If you’ve ever worked with plastic, you know how hard it can be to get other materials to stick to it. Silicone is a great option for creating a durable bond on plastic, but which options are best? And how can you apply it for best results?

In this article, we’ll explore some of the best silicone adhesives for plastic and what you need to know before making a purchase.

How Do Silicone Adhesives Work?

Before we get into silicone adhesive for plastic, we need to discuss how this material actually works. Silicone is widely used across various industries for a wide range of purposes and outshines traditional adhesives in many ways. They are known for their temperature resistance and chemical stability and are ideal for application in challenging environments.

Here’s a step-by-step breakdown of how silicone adhesives are used.

1. Surface Preparation

For these adhesives to form a strong bond, the joining surfaces must be prepared. Surface preparation involves cleaning the surface to remove any contaminants, such as oils, dust, or moisture, that could interfere with adhesion.

You may also need to wipe the surface down with solvents or apply a primer designed to improve adhesion. Whatever you do, don't skip this step — it’s key to ensuring that your adhesive effectively bonds to the surface.

2. Application

Once the surface is prepared, you can go ahead and apply the adhesive. This method of application can vary depending on the adhesive’s viscosity and the specific requirements of the job. Some silicone adhesives are applied manually, while others are applied via automated dispensing systems.

3. Curing

Now the adhesive needs to cure. This is where it transforms from a liquid or paste into a solid, elastic rubber. The curing process is initiated by the catalyst present in the adhesive formulation and occurs at room temperature or with the application of heat, depending on the type of adhesive used.

4. Bond Formation

As the adhesive cures, it forms a strong bond with the surface it’s applied to. But the ultimate strength of the bond is influenced by many factors, including the material’s mechanical interlocking with the surface textures.

Why Silicone and Plastic is a Match Made in Heaven

While there are many different adhesives that can work well with plastic, silicone adhesives stand out thanks to their unique set of properties. Their exceptional compatibility with most types of plastics allow for versatile use in diverse industries.

What’s more, they offer outstanding temperature resistance and are capable of withstanding both high and low extremes. Their superior flexibility does a great job accommodating the thermal expansion and contraction of plastics, maintaining a strong bond without cracking or weakening over time.

As if that wasn’t enough, silicon adhesives offer tremendous chemical resistance, meaning they can comfortably withstand exposure to oils and other harsh substances.

Choosing a Silicone Adhesive For Plastic

So what is the best adhesive for plastic? There really isn't a one-size-fits-all answer to this question, as so much depends on the materials involved — and your specific needs and budget. Here are some of the factors to consider when making a decision.

Compatibility With Plastic Substrates

First and most importantly, you need to make sure that the adhesive is compatible with the plastic substrates you intend to bond. Plastics vary a lot in their chemical composition, surface energy, and tolerance to solvents and temperatures.

Some plastics have low surface energy and may require specific adhesives or surface treatments to achieve adequate bonding. Make sure that whatever adhesive you choose is formulated to bond well with the type of plastic you’re using.

Adhesive Strength and Flexibility

Not all products are created equal. The best silicone adhesive for plastic will offer adequate bonding for the material in question, whether it be metal or plastic. Carefully consider the mechanical load and stresses the bond will need to withstand in its application.

For example, a high-strength adhesive may be necessary for structural applications, whereas a more flexible adhesive can be used for plastics that experience significant thermal expansion and contraction. The adhesive should maintain its strength and elasticity over the temperature range to which the bonded assembly will be exposed.

Temperature Resistance

Temperature resistance should be a key factor in your selection process. The adhesive should be able to withstand the operating temperature range of the application without degrading or losing its adhesive properties.

The good news is that most silicone adhesives offer excellent resistance to extreme temperatures, so regardless of your choice, you shouldn’t experience too much trouble here.

Chemical Resistance

If the material will be exposed to harsh chemicals, it’s important to choose a silicone adhesive that offers adequate chemical resistance. While most adhesives can withstand a certain amount of chemical exposure, some are much better suited to these conditions than others, so do your research before buying.

Curing Mechanism and Time

Some adhesives cure at room temperature, while others require heat to accelerate the curing process. Consider the production requirements — such as assembly time and handling strength — when selecting an adhesive. Fast-curing adhesives may be preferable for high-throughput applications, whereas longer curing times may be acceptable for applications where higher bond strength is needed.

Ease of Application and Processing

If you can, try to find something designed with ease of use in mind. Silicone adhesives are available in several different formats, including pastes and liquids, with some better for certain types of applications than others.

Health and Safety

The last thing you want to do when working with silicone is compromise your health or that of those you’re around. Consider the volatile organic compounds (VOCs) emitted during curing, any special handling requirements, and the adhesive’s toxicity.

Opt for adhesives with lower health risks. Review any relevant data sheets to understand the necessary safety precautions when using the product.

Environmental and Regulatory Compliance

Finally, make sure that your silicone adhesive of choice complies with environmental regulations and industry standards. This includes everything from regulations on VOC emissions to required certifications around food contact or automotive applications.

Final Tips

The most important thing to remember when choosing an adhesive is to consider the material you’re working with. Understand the properties of your plastic and look for an adhesive that’s designed for that specific material.

Always patch-test the adhesive before committing to full-scale application. This can reveal hidden issues with adhesion or compatibility that aren’t immediately apparent from the product details alone.

Pay attention to the manufacturer’s guidelines for surface prep and curing conditions to ensure optimal bond strength. And don’t forget about the operational environment of the bonded assembly — exposure to extreme temperatures and chemicals can impact the adhesive’s effectiveness. You want something that can maintain its integrity under these conditions.

Looking For a Quality Silicone Adhesive? We Have What You Need

Plastics have many unique qualities and properties. To avoid damaging them, it’s important to choose a compatible adhesive. Silicones are a great all-around choice, as they’re typically well-suited to bond with plastic and can help protect the material from harsh conditions.

But choosing a reputable adhesive can be hard, as there are so many different options on the market today. Silicone Depot offers an extensive inventory of silicone that can be bought individually or in bulk at a discounted price.

Need help finding the perfect product for your plastic-based project? Get in touch with us at 812-824-8000 to learn more.