Polypropylene is having a bit of a moment. Already one of the world’s most popular resins, accounting for roughly 20% of the world’s plastic, some recent developments bode well for its continued growth.

In addition to being lightweight and durable, polypropylene (PP) also is one of the least energy-intensive polymers to make and recycle compared to other polymers. This highly versatile material may need to be tweaked slightly with additives to achieve certain desired properties, such as glass-like clarity, but such additives are widely available and have been proven to be highly effective.

A recent report from Research and Markets predicts the global PP market will grow to $103.8 billion this year from $95.5 billion in 2021, a compound annual growth rate (CAGR) of 8.7%. It sees the market growing to just under $130 billion worldwide by 2026.

Such prospects have encouraged Heartland Polymers to build only the second new PP resin plant in the past decade and North America’s first integrated propane dehydrogenated (PDH) polypropylene facility. The Calgary-based firm began production this summer at the Alberta, Canada, plant, initially making homopolymer PP. The company said it plans to add random copolymer PP to the mix next year. Once commercial production is in full swing, Heartland expects to produce more than 1 billion pounds of PP annually, filling roughly 18 rail cars per day, seven days a week.

Welcome back on a key list

PP got another boost recently when a key environmental group returned the resin to its “widely recycled” list. How2Recycle is a Sustainable Packaging Coalition program that oversees a recycling identification system that is widely used on packaging. It had downgraded PP to “check locally” in labeling for consumers in January 2020, but this summer reinstated it to its previous status.

The Recycling Partnership’s Polypropylene Recycling Coalition said in late July that efforts to increase accessibility to PP recycling enabled the resin to regain the “widely recycled” designation. This can only help as PP aims to build on its position as the third-most widely recycled plastic, behind PET and HDPE.

This is vital because it is difficult to separate food-grade polypropylene products from non-food products at the recycling stage. The result is that the waste material currently tends to end up in waste-to-energy projects, go to the landfill, or be down-cycled into low-performance applications.

This is vital because it is difficult to separate food-grade polypropylene products from non-food products at the recycling stage. The result is that the waste material currently tends to end up in waste-to-energy projects, go to the landfill, or be down-cycled into low-performance applications.

Developing the NextLoopp

A London-based packaging recycling consultancy called Nextek Ltd. is working to close that loop. Headed by CEO and founder Prof. Edward Kosior, Nextek is striving to advance the circular economy for food-grade polypropylene. Nextek’s NextLoopp initiative, launched in October 2020, aims to support businesses wanting to use packaging that contains at least 30% recycled plastic and thereby meet the proposed UK government plastic packaging tax.

The global NextLoopp project employs mechanical recycling and is based on a decontamination technology in combination with the use of an innovative fluorescent marker sorting technology called Prism. The initiative involves more than 40 partners, including major players such as Unilever, Braskem and LyondellBasell.

This summer, an Irish thermoformed packaging producer called Mannok Pack successfully completed the first full-scale packaging production trials using NextLoopp’s PPristine-brand food-grade resins. It made various products, including 500-gram tubs for dairy spreads, that passed the necessary aesthetic and processing tests for products that contained 30% recycled content.

The packaging division of UK-based PFF Group also completed a trial using PPristine resin. This trial focused on making a 350-gram banderole pot, typically used in hot-fill applications such as porridge, where PP is typically used for its ability to cope with high temperatures.

Kosior has said the next step for the ground-breaking project will be to expand commercial production of the PPristine resins from the recycling stream and close the loop for PP packaging.

PureCycle also aims to close the loop

PureCycle Technologies Inc. is taking a different approach to advancing closed-loop recycling of polypropylene. It uses a solvent-based purification recycling technology licensed from Procter & Gamble Co. to separate color, odor and other contaminants from plastic waste feedstock. The process restores the waste PP resin to “virgin-like” quality in a product. It calls Ultra-Pure Recycled (UPR) plastic.

PureCycle broke ground on its second PP recycling facility in Augusta, Ga., this summer. When finished, the plant will be able to house up to eight PP recycling lines and have the capacity to produce about 1 billion pounds of “like-new recycled plastic annually.” The Orlando, Fla.-based firm said it expects mechanical completion, startup, and full commissioning of the site in 2024. Its first plant, in Ironton, Ohio, is nearing completion, with initial pellet production due to start by year’s end.

Packaging giant AptarGroup reported earlier this year that its collaboration with PureCycle was making good progress. Aptar is using UPR to develop hinged closures for food, beverage and cosmetics applications.

PureCycle also is partnering with Milliken & Co., a leading maker of plastic additives and colorants, to fine-tune and optimize the additives used in its UPR resin. Milliken is known for its technical expertise in PP additives and will be showcasing not only its PureCycle partnership but also its entire portfolio of such products at the K 2022 trade fair (www.k-online.com) in Düsseldorf, Germany, this October.

Its Millad® NX® 8000 ECO clarifying agent, for example, boosts PP’s clarity, enables faster production rates and reduces energy use. This additive has a UL Environmental Claim Validation label that it provides average energy savings of 10% for the production of injection molded, clarified PP parts. Other Milliken performance modifiers help to balance PP’s properties of melt flow, impact strength and stiffness while also helping to enable easier processing of both virgin and recycled polypropylene.

PP enjoys an unusual Renaissance

As noted at the outset, polypropylene is having a moment, as supported by all the business developments cited above. But perhaps nothing indicates this more than getting its day in the sun of pop culture and by no one less than the mega-star Beyoncé. Plastics News recently reported that the black-and-white bodysuit Beyoncé wears in promotional videos for her latest album, Renaissance, was fashioned from a stack of polypropylene stationery folders.

A 26-year-old Australian designer, Bethany Cordwell, hand-made the design using chips of plastic cut from PP folders. Cordwell, whose day job is as a costume designer in the wardrobe department of the Queensland Ballet Co., had her collection spotted on Instagram by Beyoncé’s styling team, who asked if they could use it.

Cordwell told Plastics News that she liked the shiny finish on PP folders, so she progressively purchased about 100 for her eight-piece collection that included the bodysuit. She then hand-cut scale-shaped pieces, each about two inches square, from the folders, with about 12,000 separate pieces going into the bodysuit alone. It took a month to hand cut all the pieces and sew them together.

So, while polypropylene never went away, it still would be accurate to say that this popular resin is truly enjoying a Renaissance.