All-cellulose composite laminates with low moisture and water sensitivity

A conventional hand lay-up and compression molding based surface selective dissolution technique was utilized to prepare all-cellulose composite (ACC) laminates with varying dissolution times, while lyocell fabric and ionic liquid (1-butyl-3-methyl imidazolium chloride) were used as raw materials. The density of composites increased with increasing dissolution time due to reduction in porosity and formation of more compact composite structure. The tensile strength of the composites increased up to 2 h dissolution time and reduced slightly for higher dissolution time. However, Young's modulus of the composites increased significantly, with increasing dissolution time. Water-absorbency at the surface of ACCs also reduced significantly with increasing dissolution time during preparation of ACCs, imparting slight hydrophobicity in the ACC-laminates prepared by using 2 h or more dissolution time. The contact angle of the composites produced with 4 h dissolution time was about 76.3 degrees and complete absorption of the water droplet took almost 24 min. Such high contact angle was obtained due to a change in chemical as well as crystallographic structure of cellulose as analyzed by ATR-FTIR and solid-state C-13 NMR, which was further supported by WAXD, TGA and DTG analysis. A different trend was observed for water and oil absorbency of ACCs based on their absorption mechanism. (C) 2018 Elsevier Ltd. All rights reserved.