Important Step in Sustainability: Polyethylene Terephthalate Recycling and the Recent Developments

Abstract

Human history has encountered massive environmental issues due to the outcomes of industrialization in today’s societies, development of industry, increasing population, etc. The rise in the level of welfare around the world and its spread throughout many different societies and countries are adding on undesirable environmental problems. This negative trend seems not to stop and unfortunately is on the rise. The persistence on failure to keep up with change and development may trigger further environmental calamity increase leading to an unsustainable world. Therefore, today’s society is called as the “Consuming Society” by many different authorities. If one would like to monitor the dimensions reached by this “Consuming Society” concept on the basis of textile sector, the examination of per capita consumption of textile fiber could be the right approach. Textile product consumption amounts are increasing in direct proportion with the increase in the world population. Unfortunately, natural fibers cannot meet the increased fiber demand. The remaining supply share in the increased fiber demand has been fulfilled with the production and consumption of chemical fibers. Therefore, the supply shortage in natural fibers has been substituted, wherever possible, by synthetic staple and filament fiber production. Natural fibers leave their throne to synthetic fibers while cotton fibers lose their throne to polyester fibers. Today we can point out polyester fibers as the most popular fiber type. Approximately 35% of the world fiber production is covered by natural fibers while the remaining 65% share is covered by synthetic fibers, and 70% of the synthetic fibers consumed are polyester fibers. Polyester is a general name for many different types of polyester fibers such as polyethylene terephthalate (PET), polylactic acid (PLA), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), etc. Polyethylene terephthalate (PET) fiber is the most important, the most produced, and the most consumed polyester fiber. Normally when one calls a fiber as polyester fiber, this fiber is mostly PET and is commonly referred to and used as polyester in public. The majority of PET production is used for fiber production in the textile sector, with 60% share, and 30% of PET production is used for bottle production. Due to the fact that polyester fibers possess obvious advantages in terms of raw material costs when compared with other fibers in the world, it is expected that the consumption quantities for the aforementioned two sectors will increase further in the coming years. Superior performance properties of PET fibers as well as their raw material cost advantages result in an increase in PET fiber production and consumption. Polyesters and similar petroleum and petroleum-derived plastics, which are not very friendly with the environment during their production and have a long natural decay time, gradually take their place among our indispensables in our lives. Their low cost causes their consumption to increase even more. The necessity of recycling these materials, the requirement for renewal in the technologies used in the production processes, and the necessity of disposing of waste materials in an appropriate way have reached levels that cannot be ignored. At this point, we can understand the actual costs of plastics only when we take into account the environmental pollution, recyclability, and their impact on our health. The most obvious example of this is the Asian countries. China and other Asian countries, which have become the center of synthetic fiber production, have a pie share of 70% in the world fiber market and some people believe that therefore they possibly might have the largest share for environmental pollution. The pressures of the countries and the environment in recycling polyester have led to improvements in the waste management industry. Thanks to this driving force, recycling is gaining importance day by day. In the economic sense, the recycling process is seen as the best way to reduce polyester waste as well as to take the advantage of their reusage for new textile products. Recycling and waste management systems are constantly changing and developing in line with new and innovative technologies. In this review chapter, recycling methods and the steps of used waste polyethylene terephthalate materials and the rebirth of waste polyester materials in new textile products along with related recent developments are comprehensively reviewed. Therefore, in this chapter, first of all, recycling processing steps of PET-based materials (cleaning, crushing, washing, drying, and chopping processes) are introduced. Then, the information regarding recycling methods such as mechanical recycling and chemical recycling is given. Afterwards, the applications of mechanically and chemically recycled PET are mentioned. Finally, the recent commercial developments regarding PET recycling are covered.