Water barrier and mechanical properties of sugar palm crystalline nanocellulose reinforced thermoplastic sugar palm starch (TPS)/poly(lactic acid) (PLA) blend bionanocomposites

Abstract

The disposal of non-biodegradable synthetic plastic wastes is linked with air, land, and marine pollutions. Incineration of plastic wastes released toxic substances into the air while recycled plastics end up accumulated in landfill and dumped into the ocean. In this study, novel sugar palm starch reinforced with sugar palm crystalline nanocellulose was blended with poly(lactic acid) (PLA) with various formulations to develop alternative materials potentially substituting conventional plastics. X-ray diffraction analysis demonstrated broad amorphous scattering background with minor diffraction peaks at 2θ of 19.4° and 22° associated with VH-type and B-type crystal structure for all blend bionanocomposites samples. Higher solubility rates were observed for PLA20TPS80 (96.34%) and PLA40TPS60 (77.66%) associated with higher concentration of plasticizers providing extra space in the polymer chains to be penetrated by water molecules. Increasing PLA content was not necessarily enhancing the water vapor permeability rate. Dynamic mechanical analysis presented a significant increment in storage modulus (E′) for PLA60TPS40 (53.2%) compared to the trivial changes of PLA70TPS30 (10%) and PLA80TPS20 (0.6%). However, significant improvement in impact strength occurred only at PLA40TPS60 (33.13%), and further addition showed minor improvement between 12 and 20%. Overall, it is noted that PLA60TPS40 demonstrated adequate functional properties to be used in food packaging application.