Effects of facile chemical pretreatments on physical-chemical properties of large clustered and small monopodial bamboo microfibers isolated by steam explosion

To explore the facile and high-efficient combining isolation method of bamboos and develop their high valueadded fiber functional materials, this study aims at investigating the effects of four chemical soakingpretreatments on physical-chemical properties of bamboo microfibers that were isolated using eco-friendly steam explosion (SE) from four local bamboo species (Chimonobambusa quadrangularis (CQ), Qiongzhuea tumidinoda (QT), Dendrocalamus giganteus (DG), and Dendrocalamus sinicus (DS)). The variations in the micromorphology, width distribution and major chemical composition of bamboo microfibers as well as their thermal stability, crystallinity, surface hydrophilicity, and macro- and nano- mechanical properties were comprehensively characterized. The CQ, QT, DG, and DS bamboo microfibers obtained by the combination of mild alkali pretreatment and steam explosion displayed the smallest width sizes (149.57, 150.76, 177.33, and 172.67 mu m), the highest cellulose contents (68.14 %, 67.62 %, 67.92 %, and 62.36 %), and the lowest hemicellulose contents (12.64 %, 17.24 %, 15.94 %, and 16.42 %) compared to their controls. Four chemical soaking pretreatments improved the thermal stability of bamboo microfibers but generally reduced their macro- and nano-mechanical properties. The elongation at break of bamboo microfibers pretreated by mild alkaline were effectively elevated. Acid-pretreated bamboo microfibers effectively increased the hydrophobicity of cellulose microfibrils with the highest water contact angle (WCA) value (56.8 degrees). IL-pretreated bamboo microfibers improved the surface roughness and hydrophilicity (WCA=44.3 degrees).