Subject to this study is the modification of an experimental two-component polyurethane (2C PUR) as an alternative adhesive for structural hardwood bonding. The 2C PUR has been adapted by calcium carbonate as filler to increase its modulus of elasticity with the aim of increasing the modulus analogue to the ones typically observed for classic amino- and phenol based adhesives. The 2C PUR system was compared with a commercial one-component polyurethane (1C PUR) and a phenol resorcinol formaldehyde (PRF) adhesive. The wetting properties of the adhesives were tested in terms of surface tension, polar and dispersive part and contact angle on European beech wood (Fagus sylvatica L.). In addition, adhesive polymer films of 2C PUR were tested for tensile strength and modulus of elasticity (E-Modulus) following ISO 527-1. The adhesives bond performance on beech wood was determined by lap-joints according to EN 302-1 in various climate conditions. The results show that 2C PUR has proper wettability properties on beech wood. Adding 60% wt filler to the polyol component increased the E-Modulus from 2.3 GPa (0%) to 4.4 GPa. The tensile strength of the modified 2C PUR polymer films was comparable with the industrial 1C PUR. Tensile shear strength and wood failure percentage of 2C PUR lap-joints were increased by adding filler and met requirements in dry and re-dried conditions according to EN 302-1. However, the addition of filler didn’t result in an improvement in wet conditions. The present study shows sufficient performance for bonding hardwood with 2C PUR in dry conditions, while the system still needs to be improvement regarding its performance in humid conditions.

中文翻译：

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用于结构性硬木粘结的二组分聚氨酯胶粘剂的弹性模量的改性

这项研究的主题是实验性的二组分聚氨酯（2C PUR）的改性，作为结构性硬木粘结的替代粘合剂。2C PUR已被碳酸钙用作填充剂，以增加其弹性模量，目的是将模量类似物提高到典型的传统氨基和酚基胶粘剂所观察到的模量类似物。将2C PUR系统与商用单组分聚氨酯（1C PUR）和苯酚间苯二酚甲醛（PRF）粘合剂进行了比较。根据表面张力，极性和分散部分以及在欧洲山毛榉木（Fagus sylvatica L.）上的接触角测试了粘合剂的润湿性能。另外，按照ISO 527-1测试了2C PUR的粘合聚合物膜的拉伸强度和弹性模量（E-模量）。根据EN 302-1，在各种气候条件下，搭接接头确定了山毛榉木上粘合剂的粘合性能。结果表明2C PUR在山毛榉木上具有适当的润湿性。向多元醇组分中添加60％wt的填料可使E模量从2.3 GPa（0％）增加到4.4 GPa。改性的2C PUR聚合物薄膜的拉伸强度与工业1C PUR相当。通过添加填料可以提高2C PUR搭接接头的拉伸强度和木材破坏率，并符合EN 302-1在干燥和重新干燥条件下的要求。但是，添加填料并不能改善潮湿条件。本研究表明，在干燥条件下，用2C PUR粘合硬木具有足够的性能，而在潮湿条件下，该系统仍需改进。