Polypropylene, abbreviated as PP, is a recyclable thermoplastic polymer widely used in many different products. PP is rugged and resistant to different chemical solvents, acids, and bases. PP’s resin identification code is 5, and it is recyclable.
The current global PP market was valued at more than $80 billion in 2014, according to Transparency Market research, and is anticipated to reach $133.3 billion by 2023.
Importance of Polypropylene Recycling
The melting point and strength of PP makes it the single most popular plastic packaging material in the United States, with approximately five billion pounds produced annually in the U.S. (2010). But according to PP production and recycling figures provided by American Chemistry Council, PP is one of the least recycled post-consumer plastics, at a rate below 1 percent for post-consumer recovery.
Because of the short lifespan of PP made packaging, the majority of these thermoplastics end up in landfills as waste. The US Environmental Protection Agency states that approximately 20 percent of solid waste produced comprises some form of plastics which include PP. Products made of PP degrade slowly in landfills and take around 20-30 years to completely decompose. This characteristic poses severe environmental concerns. Additives used in plastic products may contain toxins such as lead and cadmium. Studies suggest that cadmium contained in plastic products has the potential to percolate and can have extremely harmful consequences for a number of bio-systems. Also, the burning of thermoplastics like PP can discharge dioxins and vinyl chloride.
Recycling Polypropylene is the best available option to handle this situation in an eco-friendly and cost-effective way.
The Polypropylene Recycling Process
The recycling process involves five steps namely collection, sorting, cleaning, reprocessing by melting and producing new products from recycled PP. So, the first three steps are the same as recycling most other commodities. But the last two are critical. In the reprocessing phase, collected PP products are fed into an extruder where it is melted at 4,640 °F (2,400 °C) and cut into granules. These pellets are then ready for use in the production of new products.
Challenges and Opportunities in Polypropylene Recycling
Efforts to improve PP recycling have been ongoing. Nextek Ltd., a UK-based Plastic design and recycling consulting company and finalist of 2013 recycling innovators forum, has invented an innovative process to decontaminate food grade polypropylene for reuse in a closed loop back into food packaging.
The Nextek developed process involves two steps.The first phase involves melting PP in nearly 250 °C (500 °F) to get rid of contaminant molecules. The second and last step includes removing residual molecules during under vacuum and solidification at about 140 °C (280 °F). The products made following this process can be blended with virgin PP at a rate up to 50 percent.
But the primary challenge of polypropylene recycling is to increase the rate of polypropylene recycling and at the same time to eliminate the dangerous impact of improper disposal, however. As mentioned above, currently nearly 1 percent of PP is recycled. Only the development of new and innovative technologies help overcome this enormous challenge.
In July 2017, Proctor & Gamble announced a partnership with PureCycle Technologies in building a PP recycling plant in Lawrence County, Ohio. The goal was to recycle polypropylene into "virgin-like" quality. The demand for recycled polypropylene in the marketplace is massively underserved. According to the Association of Plastics Recyclers (APR), there is a demand for 1 billion pounds of recycled PP annually in North American alone; including 720 million pounds of ‘high-quality’ recycled PP.”
P&G developed the technology, which it is licensing to PureCycle. The initial PureCycle recycling operation was slated to begin in January 2018. It will test and calibrate the PP recycling process before opening a full production plant in 2020.