马尾松防腐材胶合性能的径向变异研究

Radial variation in bonding performance of preservative-treated Pinus massoniana wood

胶合性能径向变异的研究可为马尾松防腐集成材的原料选取提供重要依据。以35年生马尾松为试验用材,选用季铵铜防腐剂和间苯二酚-苯酚-甲醛树脂胶黏剂制备防腐材胶合试件,并检测其拉伸剪切强度及木破率,研究胶合性能的径向变异,从木材密度和胶黏剂渗透性能两方面分析胶合性能变化的原因。结果表明:沿髓心至树皮方向,马尾松防腐材剪切强度呈现出先增加(1~13 a)而后趋于稳定(≥14 a)的变化规律,不同部位对应的木破率均在90%以上,未表现出显著差异;木材密度(0.493~0.572 g/m^(3))沿径向的变化趋势与剪切强度一致,且两者之间呈较强的线性正相关性(Pearson相关系数为0.659),而径向不同部位对应的胶黏剂平均渗透深度(76.65~88.01μm)之间无显著性差异。成熟材区域对应的马尾松防腐材的胶合性能明显优于幼龄材区域,因而在生产集成材时应优先选择14年生以上的成熟材为原料。木材密度是马尾松防腐材胶合剪切强度出现明显径向变异的重要影响因子,而胶黏剂在木材中的渗透性能对其影响较小。

Pinus massoniana is one of the most widely used wood species in the forestry industry in China.P.massoniana wood has excellent mechanical properties and meets the structural material requirements,however,the drawbacks,including vulnerability to insects and fungi,multiple knots,and easiness of cracking and deforming,restrict its applications as high-performance structural materials.The preservative-treated glued laminated timber of P.massoniana wood therefore becomes one of the most promising products for structural applications,resulting in that the radial variation of wood bonding performance becomes an important index for evaluating the preservative-treated P.massoniana glued laminated timber.In this study,35-year-old P.massoniana trees were used as experimental materials,and bonding joints of the preservative-treated wood were prepared using the amine copper quart(ACQ)and reso-rcinol-phenol-formaldehyde resin as the preservative and adhesive,respectively.The tensile shear strength and wood failure ratio of the bonding joints were measured,the radial variation of bonding properties was summarized,and the reasons for the changes were analyzed from the two aspects of wood density and adhesive penetration.The results showed that the wood bonding joints with the treatment of 1.5 wt%ACQ did not significantly increase their tensile shear strengths and wood failure ratios compared with the untreated specimens.Along the direction from the pith to the bark,the tensile shear strength of the preservative-treated P.massoniana wood showed a changing trend of firstly increasing(1-13 a)and then keeping steady(≥14 a),while the wood failure ratios for different radial positions were over 90%and showed no significant difference.The radial variation trend of wood density(0.493-0.572 g/m^(3))was consistent with that of the tensile shear strength,and a strong positive linear correlation(with a Pearson correlation coefficient of 0.659)was determined between the two parameters.No significant difference was found in average penetration depths(76.65-88.01μm)of the adhesive in wood from different radial positions.The bonding performance of the preservative-treated P.massoniana wood from the mature region was obviously better than that from the juvenile regions,and thus the mature wood over 14 years was recommended to be the raw material for producing the glued laminated timber.Wood density is an important factor accounting for the radial variation of the shear strength of the preservative-treated P.massoniana wood,while the adhesive penetration has little effect on it.