Enhancing the interfacial strength of jute fiber/polylactic acid composites via surface carboxymethylation pretreatment and in situ growth of ZnO nanorods

ABSTRACTJute fibers (JFs) are considered an excellent reinforcement due to their abundant resources, environmental friendliness, low cost, lightweight, high specific strength and high specific modulus. However, they still suffer from surface defects that result in poor interfacial compatibility with polymeric matrices. This paper proposes a novel strategy that combines carboxymethylation pretreatment of JFs with in situ growth of ZnO nanorods (NRs) to enhance the mechanical properties of JFs and interfacial properties of JFs/polylactic acid (PLA) composites. The results indicate that carboxymethylation is a more effective method for removing pectin from the surface of JFs compared to conventional acid/alkali treatment. Subsequently, ZnO NRs are deposited in situ on the surface of carboxymethylation-treated JFs (c-JFs) through a seed-growth process, resulting in ZnO NRs@c-JFs. The impact of diverse process parameters, namely reaction time (t), reaction temperature (T) and concentration of zinc source (C), on the morphology and size of ZnO NRs was thoroughly investigated. Optimal process conditions were determined to be t = 6 h, T = 95°C, and C = 37.5 mmol·L−1, resulting in well-aligned ZnO NRs that completely filled up the grooves on JFs' surface. Compared to untreated JFs, the tensile strength and tensile modulus of ZnO NRs@c-JFs increased by 30.4% and 81.6%, respectively, while exhibiting lower hygroscopicity and higher thermal stability. Furthermore, JFs-reinforced PLA composites were fabricated via hot pressing and their interfacial strength was evaluated using a microdroplet debonding test. Compared to untreated JFs/PLA, the combination of carboxymethylation and ZnO growth in ZnO NRs@c-JFs/PLA resulted in a significant 334% increase in interfacial shear strength (IFSS), indicating highly improved interface bonding between JFs and PLA resin, which was primarily attributed to the formation of a 'zipper-like' mechanical interlocking structure between ZnO NRs and PLA. This study provides valuable guidance for enhancing the interface of natural fiber/polymer composites and highlights their potential applications.KEYWORDS: Nature fiber-reinforced polymer compositesjute fiberscarboxymethylationin situ depositionZnO nanorods AcknowledgementsThis work was supported by the National Natural Science Foundation of China (Grant No. 52203140 and No.52175329), Innovation Achievement Transformation and Application Project of "Insight Action" (No.62402010212) and the Scientific Research Foundation for Introduced Talents of Nanjing University of Aeronautics and Astronautics.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe work was supported by the National Natural Science Foundation of China [No. 52175329, 52203140]; Innovation Achievement Transformation and Application Project of "Insight Action" [No. 62402010212]; and the Scientific Research Foundation for Introduced Talents of Nanjing University of Aeronautics and Astronautics .