【作者】 方群；

【导师】 杜官本； 郭梦麟；

【作者基本信息】 西南林学院 ， 木材科学与技术， 2008， 硕士

【摘要】 聚合物/蒙脱土(MMT)纳米插层复合材料,是目前研究最多、最引人注目的复合材料。我国的蒙脱土矿藏资源十分丰富,独特的结构,适宜的离子交换容量,优良的力学性能及低廉的价格,使得蒙脱土成为制备新型高性能纳米插层复合材料的最重要的一类无机物。应用纳米插层复合技术,使蒙脱土以纳米尺寸对木材胶粘剂进行改良或改性是木材科学领域的新课题,具有重大的理论意义和实用价值。本论文首次提出了木材胶粘剂酚醛树脂/蒙脱土纳米插层复合的技术路线及在人造板工业中的应用。本论文的探索性研究,为木材胶粘剂酚醛树脂改性提出了新的思路,为木材胶粘剂/无机复合材料的研究开拓了新的途径。本文通过对木材用胶粘剂酚醛树脂进行纳米蒙脱土改性,利用一步和两步插层法制备了PF/MMT纳米复合材的预聚体,用高温加压的制板工艺,让树脂固化,释放的能量使树脂分子进一步插入到蒙脱土层间,从而形成纳米复合材料。通过对不同F/P摩尔比树脂添加不同蒙脱土类型、不同蒙脱土用量、不同助剂及不同合成方法等因素对酚醛树脂/蒙脱土改性树脂胶合性能的影响研究,并且利用X射线衍射(XRD),基质辅助激光解析电离飞行时间质谱(MALDI-TOF-MS),差示扫描量热法(DSC)和热机械分析(TMA)等手段对制备的复合材料进行了结构和性能的表征分析,可以得出以下结论:1、MALDI-TOF质谱图分析表明本实验中的酚醛树脂是三维的结构,PUF共缩聚树脂结构以酚醛树脂为主体,特别是聚合物的链接方式,因此PUF树脂通常具有与传统酚醛树脂相同的性能表现,不同摩尔比的酚醛树脂对插层效果没有明显的影响。2、蒙脱土对各酚醛树脂的改性作用主要表现在耐沸水煮后的胶合强度的增加。XRD的结果表明NaMMT有一定程度的插层,而不是剥离。而胶合板性能检测结果表明在酚醛树脂(PF)和苯酚-尿素-甲醛(PUF)共缩聚树脂中混入少量的钠基蒙脱土可以提高树脂的耐水性,正是由于蒙脱土层间距有少量的增加,部分酚醛树脂进入到蒙脱土层间,形成一定程度插层。3、DSC和TMA的分析表明NaMMT对PF树脂有加速固化的作用,弹性模量随着温度的作用增加,加了NaMMT的树脂的弹性模量最大值增大。为使树脂性能得到较好的改进,蒙脱土的添加量不宜太多,1%～3%是一个较合适的范围。4、胶合板性能检测结果表明,添加尿素有助于提高酚醛/蒙脱土改性树脂的性能。尿素的NH2+能与蒙脱土层间的阳离子进行交换,利用尿素把酚醛树脂分子带到蒙脱土的层间。与未加尿素的改性树脂相比,无论是干状的还是沸水煮后的树脂的胶合强度都有明显提高。5、水溶性酚醛树脂与蒙脱土有较好的相容性,可得到部分插层型的酚醛树脂/蒙脱土纳米插层复合体,胶合板性能检测结果表明,酚醛树脂/蒙脱土纳米插层复合体的干状和湿状胶合强度都有明显提如同高,复合体中的蒙脱土与酚醛树脂分子间可能通过氧原子发生了较强的连接。由于苯酚和甲醛单体较酚醛树脂分子更容易进入蒙脱土的层间,在合成树脂的过程中加入蒙脱土的一步插层法比先按传统方法合成树脂,再加入蒙脱土与之混合的两步插层法,所得的酚醛树脂/蒙脱土纳米改性树脂的性能更好。在本实验中的PF/MMT的纳米复合效应并不显著。但木材胶粘剂/蒙脱土纳米复合材料的性能存在很大的发展潜力和开发前景,值得进一步深入研究。更多还原

【Abstract】 Polymer/Montmorillonite (MMT) intercalation is one of the most widely studied and most promising nanocomposites. China is rich in Ca-MMT mineral. Due to its particular intercalation chemistry and nanoscale layering with very high aspect ratio, high strength, ion-exchangeable and swellable characteristics MMT plays an important role in producing high-performance intercalation nanocomposites. The intercalated nano-compounding of phenol formaldehyde resin with MMT is a creative thinking and practice, which has important scientific significance and attractive application prospects. The intercalated compounding with inorganic MMT at the molecular level is a pioneer concept to improve or modify phenol formaldehyde (PF) resin. In this research, the technology of compounding PF resin with MMT on a nanoscale and applying the modified resin to manufacture wood composites was systematically put forward. This exploring research would provide a new idea to modify PF resin in a new approach to prepare wood composites.MMT-modified PF resins suitable for use in bonding wood composites were prepared through in-situ intercalated polymerization and polymer intercalated polymerization using several montmorillonites. The PF resin molecules were first intercalated into the clay layers, followed by the formation of nanocomposites when the MMT-modified PF resin was cured under pressure at high temperatures. The work dealt with the use of different types and quantities of montmorillonite nanoclays in the preparation of thermosetting PF and PUF resins under different reaction conditions, such as different F/P mole ratios. It was hoped that the use of MMT in resin synthesis would improve the performance of MMT-modified the resins in manufacturing wood panels/composites. The MMT-modified resins were studied with the analyses of wide angle X-ray diffraction analysis (XRD), Matrix assisted laser desorption/ionization time of flight (MALDI-TOF-MS), differential scanning calorimetry (DSC) and thermomechanical analysis (TMA), obtaining the following results:1. MALDI-TOF spectra confirmed that the phenolic resins prepared in this study had a three-dimensional structure. The PF moieties made up the main part in the PUF resin, and the linkages also were of the PF types. Therefore, the performance of PUF resin was similar to the conventional phenolic resins. PF resins with different F/P mole ratios had no evident effect on intercalation.2. PF resins modified with MMT exhibited better water resistance. The XRD results indicated that the layers of Na-MMT were intercalated some degree rather than exfoliated. It was confirmed by measuring the plywood performance that mixing PF and PUF resins with a small percentage of Na-montmorillonite (NaMMT) nanoclay resulted in improvement of water resistance of the resins. This result was attributed to a small increase in the nanoclay interlayer distance.3. Differential scanning calorimetry (DSC) and TMA indicated that Na-MMT hads an accelerating effect on curing PF and PUF resins. The modulus of elasticity (MOE) of plywood glue joints increased with increasing curing temperatures, and the glue joints with MMT-modified resins had the maximum MOE values. The appropriate amounts of MMT used in resin synthes is ranged from 1% to 3%.4. Adding urea as an additive during PF resin synthesis helped to improve the performance of Phenol Formaldehyde (PF) /Montmorillonite(MMT) nanocomposite. Results indicated that plywood bonded with PUF/MMT resin had higher dry and wet tensile (after boiled in water for 3 hrs) strengths than those plywood bonded with PF/MMT resin. The PF molecules might have better intercalated into the nanoclay interlayer by the aid of NH2+ of urea, which was attracted to the cation of the nanoclay interlayer.5. The MMT had good compatibility with water-soluble PF resin, and partially intercalated PF/MMT nanocomposites could be obtained easily. Results indicated that plywood bonded with the PF/MMT resin synthesized by one-step process displayed higher dry and wet (3h- boil) tensile strengths than plywood bonded with the resin synthesized by the two-step process. This is attributed to the fact that during one-step synthesis small phenol and formaldehyde monomers can infiltrate easily into and polymerize in MMT layers. During the two-step process, however, bulky polymeric PF molecules can not be easily intercalated into MMT layers. It is possible that PF coupled with MMT by formation of hydrogen bonds in the intercalated layers. Although a limited effect was observed in this study, the concept of using MMT to improve the performance of PF resins was quite evident. Therefore, preparation of PF/MMT nanocomposites is worthy of further studies.更多还原