Effects of acacia gum and bentonite on the properties of composite bioplastics made of starch and acid hydrolyzed cellulose

Abstract

Abstract This work focuses on the analysis of the effect of acacia gum and bentonite addition on the properties of the biocomposite cassava starch $$\:-$$ acid $$\:-$$ hydroxylyzed cellulose films. The acid $$\:-$$ hydroxylyzed cellulose (NCE) is obtained using cellulose from Ceiba pentandra . Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analyses (TGA) coupled to differential scanning calorimetry (DSC), mechanical stress-strain tests, soil burial biodegradation, and moisture absorption tests were used to characterize the films. FTIR and XRD analyses evidenced the presence of acacia gum and bentonite in the various formulations. Crystallinity indices, from XRD, was related to improved adhesion of polymers chains due to the acacia gum addition. DSC analysis shows a retardant effect to the melting of the starch-cellulose matrix when acacia gum and/or bentonite are added. This effect was associated to improve adhesion brought by the acacia gum and the barrier to heat diffusion due to the mineral phase. The moisture adsorption is reduced of 10% and 18% upon addition of acacia gum and combine bentonite-acacia gum respectively. The interactions between the polymers chains in the starch-NCE film with the additives seems improved with the addition of acacia gum. Biodegradation test evidenced that gum and bentonite addition, through moisture adsorption reduction, induce a slowing of the degradation of all the composites films. The Young modulus of the starch-NCE is improve from 39.9 MPa to 150.7 MPa and 133.3 MPa respectively with the addition of acacia gum and acacia gum $$\:-$$ bentonite. Overall, gum and gum-bentonite addition in starch-cellulose films induce biodegradation retardation through reduce water sensitivity.