Selecting the perfect plastic material for your rigid food packaging needs can be a challenging task for a variety of reasons. From the range of materials available to the extensive list of performance specifications, functional requirements, product protection needs, and economic considerations, processors must carefully weigh all factors when deciding on the ideal material for their rigid plastic food packaging application.
Given the various material options and application requirements to consider, brand owners and converters may find it challenging to determine the ideal material that will meet all their processing, performance, and business requirements. In this blog series we will explore the attributes of various common rigid plastic food packaging materials starting with polypropylene (PP) to help provide a clear picture of some of the benefits and drawbacks of commonly used rigid food packaging materials. Continue reading to learn 8 key attributes of polypropylene (PP) for consideration when choosing a rigid plastic food packaging material.
Polypropylene Is Available in Three Different Grades
One of the intriguing aspects of polypropylene (PP) is the diversity of grades available for this polymer, each with its own unique characteristics and behaviors. While this may initially appear confusing, the benefit lies in the ability to tailor the rollstock formulation to meet the specific demands of the food packaging application.
The three main grades of PP are homopolymer, random copolymer, and impact (or block) copolymer. Homopolymer PP stands out as the most rigid grade among the three. Random copolymer PP resins incorporate ethylene, enhancing impact strength and delivering a softer texture compared to homopolymers. And finally, block Copolymer PP resins contain a higher ethylene content, resulting in a robust material with exceptional impact resistance, even in low-temperature environments. ICPG offers polypropylene rollstock formulations in all three grades to cater to a diverse range of packaging needs.
As if that weren't enough options, ICPG has developed a specialty grade called XPP, which has been specifically engineered to mimic several key characteristics of polystyrene during thermoforming and form-fill-seal processing, so that brands can replace current PS food packaging with a more sustainable and recyclable alternative packaging material.
Polypropylene Is a Semi-Crystalline Polymer
PP is a semi-crystalline polymer, which means that the material exhibits organized & tightly packed molecular chains. These crystalline regions, known as spherulites, come in various shapes and sizes, with amorphous areas interspersed between them. The level of crystallinity significantly influences the polymer's properties, resulting in a tough and heat-resistant material with a hazy appearance in its natural state.
Polypropylene Is the Fastest Growing Polymer by Consumption
The global rigid plastic packaging market was estimated at 66.7 million tones (133.4 billion lbs) in 2023 and is anticipated to grow from 2023 – 28 at a CAGR of 3.4% to 78.8 million tons (157.9 billion lbs). Within this market, global consumption of polypropylene for rigid plastic packaging was estimated at 16.1 million tons in 2023 (32.2 billion lbs) and is forecast to grow from 2023 – 28 at a CAGR of 4.2% to 19.9 million tons (39.8 billion lbs), with Asia, the Middle East and Africa as the highest growth markets.
While PET is currently the most widely used material in the consumption of rigid plastic packaging, polypropylene is expected to grow at the fastest rate of all bulk rigid plastic packaging through 2028, gaining share from PVC, PS and EPS in thermoforming applications.
Polypropylene Is the Lightest Polymer
PP stands out as the polymer with the lightest weight and lowest density among other common food packaging materials. This unique characteristic results in a 12% density reduction in comparison to PS and a 30% density reduction in comparison to PET alternatives, which translates to a higher yield (more parts) during thermoforming processes, lighter-weight parts, less solid waste by weight and reduced material consumption in comparison to PS & PET. Furthermore, the lightweight nature of PP contributes to less solid waste by weight, making it a sustainable solution for rigid food packaging needs. The chart below illustrates the impact that density has on yield and material consumption:| Material | Yield Factor | Consumption (lbs) |
| PS | 1.04 | 10,000,000 |
| PET | 1.33 | 12,780,000 |
| PP | 0.91 | 8,800,000 |
Polypropylene Performs Better in Life Cycle Analysis Than Other Polymers
Conducting a Life Cycle Analysis (LCA) can give packaging suppliers and food companies data on the environmental impact of materials and offer a way for companies to analyze the environmental impacts of an entire product life cycle, from sourcing and manufacturing, to distribution, use and end-of-life.The low density and lightweight nature of polypropylene allows for sustainability advantages vs PS & PET alternatives throughout the product lifecycle. To demonstrate by example, a lifecycle analysis was conducted using Trayak's EcoImpact-Compass sustainability platform using a standard 1 lb (454g) PS case-ready tray at 1,000,000 trays to compare the impact of switching from PS to PP or PET as the primary packaging material. The LCA considered various environmental indicators including fossil fuel use, global warming potential, water consumption, and transportation. Highlights of the analyses are summarized in the table below and emphasize the potential for a reduced environmental impact vs PS & PET:
| Indicator | PS to PP | PS to PET | PET to PP |
| Fossil Fuel Use | -18% Reduction | +3% Increase | -21% Reduction |
| Barrels of Oil | -85 Reduction | +14 Increase | -99 Reduction |
| Global Warming Potential (ton CO2 eq.) | -39% Reduction | -3% Reduction | -37% Reduction |
| Gasoline Consumed | -23,441 Reduction | -2,070 Reduction | -21,371 Reduction |
| Kilometers Driven (Passenger Vehicle) | -217,078.22 Reduction | -19.167.41 Reduction | -197,910.81 Reduction |
| Water Consumption | -60.02% Reduction | -23.50% Reduction | -47.74% Reduction |
| Gallons of Water | -10,220,399 Reduction | -4,000,989 Reduction | -6,219,411 Reduction |
Polypropylene Is a Recyclable Material
As concerns surrounding plastic waste have mounted, organizations are working to develop guidelines and standards to design packaging for recyclability that organizations across the value chain can rely on. In order for a material to be considered recyclable at least 60% of the consumer population must have access to recycling programs that accept the material, there must be a market value for the recycled material, and the material or product must be able to be correctly sorted & processed through a material recovery facility.
Polypropylene has been classified as APR Design Preferred, and is considered "Widely Recyclable" by How2Recycle, indicating at least 60% of the population has access to PP recycling programs and can be recycled at-scale dependent on other design features. In addition, there are continued investments dedicated to PP reclamation and recycling infrastructure (mechanical & chemical) that indicate a positive outlook for end markets for recycled PP and access to PCR PP moving forward.
Polypropylene Has Inherent Moisture Barrier Properties
When developing a packaging solution for shelf-stable or extended shelf-life applications, the need for effective oxygen and moisture barrier properties is critical. Polypropylene materials possess innate moisture barrier qualities with a Moisture Vapor Transmission Rate (MVTR), the measurement of gaseous H2O passage through a barrier, of 0.5 (g-mil.100 in. 2/24hr.). PP therefore excels at preserving product moisture compared to PS (10.0 g-mil.100 in. 2/24hr.), PET (2.0 g-mil.100 in. 2/24hr.), and PVC (3.0 g-mil.100 in. 2/24hr.), not only keeps out unwanted moisture but also locks in essential moisture levels. This makes it a top choice for specific food packaging needs, like bakery applications where maintaining optimal moisture content is key.
While polypropylene (PP) is not typically known for its oxygen barrier properties, the development of innovative solutions like ICPG's XPP Enhanced Barrier Polypropylene for thermoforming and form fill seal, along with the utilization of multi-layer barrier coextruded structures containing EVOH, have revolutionized its effectiveness in providing enhanced shelf-life barrier performance for specific applications.
Polypropylene Has Excellent Temperature Resistance
Polypropylene (PP) excels as a material with a high temperature resistance, with an operating temperature range up to 295°F, making it an ideal choice for microwave or hot fill applications. The material's high melting point and hot fill temperature of approximately 260°F make it a suitable material for hot-fill and microwavable applications. In addition, there are also certain grades of PP that can be used in cold temperature applications. For applications requiring freezer compatibility or transitioning from freezer to microwave, impact copolymer grades offer optimal cold temperature resistance while maintaining impact strength.
