Electron-Beam-Initiated Polymerization of Poly(ethylene glycol)-Based Wood Impregnants

The current study demonstrates that methacrylate and acrylate poly(ethylene glycol) (PEG) functional oligomers can be effectively impregnated into wood blocks and cured efficiently to high conversions without catalyst by e-beam radiation, allowing for less susceptibility to leaching, and favorable properties including higher Brinell hardness values. PEG based monomers were chosen because there is a long history of this water-soluble monomer being able to penetrate the cell wall, thus bulking it and decreasing the uptake of water which further protects the wood from fungal attack. Diacrylate dimethacrylate and dihydroxyl functional PEG of M-v, 550-575 of concentration 0-30, 60 and 100 wt % in water, were vacuum pressure impregnated into Scots Pine blocks of 15 x 25 x 50 mm in an effort to bulk the cell wall. The samples were then irradiated and compared with nonirradiated samples it was shown by IR, DSC that the acrylate polymers were fully cured to much higher conversions than can be reached with conventional methods Leaching studies indicated a much lower amount of oligomer loss from the cured to much higher conversions than can be reached with conventional methods functional PEG indication a high degree of fastening of the polymer in the wood. The Brinell hardness indicated a significant increase in hardness to hardwood levels in the modified samples compared to the samples of hydroxyl functional PEG and uncured vinyl PEC samples, which actually became softer than the untreated Scots Pine. By monitoring the dimensions of the sample it was found by weight percent gain calculations WPC %) that water helps to swell the wood structure and allow better access of the oligomers into the cell wall as this was not observed for methyl methacrylate which is well-cocumented to remain in the lumen. However dimensional stability of the viny ploymer modified blocks when placed in water was not observed to the same extent as PEG.