†Forest Biopolymers Science and Engineering, Forest Products Laboratory, U.S. Forest Service, One Gifford Pinchot Drive, Madison, Wisconsin 53726, United States.
‡Analytical Chemistry and Microscopy, Forest Products Laboratory, U.S. Forest Service, One Gifford Pinchot Drive, Madison, Wisconsin 53726, United States.
ACS Appl Mater Interfaces. 2015 Apr 1;7(12):6584-9. doi: 10.1021/am5087598. Epub 2015 Mar 19.
Understanding and controlling molecular-scale interactions between adhesives and wood polymers are critical to accelerate the development of improved adhesives for advanced wood-based materials. The submicrometer resolution of synchrotron-based X-ray fluorescence microscopy (XFM) was found capable of mapping and quantifying infiltration of Br-labeled phenol-formaldehyde (BrPF) into wood cell walls. Cell wall infiltration of five BrPF adhesives with different average molecular weights (MWs) was mapped. Nanoindentation on the same cell walls was performed to assess the effects of BrPF infiltration on cell wall hygromechanical properties. For the same amount of weight uptake, lower MW BrPF adhesives were found to be more effective at decreasing moisture-induced mechanical softening. This greater effectiveness of lower MW phenolic adhesives likely resulted from their ability to more intimately associate with water sorption sites in the wood polymers. Evidence also suggests that a BrPF interpenetrating polymer network (IPN) formed within the wood polymers, which might also decrease moisture sorption by mechanically restraining wood polymers during swelling.
理解和控制胶黏剂与木材聚合物之间的分子尺度相互作用对于加速开发用于先进木质材料的改良胶黏剂至关重要。基于同步加速器的 X 射线荧光显微镜（XFM）的亚微米分辨率被发现能够对 Br 标记的酚醛（BrPF）渗透到细胞壁的情况进行成像和定量分析。对具有不同平均分子量（MW）的五种 BrPF 胶黏剂的细胞壁渗透情况进行了成像。对同一细胞壁进行了纳米压痕实验，以评估 BrPF 渗透对细胞壁湿热机械性能的影响。对于相同的重量吸收量，MW 较低的 BrPF 胶黏剂在降低水分引起的机械软化方面更有效。MW 较低的酚醛胶黏剂的这种更高效率可能是由于它们能够更紧密地与木材聚合物中的水分吸附位点结合。有证据还表明，BrPF 互穿聚合物网络（IPN）在木材聚合物内形成，这也可能通过在膨胀过程中机械约束木材聚合物来减少水分吸收。
