Effect of borax addition on the structural modification of bentonite in biodegradable alginate-based biocomposites

Functionalized next generation biodegradable polymeric systems (bioplastics) that have better compatibility, enhanced relaxation, and thermal properties were designed using bentonite-added alginate biocomposite films in the presence of borax. A series of bentonite-added biocomposite films crosslinked with CaCl₂ were characterized by using methods like XRD, FTIR, TGA, DTA/DSC, DMA, and AFM. A plausible structural mechanism with Ca²⁺ crosslinking gel formation known as egg-box and borate ion complexes was proposed to elucidate the interactions between borax and bentonite/alginate biocomposites. Enhanced compatibility and hybrid properties of raw fillers were confirmed by mineral processing steps involving hydrocyclone purification for bentonite and recrystallization steps for borax. The structure of bentonite and also bentonite hybrid biocomposites were clearly improved upon small additions of borax into the matrix. The presence of borax was found to provide a more intercalated or exfoliated morphology for a given hybrid biocomposite structure. Borate ions dissociated in aqueous solution provided a better effect on the intercalation of bentonite by imparting new hydrogen bonding sites, diol-complexes, and didiol-crosslinking gels.