Polypropylene Foam: Boosting Sustainability and Cost Efficiency

Polypropylene (PP) foams are increasingly adopted in automotive and packaging sectors to enhance lightweighting and sustainability. (Photo: Avient)

Over recent years, polypropylene foaming has gained substantial momentum, beginning with extruded PP foam and expanding into injection and blow‑molded variants. Key markets include automotive and packaging, followed by construction, consumer goods, and industrial applications. Cost‑performance remains a major driver, especially amid recent domestic price surges due to supply constraints and robust demand. More importantly, the growing demand for foamed PP stems from sustainability imperatives—using less resin and offering greener alternatives to PS and EPS.

The automotive industry’s push toward electric vehicles (EVs) is accelerating lightweighting efforts, which in turn fuels foamed PP adoption. Packaging likewise benefits from sustainability mandates that favor reduced material use. Technological advances in both physical and chemical foaming—often combined—enable this growth. For example, Trexel’s MuCell direct‑gas injection has evolved over the past three years, achieving thin‑wall molding levels previously unattainable.

Chemical foaming agents (CFAs) from iD Additives, Avient, and Trexel now produce microcellular foams with exceptionally small, uniform cells and superior aesthetics. Concurrently, PP resin suppliers such as SABIC, Asahi Kasei Plastics, and Borealis have released high‑melt‑strength grades tailored for extruded or molded PP foam, as well as specialty reinforced compounds optimized for foaming.

A 2018 Markets & Markets analysis forecasted the global extruded PP foam market to grow at an average annual rate of nearly 7% through 2023. SABIC’s Foam & Lightweight team highlighted that their ultra‑melt‑strength PP supports extrusion for automotive, construction, and packaging, while also identifying opportunities in injection and blow‑molding where weight reduction and sustainability are critical.

Emerging packaging regulations further propel PP foam adoption, according to industry insiders. Craig Sibol, Avient’s additive product manager, expects low‑double‑digit growth in foamed PP—primarily via injection molding—though he notes supply constraints limit extrusion growth in construction.

Todd Glogovsky, Asahi Kasei Plastics North America’s executive VP of sales and technology, emphasizes that foaming and thin‑walling are continuously assessed to lower cost, weight, and cycle time. Manufacturers will select the option delivering the greatest impact on savings and performance.

Nick Sotos, iD Additives’ president, recalls that rising PP prices in 2021 sparked increased demand for foaming agents. In response, the company hosted a “Foam It or Fill It” webinar to educate stakeholders on cost‑mitigation strategies.

Trexel President Brian Bechard notes that, until recently, rising PP prices had not dramatically shifted molders toward foaming, as successful commercial parts require significant lead time and design adjustments. However, as resin prices trend upward, the economics of foaming become increasingly attractive.

SABIC’s long‑glass Stamax PP, coupled with a core‑back foaming process, earned the SPE Automotive Innovation Award for a Mini Countryman instrument‑panel carrier that achieved a 15% weight reduction.

Trends in Automotive

SABIC’s automotive division reports nearly two decades of foamed PP use in automotive parts, primarily for weight reduction through both foaming and thinner part geometries. In 2017, the company’s long‑glass Stamax PP and core‑back foaming earned an SPE Automotive Innovation Award for a Mini Countryman IP carrier that cut weight by ~15%.

Historically, foamed PP was limited to structural, non‑visible components because surface finish was inadequate. Growing demand for lightweight, aesthetic interiors and cycle‑time savings has driven the development of next‑generation PP foams with superior surface quality, aligning with the automotive industry’s goal of reducing fuel consumption and emissions.

An SABIC automotive source highlighted that the surge in EV production heightens the need for lighter parts, as vehicle weight directly impacts efficiency and range. Foamed PP compounds can reduce part weight by 8–10%, and improved flow enables thinner, more design‑flexible parts, potentially achieving 20–25% weight savings over non‑foamed equivalents.

SABIC has invested in a suite of foamable PP compounds that combine weight savings with superior surface aesthetics. Key improvements include minimizing streaks and defects, and mitigating sink marks even in thin‑wall parts. While typical interior parts are up to 3 mm thick, foaming generates internal pressure that offsets shrinkage, reducing sink marks. Optimized design and processing unlock the full potential of PP foam, with plans to enhance aesthetics for exterior applications.

Building on extensive MuCell foaming experience for filled PP automotive parts—such as instrument panels, door panels, and underhood housings—Trexel’s CEO Brian Bechard reports increased activity in unfilled PP foaming for automotive and packaging. The TecoCell CFA is recognized for delivering class‑A surface finishes in visible automotive interiors, with several parts nearing commercial launch.

While foamed PP has traditionally served non‑class‑A, non‑structural automotive zones—like battery covers and underhood components—Asahi Kasei’s Glogovsky is targeting semi‑structural applications such as floor consoles, headliners, and lower interior trim.

Borealis notes that its Daploy HMS‑PP family comprises long‑chain branched polymers offering high melt strength and extensibility. These materials blend seamlessly with standard PP extrusion grades, enabling customized foam properties across automotive, packaging, construction, and building markets.

Avient’s product manager Craig Sibol asserts that automotive demand for PP foam remains robust, driven by lightweighting initiatives and forthcoming U.S. CAFE standards. While Avient focuses on injection‑molded automotive components and select packaging, its CFAs serve both as lightweighting agents in injection molding and nucleating agents in extrusion with direct‑gas injection, creating finer foam structures.

Trexel is targeting unfilled PP for thin‑wall packaging, where MuCell enhances flow to produce thinner parts on existing presses. The company collaborates with brand owners and molders to bring commercial products to market.

Growth in Packaging

Trexel’s focus on unfilled PP for thin‑wall packaging includes containers, cups, bowls, lids, and spouts. Bechard notes that MuCell improves flow, enabling thinner parts on the same equipment, and highlights a 5% weight reduction, 15% lower injection pressure, and 20% clamp‑tonnage reduction achieved in a Chinese injection machine builder’s bowl at Chinaplas.

SABIC’s Foam & Lightweight team reports rising demand for foamed PP in e‑commerce returnable boxes, pallets, food packaging, and protective packaging. Their 2017 PP‑UMS (ultra‑melt‑strength) material launch catalyzed market growth, with significant acceleration in 2020–2021.

iD Additives’ Nick Sotos identifies industrial packaging—such as gaylords and pallets—as a major foamed PP market, while the company also expands into blow‑molded bottles, caps, and closures using its micro‑cellular Micro Fine Cell foaming agents.

Asahi Kasei’s Glogovsky sees packaging dunnage as a promising area, noting that foaming can reduce cycle time by 5–35% for parts with thick sections by decreasing material mass.

Borealis highlights that Daploy HMS‑PP resins and blends remain non‑crosslinked, ensuring that resulting extruded foams are fully recyclable—a key advantage for packaging and other plastic sectors.

Molding technician Ron Bishop demonstrates foam produced with iD Additives’ new Micro Fine Cell CFA.

Building/Construction and Other Applications

Nick Sotos identifies plastic lumber as a natural fit for PP foam, while his company also explores roofing, toolboxes, and construction levels.

SABIC’s Foam & Lightweight team pursues structural foams and pre‑fabricated building components—including house insulation, piping, and floor underlayment—while Asahi Kasei’s Glogovsky sees lightweighting as a secondary driver in this sector, primarily for shipping cost reductions.

Glogovsky considers consumer and healthcare segments on a case‑by‑case basis, focusing on cycle‑time improvements. Trexel is collaborating with a major household product company to reduce cost and resin consumption across its line, and iD Additives has partnered on consumer goods such as foamed PP hangers, with niche applications like footwear cited by SABIC’s Foam & Lightweight team.

Asahi Kasei’s Thermylene short‑glass reinforced, chemically‑coupled PP has been employed in foamed sunroof modules, substituting unfoamed long‑glass PP while delivering superior aesthetics.

Latest Advances

SABIC’s automotive division plans to launch a new line of foamed PP compounds tailored for aesthetic interior parts by early 2022, with three initial compounds promising improved surface finish.

Asahi Kasei has engineered foaming materials that enhance both aesthetics and lightweighting, including Thermylene short‑glass reinforced, chemically‑coupled PP used in foamed sunroof modules.

Nick Sotos notes that iD Additives’ Micro Fine Cell CFAs have revolutionized the company’s ability to target thinner‑wall applications.

At NPE2018, Trexel introduced the MuCell P‑Series gas system, optimized for fast‑cycle, thin‑wall packaging. Bechard explains that the system now offers screw‑tip dosing, allowing standard screws to deliver gas without sacrificing plasticating output—a critical advantage for high‑throughput packaging.

Trexel has expanded its satellite‑based dosing units with a low‑cost, high‑power central gas booster, providing molders operating multiple machines with MuCell flexibility and affordability.

Avient’s expanded portfolio of liquid and solid CFAs, along with comprehensive testing support, enables customers to push lightweighting limits while maintaining mechanical integrity. Sibol highlights that smaller cell size and surface‑property manipulation allow paint or decal application without additional corona treatment, improving production efficiency.

SABIC’s Foam & Lightweight team promotes its PP‑UMS as a next‑generation, high‑melt‑strength, foamable PP. With melt strength exceeding 65 cN, it demonstrates excellent foamability, especially for high‑expansion‑ratio parts.

SABIC’s PP‑UMS enables the creation of foamed food containers that can replace EPS, offering a more sustainable alternative.