Bio-based composites made from bamboo fibers with high lignin contents: a multiscale analysis

ABSTRACTTo meet societal and economic expectations, the bio-based composite market is developing. However, some issues remain, especially for lignocellulosic fiber composites, due to their highly hydrophilic nature which impacts the composite performance. This study focuses on bamboo fiber-polypropylene composites manufactured by film stacking using fiber mats obtained through a wet laid process. To individualize fibers, raw bamboo was cooked using an alkaline treatment: the soda process, i.e., using NaOH in order to keep a certain amount of lignin on fiber surface. A maximum surface lignin content of 81.%, measured by XPS analysis, was obtained, from the 1 wt.% NaOH concentration. The corresponding bulk lignin content, measured by Klayson method, is 21.%. The macroscopic properties of bamboo fiber-polypropylene composites were evaluated with regard to material microstructure through a multiscale analysis. The best mechanical properties were obtained for composites manufactured from bamboo fiber prepared using a 1 wt.% NaOH, which corresponds to the highest lignin content (3.5 GPa and 53 MPa for modulus and strength in tensile tests, 3.8 GPa and 64 MPa in bending tests). The good mechanical performance of the composites was attributed to the improved compatibility between the fiber and the matrix, evidenced by multiscale studies.KEYWORDS: Bio-compositesnatural fibersinterface/interphasemechanical testingatomic force microscopy AcknowledgementsLGP2 is part of the LabEx Tec 21 (Investissements d’Avenir - grant agreement n°ANR-11-LABX-0030) and of PolyNat Carnot Institute (Investissements d’Avenir - grant agreement n° ANR-16-CARN-0025-01). This research was made possible thanks to the facilities of the TekLiCell platform funded by the Région Rhône-Alpes (ERDF: European regional development fund) and the LabEx CEMAM (Investissements d’Avenir, grant agreement #ANR-10-LABX-44-01). The authors gratefully acknowledge Research and Researchers for Industries Scholarship (Grant No. PHD 60I0039) and Charoen Triphop Limited Partnership for their financial support during the research. The authors also thank Thierry Encinas and Stephane Coindeau (CMTC, Grenoble) for the XRD acquisition, and Bertine Khelifi (LGP2) for SEM images.Disclosure statementThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.Data availability statementAll data generated or analysed during this study are included in this published article [and its supplementary information files].Supplementary dataSupplemental data for this article can be accessed online at https://doi.org/10.1080/09276440.2023.2253640