Barzegar Mahsa, Lorenz Linda F, Behrooz Rabi, Frihart Charles R
Department of Wood and Paper Science and Technology, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, Imam Reza Blvd, Noor 46414-356, Iran.
Forest Products Laboratory, USDA Forest Service, One Gifford Pinchot Drive, Madison, WI 53726-2398, USA.
Polymers (Basel). 2022 Mar 22;14(7):1272. doi: 10.3390/polym14071272.
The surprising lack of literature on using the very common wood adhesive polymeric methylenediphenyl diisocyanate (pMDI) with protein adhesives may be because of perceived poor improvement of protein wet strength. Reacting pMDI with the flour (soy or canola) before adding water unexpectedly improves wood bonding compared to adding the pMDI to an aqueous protein slurry. Mixing the liquid pMDI with the oilseed flour produces a free-flowing powder with up to 50% of pMDI to flour by weight. The mixture slowly reacts since the isocyanate band in the infrared spectra remains for several days but diminishes with time. Adding pMDI increases the dry and wet strength of wood bonds using Automated Bonding Evaluation System (ABES) testing and levels off at about 50%. Similarly, adding the polyamidoamine-epichlorohydrin (PAE) cross-linker to the oilseed flour increases dry and wet bond strength, but the effect levels off at about 20% of PAE. However, the combination of these two cross-linkers added to the flours results in greater dry and wet shear strength than either one alone. In addition to tests using ABES (ASTM D 7998), the increase in strengths is also observed-but with a diminished effect-in bonding plywood using the interior plywood strength test ASTM D 906.
关于将非常常见的木材粘合剂聚合亚甲基二苯基二异氰酸酯（pMDI）与蛋白质粘合剂一起使用的文献出人意料地匮乏，这可能是因为人们认为蛋白质湿强度的改善不佳。与将pMDI添加到蛋白质水溶液中相比，在加水之前让pMDI与面粉（大豆或油菜籽）反应，意外地改善了木材粘结效果。将液态pMDI与油籽粉混合可制得一种自由流动的粉末，其中pMDI与面粉的重量比高达50%。由于红外光谱中的异氰酸酯谱带会持续数天，但会随时间减弱，所以该混合物反应缓慢。使用自动粘结评估系统（ABES）测试发现，添加pMDI可提高木材粘结的干强度和湿强度，且在约50%时趋于平稳。同样，向油籽粉中添加聚酰胺多胺 - 环氧氯丙烷（PAE）交联剂可提高干粘结强度和湿粘结强度，但该效果在约20%的PAE时趋于平稳。然而，将这两种交联剂添加到面粉中，所产生的干剪切强度和湿剪切强度比单独使用任何一种都要高。除了使用ABES（ASTM D 7998）进行测试外，在使用室内胶合板强度测试ASTM D 906粘结胶合板时，也观察到了强度的增加——但效果有所减弱。
