Bio-based polyesters for demanding long-term applications

Biopolymers are now an established part of the plastics market, but play a minor role in the overall volume of annual plastics production. One reason for this is that these green materials are rarely used in demanding technical applications. As the long-term properties are insufficient, these plastics are often used in disposable articles and are degraded during composting or through energy recovery. Making biopolymers fit for long-term use is what we want to tackle together in this joint project.

Due to their versatile properties, plastics have become indispensable in many technical applications. However, social and political pressure requires the plastics industry to bring more sustainable semi-finished and end products onto the market. This can be achieved by replacing petro-based polymers in these applications with bio-based polymers. The reasons why this has not yet been possible are not only economic but also technical properties, particularly regarding long-term stability. This applies in particular to the thermoplastic biopolymers based on aliphatic polyesters (e.g. polylactic acid (PLA), polyhydroxyalkanoates (PHA) and polybutylene succinate (PBS)) that are currently available on the market today. Due to their chemical structure, they are particularly sensitive to hydrolytic degradation and are primarily used for disposable goods. To make them attractive for end producers and suppliers, it is necessary to enable these materials  for technical applications.

This task is being adressed in the joint project presented by modifying biopolymers with additives to ensure that the long-term properties are comparable to those of currently used materials without impairing their processability and mechanical properties. Special focus is placed on the effects of thermal and hydrolytic ageing as well as UV weathering on the material properties. Additivation will contribute to enable material substitution with as few changes as possible to existing manufacturing processes in the value chain.

Participants in the joint project will gain in-depth knowledge of the long-term behavior of bio-polyesters, how it can be improved and which technical applications are accessible. Structure/property relationships, in particular with additives, will be established and previous limits will be shifted.

The project is also intended to serve as an interdisciplinary platform for players from the entire value chain in order to develop targeted solutions for the technical problems arising around the topic of "bio-based polyesters in demanding long-term applications".

Project focus & approach

Fundamental literature research and evaluation

Literature research is carried out on the selected bioplastics and the findings and data collected are summarized and evaluated. The focus is on the compilation of available data on long-term stabilization and stabilizers used. These data are benchmarked against that of petro-based plastics

Development of a specification sheet including selection of methods and definition of ageing conditions

The compiled data are presented to all partners and  discussed. The material properties to be achieved are jointly defined considering later target applications and are documented in the form of binding specifications. Subsequently, conditions for accelerated ageing and characterization methods for long-term stability are defined.

Identification, procurement and characterization of commercially available bioplastics

Additionally to a literature search, comercially available biopolymers and compounds are identified and procured for further investigations or as a basis for formulation development. Based on the available information, the material properties are benchmarked in order to make an assessment of possible applications. To overcome gaps in the available material data with regard to long-term properties, initial material tests are carried out for characterization.

Identification of commercially available additives for polyester in general and for biopolymers

In addition to the available polymers, commercially available additives are identified. The focus is on stabilizers that have been developed or are being marketed specifically for biopolymers, but also on additives that are used in petro-based plastics/polyesters for stabilization or property modification.

Modification and characterization of biopolymers with commercially available additives

Based on the data collected during material characterization and available additives , various formulations are being developed depending on the subsequent target application. The polymers and additives are then compounded on a pilot plant scale.

Assesment of possible applications of the developed compounds

The compounds produced are characterized in the same way as those commercially available and examined with regard to their long-term properties. Based on the material properties determined, a critical review is carried out by the project partners with regard to the requirements previously set out in the specifications.

The investigations may be carried out in parallel on petro-based materials used today to enable a direct comparison between bio-based and petro-based materials.

Participating partners in this joint project are empowered to,

• Identify opportunities, challenges and limitations of substituting petro-based polymers with bio-based polymers, especially in their market segment
• Realistically assess the potential of biopolymers, evaluate requirements and adapt products to the use of biopolymers
• Develop strategies for material optimization in cooperation with all market participants (raw material manufacturers, product developers, processors)
• a consideration of the cost/benefit ratio of substituting petro-based plastics with bio-based solutions

This joint project is aimed at companies along the value chain, from manufacturers of polymers and additives to companies that want to substitute individual components in their products, with a particular focus on developers and producers of finished components:

• OEMs and manufacturers of plastic components in the construction, automotive, sports and leisure, electrical and electronic components, household appliances sectors who want to substitute petro-based polymers with bio-based solutions
• Raw material and additive manufacturers who are looking for new applications for their existing portfolio
• Compounders and plastics processors who want to prepare themselves for future challenges in the use of bioplastics