【作者】 张帆；

【导师】 马建中； 徐群娜；

【作者基本信息】 陕西科技大学 ， 轻工技术与工程， 2017， 博士

【摘要】 随着人们对绿色环保的追求,天然高分子涂层材料备受研究者们的青睐。酪素作为涂层材料具有耐高温、粘结力强等优势,是皮革、造纸、包装等工业领域应用最早且最为广泛的天然高分子之一。然而,酪素涂层具有硬、脆、易长霉的缺陷,限制了其进一步应用。针对此问题,科研工作者通常会引入其他聚合物组分对酪素进行物理或化学改性。在提高酪素涂层柔韧性的同时往往会对涂膜本身的卫生性能（透气性和透水汽性等）产生不利影响。加之由于酪素自身结构复杂,酪素改性过程中的界面作用以及改性酪素乳液体系中的聚合机理研究不甚明晰且缺乏系统性。本研究提出在聚丙烯酸酯改性酪素的基础上设计并引入中空结构和无机纳米组分,获得可室温成膜的功能型纳米中空乳液,进一步将防霉剂负载于空腔,获得具有缓释防霉效果的复合载体;揭示改性过程中的相关界面作用机制,探究聚合机理以及形貌调控机制,课题具有重要的科学意义和实际意义。具体工作包括:（1）以酪素、甲基丙烯酸以及丙烯酸酯类单体为原料,采用乳液聚合法和碱溶胀法制备聚丙烯酸酯改性酪素中空微球。通过考察壳层组分中单体比例、溶胀条件、甲基丙烯酸用量等因素对乳胶粒结构及其涂膜不透明性的影响规律,优化合成工艺。TEM、SAXS、AFM、DLS测试结果显示:成功获得了可室温成膜的纳米级聚丙烯酸酯改性酪素中空微球,粒径大约为90nm左右。FT-IR结果表明:羧基链段发生了迁移。扫描电镜（SEM）结果表明中空微球乳液成膜后依然能保持中空结构。涂膜显示出优异的不透明性。皮革涂饰应用结果显示:与聚丙烯酸酯改性酪素核壳微球相比,聚丙烯酸酯改性酪素中空微球涂饰革样的卫生性能大幅提升。（2）分别采用原位共混法和原位聚合法在以上体系中引入纳米SiO₂,制备聚丙烯酸酯改性酪素/SiO₂复合中空微球乳液。具体地:一方面通过原位共混法在聚丙烯酸酯改性酪素中空微球上引入纳米SiO₂粉体。主要考察纳米SiO₂种类、纳米SiO₂用量以及偶联剂用量对复合中空微球乳液稳定性、涂膜不透明性以及机械性能的影响规律。结果表明:在溶胀前原位共混1.0%的亲水性纳米Si O₂,偶联剂用量为1.5%时,可获得卫生性能较好的复合中空微球乳液。另一方面在己内酰胺改性酪素（CPL-CA）中原位引入纳米SiO₂粒子,合成CPL-CA/SiO₂ NPs作为杂化Pickering稳定剂,进而在该稳定剂作用下,通过乳液聚合和碱溶胀法获得复合中空微球乳液。考察杂化Pickering稳定剂的乳化稳定性,探究前驱体用量和偶联剂用量对复合中空微球乳液性能与涂膜性能的影响规律。结果显示:在纳米粒子前驱体用量8%、偶联剂用量12%时获得的复合中空微球乳液涂膜的机械性能和不透明性较好。TEM、AFM结果显示两种方法均可制备出平均粒径约为160 nm的复合微球,且纳米SiO₂分布在微球最外层,有利于提高微球的结构稳定性。（3）利用聚丙烯酸酯改性酪素/SiO₂复合中空微球的内部空腔,以及复合中空微球结构随溶胀条件变化的特性,选择合适的工艺负载防霉剂,制备缓释防霉型酪素基纳米复合载体。以防霉剂的包覆效率、涂膜防霉效果为主要指标,考察了防霉剂种类、防霉剂包覆方式、防霉剂用量、包覆时间以及包覆温度对酪素基纳米复合载体的粒径以及涂膜防霉性能的影响。通过TEM、SAXS、TGA、UV-Vis等对负载防霉剂酪素基纳米复合载体的结构、微观形貌、尺寸、包覆效率等进行表征。结果显示:当在溶胀1 h后加入防霉剂,包覆温度为90℃,防霉剂用量为10.0%时,制备的酪素基纳米复合载体对防霉剂负载效率达70%,且防霉效果良好。TEM、SAXS、DLS表征结果显示:防霉剂主要分布于纳米复合载体空腔内部与表面。与不含防霉剂的酪素基复合中空微球相比,负载防霉剂后微球的粒径明显增大,约为200nm。涂饰应用结果显示:负载防霉剂后,复合载体的卫生性能明显下降,机械性能略降低。这也从侧面说明防霉剂负载到酪素基纳米复合载体的内部。（4）分别以CPL-CA、CPL-CA/SiO₂ NPs形成的乳状液为模板,探究其对聚丙烯酸酯改性酪素中空微球以及聚丙烯酸酯改性酪素/SiO₂复合中空微球乳液稳定性的影响规律,建立相关界面作用机制。考察了CPL-CA的浓度、pH等因素对乳状液在油水界面的稳定作用。通过改变KH570与TEOS质量比例,实现对CPL-CA/SiO₂ NPs表面活性的调控。结果发现:不同稳定剂的表面润湿性及其在界面的稳定方式决定了乳液聚合机理的不同。光学显微镜结果显示:CPL-CA/Si O₂ NPs具有更为优异的乳化稳定性,这是由于Si O₂粒子与CPL-CA对复合体系的乳化稳定性起着协同作用。通过追踪从液滴到乳胶粒的结构演变过程,发现CPL-CA/Si O₂ NPs可作为Pickering乳液中的固体粒子,但其聚合机理与常规Pickering乳液聚合不同。更多还原

【Abstract】 Natural polymer coating materials have attracted considerable interests along with the pursuit of environmental protection.As a kind of coating materials,casein with high temperature resistance,strong adhesion and other advantages,is the earliest and most widely used one of natural polymers in industries,especially in leather,paper-making,packaging and other fields.However,the pristine casein film is hard,brittleness and prone to mildew,which limit its application.In order to address the issues,researchers usually introduce other polymer components into casein by physical or chemical modification.Unfortunately,the modification always has an negative effect on their hygienic performance（air and water vapor permeability）although flexibility can be improved.In addition,the interface action of casein system during modification process is not obvious because of its complex structure.And researches on the relative polymerization mechanism lack of systematicness.Therefore,based on the polyacrylate modified casein system,this study put forward to design and to introduce hollow structure and inorganic nano components to obtain functional ambient film-forming emulsion.Further,anti-mould agent was loaded into the cavity thus obtaining a slow-released casein-based composite carrier.It has important scientific and practical significance to reveal the interfacial mechanism and explore the relationship between polymerization mechanism and controlled morphology in the process of modification.This work focused on:（1）Polyacrylate modified casein hollow microspheres were prepared from casein,methacrylic acid and acrylate monomers by emulsion polymerization and alkali swelling method.Effects of monomer ratio in shell components,swelling condition,methacrylic acid usage on structure of the latex particles and the opacity of coatings were investigated.The results of TEM,SAXS,AFM and DLS showed that nano scale hollow microspheres were successfully obtained,and their particle size was about 90 nm.Also,the as-prepared microsphere coatings can be formed at room temperature.FT-IR results confirmed that carboxyl groups migrated during the polymerization.SEM data demonstrated that there were many visible hollow holes on the surface and cross-section of the coatings.The obtained coatings showed excellent opacity.Application results showed that hygienic properties of the as-prepared hollow microspheres were significantly improved compared with that of core-shell microspheres.（2）In-situ blending and in-situ polymerization were separately used to introduce nano-SiO₂ thus prepare polyacrylate modified casein/SiO₂ hollow composite emulsion.Specifically,on one hand,nano-SiO₂ powders were introduced into polyacrylate modified casein system by in-situ blending.Effects of nano SiO₂ type,nano SiO₂ usage and coupling agent usage on emulsion stability,film opacity and mechanical properties of the hollow composite microspheres were investigated.The results showed that hollow composite emulsion coatings with good sanitary performance could be obtained when 1%of hydrophilic nano SiO₂ and 1.5%of coupling agent were added before swelling.And on the other hand,in-situ generated nano SiO₂ particles were introduced into the caprolactam-modified casein to synthesize hybrid Pickering stabilizer（CPL-CA/SiO₂ NPs）.Under action of the stabilizer,hollow composite emulsion was obtained by emulsion polymerization and alkali swelling routes.Emulsifying stability of the hybrid Pickering stabilizer was systematically investigated.Effects of precursor usage and coupling agent usage on performance of emulsion and and its coating were discussed.When the usage of precursor was 8%and coupling agent usage was 12%.The obtained hollow composite emulsion coatings had the expected mechanical properties and opacity performance.The results of TEM and AFM showed that the hybrid hollow microspheres produced by two methods had an average particle size of 160 nm.And nano SiO₂ were distributed on the outermost layer,which was helpful to improve the structural stability of the hollow composite microspheres.（3）Using the cavity of polyacrylate modified casein/SiO₂ hollow composite microspheres and the variable structure of hollow composite microspheres under swelling conditions,casein-based composite carrier was obtained by selecting appropriate process of loading anti-mould agent.The effects of anti-mould agent types,loading method,anti-mould agent usage,loading duration and loading temperature on particle size and their properties were investigated.Microstructure,size and loading efficiency of the as-prepared carrier were studied by TEM,SAXS,TGA and UV-Vis.The casein-based composite carrier could encapsulated 70%of the anti-mould agents when temperature was 90℃and the anti-mould agent usage was 10%adding after swelling for 1 h.Results showed that casein-based composite carrier had good anti-mildew effects.TEM,SAXS and DLS data showed that the anti-mould agent was located inside the cavity or on the surface of the carrier.Compared with casein-based hollow composite microspheres without anti-mould agent,the particle size was obviously increased to about 200 nm after loading anti-mould agent.Application results revealed that hygienic performance of the casein-based composite carrier decreased significantly while mechanical properties decreased slightly,which further illustrated that the anti-mould agent were loaded into the cavity of casein-based composite carrier,thus blocked the channel of gas molecules or water vapor molecules.（4）Polyacrylate modified casein hollow microspheres and polyacrylate modified casein/SiO₂ hollow composite microspheres were fabricated via emulsion polymerization stabilized by CPL-CA and CPL-CA/SiO₂ NPs,respectively.The related interface mechanism was established.As for CPL-CA stabilizer,effect of concentration and pH on emulsion stability in oil-water interface was investigated.By controlling KH570/TEOS ratio,surface activity of CPL-CA/SiO₂ NPs was adjustable.The results showed that CPL-CA/SiO₂ NPs with excellent emulsifying stability can be used as solid particles for Pickering emulsion.It was found that wettability of particles and stabilization of hybrid Pickering stabilizer on interfaces would affect the emulsion polymerization mechanism.Optical microscopy results showed that CPL-CA/SiO₂ NPs had better emulsifying stability than that of CPL-CA.It was proved that SiO₂particles have a synergistic effect with CPL-CA on emulsifying stability.Structure evolution from a droplet to a latex particle was observed by optical microscopy.It was found that CPL-CA/SiO₂ NPs could be regard as solid particles in Pickering emulsion.As a special hybrid Pickering stabilizer,CPL-CA/SiO₂ NPs could be applied in Pickering emulsion polymerization.Also,this mechanism differed from the conventional Pickering mechanism.更多还原