根据赞助商规格的表面。研究发现，热或电离辐射定制的结晶型和非晶型 PLA 型粘合剂树脂配方均可提供足够的强度，如通过所获得的剪切应力 [范围为 ~3.4 MPa (500 psi)] 和基材失效程度 (50 –90%) 适用于 85 g/m2 至 300 g/m2 的一系列粘合剂负载。使用 125-250 μm 范围内的无定形 PLA，通过基于乳液喷涂的应用获得接近 500 psi 的最高剪切强度值。对于用结晶或无定形 PLA 粘合剂制备的 2 层样品，两者都提供了令人满意的强度和耐浸泡性。对于 2 层和 3 层胶合板样品，使用无定形 PLA 配方可以在标准条件下实现成功的干剪切强度和 3 次循环浸泡耐水性。使用结晶形式 PLA 粘合剂配方的面板的 3 层测试即使在 300 g/m2 粘合剂负载下也不能满足 3 循环电阻指标；尽管如此，1个周期的耐浸泡是可能的。与结晶形式的聚合物粘合剂相比，无定形配方的优异性能被认为是由于改进了润湿性和基材渗透性，因为它的熔体指数高 10 倍，相对粘度低 3 倍。使用 PLA 配方（尚未经过交联或强度调整）制备的胶合板样品无法通过 I 型（外用级）胶合板所需的沸水测试指标。然而，研究结果表明，使用按配方配制的无定形形式 PLA 粘合剂和论文中描述的相关应用方法，可以达到 II 类（室内级）胶合板的 ANSI/HVPA 指标。未能通过 I 型（外饰级）胶合板所需的沸水测试指标。然而，研究结果表明，使用按配方配制的无定形形式 PLA 粘合剂和论文中描述的相关应用方法，可以达到 II 类（室内级）胶合板的 ANSI/HVPA 指标。未能通过 I 型（外饰级）胶合板所需的沸水测试指标。然而，研究结果表明，使用按配方配制的无定形形式 PLA 粘合剂和论文中描述的相关应用方法，可以达到 II 类（室内级）胶合板的 ANSI/HVPA 指标。