How Is Polyethylene Foam Produced?

Unsure how PE foam is made? Choosing the wrong type can hurt performance and increase costs. Let’s break down the process and materials in a simple way for you.

Polyethylene foam is mainly produced by heating polyethylene plastic pellets combined with a blowing agent. Under controlled conditions, the mixture expands and forms a cellular structure as it cools, usually through an extrusion process.

Knowing the basics is helpful, but how does PE foam actually come together step-by-step? What specific materials are used, and what types are available? Understanding these details can help you make smarter choices. Let’s walk through the raw materials, production process, firmness levels, and how it compares to similar foams like EPE. Stick with us for a clearer look at how PE foam is made.

What materials are used to make polyethylene foam (PE foam)?

Selecting the right materials can seem complicated, but using the wrong ones leads to poor foam quality and performance problems. Here, we’ll break down the key ingredients needed to produce dependable PE foam.

The primary raw material for PE foam is polyethylene (PE) resin, typically in pellet form. Essential additives include a blowing agent to form the foam's cells, along with optional cross-linking agents, colorants, or stabilizers, depending on the desired final properties.

Let's take a closer look at what goes into the PE foam we create at TOPSUN. It all begins with the base plastic:

●Polyethylene (PE) Resin: This is the core material, typically supplied as small, solid pellets. We can choose from different types of PE, such as Low-Density Polyethylene (LDPE) for softer, more flexible foam, or High-Density Polyethylene (HDPE) for stiffer, more rigid foam. The selection depends entirely on the foam’s intended purpose.

●Blowing Agent: This key ingredient forms the foam's structure. When the plastic is heated and processed, the blowing agent releases gas, creating tiny bubbles or cells within the material and expanding it into foam. Blowing agents can be chemical (breaking down to release gas) or physical (such as injecting nitrogen or hydrocarbons).

●Cross-linking Agents (Optional but Common): For specific types of PE foam, such as XPE and IXPE, special chemicals are added. These agents form strong chemical bonds between the polyethylene molecules during processing. This cross-linking enhances the foam's strength, heat resistance, and results in a finer, more consistent cell structure.

●Other Additives: Depending on the intended use, we might incorporate colorants for specific aesthetics, UV stabilizers for outdoor durability, or fire retardants to meet safety regulations. 

How to produce PE foam?

Confused about how PE foam is made? Not understanding the process can impact quality control and material selection. Let's go over the typical steps involved in producing PE foam.

PE foam is primarily made through an extrusion process. Polyethylene resin and additives are melted and blended in a machine known as an extruder. A blowing agent generates gas bubbles, causing the mixture to expand as it passes through a shaped opening (die). The foam is then cooled and formed into sheets, rolls, or planks.

Let me guide you through the typical process, from plastic pellets to finished foam sheet or roll, as we often manage with our suppliers here at TOPSUN. The most common method we use is extrusion.

●Melting and Mixing: Solid PE resin pellets, along with any required additives like colorants or stabilizers, are fed into a heated barrel called an extruder. Inside, a rotating screw melts the plastic and thoroughly blends the ingredients into a hot, thick liquid.

●Blowing Agent Injection: The blowing agent is injected under high pressure into the molten plastic at a designated stage in the extruder, where it dissolves or disperses uniformly into the polymer melt.

●Extrusion and Expansion: The pressurized mixture is forced through a shaped opening, known as a die. As the molten plastic exits the die, the pressure drops quickly, causing the dissolved blowing agent to form gas bubbles. This rapid expansion creates a cellular foam structure. The shape of the die dictates whether the foam comes out as a flat sheet, a round profile, or another shape.

●Cooling and Solidification: The freshly produced foam rapidly cools, typically through exposure to air or water. This cooling process hardens the plastic, locking in the bubbles and stabilizing the foam's final shape and cellular structure.

●Cross-linking (for XPE/IXPE): This is where specific types are made.

1.XPE (Chemical Cross-linked): In this process, chemical cross-linking agents are introduced during mixing. The heat from the extruder activates these agents, forming bonds between polyethylene (PE) molecules either before or during expansion. This method is widely used in the Chinese market.

2.IXPE (Irradiated Cross-linked): In this method, cross-linking occurs after the foam sheet is extruded and cooled. The solid sheet is exposed to an electron beam (irradiation), where high-energy radiation induces molecular cross-linking. Compared to XPE, IXPE typically exhibits a smoother surface, finer cell structure, and enhanced physical properties—making it ideal for high-performance applications. However, the advanced technology and superior results come at a higher cost.

Is polyethylene foam soft or hard?

Need the perfect balance of softness and support?Not all PE foam performs the same—choosing the wrong firmness can leave your product under-protected or overly rigid. Let us guide you through the ideal density and structure for your specific application.

Polyethylene foam typically falls between soft cushioning and rigid materials—firmer than plush PU foams but more flexible than hard plastics. Its exact firmness can vary significantly, from flexible to stiff,depending on its density and specific type.

When clients like Sarah ask if PE foam is soft enough for comfort layers in PPE, or when David needs assurance of its rigidity for industrial protection, I explain that "hardness" in PE foam isn't a single value. It exists on a spectrum. Compared to the squishy polyurethane foam in your sofa, most PE foam feels noticeably firmer and more resilient. It holds its shape better under pressure.But within the PE foam family, there's significant variation:

●Density is Key: This is the biggest factor. Low-density PE foam (like some packaging grades or EPE) feels lighter and relatively softer or more flexible. High-density PE foam is much heavier, stiffer, and offers more resistance to compression. We specify density based on the required cushioning or support.

●Base Polymer Type: Foam made from LDPE (Low-Density Polyethylene) resin tends to be more flexible than foam made from HDPE (High-Density Polyethylene) resin, even at similar densities.

●Cross-linking: Cross-linked PE foams (XPE and IXPE) generally feel firmer and more robust than non-cross-linked foams of the same density. The cross-linking improves the foam's structural integrity, making it spring back better after compression and feel more solid. IXPE, with its finer cell structure, often feels smoother and slightly firmer than XPE.

So, can PE foam be"soft"? Yes, relatively speaking, lower density grades can be quite flexible. Can it be"hard"? Absolutely, higher density and cross-linked types provide significant rigidity. We help select the precise grade to balance protection, support, and sometimes comfort, ensuring the foam meets the specific mechanical requirements of the application.