Identification of biodegradable plastics using differential scanning calorimetry and carbon composition with chemometrics

Abstract

Biodegradable plastics have become an important commodity to replace non-degradable plastics and alleviate environment pollution. It is important to identify instances of counterfeit and mislabeled biodegradable plastics in the marketplace to avoid sustainability fraud and improve plastics waste recycling. In this study, differential scanning calorimetry (DSC) and elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) were used to analyze biodegradable plastics (polylactic acid (PLA), poly butylene adipate-co-terephthalate (PBAT), PBAT/PLA blend (PBAT+PLA)) and non-degradable plastics (polyethylene terephthalate (PET), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP)). A verification model was built using orthogonal partial least squares-discriminant analysis (OPLS-DA). Results showed that the melting point of biodegradable and non-degradable plastics ranged from 120 °C to 176 °C and 105 °C to 253 °C, respectively. The melting points of biodegradable PLA and non-degradable PP overlapped. The δ13C values of biodegradable and non-degradable plastics ranged from -25.8 ‰ to -11.6 ‰ and -32.3 ‰ to -25.4 ‰, respectively. The % C of biodegradable and non-degradable plastics ranged from 36.0% to 61.0% and 56.4% to 85.3%, respectively. Three OPLS-DA models were established by combining DSC variables, δ13C values and % C. The PLA discriminant accuracy of these models was 100%, suggesting this approach holds promise for the regulation and identification of biodegradable plastics in the marketplace.