Development of biodegradable hot-melt adhesive based on poly-ε-caprolactone and soy protein isolate for food packaging system

A biodegradable hot-melt adhesive was developed from poly-ε- caprolactone (PCL) and soy protein isolate (SPI). PCL and SPI were mixed at varying ratios with plasticizers (coconut oil and PEG400). Thermal properties of PCL:SPI hot-melt adhesive were characterized with a differential scanning calorimeter (DSC) and softening point measurement. The surface morphology of PCL:SPI blend was examined by scanning electron microscopy (SEM). Tensile strength and elongation of PCL:SPI hot-melt adhesive films were measured using Instron testing machine. Lap shear strength of PCL:SPI hot-melt adhesives on medium density fiberboard was determined according to TAPPI UM633 method. The melting point and crystallinity of PCL in the blends decreased as the SPI content increased. The softening points of PCL:SPI hot-melt adhesive were about 59-75°C. As the SPI concentration was increased, the tensile strength of its films decreased. The elongation of the PCL:SPI hot-melt adhesives varied with the type of plasticizer. Lap shear strength of PCL:SPI hot-melt adhesive was about 1.9 MPa.