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Plastics & Elastomers

Polypropylene Performance Developments Move Forward!

Donald Rosato – Dec 3, 2020

TAGS:  Polypropylene    

This article was first published in 2019 and is revised in 2020.

Polypropylene AdvancesPolypropylene (PP) is the second-most widely produced volume plastic after polyethylene. The global production of PP resin is 56 MMT (Million Metric Tons) in 2018 and is estimated to reach 83 MMT by 2025, at a CAGR (Compounded Annual Growth Rate) of 5.85%. The PP end-use market is US$97 billion in 2018 and will reach US$147 billion by 2025 for a 6% annualized growth.

The packaging sector represents more than 30% of global PP demand in 2018, driven by demand from number one India trailed by China

Other major PP end-uses include:

  • Electrical/electronic and equipment manufacturing, both at approximately 13% each
  • Household appliances and automotive both consuming at 10% each
  • Construction materials follow at 5%, and
  • Very diversified applications together make up the remaining fifth of global PP consumption

Major PP resin suppliers include:

In order to be ahead in the market, it is important to stay up-to-date with improvements in PP resin developments. Let's take a look...

Polypropylene Resin Developments

Novel resin development is taking place in the field of high melt strength variants for use in foamed PP compounds. End-use markets for foamed PP include automotive, packaging, building and construction, and industrial. Key resin developers in this technology are Borealis, SABIC, and others such as Braskem and Japan Polypropylene.

PP Chemical Structure (L), PP Living Hinge from Bottle to Cap (R)
Credits: Plastics Institute of America

Borealis Daploy™ HMS PP Foaming Grade

High melt strength polypropylenes are tailored to have long chain branching that in turn gives them simultaneously their mechanical strength and elasticity. Borealis is the current market leader in the field with its Daploy™ HMS PP grades that exhibit a broad foaming range process window. Typical foam density for specific applications are:

  • 80-600kg/m3 (grams per cubic meter) in packaging applications such as cups or bowls
  • 40-350kg/m3 in automotive parts such as roof and door liners, impact absorbers, and ventilation ducts, and
  • 60-200kg/m3 in building insulation products

High melt strength and extensibility of Borealis HMS PP grades allow tailoring of foam properties by adding linear polymer component while keeping good foamability as shown in the two figures that follow:

Borealis HMS PP Force Versus Drawdown (L), and Tensile Modulus Versus Density (R)
Borealis HMS PP Force Versus Drawdown (L), and Tensile Modulus Versus Density (R)

Rheology Curves Comparing Traditional Linear PPs & Borealis Daploy HMS PP Foaming Grade
Rheology Curves Comparing Traditional Linear PPs (Green)
and Borealis Daploy™ HMS PP Foaming Grade (Orange)

In the above graphic, there is a rheological, contrast between traditional linear PPs and high melt strength (HMS) PP with its defined high-performance foaming window.

With HMS PP it is even possible to manufacture extremely low 20–50 kg/m3 density foams. These extruded foams have very finely delineated and uniform cell structure. These type foam structures are beyond the capability of standard linear PPs that fall well outside the high-performance HMS foaming window. Additionally, Borealis HMS PP is blendable with standard PP and broader polyethylene extrusion grades, as well as being processable on the vast majority of established foam extrusion equipment. This capability offers endless opportunities to custom tailor foams to very specific end-use applications and that these parts are fully recyclable.

Borealis HMS PP Applications
Borealis HMS PP Automotive Lining (L) and Food Container Foam Applications (R)

SABIC's Ultra Melt Strength (UMS) PP

Continuing, SABIC has continued to earnestly develop its version of a high melt strength PP. Their Ultra Melt Strength (UMS) PP resin – SABIC® PP-UMS HEX17112 has an excellent melt flow/strength of 65 centimeters Newton (cN). It is bringing unprecedented light-weighting levels to automotive applications such as interior instrument panel carriers, panel reinforcement pillars, and related flooring/guard supports.

Foaming technology with its strong focus on part wall downgauging is opening a broad array of sustainable applications in not only automotive, truck/bus, mass transportation, building insulation, but also packaging containers of all sorts to assist in minimizing food waste globally.

SABIC Foam PP Molded Instrument
SABIC's Foam PP Molded Instrument Panel Carrier

Braskem's Amppleo 1025MA PP Grade

Next Braskem has been evolving their own branched, high melt strength PP. Their Amppleo 1025MA grade has a very good cost performance melt strength at 50 centimeters Newton accompanied by a flexural stiffness of 2.3 Giga Pascals (GPa). The development focus here is on low to medium density foam applications that utilize a broad range of chemical as well as physical blowing agents. It is quite adaptable to established inline and tandem extrusion manufacturing systems.

Related Read: The Definitive Guide to Polypropylene (PP)

Metallocene Catalyzed Technology Based Japan Polypropylene's Waymax EX Grade

Finally, Japan Polypropylene is offering a high melt strength PP as a Waymax EX grade. It is based on metallocene catalyzed technology and exhibits a high melt flow rate, melt strength, and strong resistance to strain hardening. Their foamable grades possess high foam expansion ratios, in addition to consistent fine cell structure.

Aaron’s Recycled Polypropylene Featuring Milliken’s Modifiers

Aaron Industries has launched its new high melt flow recycled polypropylene (PP) compound. JET- FLO™ Polypro, which features DeltaMax™ Performance Modifiers from Milliken & Company. According to the company, it is among the first recycled PP materials to combine two properties that are normally mutually exclusive:

  1. Extremely high melt flow index (MFI of 50-70 g/10 min), and
  2. Good impact performance (Notched Izod of 1.5-2.0)

In addition to its environmental benefits, JET- FLO™ Polypro opens the door to new application opportunities, including new parts with more-complex designs and thinner-wall geometries, such as DVD cases, caps and closures, etc. From a processing standpoint, faster cycle times help avoid molded-in stress that can cause warpage.

Solving End-of-Life Challenge by Restoring Used PP into Virgin-like Resin

PureCycle Technologies has partnered with Milliken & Company and Nestlé S.A. as it moves forward with plans to open its first plant to restore used polypropylene (PP) plastic to 'virgin-like' quality with a revolutionary recycling method.

PureCycle Technologies will make high-quality, recycled PP widely available for purchase across industries. This technology demonstrates P&G's commitment to sustainability and helps in achieving P&G's 2020 recycling goals:

  • Doubling the use of recycled resin in plastic packaging and
  • Ensuring 90 percent of product packaging is either recyclable or programs are in place to create the ability to recycle it

Polypropylene Blend Material Advances

Polypropylene (PP) blend material advances are playing an increasing role where end-use customers are requiring improved mechanical toughness in not only specialized markets such as medical, as well as major automotive applications to meet ever demanding specifications. Technologies like specialty impact modification and innovative blend compounds will play a key role here.

Related Read: Self-Reinforced PP - A Rising Star for New-age Cars

Lyondellbasell's Impact Enhancing Plastomer for PP

Lyondellbasell has developed a successful impact enhancing plastomer that is very compatible with Polypropylene (PP). A plastomer is basically a material that combines the features of elastomers and plastics, such as rubber-like elastic properties with the plastic processing capability. When blended with PP, this LyondellBasell plastomer enhances PP softness, break elongation, elastic rebound. It increases transparency while simultaneously minimizing surface whitening from stretching. Purell is the impact modifier grade family. It is sold in a free-flowing pellet form as Purell KT MR07. PolyButene-1 (PB-1) is the base resin.

Next, metallocene chemistry is used for production purposes. The chemical structure is that of an isotactic, crystalline polyolefin with a high molecular weight. This feature provides the opportunity to create a broad range of PP blend materials including very low temperature variants. Lyondellbasell is currently market developing medical applications such as standard and multi-channeled lumen tubing, as well as IntraVenous (IV) bags.

LyondellBasell Impact Modified PP Medical Tubing
LyondellBasell Impact Modified PP Medical Tubing

Key medical market performance features include:

  • Low leachability and extractability
  • Excellent resistance to kinking
  • Sterilizability, and
  • Weldability

Other specialty impact modifier application areas include: appliances, bottles and vials, medical devices, and medical film.

Akro-Plastic’s PA66 and PP Blend Compound

Continuing, specialty material supplier Akro-Plastic’s AKROMID® A3 GF 30 4 L black (4678) is a good example of an innovative blend compound. Basically, it is a combination of Polyamide (PA, nylon) 66 and polypropylene (PP). This compound blend is extremely mechanically tough, has excellent resistance to hydrolysis, and with the PP component is easily tailorable over a range of density or overall weight reductions with lower use of PA66. When this blend is 30% glass reinforced it has equivalent properties at 15% reduced cost over traditional glass filled nylon grades.

Akro-Plastic’s Nylon 66/PP Automotive Cooling Water Pipe Cross Section
Akro-Plastic’s Nylon 66/PP
Automotive Cooling Water Pipe Cross Section

Major applications include functional parts in the heating and cooling systems in the automotive industry, where weight and cost reduction are required. Akro-Plastic recommends from a processing standpoint that only dehumidifying or vacuum dryers be used. Extensive drying can cause filling problems and surface defects.

Polypropylene Additive Enhancements

Recent Polypropylene (PP) additive developments have focused on a tale of two major global plastic end-uses, namely packaging and automotive. In the highly competitive plastic film packaging market where performance is always front and center attention wise, incremental additive improvements can substantially improve production efficiency.

Elsewhere, for example, natural fiber reinforced PP bio-composite compounds are finding increased usage in durable interior automotive applications where end-users need to meet more sustainable goals.

Let's see some of the latest PP additive advances...

Dow's Silicone Slip Additive

Dow's Performance Silicones fully commercialized PP homopolymer (75%)/Siloxane (25%) additive provides a better process efficiency slip in PP packaging films. The additive system is available in a pelletized form and can be masterbatch compounded. It is best suited for use in Biaxially Oriented PP (BOPP) films. The specific grade designation is HMB-6301. It provides a low dynamic Coefficient of Friction (COF) at low loadings – for example 0.2 to 0.3 film-on-film dynamic COF levels at an addition rate of 2-5 wt%.

COF (L) of Oriented PP Film vs. Dow’s HMB-6301 Additive Percent (R) Over Time at 60°C
COF (L) of Oriented PP Film vs. Dow’s HMB-6301 Additive Percent (R) Over Time at 60°C

Dow’s system provides very stable and long-term slip performance while not penetrating through barrier food films that in turn:

  • Maintains excellent film transparency
  • Minimizes film surface bending or break, and
  • Increases film line output

It also complies with the EU 10-2011 food contact regulation and FDA approval is currently near conclusion. Anticipated applications at the outset will include food bags, candy wrappers, and related packages and pouches.

Dow Silicone Slip Additive Coated BOPP Candy Wrappers
Dow Silicone Slip Additive Coated BOPP Candy Wrappers

Dow’s additive system neutralizes traditional film slip agent shortcomings namely, migration from the film surface and time sensitive/higher temperature degradation. From a positive performance perspective, the slip additive’s masterbatch capability allows for excellent film surface printing and metallization for brand package design promotional purposes. An equally important aspect of this novel slip additive is that its surface controlled, consistent coefficient of friction (COF) maximizes productivity in form/fill/seal packaging machinery where maintaining a clean, machine facing surface is critical without random, contaminated slip agent migration to the wrong surface.

Traditionally, erucamide type waxes are extensively used as oriented PP film slip agents. A major drawback here is migration through the film surface that in turn causes haze in clear product packages, as well as interference with film winding and finished surface printability on the inner non-slip film side. Similar to Dow Performance Silicones, Ampacet and Croda are also pursuing parallel additive development routes here.

Natural Fiber Filled PP Compound in Automotive Performance Materials (APMs)

Automotive Performance Materials (APM) applied use of a natural fiber additive reinforced PP bio-composite compounds in a continuing success in the European automotive market that is simultaneously improving plastics recycling and circular economy goals. Weight reduction is a major technical market driver in the global automotive market that not only improves vehicle fuel efficiency but simultaneously reduces greenhouse gas emissions, fulfilling circular economy goals.

When traditional mineral glass fillers are replaced by natural fibers like industrial hemp, an up to 25% weight reduction is achievable that in turn allows for thinner part moldings. APM has established a strong natural agro-fiber quality control program to ensure product consistency for compounding purposes. This leads to uniform injection molding parameters being met such as fiber pre-drying, lower injection temperature, and fiber burning avoidance.

APM’s development is an improved 20% short natural fiber filled PP compound. Main characteristics of their NAFILean PP-NF20 are as follows:

  • 20% industrial hemp filled compound
  • Reduced density (0.98 g/cm3)
  • Achieves weight savings of up to 25%
  • Wall thickness reduction (of 2.5 to 2mm)
  • Designed for automotive structural parts
  • Crash performance equal to conventional materials
  • Good thermal and mechanical properties
  • Low odor and low VOC (Volatile Organic Compounds)
  • Reduces environmental impact by 20-25% throughout components life cycle

APM’s NAFILean PP-NF20 Natural Fiber/PP Automotive Compound
APM’s NAFILean PP-NF20 Natural Fiber/PP Automotive Compound

Furthermore, this natural fiber additive based compound has been trialed and confirmed throughout the automotive end of life PP recycling process. Glass fiber filled PP has not had similar recycling success. With its low 0.98 g/cm3 density it is easily, injection moldable on standard machines. Property wise, there is high flexural modulus stiffness and good finished part durability for interior automotive applications at present. For example, a molded natural fiber reinforced PP has been commercialized in the Alfa Romeo Giula instrument panel that weighs 3.5 kilograms, which is over 1 kilogram less compared to a previously specified long glass fiber additive reinforced polyethylene part.

AMP NAFIlean Biocomposite Peugeot 508 Instrument & Door panel Parts (Green)
AMP NAFIlean Biocomposite Peugeot 508 Instrument & Door panel Parts (Green)

Milliken Millad® NX™ 8000 Clarifier for PolyPropylene (PP)

Milliken’s Millad® NX™ 8000 clarifier additive helps PolyPropylene (PP) producers and converters to stay ahead of packaging, appliances, medical, houseware and food storage trends by achieving unprecedented transparency. This innovative clarifier generates significant energy savings and faster production in injection molding.

Milliken’s Millad® NX™ 8000 PP Clarifier Consumer Product Container (L), Recycled PP Pellets (R)
Milliken’s Millad® NX™ 8000 PP Clarifier Consumer Product Container (L), Recycled PP Pellets (R)

Suitable for all thermoplastic conversion processes, Millad® NX™ 8000 makes PP a viable alternative to glass or amorphous polymers like:

PP clarified with Millad® NX™ 8000 encompasses the growing demand for clear, attractive products and sustainable, cost- efficient production.

Traditional clarifiers require a minimum temperature of around 220°C before they will dissolve in PP. At this temperature, the fibrous network is not properly formed, preventing high transparency. Millad® NX™ 8000 has improved solubility characteristics in PP which allow processing at lower temperatures. This creates a broader, more robust processing window and a dramatic improvement in the clarity of polypropylene.

Packaging Made Using Milliken’s Millad® NX™ 8000 Clarifier
Packaging Made Using Milliken’s Millad® NX™ 8000 Clarifier

Find the Suitable Polypropylene Grade to Match Your Applications Needs

View a wide range of polypropylene grades (homopolymer, copolymer, random, etc.) available today, analyze technical data of each product, get technical assistance or request samples.

2 Comments on "Polypropylene Performance Developments Move Forward!"
PRAMOD S Oct 9, 2021
Would there be a grade of PP Powder with additive(s) for UV protection and having a property and particle size conducive for fluidized bed coating ? Other requirements stipulated are 1). Ozone proof 2). Zinc Chloride proof 3). 40 year outdoor life 4) Temperature rating between: - 50 deg. C to +95 Deg C. Please advise and oblige. Pramod K Sethi performance Polymers & Coatings, Bangalore , India pksethi@polyfluoroltd.com sethipramod10@gmail.com
GOURDON B Jun 11, 2019
Thanks for this good review upon PP. I am surprised of its 56000 KT world production. It was around 42000 KT in 2015 ! I appreciate this document OK . Bernard GOURDON

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