Barrier Properties and Hydrophobicity of Biodegradable Poly(lactic acid) Composites Reinforced with Recycled Chinese Spirits Distiller’s Grains

Abstract

Adding natural biomass to poly(lactic acid) (PLA) as a reinforcing filler is a way to change the properties of PLA. This paper is about preparing PLA/biomass composites by physically melting and blending Chinese Spirits distiller’s grains (CSDG) biomass and PLA to optimize the composite performance. Composites of modified PLA (MPLA) with varying amounts of CSDG were also prepared by the melt-mixing method, and unmodified PLA/CSDG composites were used as a control group for comparative analysis. The functional groups of MPLA enhanced the compatibility between the polymer substrate and CSDG. The composite water vapor/oxygen barrier and mechanical properties were studied. It was found that the barrier and mechanical properties of MPLA/CSDG composites were significantly improved. SEM was adopted to examine the tensile section structure of the composites, and the compatibility between the filler and the matrix was analyzed. An appropriate amount of CSDG had a better dispersibility in the matrix, and it further improved the interfacial bonding force, which in turn improved the composite mechanical properties. X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were conducted to determine the crystalline properties and to analyze the stability of the composites. It was found that the CSDG content had a significant effect on the crystallinity. Barrier and biodegradation mechanisms were also discussed.

Effect of Biochar Addition on Mechanical Properties, Thermal Stability, and Water Resistance of Hemp-Polylactic Acid (PLA) Composites

“…In general, polysaccharides are known to influence surface properties when used in polymeric composites as fillers; one of their main effects is to lessen the water repellency of the materials. Despite this decrease caused by hemp fibers, the value of WCA obtained in this study (up to 109°) is still higher compared to the 85° reported in prior research [ 41 ] for PLA reinforced by 30 wt% distiller ’ s grain (a by-product from ethanol fuel industries) fibers.…”

“…They reported that the lack of adhesion between the matrix and the filler contributed to the formation of micro-voids in the internal structure of the composite responsible for increasing the water uptake. In a similar experiment [ 41 ], the increase of WA rate in PLA-grain fibers composites was explained by the occurrence of hydroxyl groups in natural polymers (i.e., cellulose, hemicellulose, and lignin).…”

“…However, 20 wt% BC decreased the T g value from 58.8 °C to 52.9 °C, which indicates that a high amount of BC increased the mobility of PLA molecular chains. Chen et al [ 41 ] studied the isotherms of PLA reinforced by variable concentrations of recycled grains derived from the distillation of Chinese spirits (from 10 wt% to 50 wt%). Their results suggested that T g diminished with the increase of filler content because of the occurrence of polar groups in the filler ’ s molecules.…”

“…Similar findings were also found by Silva et al [ 52 ], who commented that the incorporation of eucalyptus fibers in PLA led to an increment in the overall permeability and diffusion velocity of water molecules in the studied composites. Chen et al [ 41 ] explained the increase of the WA rate in the PLA distiller ’ s grain fibers composites with the occurrence of hydroxyl groups in natural polymers (i.e., cellulose, hemicellulose, and lignin). Finally, the WA of hemp-PLA continued to increase as the BC was added.…”

Improvement in Thermal Stability of Flexible Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) Bioplastic by Blending with Native Cassava Starch

“…This is due to its excellent biodegradability, biocompatibility and compostability, as well as being environmentally friendly and having good processability and feasibility for an increased production scale [ 5 , 6 ]. However, the low flexibility of PLLA, due to its high glass-transition temperature (T g , around 60 °C), limits its use in many applications [ 7 , 8 , 9 ]. High-molecular-weight PLLA- b -poly(ethylene glycol)- b -PLLA triblock copolymers (PLLA-PEG-PLLA) have exhibited more flexibility than PLLA because of the high flexibility of PEG middle blocks [ 10 , 11 , 12 ].…”