The journey of creating saf-Tglo® eco E1™

The aerospace industry’s goal to achieve net zero carbon emissions by 2050 has been a key motivator for manufacturers like us. As lighting experts, we are a small part of the puzzle, but it’s important for every organisation – big or small – to do its bit in contributing to a greener future. Over the last few years, a lot of work has been happening behind the scenes to innovate with sustainability at the front of mind. 

 At the Aircraft Interiors Expo (AIX) 2024, we unveiled the world's first sustainable emergency floor path marking system, saf-Tglo® eco E1™. This innovative, biodegradable version of our saf-Tglo® range is an important step in the evolution towards more eco-friendly aviation product design. The eco E1™ floor path marking solution not only ensures passenger safety and cabin aesthetics, but also addresses the urgent need for sustainable alternatives compared to what is already on the market. 

Tracy Vyas-Middlecoat, our Research and Development Scientist, is the technical lead for eco E1™. She worked with the wider team and a student at University College Dublin, who carried out their master’s thesis with STG. 

Tracy took us through the detailed process of creating the latest product.

The first step of the process

 The first step was to search for a sustainable material for the track as it makes up the bulk of the product. Polycarbonate is a popular material used in aircraft interior products as it is strong, sturdy and long lasting. However, research highlighted that, due to its complex chemical structure, recycling is complicated - while chemical recycling has the potential to fully break it down, this process is currently mostly at the academic level and is only just entering the commercial market. Mechanical recycling is commercially available, however can raise issues in traceability – something that is vital for use in aerospace settings.

We gathered the feasible material options on the market, from post-consumer recycled polycarbonate, to polymers made from bio-oils, and even a sugar based polycarbonate equivalent, and used these to run manufacturing trials. It was a process of trial and error, and we had some spectacular failures, like the sugar-based material, which in raw form was transparent, but once melted, turned bright opaque white and jammed inside the extruder like caramel – but at least the smell was nice!

During the extruding process at our supplier, we learnt about their inhouse recycling system for the waste material which piqued our interest. We investigated mixing 50% of the recycled material with virgin material which worked surprisingly well. Compared to some of the other recycled materials which would have to be shipped in from overseas, this is a closed loop system which is beneficial from both a traceability viewpoint, but also reduces the carbon footprint.

Our aim was to increase sustainability across the full life cycle. We have no control over the end of life of our product. We would love everyone to recycle it, but we know that most consumers will remove it from the aircraft and put it into landfill – we wanted to cover all our bases and utilise something that would not leave a trace, no matter what the disposal route. This is why we have also included a biodegradable additive in the track, which will remain inert whilst the product is in service, but when disposed, will fully break the polycarbonate down into its base elements, leaving no forever plastics.

Finding the insert material

Insert material comes in sheet form and is generally made by the mile for commercial purposes, which meant it was not feasible to run any extrusion trials. Luckily, we found a UK company that offered sheets made from mechanically recycled materials. We worked with them to create bespoke sheets which are made from 80% recycled content, are 20% lighter than the sheets used in existing saf-Tglo® products, and lead to an assembly that is 80% lighter than STG legacy products. This is a significant improvement to the product as weight saving is directly correlated to the amount of fuel burnt on an aircraft.

Onto the resin 

Finding the resin was the most challenging part of the process. Our PL material is currently held in a solvent based resin which introduces VOCs (volatile organic compounds) into the atmosphere. This is detrimental to the environment but also can create an unpleasant odour during the manufacturing process. We wanted to move away from solvent-based resins and investigate water-based options. This was difficult as these resins are more commonly used for fabric printing as they require a porous surface to bond with. It required many trials, however we ended up with the perfect recipe using water-based resin and plant based materials, which meet the same standards as our solvent-based equivalent.

Rigorous testing 

Once we had found our materials, we performed fitness for purpose tests. We test flame retardancy, how well the product deals with exposure to fluids found in and around the cabin, and robustness by rolling a 150-kilogram galley cart over the assembly for 10,000 cycles, which is equivalent to 35 years of service. We conduct this initial round of testing to assess the feasibility of the prototype, ensuring that when we proceed to formal qualification testing, we have complete confidence in the product.

Plans for the future  

From start to finish, the process of designing and launching saf-Tglo® eco E1™ took a year and a half. We are incredibly proud of this product and everyone for their hard work. saf-Tglo® eco E1™ delivers sustainability improvements across the product lifecycle, without compromising passenger safety, reliability, performance, or aesthetics. Finding the perfect materials required a considerable amount of trial, error and perseverance, however the key takeaways have been invaluable. We gained knowledge in Environmentally Sensitive Design which has been helpful for future development. This new approach for eco E1™ also led to two new patents for STG. 

The STG team is looking forward to applying this knowledge and new-found materials to the next project, which we look forward to launching very soon. 

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