Virgin nylon or recycled

Nylon is a collective name for synthetic fibres derived from polyamides, which are large molecules with specific chemical properties. The best known are nylon 66, nylon 6, nylon 610 and nylon 11, for example, whose chemical properties differ [1]. The name can also have polyamide before the number, and then nylon 66 is also known as polyamide 66. The numbers in the name indicate the number of carbon atoms in the smaller molecules. These polyamides are produced with carbon-based chemicals found in coal and petroleum, which are fossil fuels [2].

Photo: Silver Bobbin

In the production of nylon, they are spun from the molten form into fibre by cooling and then stretching several times to strengthen the fibre [1]. Nylon 6 and nylon 66 are the second most important synthetic fibres, and we often use them in blends with natural fibres. Their main characteristics are their abrasion resistance, toughness, relatively high tensile strength and elasticity in both dry and wet conditions. Nylon became commercially available during World War II and was significant because of its quality and strength [3]. It also became a popular alternative to silk pantyhose, which was in short supply during World War II.

Today, low-quality nylon is the norm, and most nylon garments do not last very long, but high-quality nylon is more durable and can last longer [3]. Northeast Asia is the centre of nylon production; in 2015, Asia accounted for two-thirds of the world’s nylon production [4]. Although less nylon is produced compared to polyester, nylon requires more energy to produce [3]. Nylon requires almost three times as much energy compared to that needed to make cotton. The energy consumption of nylon is reported to be between 250-262 MJ of energy per kg of fibre [5]. Producing nylon also results in the emission of the potent greenhouse gas nitric oxide [6]. Nitrogen oxide is 310 times more harmful than carbon dioxide in terms of its effects on the greenhouse effect [3]; it is also a persistent gas in the atmosphere that can reduce the critical ozone that protects us on Earth from harmful UV radiation [7].

Photo: Silver Bobbin

Dyeing nylon is not environmentally friendly because the fibre is unsuitable for natural or more environmentally friendly chemical dyes [3]. Thus, dyeing the fabric leads to extensive water pollution. At the same time, the material is produced in countries with weak environmental protection laws, making nylon a significant contributor to water pollution. However, nylon requires less water consumption in production than other fibres.

Nylon is not biodegradable and will, therefore, accumulate in the environment. The two primary sources of microplastic pollution in aquatic environments are nylon fishing nets and synthetic textiles that release microplastics during washing [3]. Nylon can be recycled, although it is more complex than recycling polyester. However, recycled nylon is more environmentally friendly than virgin nylon. Recycling nylon is not economically beneficial as it is cheaper to buy new polymers. We also have to clean nylon fabrics thoroughly before they are recycled. Nylon melts at low temperatures, and some microbes, bacteria, or contaminants can survive. There is, therefore, a need to expand the availability of recycled nylon to consumers. Some producers of sustainable nylon, such as Econyl and Aquafil, produce nylon from old fishing nets and other waste they collect from the sea, facilitating a more circular closed loop and reducing waste and emissions.

Another significant development in pursuing sustainable nylon production involves using wood waste as a raw material, thereby reducing hazardous waste generation [3]. Recycling nylon offers the added benefit of minimizing the disposal of petroleum-based chemicals in landfills and mitigating the release of toxic emissions into the atmosphere. Furthermore, recycled nylon exhibits a 27% reduction in its consumption of natural resources compared to virgin nylon, resulting in a 28% reduction in greenhouse gas emissions. What’s more, recycled nylon is itself recyclable. Nylon 66, in particular, is tough to recycle, and when burned, it releases toxic gases such as dioxins, nitrogen oxides and hydrogen cyanide [5]. Nylon fibres differ based on their energy consumption, water consumption and greenhouse gas emissions. For example, 1 kg of Nylon 66 requires 138.62 MJ of energy and 663 kg of water compared to Nylon 6, which requires 120.47 MJ of energy and 185 kg of water.

Sources

May 2022, TÄNKOM | Revised May 2024 RETHINK

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