On the Mechanism of Electron Beam Radiation-Induced Modification of Poly(lactic acid) for Applications in Biodegradable Food Packaging

• Published in: Applied sciences Vol. 12; no. 4; p. 1819
• Main Authors: Grosvenor, Eleanor C., Hughes, Justin C., Stanfield, Cade W., Blanchard, Robert L., Fox, Andrea C., Mihok, Olivia L., Lee, Kristen, Brodsky, Jonathan R., Hoy, Ann, Uniyal, Ananya, Whitaker, Sydney M., Acha, Chris, Gibson, Kalina, Ding, Lilly, Lewis, Catherine A., González López, Lorelis, Wentz, Charlotte M., Sita, Lawrence R., Al-Sheikhly, Mohamad
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.02.2022
• Subjects: alkoxyl free radical decay; Backbone; Biodegradability; Biodegradation; Calorimetry; Differential scanning calorimetry; Dosimetry; electron beam radiation; Electron beams; Electron paramagnetic resonance; Electron spin resonance; Food irradiation; Food packaging; Fourier transforms; Hydrogen atoms; Irradiation; Liquid chromatography; Microscopy; Packaging; Permeability; Peroxidation; Peroxyl radicals; Physical properties; poly(lactic acid); Polylactic acid; Polymers; Radiation; Radiation effects; Radicals; Resonance; Silicon wafers; Spectrometry; Water vapor; X-ray diffraction; United States > US; Japan
• ISSN: 2076-3417; 2076-3417
• DOI: 10.3390/app12041819

Poly(lactic acid) (PLA) is a biodegradable polymer used for food packaging. The effects of electron beam radiation on the chemical and physical properties of amorphous PLA were studied. In this study, amorphous, racemic PLA was irradiated at doses of 5, 10, 15, and 20 kGy in the absence of oxygen. Utilizing electron paramagnetic resonance spectrometry, it was found that alkoxyl radicals are initially formed as a result of C-O-C bond scissions on the backbone of the PLA. The dominant radiation mechanism was determined to be H-abstraction by alkoxyl radicals to form C-centered radicals. The C-centered radicals undergo a subsequent peroxidation reaction with oxygen. The gel permeation chromatography (GPC) results indicate reduction in polymer molecular mass. The differential scanning calorimetry and X-ray diffraction results showed a subtle increase in crystallinity of the irradiated PLA. Water vapor transmission rates were unaffected by irradiation. In conclusion, these results support that irradiated PLA is a suitable material for applications in irradiation of food packaging, including food sterilization and biodegradation.