【作者】 武国峰；

【导师】 蒲俊文；

【作者基本信息】 北京林业大学 ， 林产化学加工工程， 2012， 博士

【摘要】 本论文研究了由低分子功能性单体(简称：AMU)、增塑剂(尿素)、催化剂等组成的复合型木材改性剂对速生杨木的功能性改良,分别从宏观、微观两方面研究了化学改性、压缩密实化及热处理对速生杨木物化性能的影响,揭示了复合型改性剂与速生杨木材原位聚合反应的机理,主要的结论归纳和创新性如下：(1)采用脉冲式加压浸渍机将复合型木材改性剂浸渍到木材纤维的细胞壁和细胞腔内,结果发现化学浸渍处理减缓了速生杨木材干燥过程中水分的挥发,根据百度试验中干燥缺陷及干燥速度分级标准,速生杨的综合干燥特性等级经过浸渍处理后由二级变为一级,流变特性分析表明改性木的塑性增加,应力松弛降低,改性木损耗角正切值提高；(2)厚度5.5cm的速生杨木浸渍材干燥时间约为130h,最高温度为130℃,根据GB/T 6491-1999测得,浸渍处理的速生杨木的干燥质量达到了国家一级材标准；厚度7.0cm的速生杨浸渍材,在压缩率为21%,最大压强为8MPa时的压缩干燥时间为100h；高温快速干燥可行的原因在于木材改性剂增加了木材的塑性、取代了水分在木材中的空间位置,避免了细胞微观构造在水分快速挥发时发生的皱缩、开裂等结构性破坏,还降低了木材的干燥应力；(3)原位聚合反应在木材内部形成了网状结构,改性木的气干、绝干和基本密度最大提高70%、71%和41%,化学浸渍处理再压缩密实化后提高了109%、83%和74%；改性木的抗弯强度、抗弯弹性模量、顺纹抗压强度最大提高59.9%、81.1%和40.2%,化学浸渍处理再压缩密实化后提高了55.5%、93.4%和71.0%,未浸渍处理木材72h吸水性为116.6%,改性木72h的吸水性最小降低到了76.2%,化学浸渍处理再压缩密实化木材的48h吸水性从123%降低到了91%；(4)速生杨木化学改性后热稳定性提高,氧指数明显增加到了43.2%,阻燃性提高,FTIR显示AMU中的-OH和-NH2与木材结构中-OH发生了原位聚合反应并有氢键间的缔合作用,SEM和EDAX显示改性木横截面上的导管及木纤维的微孔结构被木材改性剂填充,氮元素均匀的分布在木材细胞壁及细胞间隙,13C-NMR分析表明纤维素的结晶结构没有被破坏,只是纤维素结构中的非结晶区发生了醚化反应；(5)速生杨木浸渍材经过压缩干燥处理后,木材的细胞和导管明显被挤压,呈现不规则的多边形,木纤维和导管内的空间被挤压,木材的结构未被破坏,断面密度分布均匀,木材表面的XPS图谱分析表明半纤维末端不稳定羟基发生氧化作用,木材改性剂与木材组分间发生醚化反应；(6)由于改性木中不稳定的小分子物质在热处理过程中分解挥发,热处理后木材的气干、绝干和基本密度最大降低了6.80%,4.37%和6.82%,但力学性能有所提高,抗弯强度、抗弯弹性模量和顺纹抗压强度最大提高了47.04%、36.72%和35.68%,热处理提高了改性木的耐水性,使得72h吸水性从113.4%降低到了81.8%,主要是因为热处理时木材中的改性剂与木纤维的羟基继续发生交联聚合反应,致使木纤维的羟基含量降低,尺寸稳定性提高。更多还原

【Abstract】 The aim of this research is to study the in-situ polymerization mechanism of wood modifier in wood. The influence of wood modifier on wood drying and rheological properties of modified wood were also studied in the paper. The wood modifier, AMU (Low molecular functional monomer) and urea, was impregnated into the fast grown wood by pulsed pressure impregnating machine. The drying process was complete including fast drying technology, hot-press drying technology, and heat-treated method. The changes of microscopic structure, mechanical properties, and chemical composition of modified wood after the three different treatments were discussed. The main conclusions are summarized as follows:(1) Water volatile was slower than the untreated wood in the drying process. The characteristics and quality of the modified wood attained Grade I according to Chinese Standard, while the unimpregnated wood just Grade II. Plasticity and tgδof modified wood was enhanced as the stress relaxation was reduced.(2) The impregnated wood drying with thickness of 5.5cm needed 130h with the initial temperature of 90℃and end temperature of 130℃. The drying quality was Grade I according to GB/T 6491-1999. It takes 100h for compression drying with compression rate at 21% and maximum pressure of 8MPa.(3) The air-dried density, over-dried density and basic density were improved 70%,71% and 41%, while 109%、83% and 74% with the compression rate of 21%. The bending strength, flexural elastic modulus, and compressive strength to grain increased by 59.9%,81.1%, and 40.2%, while 55.5%、93.4% and 71.0% for the compression wood. The 72h hygroscopy of unimpregnated wood was 116.6% while the impregnated wood was 76.2%. The 48h hygroscopy of unimpregnated wood was 123% while the impregnated wood was 91%.(4) The thermal stability increased as the AMU and urea increased. Oxygen index was also increased as result of the existence of wood modifier. As wood temperature increased during the drying process, chemical bonding was produced between wood and AMU (-OH) as result of in-situ polymerization between wood and AMU. SEM and EDXA showed that the transaction of unimpregnated and impregnated wood. The cell wall and vessels were filled with wood modifier and has been deformed by the compression during the drying process. The Nitrogen element was distributed in wood cell walls and intercellular spaces and the lumen. 13C NMR showed the crystalline structure of cellulose was not damaged, while the etherification reaction seemed occurred in the non-crystalline regions.(5) The section density distribution of modified wood was uniform. The transformation of wood cell and vessel were observed using SEM. The vessel appeared irregular polygon in the modified wood after hot-press drying process. The modifier particles distributed as rod-like or discontinuous in the wood cell. XPS showed that the oxidation occurred in the hemicelluloses, and etherification occurred between wood and wood modifier.(6) The weight loss of air-dried density, over-dried density and basic density were6.80%,4.37%, and 6.82%. The bending strength, flexural elastic modulus, and compressive strength to grain increased by 47.04%,36.72% and35.68%. The 72h hygroscopy of unimpregnated wood was 113.4% while the impregnated wood was 81.8%.更多还原