Utilizing textile waste can help facilitate the production of sustainable products that reduce environmental pollution. To this end, a paper published in Construction and Building Materials has presented a technique to recycle denim waste to produce 3D needled denim/polypropylene composite materials.
Study: Development of 3D needled composite from denim waste and polypropylene fibers for structural applications. Image Credit: Vannaweb/Shutterstock.com
Textile Waste: A Growing Problem
The global textiles market is estimated to be worth almost £1,000 billion according to Grand View Research. With the growth of the textiles industry, however, there has come a major problem: waste. More than 150 billion tons of textile waste is estimated to be produced globally per year from both production and clothes disposal. Compounding this issue is the recycling rate of textiles, with only 20% of waste recycled. Most waste is either buried or burned, which damages the environment.
Moreover, there is an issue with resource scarcity due to a growing world population and demands upon the textile industry. These problems highlight the pressing need for effective and environmentally sound recycling and reuse strategies for textiles waste.
Recycling and Reusing Denim as Engineering Materials
One of the most commonly used materials in the textiles industry is denim. This material is composed of nearly 100% cotton fibers. Denim can be recycled by either physical or chemical methods. In chemical methods, the dye is stripped from the denim fibers, with high recovery rates. Physical recycling methods are low cost but affect the economic value of the recycled materials.
Numerous studies have been carried out recently into the use of denim as engineering materials, reducing the dependence on fossil fuels and related products. Engineered fiber composites have high specific strength, making them attractive alternatives for numerous industries.
Recent Studies
Recent studies into the use of denim waste as composite reinforcement materials. A study by Temmink et al. trimmed denim jeans to fabricate materials to reinforce biocomposites. The resulting material exhibited higher mechanical properties but was limited by the denim waste’s size.
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Petrucci et al. used denim fibers to reinforce polypropylene using injection molding, but the short length of the fibers (under 5mm) used in the study limited the mechanical properties of the composites.
Meng et al. used longer denim fibers (15-25 mm) and combined resin transfer molding and needle-punching to create a 3D needle-punching/epoxy composite that displayed enhanced mechanical properties. However, a drawback to this method was that using epoxy resin as a thermosetting material presented recovery and cost challenges.
Improving the Techniques
Polypropylene (PP) is a cost-effective material for use as a thermosetting matrix that can be reinforced with denim fibers. These materials can be produced in short cycle times using compression molding techniques.
In the study published in Construction and Building Materials, a needle-punching/compression molding technique was developed to fabricate denim waste fiber-reinforced polypropylene composites Processing parameters for compression molding were optimized by using response surface methodology. To explore the possibility of using non-decolorized materials, the effects of dyes and treatments of the dye fibers were explored.
Mechanical properties of the waste denim fibers were compared to cotton fibers to clarify the differences between them. Results of the testing demonstrated higher bonding strength, shear strength, and bending strength in the composite materials.
Denim fibers were also observed to be more hydrophobic than cotton fibers, which give them superior bonding affinity with the polypropylene matrix. The reason for this is the presence of dyes reducing the material’s hydrophilicity.
The team also carried out a performance comparison between the composite material and wood-based panels to confirm the material’s potential for use in the field of furniture manufacturing. The composite denim waste/polypropylene materials are cost-effective, making them a good choice for raw materials.
Furthermore, the composites displayed better resistance to water swelling, making them a durable option for this purpose. Moreover, the formaldehyde content of these composites is significantly reduced, making them ideal for storage boxes and other products.
Waste Denim/Polypropylene Composites: The Future
The enhanced mechanical properties, hydrophobicity, and lack of formaldehyde content was found to be advantageous for the waste denim/polypropylene composites. The use of the composites as furniture materials demonstrated the enhanced properties of the denim waste and shows the potential for this material to be used for commercially viable products in industries such as furniture and architecture.
The straightforward, optimized, cost-effective fabrication method presented in the study shows that waste from the textiles industry can be utilized to manufacture novel biocomposites with greatly improved mechanical properties. Through innovative approaches such as this, the problem of textiles waste can be largely eliminated, creating a more sustainable, environmentally-friendly textile industry.
Further Reading
Wang, S et al. (2021) Development of 3D needled composite from denim waste and polypropylene fibers for structural applications [online] Construction and Building Materials 314 Part A | sciencedirect.com. Available at: https://www.sciencedirect.com/science/article/pii/S0950061821033201
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