Compatibility Interface Construction And Performance Research On Mussel Biomimetic Modification Of Bamboo Fiber Enhanced Polylactic Acid Composites

Bamboo fiber/polylactic acid（BF/PLA）composites has broad application prospects in food packaging,medical and engineering fields due to their advantages of high strength,degradability,good biocompatibility,and excellent processability.However,the poor interfacial compatibility between bamboo fiber and PLA limits the further development of BF/PLA composites.The surface of BF was modified with dopamine and tannin,and a multi-scale modification system was designed to construct a functionalized biomimetic modified coating on the surface of BF.Through functional molecular design and interface structure control,a green,mild and controllable interface modification method is proposed to improve the interface bonding strength between BF/PLA.In order to prepare BF reinforced polymer composites,bamboo resources can be efficiently utilized.The main research conclusions were as follows:（1）Co-deposition of PDA/PEI hybrid polymeric functional modified coatings on BF using Dopamine/Polyethyleneimine（DA/PEI）Michael addition or Schiff base reaction.The composition of the copolymerization system and the effect of PEI addition amount on the copolymerization system and the properties of the composite were systematically studied.PEI accelerated the polymerization process of PDA and suppresses the agglomeration of large particles during the polymerization of PDA.The PDA/PEI hybrid polymer coating was successfully co-deposited on the BF surface,when the mass ratio of DA/PEI was 1:1,the hybrid coating achieved uniform coating on the BF surface.At this time,the interface properties of the co-deposition BF/PLA were best,and the flexural strength,tensile strength and impact strength were increased by 9.43%,7.66%and 35.04%,respectively.（2）Based on the excellent reactivity of PDA/PEI hybrid polymerization functionalized modified coating,nano-silica（Si O₂）and（3-mercaptopropyl）trimethoxysilane（MPTMS）were introduced into PDA/PEI modified bamboo fibers（PBF）surface,further optimize the surface properties of BF,and construct multi-scale organic-inorganic hybrid modified coating.The interfacial enhancement effect of inorganic nano-Si O₂ and organic modifier MPTMS was studied.After the synergistic reinforcement,the interfacial compatibility between the BF and the PLA matrix was improved;the tensile strength,flexural strength and impact strength of the composite were increased by 29.48%,29.67%,and 48.73%,respectively.（3）Based on the outstanding adhesion and modifiability of the PDA coating,an efficient and mild"co-deposition method"was used to co-deposit PDA and hydrophobic cardanol siloxane（AC）on the surface of bamboo fibers to prepare an excellent hydrophobic coating.The surface of the fiber was mainly composed of PDA and aliphatic side chains of cardanol,and a coating with excellent reactivity and hydrophobicity was constructed on the surface of the bamboo fiber,thereby enhancing the infiltration and chemical bonding of the PLA matrix to the BF.After modification,the interface of the composite was optimized,the mechanical strength was improved,the surface free energy of the composite material system was significantly reduced,and the hydrophobicity was enhanced.（4）Inspired by the excellent adhesion structure properties of polydopamine,adhesion proteins ha strong metal coordination and complexation ability,and can form stable complexes with metal oxides and metal ions.Choose tannic acid（TA）and Fe³⁺as raw materials,,in a simulated dopamine polymerization environment,a metal-polyphenol modified coating was formed on the fiber surface through the interaction of tannic acid and Fe³⁺（TA@Fe）coordination bonds to improve the interfacial properties between the bamboo fiber and the PLA matrix.The TA@Fe³⁺metal-polyphenol network successfully attached to the fiber surface and increased the surface roughness of the fiber,enhanced the mechanical condensation between the fiber and polylactic acid,improved the interface properties,and increased the flexural strength,tensile strength and impact strength by 52.93%,33.07%and 69.36%,respectively.