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    DSC法研究水分含量对低分子量MUF树脂固化特性的影响

    Effects of moisture content on curing characteristics of low molecular mass melamine-urea-formaldehyde (MUF) resin by differential scanning calorimetry (DSC) method

      摘要
    • 摘要:
        目的  探究水分含量对低分子量三聚氰胺脲醛（MUF）树脂溶液固化特性的影响，为阐明树脂浸渍材在不同干燥阶段、不同空间层位中的树脂固化特性提供数据支撑。
        方法  以实验室自制的MUF树脂溶液为研究对象，将其稀释成20%、30%、40%、50%后进行升温差示扫描量热测试（DSC），通过外推法消除升温速率对峰顶温度的影响，拟合求解其最佳固化温度，定性阐述水分含量对MUF树脂固化特性的影响，并运用Kissinger微分法和Flynn-Wall-Ozawa积分法计算20%、30%、40%、50%树脂溶液固化反应的表观活化能，定量分析水分对树脂固化特性的影响。
        结果  随着MUF树脂溶液质量分数的降低，DSC曲线中峰顶温度整体上呈现向高温方向偏移的趋势，但是在升温速率15和20 ℃/min条件下，20%树脂溶液DSC曲线的峰顶温度峰位置向低温区域发生了偏移；通过外推法得到的20%、30%、40%、50% MUF树脂溶液的最佳固化温度分别为93.99、90.71、85.46和79.71 ℃；运用Kissinger微分法计算得到其表观活化能分别为92.94、82.37、65.93和50.68 kJ/mol，其结果与Flynn-Wall-Ozawa积分法验算结果相近。
        结论  整体上，消除升温速率的影响后，水分对树脂固化反应起阻碍作用，并且水分越多，阻碍效应越明显；但在较高升温速率（15和20 ℃/min）条件下，20%MUF树脂溶液的DSC测试结果表明水分促进树脂固化反应，这可能是由分子运动加剧造成的。

       

      Abstract:
        Objective  In order to clarify the resin curing characteristics of the resin impregnated wood in different spatial layers during different drying stages, the effects of moisture content on resin solution curing process were studied.
        Method  The melamine-urea-formaldehyde (MUF) resin solution prepared in the laboratory was diluted to 20%, 30%, 40% and 50%, respectively. Then, they were analyzed by differential scanning calorimetry (DSC) method. Without the effect of heating rate, the optimum curing temperature was obtained by extrapolation method to clarify the effect of moisture on MUF resin curing characteristics qualitatively. The apparent activation energy of resin solution, which was diluted to 20%, 30%, 40% and 50%, was calculated by the Kissinger differential method and Flynn-Wall-Ozawa integral method, to quantify the effect of moisture on resin curing process.
        Result  The peak temperature (Tp) tended to shift to the higher temperature with the decrease of mass fraction of MUF resin solution. Under the heating rate of 15 and 20 ℃/min, the Tp of 20% resin solution shifted to the lower temperature region. The optimum curing temperatures of 20%, 30%, 40% and 50% MUF resin solution were 93.99, 90.71, 85.46 and 79.71 ℃, respectively. And their apparent activation energies calculated by Kissinger differential method were 92.94, 82.37, 65.93 and 50.68 kJ/mol, respectively, which were similar to those of the Flynn-Wall-Ozawa integral method.
        Conclusion  Generally, the moisture hinders the resin solution curing reaction in the absence of heating rate effect, and the blocking effect increases with the increase of moisture content. However, in the condition of higher heating rate (15 and 20 ℃/min), the DSC result of 20% resin solution shows that the moisture promotes the resin curing process, which might due to the drastic molecular movement.

       

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