摘要
采用脲醛预缩液(UFC)制备甲醛和尿素物质的量之比为1.3∶1的脲醛树脂,并在"碱-酸-碱"制备工艺的3个阶段分别加入大豆蛋白(SPI)降解液进行改性。对改性后脲醛树脂的性能进行对比分析,并借助核磁共振(13C-NMR)和动态热机械性能(DMA)分析改性后脲醛树脂的结构特征及热机械性能。结果表明,与普通脲醛树脂相比,UFC制备脲醛树脂的胶合强度提高了16%,游离甲醛降低了33%;而采用UFC和SPI降解液制备脲醛树脂,树脂胶合强度变化不大,当SPI降解液加入量为10%时,其游离甲醛可降低50%。13C-NMR分析表明,在第3个阶段加入SPI降解液,可以降低脲醛树脂中的醚键含量并提高桥键含量,使树脂具有较高的交联度和较低的游离甲醛。DMA测试结果表明,在第3个阶段加入SPI降解液所制备的脲醛树脂具有较高的热机械性能和热稳定性。
Urea-formaldehyde(UF) resin is most widely used in wood industry, such as the manufacturing of particle-board, plYwood, medium density fiberboard and other nonstructural wood products. UF has several properties that are de-sirable for industrial application, including simple manufacturing process, relatively lower price, easy to access, highinitial viscosity and bonding strength. However, it also has some limitations such as poor water resistance and high brit-tleness, short shelf life and high free formaldehyde emission. The key to reduce formaldehyde emission of UF resin prod-ucts was lowering the mole ratio of formaldehyde to urea (n (F) :n (U)). A new low mole ratio UF (n (F) :n (U)= 1.3:1. O) resin was prepared with urea-formaldehyde preeondensate (UFC) , urea and degraded soy protein. The degradedsoy protein was added in the three stages of the ' alkali-acid-alkali' process. The structural characteristics and thermalmechanical properties of this new UF resin were studied by 13C nuclear magnetic resonance (13 C-NMR) and dynamicmechanical analysis (DMA). The results indicated that the bonding strength of the UF prepared with only UFC increasedby 16% and the content of free formaldehyde decreased by 33%. The bonding strength of the UF prepared with UFC anddegraded soy-protein changed little, but the content of free formaldehyde decreased by 50%. The 13C-NMR resultsshowed that the methylene bridge content increased and methylene ether bond content decreased when the degraded soyprotein was added in the third stage. The final resin system had high polyeondensation and crosslinking degree and lowfree formaldehyde emission. DMA results showed that when the degraded soy protein was added in the third stage, thisnew UF resin could improve the thermal mechanical performance and thermal stability of the plywood products.
出处
《林业工程学报》
北大核心
2016年第1期31-36,共6页
Journal of Forestry Engineering
基金
国家林业公益性行业科研专项(201304505)
云南省应用基础研究重点项目(2013FA038)
云南省中青年学术带头人后备人才项目(2011HB024)
“十二五”国家科技支撑计划(2012BAD24B03)
关键词
脲醛预缩液
大豆蛋白
脲醛树脂
结构特征
热机械性能
urea-formaldehyde precondensate
soy protein
urea-formaldehyde resin
structural characteristics
thermalmechanical properties