Influence of recycling of poly(lactic acid) on packaging relevant properties

The most promising representative of biodegradable plastics in packaging applications is polylactide (PLA). Despite this, there is only a small market of PLA in Europe. Reasons for that are the high price of PLA raw material and the lack of knowledge of the behavior in packaging applications. It has a number of peculiarities so producers of plastics packaging hesitate to use it. Like other polyesters, it can degrade at increased temperatures in the presence of moisture by hydrolysis whereby it loses its physical and chemical properties. In all production processes, production waste is generated (i.e., stamping grids or edge trim). In most cases, this waste is used. It is not known in detail, how an internal recycling process will influence the final product properties. One problem is hydrolysis by which the production waste is partially degraded. Target of this study is to analyze the recycling process of PLA within the context of necessary process adaptions and the effects upon ecological efficiency. Films for packaging containing multiple types and amounts of production waste will be produced by extrusion and tested concerning their mechanical properties. The analysis of the recycling behavior showed that internal PLA production waste is well suitable for recycling. The influence of the recycling on the molecular weight is negligible. The effect on the viscosity and thus on the extrusion process is higher. Packaging relevant properties like mechanical or optical properties are hardly influenced. Especially recycling with a recycling quota of up to 50% has an insignificant effect on the film properties.