## 4 Conclusions  
Despite the fact that electron beam radiation provides a high dose rate and the absence of oxygen, the EPR and GPC results demonstrate that the predominant effect of radiation is the scission. The EPR results clearly show the formation of alkoxyl and C-centered radicals upon irradiation. The GPC data confirm the EPR results that the predominant effect of radiation is the scission. Upon irradiation with 20 kGy, \(M_{n}\) and \(M_{w}\) of the unirradiated samples decreased from 126,200 Da and 201,400 Da to 74,200 Da and 141,000 Da, respectively. The abstraction of H-atoms by alkoxyl radicals from neighboring molecules can also contribute to the formation of C-centered radicals. The GPC results also reveal the absence of higher-molecular-weight chains, which directly demonstrate the absence of crosslinking reactions of these C-centered radicals. This can be explained by the fact that these C-centered radicals react with the oxygen very rapidly since the irradiated samples  
Figure 11: Water vapor transmission rate of PLA at 5 different doses: 0 kGy (light green), 5 kGy (dark blue), 10 kGy (light blue), 15 kGy (pink), 20 kGy (yellow). Each point represents the average of samples measured at each dose.  
Figure 10: (**a**) Polymer dispersivity as a function of absorbed dose of 0, 5, 10, 15, and 20 kGy, where dispersivity is the weight average over number average molar mass; (**b**) number average molar mass M\({}_{n}\) versus absorbed dose of 0, 5, 10, 15, and 20 kGy.  
were exposed to air after irradiation. Due to the relatively low dose (maximum 20 kGy) and, consequently, the small induced scission yields, we have found that there is no change in \(T_{g}\), only negligible (minor) changes in crystallinity, and no effect on water vapor transmission rate. Gel fraction measurements to measure crosslinking density were unsuccessful, as the gel point could not be reached. The absence of the formation of the three-dimensional gels supports the GPC findings. The presence of oxygen after irradiation can also contribute to the prevention of gel formation, since the reaction of C-centered radicals with oxygen compete to produce the corresponding peroxyl radicals. Finally, the change in oxidation index is very low, which is a good indicator that the irradiated PLA within this range of doses undergoes minimal degradation.  
The main objective of this study is to evaluate the viability of PLA as a biodegradable food packaging material. Our results show that the irradiation has no effect on the aforementioned physical properties of the PLA. Therefore, this small degradation will enhance the biodegradability of this polymer for food irradiation and sterilization applications.  
Not applicable.  
Data availability StatementData are available from the authors upon reasonable request.  
AcknowledgmentsKim [PERSON], [PERSON], the Gemstone Program at the University of Maryland, [PERSON], [PERSON], [PERSON], and [PERSON]. Conflicts of InterestThe authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. The statements, findings, conclusions, and recommendations are those of the authors and do not necessarily reflect the view of Maryland Sea Grant, the National Oceanic and Atmospheric Administration, or U.S. Department of Commerce.