Novel bio-based polyester resin for the composite industry

The plastic industry is one of the most important sectors in Europe. However, the management of plastic dumps has become one of the most important and urgent environmental problems. Indeed, the increase in the production of disposable plastics exceeds the world’s capacity to deal with them. Plastic dumps are a major threat to our ecosystems. 

Consequently, the circular economy requires, as the main strategy, optimal and real management of waste to develop an effective economy with after-use plastic to promote higher plastic recycling rates and to prevent further accumulation of plastic waste on land and in the sea. 

Recycling of thermoset resins 

In contrast to thermoplastic resins, thermoset resins cannot be melted to be recycled because of their internal chemical structures, indeed, the chemical bonds of this kind of material are irreversible, so once heated the bonds harden and make difficult the recycling of thermosets. Therefore, most thermoset resins are not recycled, indeed, 41.6% are incinerated and 27.3% are deposited in dumps. Thus, improvements are needed to provide cost-effective solutions with high biobased contents and high performance to respond to demanding applications for fibre reinforced polymer composites industry, commonly named composites industry.

Composites are known to be materials with high mechanical performance while being light and have very high durability which makes them very attractive for many industries such as the construction, aeronautics boating and civil engineering sectors. However, these materials still present several limitations, in particular regarding the management at the end of life (EOL) due to the complexity and the difficulty to apply eco-design which involves the generation of high quantities of plastic waste, more precisely complex plastic mixtures, which are very difficult to upgrade.

What are the advantages of polyester resin?

• Durability
• High resistance to corrosion 
• High resistance to water
• High resistance to chemicals 
• High mechanical properties (example: Hingh-impact strengh) 
• High thermal resistance 

Polyester resin use

• Construction sector as furniture (example: Bathroom shower)
• Automotive (car body parts)
• Naval (boat hull)

New processes for the recyclability and valorisation of composites

In this sense, the EOCENE project, led by a consortium of Spanish companies and funded by the Spanish government within its strategic program España Circular 2030 EEEC, aims to obtain all composites compounds, namely polymeric resins, charges and reinforcing fillers, from renewable sources and develop sustainable technologies for obtaining controlled processes for recyclability and valorisation of generated residues. 

However, the compounds used for composite formulations are not recyclable and use fossil resources, for example, the unsaturated polyester resins used in many cases as a polymeric matrix in the composite industry. In addition, most of the reagents used for the formulations are very toxic to both health and the environment, such as the styrene diluent used to produce unsaturated polyester. For this reason, there is a real interest to develop new, more sustainable thermoset polymers. In other words, the project will allow to develop new thermoset polyesters with high bio-based percentages. In order to achieve this development, two research lines will be covered:

1. The first line is the development of monomers and precursors as biobased organic compounds obtained by means of fermentation from the waste of the agri-food industry and also organic compounds derived from natural materials such as vegetable oil which are included in the formulation of commercial resins. 
2. The second line is the formulation of fully biobased, unsaturated polyester by replacing traditional resins and diluent reagents with biobased organic compounds. This substitution allows to reduce fossil-based organic compounds in the composite industry and allows to reduce the carbon print of companies.

Furthermore, the goal of this project is not only the substitution of fossil-based monomers but also the development of a synthetic process as sustainable as possible. So, to develop biobased monomers, the toxicity of each reagent and solvent is taking account to maximize the use of natural products. All products developed during this project are included in the final formulation of the unsaturated polyester matrix which will be used to design the new biobased composites. 

The other compounds used in the design of the composite are developed and obtained from renewable natural resources. All these compounds are developed taking into account the indispensable properties of a composite material. Consequently, all the final composites need to be developed without a significant loss of mechanical and thermal properties. 

To sum up, the main goal of the EOCENE project is to obtain biobased composites for many industries by developing new biobased monomers and precursors used for the formulation of new bio-based and more eco-friendly thermoset resins. Similarly, the fillers used to reinforce the polymeric matrix are developed from natural and renewable resources. 

All these developments allow:

• To reduce the use of non-renewable compounds by around 25% 
• To reduce the carbon footprint from 20 % 
• To decrease from 25% in the generation of hazardous waste generated by the handling of basic polymeric resins or curing agents such as styrene, which present a high cancer risk. 
• To reduce from 40% and 80% the composite waste which is respectively sent to landfills and to incineration areas, regarding the current situation of the companies in the consortium of EOCENE.

Source

AIMPLAS blog, press release, 2022-10-07.

Supplier

AIMPLAS (Asociación de Investigación de Materiales Plásticos y Conexas)
Aitiip Centro Tecnológico
Spanish government - La Moncloa

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