Development of poly(lactic acid)/lignin composite films coated with beeswax for food packaging applications

Abstract

In this work, PLA/lignin composite films have been developed for packaging applications. The composite films were prepared by a solution casting method. The lignin was prepared from black liquor from the paper industry, by extracting with acetic acids at 50°C. Scanning electron microscopy (SEM) was used to study the size and shape of the lignin particles. The lignin contents in PLA matrix were 0.5, 1, 3 and 5 phr. The SEM results showed that as the lignin content increased, the surface roughness and voids increased except at 1 phr and 5 phr. Fourier-transform infrared (FTIR) spectroscopy was used to study the interactions between PLA and lignin. The results of the PLA/lignin composite film showed a reduction crystalline with the change of the diffraction peak around 2θ = 19° by X-ray diffraction (XRD). The lignin reduced the tensile strength of PLA/lignin films, whereas the composite film at 1 phr of lignin was more elongation than neat PLA. Thermal stability of PLA/lignin composite films increased with the addition of lignin. UV-Vis analysis indicated reduced light transmission with increasing lignin contents in UV region. The scavenging activity also increased with the amount of lignins by DPPH method. The lignin increases the impermeable physical barriers in the PLA so reducing the effect of water vapor transmission rate (WVTR). The addition of lignin to PLA did not significantly change the contact angle of PLA. Then select the appropriate amount of lignin for beeswax coating. The beeswax dipping coating maintains the film good mechanical and antioxidant properties. The film obtained after the coating increased roughness by SEM and increased water contact angle by WCA measurement as the beeswax concentration increases.

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