Testing methods
Several tests can be performed on a certain plastic in order to determine whether a potential additive increases its biodegradability.
Comparison of the changes in physical properties of the plastic both with and without potential biodegradable additives throughout the degradation process can provide insight into the efficacy of the additive. If the degradation is significantly affected with the addition of the additive, it could indicate that biodegradation is improved.[11] Some important physical properties that can be measured experimentally are tensile strength, molecular weight, elasticity, and crystallinity. Measuring the physical appearance of the plastic before and after potential microbial biodegradation can also provide insight into the efficacy of the degradation.[12]
Thermal analysis is a useful method for characterizing the effects of degradation on the physical properties of polymers. Information about the thermal stability and the kinetic parameters of thermal decomposition can be obtained through thermogravimetric analysis. These kinetic parameters provide information about the breakdown of molecular chains, an indicator of degradation. From measurements of enthalpies in the melt state and the crystalline state, the evolution of the crystallinity content of plastics can be recorded. Changes to crystallinity can indicate that degradation was either successful or unsuccessful. Lamellar thickness distribution of the plastic can also be measured using thermal analyses.[5]
Another way to determine the efficacy of biodegradation is by measuring the amount of carbon dioxide and/or methane produced by the microorganisms that are degrading the plastic. Since carbon dioxide and methane are products of the microbial degradation process, large amounts of these products in the air indicate that the synthetic plastic has been consumed and converted into energy.[6]
