Experimental Determination of Molecular Weight-Dependent Miscibility of PBAT/PLA Blends

Abstract

Blends of poly(butylene adipate-co-terephthalate) (PBAT) and polylactide (PLA) have attracted the attention of academia and industry as a sustainable material. Unfortunately, this combination results in problems related to poor miscibility on the molecular level. This study mainly aims to determine the influence of molecular weights on the miscibility of PBAT/PLA blends. First, polymers with various molecular weights were obtained by the hydrolysis of PBAT and methanolysis of PLA. Second, the two components were solution-blended with different molecular weights and weight ratios. Third, each blend was heated to the molten state and subsequently stored at room temperature. Finally, the samples were tested using DSC and SEM. The thermal analysis indicated that the difference in glass transition temperature between both components decreased from about 91 °C to 57 °C and 0 °C, as the number-average molecular weights (Mn) decreased from 52/127 to 9.4/9 and 6.3/6.6 kg/mol. Moreover, the morphology changed from phase-separated with dispersed large particles gradually to uniform and homogeneous. This experimental work validated the trends predicted in the previous study, namely that PBAT/PLA blends changed the state from immiscible to partially miscible to fully miscible with decreasing Mn values. Moreover, we discussed the influencing factors such as weight ratio, temperature, and molecular structure on the miscibility. Based on the results, this work contributes to developing partially miscible and compatible blends without additives.

Electron Beam-Induced Compatibilization of PLA/PBAT Blends in Presence of Epoxidized Soybean Oil

“…The cavity sizes determined in this study are much smaller than in comparable studies [ 1 , 24 ]. This is an indication that PBAT may not have been completely dissolved.…”

“…It is part of recent studies to blend PLA with other biobased and/or biodegradable polymers to enhance its elongation at break and impact strength. However, poor compatibility between different polymers in blends often limits their mechanical and physical properties [ 1 , 2 ].…”

The Use of Branching Agents in the Synthesis of PBAT

“…PBAT is currently regarded as a raw material or as a component of polymer composites that are designed to replace polyolefins in packaging and other fields of application [18][19][20][21][22][23][24][25]. Among these composites, PBAT blended with poly(L-lactide) (PLLA) and/or with starch has been studied intensively [26][27][28][29][30][31][32][33][34][35], but the poor miscibility of PBAT with these polymers on a molecular level makes it difficult to develop materials of the highest quality [31]. In packaging applications of both PBAT and PBAT-based composites, it is necessary to produce ultra-thin film using conventional technologies that were previously used in the polyolefin industry.…”

Blending of Low-Density Polyethylene and Poly(Butylene Succinate) (LDPE/PBS) with Polyethylene–Graft–Maleic Anhydride (PE–g–MA) as a Compatibilizer on the Phase Morphology, Mechanical and Thermal Properties

“…Therefore, this outcome was consistent with the data obtained from mechanical strength, where the blends with the incorporation of 5 phr PE–g–MA demonstrated the optimal TS with respect to the 7 phr PE–g–MA. The reduced miscibility of the blend [ 73 ] resulted from the combination of LDPE with a greater M w , 126,000 g/mol [ 74 ] and PBS with a lower M w , 65,000 g/mol [ 75 ]. The aggregation of compatibilizer increased as the content of PE–g–MA exceeded 5 phr due to the higher M w of PE–g–MA, 31 200–112,500 g/mol [ 76 ].…”