An Overview of Polypropylene Recycling

New technologies promise to help boost recycling rate.

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Polypropylene, abbreviated as PP, is a recyclable thermoplastic polymer widely used in many different applications including automotive components, reusable containers of different types, plastic parts, packaging and labeling, loudspeakers, polymer banknotes, stationery, and textiles, including carpets, ropes, and thermal underwear. PP is rugged and resistant to different chemical solvents, acids, and bases. All plastic products are stamped with recycling identification codes based on the type of resin used.

PP’s resin identification code is 5, and it is recyclable.

The current global PP market is valued at more than $80 billion, 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 used plastic packaging in the United Kingdom and the United States, with approximately five billion pounds produced in 2010 alone in the United States. 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 PP foam.

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 become completely decomposed. This characteristic poses a severe effect on our environment. 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. Again, burning of thermoplastics like PP can discharge dioxins and vinyl chloride. This problem makes environmental pollution resulting from PP burning a serious issue to consider.

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 4640F (2400C) and cut into granules. These pellets are then ready for use in the production of new products. The use of current technologies makes it easier for companies to melt PP and introduce it into the production of new items.

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. Other plastic waste streams, notably PET, also have developed food-grade recycling technologies. Many think this is a significant improvement in polypropylene recycling industry and rate of polypropylene recycling is expected to increase rapidly in the near future.

The Nextek developed process involves two steps.

The first phase involves melting PP in nearly 250 Celsius (500 degrees Fahrenheit) to get rid of contaminant molecules. The second and last step includes removing residual molecules during under vacuum and solidification at about 140 Celsius (280 Fahrenheit). 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 improper disposal of Polypropylene.

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. It will recycle polypropylene into "virgin-like quality. There is a massive underserved demand for recycled polypropylene in the marketplace.

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, a portfolio company of Innventure, a Wasson Enterprise Partnership, also based in Chicago. The initial PureCycle recycling operation is slated to begin in January 2018. It will test and calibrate the PP recycling process before opening a full production plant in 2020.