糠醇-己内酰胺协同改性松木理化性能

Physical and chemical properties of Pinus massoniana synergic modified with furfuryl alcohol-caprolactam

糠醇改性木材拥有较多的优点,如优异的耐腐性、耐候性、硬度等,然而经过糠醇改性的木材脆性增加,抗弯性能以及抗剪切性能均有所降低。这一缺点极大限制了糠醇改性木材的应用范围,可通过加入柔性物质己内酰胺以提高糠醇改性木材的韧性。己内酰胺是聚酰胺切片的原材料,韧性较强,常用来制备纤维等柔性材料。将己内酰胺与糠醇复合改性剂协同处理马尾松,通过X射线能谱仪(EDS)、抗弯性能分析、数字图像分析(DIC)以及接触角测试分析研究协同改性对松木早晚材微观构造、元素分布、力学性能和疏水性等的影响。能谱结果表明:由于早晚材结构差异,协同改性剂在早材细胞壁和细胞腔中反应程度更高,聚合物含量更丰富。晚材构造阻碍了改性剂在其内部的渗透,导致晚材反应程度低于早材。木材疏水性结果表明,协同改性大幅提高了木材的疏水性。力学性能以及数字图像分析结果表明,协同改性不仅提高了木材的静曲强度和弹性模量,而且降低了糠醇改性导致的木材脆性。

The growing concern for environmental protection,sustainable development and biodiversity conservation has led to increased restrictions on the trade in natural high-quality wood worldwide and there are efforts to limit the amount of harvesting to ensure the long-term health of forests and ecosystems.However,the demand for wood products is increasing and natural high-quality wood resources are decreasing.As a result,attention has been focused on how to utilize fast-growing wood species to replace traditional species.In view of the poor dimensional stability and mechanical strength of most fast-growing wood products,there is a need for a more environmentally friendly,less pollution and non-hazardous modifier like furfuryl alcohol for wood modification.Furfurylated wood has many advantages,such as excellent corrosion resistance,weather resistance,hardness,etc.However,it has drawbacks of high brittleness and poor flexural and shear resistance,which greatly limits the application range of furfurylated wood.In order to address these issues,researchers commonly use delignification and heat-pressing,as well as impregnation of flexible substances.Although the delignification and heat-pressing can effectively improve the mechanical properties of wood,one of the most popular reaction mechanisms of furfuryl alcohol modification is the chemical cross-linking of furfuryl alcohol molecules with wood cell wall components,which reacts mainly with lignin in the cell walls of wood during the curing process.Enhancement of mechanical properties of furfurylated wood by impregnation with flexible substances is more reasonable.In this study,the toughness of furfurylated wood was improved by adding flexible caprolactam.Caprolactam is the raw material of polyamide slice,which has strong toughness and is commonly used to prepare flexible materials such as fibers.The caprolactam and furfuryl alcohol were mixed and used to treat masson pine.The effects of synergic modification on the microstructure,element distribution,mechanical properties and hydrophobicity of pine wood were examined by the energy dispersive spectroscopy(EDS),bending test,digital image analysis(DIC)and contact angle analysis.The EDS results showed that the synergic modification rendered higher degree of reaction and more polymer was distributed in the cell wall and cavity of the earlywood.The smaller tracheid and more aspirated pits of latewood hindered the penetration of modifiers,resulting in lower degree of reaction.The contact angle measurement results showed that the synergic modification greatly improved the hydrophobicity of wood.The results of mechanical test and DIC showed that the synergic modification not only improved the static bending strength and elastic modulus of the wood,but also improved its toughness.