【作者】 王磊；

【导师】 沈一丁； 李仲谨；

【作者基本信息】 陕西科技大学 ， 应用化学， 2011， 博士

【摘要】 水性聚氨酯(WPU)是一种以水为分散介质的聚氨酯体系,由于其无毒、环保、使用安全,已经引起了国内外的广泛关注。水性聚氨酯具有优良的柔韧性、耐冲击性、耐磨性和耐低温性能等特点,其作为鞋用胶黏剂的应用更是成为近年来研究的热点。本论文通过复合改性制备了一系列阴离子型水性聚氨酯胶黏剂乳液,并详细研究了复合体系的结构与性能,探讨了其与皮革纤维基质材料的黏结,成膜作用机理。以下为本论文主要内容:1.本课题首先制备了一种阴离子水性聚氨酯胶黏剂乳液。研究表明,-COOH含量对水性聚氨酯胶黏剂的耐水性能、力学性能和乳液稳定性有较大影响。随着-COOH含量的增大,胶膜的拉伸强度增强,硬度提高,但耐水性下降。当-COOH含量低于1.45%后,胶黏剂乳液不稳定。TMP含量的增加可有效改善水性聚氨酯胶膜的耐水性和力学性能,但是w(TMP)大于2.0%时,乳液趋于不稳定。-NCO/-OH摩尔比对水性聚氨酯胶膜的耐水性能无明显影响,随着-NCO/-OH摩尔比的增大,胶膜的拉伸强度逐渐增大,胶膜变硬。当w(-COOH)为1.60%,-NCO/-OH摩尔比为1.4,w(TMP)为1.0%时,可获得相对综合性较好的水性聚氨酯胶乳。水性聚氨酯固含量提高时,皮革-橡胶的T-剥离强度提高。随着n(NCO)/n(OH)值、COOH含量、TMP用量、聚氨酯相对分子质量的增大,T剥离强度先增加后减小。经测定,以固含量为35%的聚氨酯乳液,作为皮革、橡胶的胶黏剂,其剥离强度为12N/(2.5cm)。因此要获得性能更优的产品,在上述研究的基础上,还需要对水性聚氨酯胶黏剂进一步进行改性。2.在水性聚氨酯制备方法的基础上,加入小分子扩链剂BDO,采用HEA封端聚氨酯预聚体,选用MMA和BA为自由基聚合单体,AIBN为引发剂,制备了一系列丙烯酸酯改性的水性聚氨酯胶黏剂。得到的水性聚氨酯分散体固含量均可达到40%以上。利用丙烯酸酯改性水性聚氨酯胶黏剂,一方面可提高干燥速率,提高水性聚氨酯胶黏剂与皮革纤维的黏结强度。另一方面可降低成本。FTIR表明,丙烯酸酯类单体反应较完全。TEM表明,改性水性聚氨酯乳液中乳胶粒子分布比较均匀。粒径分析表明,改性后水性聚氨酯乳液粒子粒径增大。TG分析表明,丙烯酸酯改性提高了聚氨酯的热稳定性,同时增加了体系的交联程度。DMA表明,改性后聚氨酯交联密度增大,具有较高的玻璃化转变温度。随HEA用量和丙烯酸酯(PA)用量的增加,水性聚氨酯的交联密度逐渐增大,有效提高了水性聚氨酯胶黏剂的黏接强度、耐水和耐热性能。当MMA与BA质量比为4:2时,剥离强度为52.9 N/(2.5cm),胶膜的拉伸强度为19.6MPa,断裂伸长率为533.7%,此时胶黏剂即具有优异的黏接强度和力学性能,又保持了良好的柔韧性。小分子扩链剂BDO可有效提高水性聚氨酯胶膜的力学性能,但BDO用量不宜超过1.5%。综合考虑各因素,确定丙烯酸酯改性水性聚氨酯胶黏剂的制备条件:w(-COOH)为1.6%、w(TMP)为1.0%、w(HEA)为4%、w(PA)为30%、m(MMA):m(BA)为4:2,w(BDO)为1.5%。此时水性聚氨酯胶黏剂的耐水性、耐热性和柔韧性优异,黏接强度可达52.9 N/(2.5cm)。加入丙烯酸酯进行乳液聚合有效提高了此系列胶乳的固含量,固含量可达45%,提高了胶黏剂的干燥速度。研究了水性聚氨酯乳化过程中相转变的影响因素。实验结果表明,随着软段分子量升高,体系的相转变点后延;n(NCO)/n(OH)值减小、羧基含量增大、中和度增加以及HEA用量的增加,都会导致体系的黏度增高,增加相转变发生所需的水含量。3.采用葡萄糖作为内交联剂,将葡萄糖引入聚氨酯分子主链上,制得固含量达50%以上的水性聚氨酯胶黏剂,其具有干燥速度快、初黏力大和耐水性好等特点,改性水性聚氨酯胶黏剂的综合性能显著提高。通过FTIR分析,证实了葡萄糖已引入聚氨酯主链。XRD表明,经葡萄糖改性的聚氨酯结晶度显著下降,属于非晶态聚合物,说明葡萄糖本身已经完全转化。随着葡萄糖含量增加,乳液稳定性略有下降。制备的聚氨酯乳液属于假塑性流体。增加葡萄糖交联剂的用量,乳液黏度先增大后减小。随着葡萄糖用量的增加,体系交联度增大,聚氨酯热分解温度明显升高。葡萄糖的加入使乳胶膜的表面自由能下降,体系的耐介质性得到改善。提高葡萄糖的用量,胶膜的拉伸强度增强,断裂伸长率逐渐降低,胶液的固化速度提高。当葡萄糖用量从0%增加到4.68%时,T-剥离强度由57.3N/(2.5cm)上升至116.1N/(2.5cm)。初步探讨了水性聚氨酯的粘结作用机理,粘合力是润湿吸附能力、扩散能力、化学键合以及机械嵌合的综合作用。4.采用葡萄糖作为内交联剂,利用羧基丁苯胶乳液(CSBL)物理改性水性聚氨酯,制得固含量达50%以上的水性聚氨酯胶黏剂。重点考察外加高分子乳液对合成水性聚氨酯乳液性能的影响,探讨了水性聚氨酯乳液与羧基丁苯胶乳液的协同作用。当CSBL与聚氨酯的质量比高于1︰2时,乳液趋于稳定。TEM照片显示乳胶粒子呈球形颗粒结构,粒径分布均匀。加入CSBL改性的水性聚氨酯乳液粒径呈现双峰分布。探讨了高固含量水性聚氨酯分散体的合成机理。固含量达60%的水性聚氨酯乳液表现为触变性流体,固含量低的水性聚氨酯乳液基本不具备触变性。当CBSL用量增加,水性聚氨酯耐热性能得到改善。与单独的水性聚氨酯乳液和CSBL相比,CSBL乳化得到的水性聚氨酯乳液成膜力学性能得到明显增强。当CSBL的用量为50%时,改性聚氨酯胶黏剂的剥离强度达到最大值。更多还原

【Abstract】 Waterborne polyurethane (WPU) is a new type of polyurethane system with water as the dispersion medium. Because WPU is non-toxic, environmentally friendly and safe, it has attracted widespread attention at home and abroad. The application of waterborne polyurethane as shoe adhesives has become a hotspot of recent research due to the excellent flexibility, impact resistance, abrasive resistance and low temperature resistance. The authors prepared series of anionic waterborne polyurethane latex by composite modification, and a detailed study of the structure and properties of complex systems to explore the mechanism of their synergy. The main content of this paper is as followings:1.A water-based polyurethane adhesive was prepared. -COOH content has great effect on the water resistance, mechanical property and stability of WPU. The tensile strength of the WPU films increased with the increasing -COOH content while the water resistance decreased. The emulsion is unstable when w(COOH) is less than 1.45%. Increasing TMP content can improve water resistance and mechanical property of WPU films, the proper w(TMP) is 2%. The tensile strength of the WPU films increased with the increasing -NCO/-OH molar ratio. WPU with better combination property can be obtained when w(-COOH) is 1.60%,-NCO/-OH molar ratio is 1.4 and w(TMP) is 1.0%. T-style peeling strength increased with the increasing solid content of WPU adhesive. T-style peeling strength increased and then decreased with the increasement of n(NCO)/n(OH), COOH content, TMP content and molecular weight of polyurethane. When the WPU with solid content of 35% is used as leather adhesive, the T-style peeling strength is 12 N/(2.5cm). The polyurethane adhesive need to be further modified.2.A sery of modified waterborne polyurethane was prepared with BDO as chain extender, HEA as endcapper, MMA and BA as monomers and AIBN as initiator. The solid content of prepared waterborne polyurethane is more than 40%. After modification, the drying rate of WPU adhesive and the bonding strenghth can be both improved. On the other hand, production cost of waterborne polyurethane decreased. FTIR analysis indicates that acrylate has reacted. The morphology of emulsion were observed by Transmission Electron Microscope(TEM). TEM images display that the particles were well dispersed. The particle size of WPU increased and the distribution width becomes wider after the modification.TG analysis indicates that crosslinking degree and thermal stability of WPU modified with acrylate is increased. DMA showed that the modified WPU has a higher glass transition temperature. The adhesion, water resistance and thermal stability were improved by the increasing HEA and acrylate dosage. T-style peeling strength is 52.9 N/(2.5cm) as the mass ratio of MMA and BA is 4:2. The tensile strength of the WPU films is 19.6MPa, the elongation at break is 533.7%, the adhesive has good mechanical property and flexibility. BDO as chain extender can improve mechanical property of WPU, the proper w(BDO) is 1.5%. When the w(-COOH) is 1.6%, w(TMP) is 1.0%, w(HEA) is 4%, w(PA) is 30%, m(MMA):m(BA) is 4:2 and w(BDO) is 1.5%, The modified WPU has good water resistance, thermal resistance and flexibility, the bonding strength can reach 52.9 N/(2.5cm). The solid content of WPU with acrylate can reach 45%, which can improve the drying rate of WPU adhesive.With the increasing of the molecular of soft segments, the phase inversion delays. The decrease of NCO/OH molar ratio, increase of carboxyl content, HEA content and neutralization degree will increase the viscosity of system and more water was needed for the phase inversion.3. The natural glucose was introduced to the polyurethane mainchain as crosslinker, the waterborne polyurethane with solid content of 50% can be prepared. Combination property of the modified waterborne polyurethane can be improved evidently.The FTIR test results indicated that the glucose has been introduced into the main chain of polyurethane. XRD indicated that the degree of crystallinity decreased after the glucose has been introduced to the polyurethane, which showed the glucose has reacted with -NCO . With the increasing of glucose content, the stability WPU decreased. The WPU is stable when solid content of WPU is less than 60%. Dynamic rheological investigation showed that loss modulus(G’’) and storage modulus(G′) both increased with oscillation frequency. Viscosity of the polyurethane emulsion increased and then decreased with the increasement of glucose content.The decomposition temperature of WPU films increased with increasing glucose content. Surface free energies decreased with addition of glucose and the medium resistance of WPU films is improved. Water and solvent absorption decreased with increasing R value. The tensile strength of the WPU films increased and the elongation at break decreased with increasing glucose content. As the glucose content increases from 0% to 4.68%, the T-style peeling strength increases 57.3N/(2.5cm) to 116.1 N/(2.5cm). The curing time of WPU samples were decreased with increasing glucose content. The bonding mechanism of WPU adhesives was investigated.4. The glucose was introduced to the polyurethane mainchain as crosslinker, the deionized water and carboxy styrene-butadiene latex were added to the polyurethane system and the waterborne polyurethane with solid content of 50% can be prepared. The effect of carboxy styrene-butadiene latex on properties of the waterborne polyurethane was studied in this chapter and synergistic action between waterborne polyurethane and carboxy styrene-butadiene latex was investigated. TEM photos show that WPU emulsion and CSBL werewell-dispersed with round appearance. The average particle size of WPU emulsion increases from 58.45nm to 70.7nm with increasing w(glucose). WPU emulsified by CSBL has bimodal distribution. The synthesis mechanism of WPU was investigated.The rheological behavior of polyurethane emulsion was studied. WPU emulsion exhibiting pseudoplastic liquid behavior. WPU emulsion with high solid content of 60% has thixotropy, while WPU emulsion with low solid content has no obvious thixotropy. When CSBL content increases, the WPU will be well emulsified, so the thermal stability of WPU increases. Compared with WPU and CSBL films without modification, mechanical property of polyurethane films modified by carboxy styrene-butadiene latex increased obviously. T-style peeling strength of the modified adhesive reach maximum when the w(CSBL) is 50%.更多还原