Recycling and injection moulding of aeronautical post-consumer low density polyethylene

Ailish Chauhan, Teodora Cosovic, Shahil Hamid, Arnav Kapur, Anshul Khattar and Chuanhao Xu

Community Partner: WorldView
Degree: Bachelor of Applied Science
Program:
- Materials Engineering
Campus: Vancouver

The challenge

Passengers journey to the edge of space inside a pressurized capsule that is lofted by a helium-filled low-density polyethylene (LDPE) balloon.

World View is an emerging space tourism company that is developing a balloon and capsule system to take people on eight-hour flights 100,000 feet into the stratosphere. Each balloon is single-use only, and World View asked us to develop a proof of concept to repurpose the used LDPE balloon films to create components they could use elsewhere in their operations.

Our inspiration

The CEO of World View shared his vision with us that taking people to the edge of space can help deepen understanding and appreciation of everything we have on earth. The company’s desire to reduce their carbon footprint and repurpose and reuse their single-use materials is part of that vision.

About WorldView's Vision

Our design process

There were three main stages to this work. First, we had to produce LDPE pellets from the balloon films provided by World View. We then needed to custom design and create an injection moulding tool. Finally, we needed to manufacture the product, a simple L-bracket that could be used in the World View capsule.

One challenge was that the injection moulding machine requires pellets as inputs, and we weren’t able to produce these pellets at UBC. We had to look beyond the university to find a company for support – and we were lucky to connect with Marek Gnatowski , the president of Polymer Engineering, who shared both his expertise and lab space to help us produce the pellets.

Another challenge was creating the mould. A high quality, industry-standard mould would be made from either aluminum or stainless steel using a CNC machine; however, this process is very expensive and only viable at a larger scale. We spoke with Dr. Casey Keulen an Assistant Professor who manages the materials lab at UBC about using 3D printed moulds instead. After evaluating our options, we chose stereolithography 3D printing technique to print our mould as it has higher precision than other 3D printers and can print with thermoset resin– which brought our mould production costs down to $75 compared to $5,000 for a metal mould.

Our project was actually the first time that UBC’s new injection moulding machine was used, which introduced some trial and error. LDPE is very soft, so finding the right pressure and speed for the injection moulding required multiple trials. Our work designing and 3D-modelling the part in SolidWorks and ABAQUS to simulate how heat and stress would transfer around the mould enabled us to make accurate predictions about failures so that we could fine-tune the process and produce a viable L-bracket.

What excited us most

The project brought together everything we’ve learned over our degree for the last four years. It was very fulfilling to design the entire process, end to end – from initial idea to developing a process and then producing the final product.

It was exciting to learn about World View’s vision for space tourism and hear their leaders talk about making their business as sustainable as possible. Networking and learning from others – not just our supervisor Dr. Sergey Kravchenko, but also a PhD student working with him who helped us with the model and Dr. Marek Gnatowski at Polymer Engineering – was also a highlight.

Materials Engineering

What we learned

The process of producing pellets for injection moulding was more complicated and took longer than we thought, requiring multiple steps and machines to get pellets of the consistent size and quality required for the injection moulding machine.

It was also more complex to create the injection mould than we had anticipated. A lot of research needs to go into producing a mould – particularly an epoxy mould, because it is less stiff than a standard metal mould. You need to get the dimensions just right so it won’t crack under high pressure.

Our project’s future

We delivered the proof of concept to World View. The next step would be additional research on material development to produce parts that have more applications or that are stronger. We used an SLA 3D printed mould to produce the part, but a CNC mould would be preferable in terms of durability and the ability to scale up production.