Fraunhofer Cluster of Excellence Circular Plastics Economy CCPEBioplastics for long-lasting applications
Bioplastics made from renewable raw materials conserve fossil resources and reduce greenhouse gas emissions. However, undesirable hydrolytic degradation often stands in the way of their use in technical applications. Employees of the Fraunhofer CCPE are therefore investigating various plastic additives in order to modify the service life of bioplastics and expand their range of applications.
The raw materials for the production of bioplastics are obtained from plant-based materials such as corn, sugar cane or sugar beet. For example, the monomer of the most common bioplastic PLA (polylactic acid) comes from the fermentation of sugar. Due to their chemical structure, bioplastics are sensitive to external influences such as moisture. On the one hand, this makes the material biodegradable, which is particularly advantageous if the material remains in the environment and is to be degraded there. One example is its use in mulch films. On the other hand, the reduced stability creates barriers for long-lasting applications and processing, where the focus is on issues such as temperature, residual moisture and crystallization behaviour.
In order to expand the range of applications for bioplastics, it is therefore necessary to incorporate additives. These are primarily hydrolysis inhibitors that react with the moisture penetrating into the plastic from the environment. The polymer chains can thus be protected against hydrolytic degradation and the desired properties can be maintained over a longer period of time. However, comparatively high concentrations are required for long-lasting protection, which can have a negative effect on the crystallization behaviour of PLA and on the long-term service temperature.
To compensate for this deficit, additional co-stabilizers can be added to stabilize the polymer chain, increase longevity and lead to a synergistic interaction with the hydrolysis inhibitor. This makes it possible to reduce the additive content while maintaining or improving polymer stability. In the case of hydrolysis aging in water at 60°C, the addition of such a stabilizer package extends the time until significant degradation of the polymer chains occurs from less than 50 to more than 1,000 hours (PLA without additives vs. PLA with additives). The processing behavior can also be further optimized by adding additional additives.
Details of the work described will be published shortly. The processing and customized adjustment of the service life of bioplastics are key elements of the Fraunhofer Cluster of Excellence Circular Plastics Economy CCPE. Please feel free to contact us.