聚多巴胺仿生强化竹塑界面的影响机制与增容机理研究

Bamboo plastic composites serve the efficient utilization of forest resources, whose key problem lies in the interface compatibility: the surface of the bamboo flour gives the poor affinity with the surface of the thermoplastic, which compromises the composite performance, thus hindering the application as engineering materials. The super adhesive protein of the marine shellfish can achieve the firm adhesion between the shellfish and various surfaces with the excellent weather-resistance, thus providing the inspiration for enhancing the bamboo plastic interface; however, the direct utilization of the adhesive protein suffers the high cost, complicated process, and extremely-low yield. To simulate the molecular structure of dopa - the key component of the adhesive protein, polydopamine (PDA) is employed in this research to synthesize nano-modifiers for creating the BPC interface with the high compatibility and weather-resistance, which is aimed to solve two scientific problems: A. To elucidate the compatibilization mechanism of PDA: the thermal and moisture stability, and mechanical properties of the PDA modified bamboo flour and BPC will be evaluated, the micro-morphology, crystalline structure, chemical elements and functional groups of the surface of the bamboo flour and BPC, and the relaxation process of molecular movements, creep and relaxation, dynamic visco-elasticity, thermal expansion, rheology, melting and crystallization of the BPC interface will also be characterized, which will be used to investigate the enhancement effect of PDA on physical and mechanical properties, and the interface combination. B. To reveal the effect mechanism of PDA modification: Three key factors (conditions in the synthesis of PDA modifiers, conditions in the modification of the bamboo flour, and conditions in the preparation of BPC) will be considered, and the quantitative correlation between levels of these factors and results of the performance and interface of the bamboo flour and BPC will be established. This research will lay a theoretical foundation for the bionic enhancement of the bamboo plastic interface.

发展竹塑复合材料（BPC）是对森林资源高效利用，关键科学难题在于界面相容性：竹粉表面与热塑性高聚物亲和力差，制约复合性能、阻碍工程应用。海洋贝类的超级粘附蛋白能使其牢固附着于各种基材、久经冲蚀而不剥离，为BPC界面增容提供了启发，但直接利用成本高昂、工艺复杂、产量极低。本项目对其关键成分多巴分子仿生，以聚多巴胺（PDA）合成纳米增容剂构建高相容耐老化BPC界面，拟解决两个科学问题：A. 阐明PDA增容机理：评价PDA改性竹粉与BPC的热湿稳定性、力学性质，表征二者表面的微观形貌、结晶结构、元素与官能团，及BPC界面的分子弛豫、蠕变松弛、动态粘弹、热膨胀、流变、熔融结晶，考察PDA对物理力学与界面结合的强化效应。B. 揭示PDA仿生强化影响机制：关注三个影响因子，即PDA合成条件、竹粉改性条件、BPC制备条件，将建立因子水平与性能界面指标间的定量关联。本项目将为竹塑界面仿生强化奠定理论基础。

竹塑复合材料是原料广泛、价格低廉的可持续绿色材料，经济价值高、市场潜力大。但竹子和塑料较差的相容性制约着其的发展。本项目借助贻贝黏蛋白启发的聚多巴胺（PDA）改性竹粉，增强了与热塑性聚合物的相容性，阐明了改性条件对界面增容的影响机制，结合微观测试及热分析揭示了增容机理。重要结果和关键数据包括：（1）采用直接混合、浸渍负载和原位沉积三种技术对竹粉进行PDA改性并制备复合材料，研究了竹粉微观形貌及复合材料力学性能、界面微观形貌。原位沉积改性竹粉表面最平滑，分支最少；浸渍负载改性竹粉表面较平滑，依然有分支和毛糙；直接混合改性竹粉表面基本没有变化。原位沉积法改性竹粉与基质更相容，制得复合材料的力学性能最优，其弯曲强度、弯曲模量、拉伸强度、拉伸模量和冲击强度分别提高了35.1%，23.9%，42.3%，39.9%和65.7%；浸渍改性法对竹粉的改性效果次之，直接混合法几乎没有效果。（2）采用原位沉积法以不同浓度多巴胺溶液处理竹粉，模压成型制备了复合材料，比较了竹粉表面化学结构、结晶性能、纳米尺寸微观形貌以及复合材料的熔融行为、热稳定性、动态力学性能、吸水性，揭示了复合材料对竹塑界面的强化机理。光谱分析表明，改性对竹粉表面官能团影响微弱，适宜的改性液浓度能减少游离羟基；原子力显微镜测试表明，多巴胺氧化自聚形成的PDA纳米微粒大小约77 nm，负载量较低时可提高竹粉表面粗糙度；量热分析发现，PDA的存在提高了复合材料结晶度，且结晶度随PDA负载量提高而增大；热重分析证明，经PDA改性后，复合材料各阶段的起始热解温度提高，但PDA负载量影响微弱；动态力学分析表明，改性复合材料具有较高的储能模量及较低的损耗因子，证明改性提高了竹粉在复合材料中的分散性及与基质的相容性，多巴胺改性液浓度为1.0 mg/mL时，动态力学性能最优；多巴胺溶液改性可以降低复合材料的吸水性，最大降低效果为4.32%。综上，本项目为发展高性能竹塑复合材料、高效科学利用森林资源开辟了新的思路，为竹塑界面仿生强化奠定了理论基础。