Adhesives for Polystyrene Foams

What Is Polystyrene Foam?

Polystyrene foam is a type of closed-cell foam made from styrene monomers. While polystyrene can come in a rigid plastic form, there are two main subtypes of polystyrene foam—expanded polystyrene (EPS) and extruded polystyrene (XPS).

Expanded polystyrene is made of small beads fused together and is more porous and lightweight. It is typically water-resistant and impact-resistant. It also has great dimensional stability and low thermal conductivity. You can find expanded polystyrene foam in packaging, construction, or craft applications. It is also the type of polystyrene foam used to make disposable cups.

Extruded polystyrene is a rigid, dense, and durable foam made into boards. It has an especially high thermal resistance for its thickness and is also mostly water-resistant. It is used almost exclusively in construction and insulation applications.

Gluing Polystyrene Foams

While polystyrene foams are commonly used in industrial applications, it can be difficult for some adhesives to bond to them. Finding the right adhesive for polystyrene foam is crucial for lasting success.

Both EPS and XPS are sensitive to solvents and heat as they can deform, melt, or dissolve their surface. Because they are more sensitive substrates, using a glue that will not damage the polystyrene foam you are using is critical to getting a successful bond. Expanded polystyrene is also more vulnerable to solvent damage, so the best adhesive for extruded polystyrene may not be the best adhesive for expanded polystyrene.

Another issue with bonding polystyrene foams is their low surface energy, which can limit natural adhesion and make it more challenging for adhesives to wet out the surface. The closed-cell structure of the polystyrene foams doesn’t help, as this can also limit adhesion and mechanical interlocking.

Typically, the solution is proper surface preparation of the polystyrene or choosing an adhesive that is designed to bond difficult substrates. Because polystyrene foam is already so sensitive, what you can do for surface preparation is limited, so a specialty polystyrene foam adhesive is required.

While these polystyrene adhesives have been used successfully in the past, every application is unique. It is important to identify the type of polystyrene foam as expanded polystyrene is especially sensitive to solvents. Also consider factors like environmental conditions and production processes. For best results, test the adhesive in small batches first or get an adhesive recommendation from an expert.

Types of Glue for Polystyrene Foams

When it comes to choosing a polystyrene foam glue, there are a lot of key considerations. The first step is knowing what types of glues not to choose. When looking for an adhesive for polystyrene foam, there are a lot of glues that are not compatible with this material.

Be cautious of:

• Solvent-based adhesives (including many spray adhesives) that can dissolve the surface
• High-heat adhesives that can melt the foam
• Adhesives that are not foam-safe
• Adhesives that require harsh pre-treatments for surface preparation
• Multi-purpose adhesives that do not specify being compatible with foam

Instead, start by looking at these types of adhesives for polystyrene foams:

• Foam-Safe Spray Adhesives Spray adhesives can be a great glue for polystyrene foams as they can easily provide even coverage for large bonding areas. Just make sure the adhesive is safe for polystyrene foam without any harmful solvents.
• Water-Based Adhesives: These adhesives are generally safe for use on foams as they use water as the primary solvent. They can take longer to dry and may slow down the production process.
• Low-Temperature and Foam-Safe Hot Melts: The low application temperature of these adhesives keeps them from melting the foam, and the foam-safe formulation prevents damage to the surface. These hot melts are a good choice for quick bonding.
• Polyurethane Adhesives: These adhesives can provide a strong, industrial bond for polystryene foams so long as they are compatible with them.

Because many adhesives are not suited for polystyrene foam, it is important to review a product’s technical datasheet for substrate compatibility or speak with an expert.

How to Glue Polystyrene Foams Without Damaging Them

Because polystyrene foams are sensitive to heat and solvents, they can be moderately difficult to bond. Choosing a specialty glue for polystyrene foam is one way to overcome these challenges, but it must also be applied correctly with the right surface preparation. Surface preparation for gluing polystyrene foam can vary, but typically you should take the following steps:

1. Cut and pre-fit the polystyrene foam so you have the necessary sizing.
2. Clean and degrease the surface of the foam to remove contaminants that could weaken the bond. Do not use solvent-based cleaners, such as alcohol or acetone, since they could damage the surface.
3. While abrasion of polystyrene foam is usually not recommended, abrasion may be important for the other substrate if you are gluing polystyrene to another material. Always re-clean the surface of an abraded material to remove loose dust left behind.
4. Let the substrate surfaces dry completely before applying your adhesive as moisture could weaken the bond.
5. Apply the adhesive evenly and at the recommended application temperature.
6. Use clamps or mechanical fasteners if recommended, and let the adhesive set completely before handling.

Every application is slightly different. Always follow the manufacturer’s specific recommendations for surface preparation for best results.

Get the Right Product

Because it is a sensitive and challenging substrate to bond, polystyrene foam requires careful adhesive selection. The wrong adhesive can cause damage or result in a weak bond. Avoid these mistakes with our help.

We carry a wide selection of adhesives for foam, including those for EPS and XPS. Get the best adhesive for polystyrene foam for your needs with a personalized adhesive recommendation based on your foam type, application, production environment, and budget. Contact us to get started, or fill out the form below.