Low-cost mussel inspired poly(catechol/polyamine) coating of bamboo fibers surface and its use as a reinforcement of PLA matrix

Bamboo fibers/polylactic acid composite is a new fully biodegradable composite with broad application prospects. However, the poor interfacial compatibility between hydrophilic bamboo fiber (BF) and hydrophobic polylactic acid (PLA) polymer is the key problem that affects the overall performance of composite. Therefore, improving the hydrophobicity of the BF using new and more effective modification methods is of great importance. In this paper, an effective low-cost catechol/polyamines system was used to replace expensive dopamine to enhance the hydrophobicity of the bamboo fiber surface. The effects of catechol and various polyamines combinations and molar ratios on the surface characteristics of the modified bamboo fiber and the properties of BF/PLA composites were explored. Results showed that when using catechol/tetraethylenepentamine (TEPA) combination and molar ratio of 1:1, the composite has shown the best mechanical properties, in which the flexural strength and modulus, tensile strength and modulus and impact strength are increased by 18.8%, 20.9%, 16.8%, 10.9% and 18.6% respectively compared with the unmodified composite. In addition, it also showed improved thermal properties. This indicates that the surface modification had significantly enhanced the interfacial adhesion between the bamboo fiber and the resin matrix. In comparison with the dopamine modification method, the catechol/polyamine modification strategy is very cheap (only 1% of the cost of dopamine) and its reaction time is shorter. Moreover, it has versatility and is more suitable for large-scale production of high-performance composites.