硅烷偶联剂KH550改性纳米纤维素及其增强水性丙烯酸复合涂料研究

发布时间：2018-12-30 21:16

【摘要】：纳米纤维素以其独特的性能成为一种优良的聚合物增强材料,采用纳米纤维素复合水性涂料,有望改善水性涂料的漆膜性能,扩展纳米纤维素在水性涂料领域的应用。以往的研究中,纤维素纳米晶(CNC)已被较多地应用于增强水性涂料,但纤维素纳米纤丝(CNF)的应用还不多,主要原因是其在水相中的分散稳定性和与有机聚合物基质的相容性还没完全解决。鉴于此问题,本研究提出采用双亲性化学偶联剂来改性纤维素纳米纤丝并使其与水性涂料基体形成化学交联,从而实现纤维素纳米纤丝在水性涂料中的均匀分散、长期稳定和良好的界面亲和性,进而综合提高涂料的成膜性能。论文首先通过化学预处理结合高强度超声波的方法制备了纤维素纳米纤丝,考察了添加不同比例的硅烷偶联剂(KH550)对其表面接枝改性和分散稳定性的影响效果,并将改性后的纤维素纳米纤丝水悬浮液添加到水性丙烯酸涂料中,制备得到纳米纤维素复合涂料并通过浇铸法和刷涂法得到相应的复合涂膜。通过透射电子显微镜、傅里叶红外变换光谱、X射线光电子能谱、旋转流变仪、差式扫面量热仪和万能力学实验机等手段对改性纤维素纳米纤丝的分散状态、表面化学结构、流变和相转变特性,对复合涂料及其所制成复合涂膜的成膜特性、透明性、光泽度、微观形貌、断裂形式、热机械性能、硬度和耐磨性等进行了综合考察。主要结果如下：(1)纤维素纳米纤丝水悬浮液的浓度对其分散稳定性有很大影响,浓度过低在制备完成后很快就会出现沉降分层现象,浓度过高会出现凝胶现象。采用KH550可以提高纤维素纳米纤丝在水中的分散稳定性,但是添加量过少或过多都不能达到最好的效果。实验表明添加量为0.16%时,水悬浮液可保持长期稳定状态。(2)经过KH550改性后的纤维素纳米纤丝在涂料中能够分散均匀,且与涂料有良好的界面相容性。改性纤维素纳米纤丝水悬浮液的添加量会对复合涂料的整体产生影响,随着纤维素纳米纤丝添加量的增加,复合涂料的粘度、弹性模量、玻璃态转变温度、硬度和耐磨性等均明显提高,其中弹性模量最高可提高5倍,硬度提高2级,磨损量降低35%。(3)复合涂料成膜后具有良好的光透明性,纤维素纳米纤丝在漆膜中均匀分散,不会形成团聚而影响可见光的透过率,其可见光透光率可保持在80%-90%,光泽度几乎没有变化。综上表明,采用适量的KH550改性后的纤维素纳米纤丝来增强水性丙烯酸涂料,不会明显影响其透光性和光泽度,但可显著提高涂料的综合性能。
[Abstract]:Nanocellulose has become an excellent polymer reinforced material with its unique properties. The application of nano-cellulose composite water-based coatings can improve the film properties of water-based coatings and expand the application of nano-cellulose in water-based coatings. In previous studies, cellulose nanocrystalline (CNC) has been widely used in water-based coatings, but cellulose nano-fiber (CNF) has not been widely used. The main reason is that the dispersion stability and compatibility with organic polymer matrix in aqueous phase have not been completely solved. In view of this problem, an amphiphilic chemical coupling agent was proposed to modify cellulose nanofilaments and form chemical crosslinking with waterborne coatings matrix, so as to achieve uniform dispersion of cellulose nanofilament in waterborne coatings. Long-term stability and good interface affinity, and then improve the film-forming properties of the coating. Cellulose nanofilaments were prepared by chemical pretreatment and high intensity ultrasound. The effects of silane coupling agent (KH550) on the surface grafting modification and dispersion stability were investigated. The modified nano-fiber water suspension was added to the waterborne acrylic coatings to prepare the nano-cellulose composite coatings and the corresponding composite coatings were obtained by casting and brushing methods. By means of transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, rotary rheometer, differential scanning calorimeter and universal mechanical tester, the dispersion state and surface chemical structure of modified cellulose nanofilament were studied. The properties of film formation, transparency, gloss, micromorphology, fracture, thermo-mechanical properties, hardness and wear resistance of composite coatings and their films were investigated. The main results are as follows: (1) the concentration of cellulose nanofilament aqueous suspension has a great influence on its dispersion stability. When the concentration is too low, the phenomenon of sedimentation and delamination will occur soon after the preparation, and the phenomenon of gel will occur when the concentration is too high. KH550 can improve the dispersion stability of cellulose nanofilament in water, but too little or too much addition can not achieve the best effect. The experimental results show that the water suspension can maintain a stable state for a long time when the addition amount is 0.16. (2) the cellulose nanofilament modified by KH550 can be dispersed uniformly in the coating and has good interface compatibility with the coating. The content of water suspension of modified cellulose nanofilament will have an effect on the whole composite coating. With the increase of the amount of cellulose nanofilament, the viscosity, elastic modulus and glass transition temperature of the composite coating are increased. The hardness and wear resistance of the composite coatings were obviously improved. The elastic modulus was increased by 5 times, the hardness was increased by 2 grades, and the wear amount was reduced by 35. (3) the composite coatings had good transparency after forming film. Cellulose nanofilament was uniformly dispersed in the paint film and could not form agglomeration which affected the transmittance of visible light. The visible light transmittance of cellulose nanofilament could be kept in the range of 80-90 with almost no change in glossiness. The results show that proper amount of cellulose nanofilament modified by KH550 to strengthen waterborne acrylic coatings will not obviously affect its transmittance and gloss, but can significantly improve the comprehensive properties of the coatings.
【学位授予单位】：东北林业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O636.11;TQ637

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