Having described the structure of the composites in my previous post, we can effectively investigate the environmental impact of the production of the laminates, which are manufactured with various methods. The hand lay-up is still quite popular, although the vacuum bagging and infusion are gaining momentum, due to the superior finished product.
In all cases the process has to be in a controlled environment, in respect of temperature and humidity, necessitating air-condition, with all the energy requirements of it. Yet this is a lesser challenge.
Aforementioned manufacturing methods require that the fibre reinforcements will be cut to the defined dimensions, then laid in the mould before impregnated with resin. This step alone introduces by average a 30% scrap, namely from the very beginning one-third of the fibres is thrown away. As the process of hand lay-up and vacuum bagging involves saturating the fibres with abundant resin that is later removed, either by pushing it out or sucking it, we understand that a lot of resin is also scrapped during the production process as well.
Since the production of composites is generating so much scrap, recycling of the materials becomes more profound. Adding the finished product when approaching the end of life to the overall waste, recycling becomes paramount.
Carbon fibres are presently recyclable through pyrolysis and solvolysis. In the former method, the fibres are burned to a temperature that can shift them to their original liquid state and restart the process of manufacturing them. Yet this is generating gases that are released to the atmosphere and is consuming a lot of energy, while the renewed fibres have lesser strength. Solvolysis is a chemical treatment, consuming 1/10 of the energy necessitated for original carbon fibre production process and the end fibre has about 95% of the original strength. It is though a very complex method, heavily depended on the original carbon fibres and their production procedure, which to the recycling facility may not be disclosed, therefore it is making very little profit.
Luckily there are pioneers like ELG that are not discouraged by the financial hindrances or Shocker composites that have further developed solvolysis to incline processing, so that they can control the end surface of the fibres.
Connora composites are more focused on the primary production procedure of the composites with alternative hardeners that can be set to conditions that reverse the setting of the plastics, hence retrieving the resin and fibres. Many companies are pledging to recycling their composites, with BMW using in their i-line 10% of recycled material and Boeing committing to have, by 2025, 95% of their composites recycled.
Core materials used in sandwich structures should have a better treatment when their reach their end of life. They are usually SAN foam or PVC foam. SAN foam is about 70-80% styrene, a carcinogenic substance that we would better live without. The PVC foam is recyclable, but recycling it without subsidies is not sustainable financially, therefore is not attracting investors.
Considering that modern designs are quite unique in shape, have high strength demands with little tolerance to weight, composites are an integral part of production. They need though to be aligned with our nature.
- Resin can originate from corn or sugarcane crops and vinyl ester from cardanol. Such methods need to become mainstream;
- Develop further on the manufacturing of composite with procedures that support their recycling, whether that means different hardeners or other components. Invest towards that mindset;
- Solvolysis is promising, if the recycling is coupled with the original manufacturer that has all the information about the formation of the fibres, it can ensure that the new fibres have their former strength, without losing proprietary rights;
- Focus on possibilities to reuse the products themselves;