Biobased composite recycling

The University of Limerick, as part of an EU project, is researching using biobased bonding materials (BBM) to find new ways to recycling end-of-life composite parts.

The VIBES project is an EU program focused on finding ways to improve the recyclability of thermoset composite materials. Plans are to develop ways to separate and recover materials from end-of-life composites using reversible biobased bonding materials (BBM).

The research project has a duration of 48 months and a budget of almost €5.3 million, funded the European Union’s Framework Programme for Research and Innovation, Horizon 2020.

According to the project website, “the end-of-life of thermoset composites in particular poses a technical difficulty due to their inherent complexity, generating plastic waste.” Currently most of the thermoset composite waste is not properly recycled and it is either incinerated (42.6%) or diverted to landfill (24.9%). “There is a need to develop and ensure a systematic circular ecosystem for these materials as a priority in Europe, in order to be able to contribute to the EU’s 2050 long-term strategy for a climate-neutral Europe,” the website said.

“The VIBES project will develop and demonstrate a new, greener, cost-efficient, and non-toxic recycling technology solution that aims to decrease the amount of non-biodegradable polymers sent to disposal or discharged to the environment by at least 40%.

“Once this technology has been optimised and scaled-up to a pilot semi-industrial environment, the products obtained from the new recycling process will return to the market by means of their valorisation as new feedstocks for different chemicals or building blocks and by upcycling into new industrial products.”

The project consortium comprises 13 partners across seven EU member states (Spain, France, Ireland, Germany, Belgium, Italy, Greece): three research and technology organisations, seven SMEs, one large company, one public body, and one university – which is the University of Limerick, Ireland.

VIBES builds on work already done at the university as part of LIBRE, another EU project that aimed to use feedstock from the pulp and paper industry, blended with a biopolymer precursor fiber, to create a more resource-efficient and sustainable carbon fiber production process.

Environmental impact

For VIBES, researchers at Limerick will be involved in the development of the recycling technology and the testing of the new composites for construction, aerospace and naval applications, according to project lead and senior lecturer at the School of Engineering, Dr Maurice N Collins (pictured). “These new composites could eliminate waste in end-of-life composites and create a circular ecosystem for these materials,” he explained. “[They] will be fully biobased along with the recycling technology itself and this will lead to reduced environmental impact by reducing the use of primary materials, harmful chemicals and landfilling.”

According to Dr Collins, the resulting composite materials will have intrinsic recycling properties but also improved performance. They will be assessed on a cost ratio in applications in three high-performance industrial sectors such as aeronautical, construction and naval.

“The green recycling technology will be designed and implemented as a pilot in semi-industrial environments to separate and recover composite components as new feedstocks for the development of new products,” he said.

For Dr Collins, composite recycling has a lot of issues to resolve. “Currently, thermoset composite waste is diverted to landfill or incineration,” he told me. “The process to separate composite materials is costly in materials, energy and time. Concerning the composite materials, in Europe alone, 40,000 tonnes of composite waste are deposited in landfills annually (2015) and 306,000 tonnes of composite waste were accumulated worldwide. In addition, the increasing demand for lightweight materials in sectors such as the aeronautical (5.3% CAGR 2018-2023), wind energy (4.7% CAGR 2018-2023), transportation – including automotive (3.8 % CAGR 2018-2023), construction (4.0% CAGR 2018-2023), and other end-use industries will continue to drive composites growth. Nowadays composite materials are stored in landfills, including aircraft, wind blades and railway cemeteries, and very often dedicated to energy recovery (burned/thermally recycled).

“Due to their inherent heterogeneous nature of the matrix and their reinforcement, at present, the resin part is incinerated (thermal recycling) and the reinforcement (usually glass fiber and carbon fiber) is recovered and reused as reinforcement (although the fiber microstructure is usually damaged and cannot be used for the same purpose. Furthermore, incineration involves toxic substances which may affect the living organisms as well as the environment (soil and water). Thermoset resins often contain volatile organic compounds and are non-biodegradable.”

Molecular debonding

I asked Dr Collins about the science behind the research project.

“The aim of this project is to develop biobased moieties, of which degradation can be triggered under controlled external stimuli,” he explained. “Molecular debonding is subdivided into two main mechanisms according to an economic and sustainable point of view: 1) by modifying the conventional crosslinked resin via inclusion of three-dimensional stable assembly (supramolecular approach) and 2) by introducing dynamic bonds in their networks (D-A & vitrimers approaches). In addition, these moieties can be designed and introduced inside the resin, on top of the fiber surface or in between, generating a complex bonding material which is functional in the interphase of the designed composite.

“The project tackles the development of degradable BBM which are specific solutions for epoxy, polyester and vinylester oil based and biobased thermoset resins in combination with different origin fibers: carbon fiber, biobased carbon fiber, glass fiber and flax fibers. In addition to the development of biobased bonding materials, the VIBES project will design and develop biobased thermoset composites based on biobased resins (epoxy, polyester and vinylester) and on biobased fibers.

I asked him if he thought companies are concerned enough about composites recycling?

“I think progress can be made in that field. And new technologies are being developed to make composites easier to recycle. Progress is being made right now at lab scale, that needs to be developed in industry and eventually spread out to all new composite materials developed.”