All-cellulose composite laminates prepared from pineapple leaf fibers treated with steam explosion and alkaline treatment

Abstract

Pineapple leaf fibers with diameters of 43 ± 0.1 µm were treated by two different approaches: the alkaline treatment and the combination of the steam explosion and alkaline treatment. The observations revealed the steam explosion process efficiently provided 3.4 µm diameter fibers with a less amount of lignin and a higher proportion of cellulose, compared with the alkaline-treated fibers. The steam-exploded fibers showed higher crystallinity and more thermal stabilities than the alkaline-treated fibers. No structural change from cellulose I to cellulose II was detected from both treated pineapple leaf fibers. Subsequently, all-cellulose composite laminates were prepared from these two types of treated pineapple leaf fibers mats. The higher tensile strength and modulus were obtained from the steam-exploded pineapple leaf fibers composite laminates due to larger surface areas of the fibers interacted with the cellulose matrix. Fracture morphology of the composites was studied after tensile deformation. The combination mechanism of fiber breakage and fiber pull-out deformation was observed from the steam-exploded pineapple leaf fibers composite laminates, whereas only fiber pull-out mechanism was found from the alkaline-treated pineapple leaf fibers composite laminates. The fiber width and amounts of the matrix filling in pores in a mat were found to dominate the mechanical properties of the all-cellulose composites.