Researchers discuss recycling 3D printed nylon composites

A new article in the journal Sustainability explored the recycling of 3D printed nylon composites with the aim of improving the sustainability of the additive manufacturing industry. The research was conducted by scientists from the United Arab Emirates University in the United Arab Emirates.

Study: Characterization and sustainability potential of recycling 3D printed nylon composite waste. Image Credit: Joaquin Corbalan P/Shutterstock.com

The scale of plastic and polymer composite waste

According to some reports, by 2050 there could be more plastic waste in the ocean than fish. The critical problem of large quantities of polymer and composite material waste entering the natural environment has crystallized industry and government action to limit the ecological damage it causes.

Block diagram of the material preparation process.

Block diagram of the material preparation process. Image credit: Al-Mazrouei, N et al., Sustainability

The National Geographic Society has estimated that there are currently 5.25 trillion pieces of plastic debris in the ocean, ranging from whole products to microplastic fragments. Microplastics pose a particular problem because they can be consumed by marine organisms and enter the food chain, causing damage to human and animal health. Plastic waste finds its way from the surface to the depths of the ocean.

3D printing and waste

The field of additive manufacturing has provided innovative solutions to many industries due to the design freedom and cost-effectiveness of 3D printing technologies. One of the characteristics of 3D printing is the reduction of waste compared to traditional manufacturing techniques. Products are built layer by layer from raw materials.

While waste is greatly reduced when 3D printing, there are still critical issues with waste in the industry that impact its overall sustainability. Products, especially composite filaments that are produced by commercial fusion deposition modeling techniques, are an additional source of plastic waste that complicates environmental remediation efforts.

Waste can be generated during additive manufacturing processes due to issues such as poor filament quality, hardware failures, slicing errors, and print bed adhesion issues. Recycling waste can be a complicated process, for example in the case of composites incorporating glass fibers and carbon fibers due to the toxic heavy metals produced during manufacture.

Tensile testing machine.

Tensile testing machine. Image credit: Al-Mazrouei, N et al., Sustainability

Recent studies have focused on combining different synthetic fibers and polymers to improve the properties of composites made by 3D printing methods, such as carbon fibers, glass fibers, and nylon fibers. Specific material challenges are associated with each reinforcing fiber, with different effects on the properties of the final product observed by researchers.

Challenges with dimensional quality control and consistency of material properties lead to problems recycling 3D printed polymer composite waste. However, the recycling of certain waste is possible but limited. In the case of materials incorporating carbon fiber, 30% of the waste can be recycled. Prototyping parts produced using FDM techniques can be recycled and reused.

The research

Recognizing the inherent difficulties in manufacturing 3D printed polymer composites and the recyclability and reuse of waste produced during processing, the authors produced recycled blended polymer composites.

The researchers mixed 3D-printed composite waste, carbon-fiber reinforced nylon, and glass-fiber reinforced nylon. This approach produced recycled composite sheets of CFGF/nylon materials. Filaments from 3D printing waste were used, offering a solution to improve the circularity of these materials. The composites were produced using different mix compositions.

To produce the composite sheets, the authors used a process that combines compression molding and a dual-extruder machine. The thermal and mechanical properties of the composite sheets produced were evaluated. Mechanical properties such as modulus of elasticity, toughness, tensile strength and ductility of composite materials were evaluated. FTIR and thermogravimetric analysis were used in the study.

Study results

The article demonstrated the relevance of recycled 3D printing waste for the manufacture of new functional products. Analysis of composite sheets incorporating different blends of carbon fiber, glass fiber, and nylon fiber reinforced materials revealed several important properties of each material.

Comparison of toughness of composites.

Comparison of toughness of composites. Image credit: Al-Mazrouei, N et al., Sustainability

The highest toughness and ductility were observed in pure glass fiber/nylon reinforced polymer composites. Although this was the highest result observed, the authors also found that adding 20% ​​by weight of fiberglass/nylon to carbon fiber/nylon composites increased their tensile strength. Increasing fiberglass/nylon from 50 to 60 wt% improved the elastic modulus, but at 80 wt% it decreased.

Thermal analysis revealed that pure carbon fiber/nylon composites possess a high degradation temperature compared to pure fiberglass/nylon composites. In addition, the incorporation of fibreglass/nylon decreases the degradation temperature of the composite.

In summary

The recyclability of 3D printing waste is currently a key area of ​​research in the industry. Being able to recycle and reuse polymers and composite materials will improve the sustainability and circularity of additive manufacturing and therefore the many industries that are increasingly using 3D printing methods.

The team behind the paper said the results of their study could be used in research into the recycling of many 3D-printed filament waste, providing several innovative opportunities for future research.

Further reading

Al-Mazrouei, N et al. (2022) Characterization and sustainability potential of recycling 3D printed nylon composite waste Sustainability 14(17) 10458 [online] mdpi.com. Available at: https://www.mdpi.com/2071-1050/14/17/10458

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