An Overview of Polypropylene Recycling

New technologies promise to help boost recycling rate.

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.

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 EPS foam.

Because of the short life-span of PP made packaging, 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 approximately 20-30 years to become completely decomposed.

This 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 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, shorting, cleaning, reprocessing by melting, and producing new products from recycled PP. So, the first three steps are the same as recycling most other products. 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 little granules. These granules 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 produce new products from it.

Challenges and Opportunities in Polypropylene Recycling

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 re-use 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 step involves melting PP in nearly 250 Celsius (500 degrees Fahrenheit) to get rid of contaminant molecules. The second and last step involve 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 main challenge of polypropylene recycling is to increase the rate of polypropylene recycling to get rid of 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 can play the most important role in overcoming this vast challenge.