Morphological characteristics of stearic acid-grafted starch-compatibilized linear low density polyethylene/thermoplastic starch blown film

• LLDPE/TPS blend films with a weight ratio of LLDPE:TPS of 60:40 were prepared by blown film extrusion.
• ST-SA with a substitution degree of 0.01 could be used as a compatibilizer for the LLDPE/TPS blend system.
• The blend showed reduced TPS phase size and size distribution in the LLDPE matrix when ST-SA was loaded.
• The optimum compatibilizing effect of the blend was achieved by incorporating 1% of ST-SA.
• ST-SA compatibilizer could interact with TPS via H-bond formation and with LLDPE through hydrophobic interaction.

The objective of the present work is to verify the possibility of using stearic acid-grafted starch (ST-SA) as a novel compatibilizer for a blend system consisting of linear low density polyethylene (LLDPE) and thermoplastic starch (TPS). ST-SA was successfully synthesized, as confirmed by FTIR and 1H NMR techniques. The obtained ST-SA was compounded with LLDPE and TPS in a twin-screw extruder. A weight ratio of LLDPE:TPS was fixed at 60:40, while ST-SA concentrations were varied from 1% to 5%. The blends were further converted into films by blown film extrusion. Incorporation of ST-SA improved the extrusion processability and melt flowability of the LLDPE/TPS blends. In addition, the blends became compatible and homogeneous when ST-SA was loaded due to the increased interfacial adhesion between LLDPE and TPS phases. The results suggest that ST-SA, particularly at a content of 1%, could serve as an effective compatibilizer for the immiscible LLDPE/TPS blend system.

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