A bioplastic with high strength constructed from a cellulose hydrogel by changing the aggregated structure

Abstract

The direct use of cellulose to fabricate materials such as common plastics as synthetic polymers has hardly been investigated. In the present paper, bioplastics of a new class are constructed, for the first time, by hot-pressing cellulose hydrogel, and are different from common plastics in terms of their processability. The cellulose hydrogels were prepared from cellulose solution in an alkali hydroxide/urea aqueous system with cooling by physical cross-linking. Due to the removal of cellulose molecules in the hydrogel state, the hot-pressing induced a transition in the aggregated structure in the cellulose bioplastics, leading to a plastic deformation. The results from ¹³C NMR, SEM, and FT-IR confirmed that a radial orientation of cellulose molecules occurred in the planar direction of the plate, whereas an increase of amorphous zones appeared in the vertical direction. The resulting cellulose bioplastics were transparent, as a result of the uniformly orientated structure. Moreover, the cellulose bioplastic exhibited much higher tensile strength, flexural strength and thermal stability as well as a lower coefficient of thermal expansion than common plastics and regenerated cellulose films. The whole life cycle assessment showed that the cellulose bioplastic is an environmentally friendly material. This work opens up a completely new avenue to construct a valuable bioplastic directly from cellulose pulps rather than their derivatives.