本文關(guān)鍵詞： 楊木 低分子量樹脂浸漬 浸漬材干燥 固化溫度 物理力學(xué)性能　出處：《中國(guó)林業(yè)科學(xué)研究院》2017年博士論文　論文類型：學(xué)位論文

【摘要】：低分子量樹脂浸漬改性是提高速生材物理力學(xué)性能的有效手段。然而,樹脂浸漬改變了“木材-水分”體系和木材孔隙結(jié)構(gòu),造成浸漬材干燥過程中水分遷移減慢,并且干燥后樹脂難以完全固化,限制了其推廣應(yīng)用。本文以低分子量三聚氰胺改性脲醛樹脂(MUF)浸漬楊木為研究對(duì)象,探討了不同干燥前預(yù)處理及干燥方式對(duì)浸漬材內(nèi)部樹脂溶液的影響;重點(diǎn)研究了干燥過程中樹脂對(duì)水分以及水分遷移、水分對(duì)樹脂固化的影響規(guī)律,并闡明了干燥過程中水分遷移和樹脂固化的相互關(guān)系;揭示了干燥后固化溫度對(duì)浸漬材物理力學(xué)性能的影響機(jī)理。研究結(jié)果對(duì)于樹脂浸漬材干燥基準(zhǔn)的優(yōu)化和樹脂改性技術(shù)的推廣應(yīng)用具有重要理論價(jià)值和現(xiàn)實(shí)意義。論文的主要結(jié)論如下:1.干燥前預(yù)處理及干燥方式影響浸漬材內(nèi)部樹脂溶液中的水分遷移和樹脂相態(tài)變化進(jìn)程,進(jìn)而導(dǎo)致樹脂在木材內(nèi)的含量和空間分布有所差別,表現(xiàn)出不同的改性效果。相同干燥方式下,置于高濕度環(huán)境或樹脂溶液中的預(yù)處理比氣干預(yù)處理更有利于樹脂擴(kuò)散至木材細(xì)胞壁中,從而獲得更高的細(xì)胞壁容脹率和吸水抗脹率;相同預(yù)處理后,濕干燥比直接干燥更有利于樹脂進(jìn)一步擴(kuò)散到木材細(xì)胞壁中并在木材內(nèi)部良好固著,從而獲得更高的增重率、細(xì)胞壁容脹率以及吸水抗脹率。2.MUF樹脂浸漬處理并未改變?cè)嚇訖M向弛豫時(shí)間(T2)譜中的峰個(gè)數(shù)和峰歸屬,但延長(zhǎng)了含水率在纖維飽和點(diǎn)以上時(shí)木射線和木纖維內(nèi)自由水的T2值,縮短了含水率在纖維飽和點(diǎn)以下時(shí)結(jié)合水的T2值。T2譜中的3個(gè)峰從左至右分別對(duì)應(yīng)結(jié)合水(峰I)、木射線和木纖維中內(nèi)的自由水(峰II)以及導(dǎo)管內(nèi)的自由水(峰III)。含水率在纖維飽和點(diǎn)以上時(shí),生材試樣峰II對(duì)應(yīng)的T2為58.05 ms,飽水材試樣峰II左移至45.53 ms,MUF樹脂浸漬材試樣峰II右移至80.26 ms。含水率在纖維飽和點(diǎn)以下時(shí),生材、飽水材以及MUF樹脂浸漬材試樣的峰I都不斷左移,但低含水率階段時(shí)浸漬材左移更明顯,T2更短。3.MUF樹脂浸漬處理降低了干燥過程中自由水和結(jié)合水的遷移速率,并形成了更明顯的含水率梯度。含水率在纖維飽和點(diǎn)以上時(shí),MUF樹脂浸漬材試樣導(dǎo)管內(nèi)自由水以及木射線和木纖維內(nèi)自由水的平均干燥速率明顯降低,分別為6.0%/天和7.5%/天,約為飽水材試樣對(duì)應(yīng)細(xì)胞內(nèi)自由水平均干燥速率的一半。含水率在纖維飽和點(diǎn)以下時(shí),結(jié)合水?dāng)U散速率明顯減慢。整個(gè)干燥過程中,相比于生材試樣和飽水材試樣,MUF樹脂浸漬材試樣芯層中的水分向外遷移受阻,含水率梯度更為明顯。4.MUF樹脂浸漬材干燥過程中,內(nèi)部水分散失始終伴隨著樹脂不斷縮聚固化。其在動(dòng)態(tài)粘彈性能時(shí)間譜中表現(xiàn)為:干燥開始后,MUF樹脂浸漬材相對(duì)儲(chǔ)存模量先快速增加并達(dá)到峰值,然后小幅增加并趨于平衡;相對(duì)損耗模量先快速增加并達(dá)到峰值,形成一個(gè)明顯的力學(xué)損耗峰,此后逐步降低并趨于穩(wěn)定。5.低場(chǎng)核磁共振(LF-NMR)和動(dòng)態(tài)熱機(jī)械分析(DMA)表明,干燥過程中水分遷移和蒸發(fā)始終伴隨著浸漬材內(nèi)樹脂的相態(tài)變化并相互影響。含水率在纖維飽和點(diǎn)以上時(shí),自由水起到稀釋劑和能量壁壘作用,延緩樹脂的縮聚,而自由水的遷移和蒸發(fā)有助于樹脂縮聚固化。另一方面,樹脂不斷縮聚引起的相態(tài)變化對(duì)大毛細(xì)管和微毛細(xì)管系統(tǒng)的堵塞、對(duì)水分吸著點(diǎn)的覆蓋又降低了自由水和結(jié)合水的遷移速率。兩者的相互影響在木材不同層位中的表現(xiàn)有所不同,芯層中水分遷移和樹脂相態(tài)變化進(jìn)程受到表層中水分遷移和樹脂相態(tài)變化的牽制和影響。6.干燥結(jié)束后,樹脂多以半球形凸起或者球形顆粒附著于導(dǎo)管和木纖維細(xì)胞腔內(nèi)壁上,對(duì)導(dǎo)管徑/弦面壁及其上面的紋孔膜有較大程度的覆蓋,在木纖維內(nèi)的分布相對(duì)較少,零散的分布于細(xì)胞腔內(nèi)壁上,而對(duì)木射線細(xì)胞腔有較為明顯的填充。其中,導(dǎo)管中樹脂顆粒直徑或者半球形凸起的最高高度基本不超過5μm,木纖維內(nèi)樹脂顆粒直徑或者半球形凸起的最高高度基本不超過2μm。7.干燥后固化溫度影響MUF樹脂浸漬材的水蒸汽吸附性能,并對(duì)各項(xiàng)力學(xué)性能有顯著影響(α=0.01)。60°C、80°C、100°C、120°C、140°C溫度固化處理后,MUF樹脂浸漬試樣在95%相對(duì)濕度下的吸濕平衡含水率分別為30.03%、20.47%、14.94%、14.49%、~(13).99%,100°C處理的素材試樣的吸濕平衡含水率為21.21%;隨著固化處理溫度升高,MUF樹脂浸漬試樣的抗彎強(qiáng)度和抗彎彈性模量表現(xiàn)出先升高后降低的趨勢(shì),端面硬度逐漸增加,徑面硬度呈波動(dòng)變化,弦面硬度先增加后降低。FTIR與~(13)C CP/MAS NMR分析證明,固化溫度越高,樹脂中羥甲基含量越少、氨基上活性氫被取代的越多,表明活性基團(tuán)之間的脫水縮聚越完全,導(dǎo)致樹脂的交聯(lián)程度變高、內(nèi)聚強(qiáng)度增大、吸濕性基團(tuán)減少。
[Abstract]:Low molecular weight resin impregnation modification is an effective way to improve the fast-growing wood physical and mechanical properties. However, the change of resin impregnated wood water system and wood pore structure, resulting in slow moisture migration of impregnated wood drying process, after drying and curing resin is difficult to complete, the application was limited. In this paper, low molecular weight the amount of melamine modified urea formaldehyde resin (MUF) impregnated poplar as the research object, discusses the effects of different drying pretreatment and drying methods on the impregnation material within the resin solution; focus on the resin drying process on the migration of water and moisture, influence of moisture content on the curing of the resin, and clarifies the relationship between drying in the process of moisture transfer and resin curing mechanism; effect of curing temperature on the physical and mechanical properties of the impregnated wood after drying was revealed. The results for the resin impregnated wood drying schedule and optimization Has an important theoretical value and practical significance to promote the application of resin modified technology. The main conclusions of this paper are as follows: the phase change process of water transfer 1. drying pretreatment and the drying effect of impregnation material within the resin solution and resin, which resin in wood. The content and spatial distribution difference, showing sex the effect of different drying methods. The same, placed in a high humidity environment or resin solution pretreatment than gas intervention was more beneficial to the resin spread to the wood cell wall, so as to obtain higher cell wall volume expansion ratio and water absorption rate of anti swelling; the same after pretreatment, wet drying is more conducive to resin to the further spread of the wood cell wall and good fixation in wood, resulting in higher growth rate, inflation rate and water absorption capacity of cell wall anti swelling rate of.2.MUF resin impregnation treatment did not change the sample 妯悜寮涜鮑鏃墮棿(T2)璋變腑鐨勫嘲涓暟鍜屽嘲褰掑睘,浣嗗歡闀夸簡(jiǎn)鍚按鐜囧湪綰ょ淮楗卞拰鐐逛互涓婃椂鏈ㄥ皠綰垮拰鏈ㄧ氦緇村唴鑷敱姘寸殑T2鍊，

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