Best Adhesives for Plastic Bonding

To find the optimal adhesive for your project, consider your manufacturing assembly process, component’s end-use environment and essential adhesive properties. It will also be helpful to familiarize yourself with common adhesive options.

Epoxy

Epoxy adhesives are versatile bonding agents that generate strong, lasting bonds between many types of plastic. They have a dual-component composition of resin and a hardening agent. After these components are mixed and the epoxy is applied, the rigid adhesive forms a durable bond that resists moisture, chemical substances, and heat. Hardened epoxy adhesive is strong enough to handle heavier loads.

Cyanoacrylate

Commonly referred to as super glue, cyanoacrylate (CA) is a fast-drying adhesive that creates a strong bond almost immediately with smooth plastic surfaces. In addition to quickly joining components, this adhesive type is ideal for making small repairs. It forms an instant bond with many plastics, such as rigid PVC, polymethylmethacrylate (PMMA), ABS, polycarbonate (PC). At Toagosei, Industrial Krazy Glue™ is our well-known Aron Alpha® line of high-performance cyanoacrylate instant adhesives.

Polyurethane

Polyurethane (PU) adhesives form a durable, rigid bond with many different types of plastic. They’re also an ideal choice for bonding plastic to alternate materials like metal or wood. While they take longer to cure than some other adhesive varieties, once dried, they’re effective in withstanding temperature fluctuations, vibrations, or even impact for a strong, reliable connection.

Acrylic

Also called acrylic glue and resin, this type of adhesive is a typical option for plastic bonding applications due to its versatility and performance. Acrylic adhesives come in tape, liquid, and gel formats, and they create strong bonds that offer UV light, moisture, and chemical resistance. One of their more unique features is that they’re a great choice for bonding translucent or transparent plastic materials, making them well-suited for acrylic, polyethylene terephthalate (PET), and PC plastics.

Silicone

Silicone adhesives are a reliable solution for bonding plastic materials that are soft or flexible. They offer good moisture resistance, making them applicable for indoor or outdoor use. Since these adhesives maintain their flexibility post-curing, they’re also a good choice for applications that incorporate movement. Plastic automotive and electronic components often use silicone adhesives for their ability to handle high-heat conditions.

Hot Melt

Offering good tackiness, hot melt is an affordable option for everything from temporary plastic bonding and lighter-duty assembly applications to arts and crafts. The adhesive is available in various formats, such as sticks, bricks, pellets, sheets, and pouches. It bonds rapidly and is suitable for lightweight plastics and projects in which durability is not a primary concern. In heavy-duty applications or those that require a lasting bond, however, hot melt may not deliver sufficient strength.

Vinyl Adhesive

This adhesive type is uniquely developed for vinyl plastic bonding applications. Compatible with such materials as PVC, vinyl adhesives are useful for repairing the siding or flooring of a building as well as furniture upholstery. They form a strong bond that can withstand moisture, heat, and chemical exposure.

Plastic Bonding Challenges

Plastic materials are incredibly diverse, and it can be challenging to find the best adhesive for a given material or application. To ensure success, some important factors to keep in mind include:

  • Challenging Environments: Exposure to moisture, UV radiation, chemicals, and other conditions or substances can negatively impact certain adhesive materials, gradually weakening the strength of their bonds.
  • Thermal Expansion Coefficient: Temperature is another environmental factor to consider. With a higher thermal expansion coefficient than materials like metal, plastics experience greater changes in shape and volume when exposed to fluctuating temperatures. In plastic bonding, these changes can create stress along the bond line and eventually cause adhesives to fail.
  • Incompatible Materials: Only certain combinations of plastics and adhesives are compatible with one another. It’s crucial to verify that your materials are physically and chemically capable of forming a bond. For example, an incompatible adhesive can result in loss of bond strength, as well as haze or cracking in amorphous plastics.
  • Low Surface Energies: Being aware of your substrate’s surface energy will help you determine which adhesives will effectively wet it out for good adhesive flow and maximal bonding. Most plastics have surface energies ranging between 18 and 47 dynes/cm; the higher the surface energy, the easier it is for that plastic to bond. For low surface energy plastics such as polypropylene (PP) or polyethylene (PE), a primer such as Aron Alpha PP Primer can be used to promote adhesion.
  • Suboptimal Surface Conditions: Surfaces that are dirty, oily, or even excessively smooth are more challenging for bond formation. Taking steps to first prepare a bonding surface will improve the adhesive’s ability to successfully adhere.

Surface Preparation for Optimal Bonding

Creating a clean, roughened surface and, if necessary, modifying your substrate’s chemical composition are common preparatory steps for plastic bonding.

Contamination Removal

One of the easiest and most effective methods for improving adhesion is to remove any contaminants from bonding surfaces. Since adhesives function by bonding with the plastic’s surface molecules, unwanted particulates decrease the available surface energy and result in lower-quality adhesive bonds. You can remove dust, dirt, oils, and other contaminants using such techniques as manual degreasing, abrasive blasting, and chemical or laser cleaning.

Surface Roughening

While it’s not always necessary to alter plastic’s surface texture, taking the time to do so will result in a stronger bond. Smooth surfaces provide less contact area for adhesives to grip and bond with, and plastics typically possess a low surface free energy already. Roughening a surface using abrasive blasting, chemical etching, or laser texturing produces small voids in the surface for the adhesive to fill.

Chemical Composition Alteration

The chemical elements of a plastic surface and the way in which their atoms are arranged can also impact bond strength and adhesion. Using various chemical procedures, laser texturing techniques, and plasma treatments, you can modify the chemical composition of a plastic surface. Introducing or eliminating surface elements as well as breaking atoms’ chemical bonds for rearrangement all serve to produce an improved bonding surface.

Application Tips for Plastic Bonding

By following some standard application tips from our experts, you can ensure your project achieves the lasting results you need. As discussed, be sure to first verify that your chosen adhesive is compatible with the plastic you’re using. You’ll also want to prepare plastic surfaces through contaminant or oil removal and abrasion. We typically recommend acetone or isopropyl alcohol (IPA) formulations for cleaning over petroleum-based options. You might apply a primer to your surfaces as well, especially if you’re working with nylon, polyester, or acetal.

Additionally, we suggest:

  • Using gloves to handle plastic components as your skin’s natural oils can otherwise cause bond line failure
  • Etching one surface side prior to bonding If you’re working with polytetrafluoroethylene (PTFE) or its blends
  • Utilizing a lap joint or related design to distribute stress more evenly along bond lines and compensate for changes like thermal expansion

Aron Alpha® Plastic Bonding Adhesives

If you’re looking for the best adhesive for plastic parts, you can achieve a lasting, durable bond with Toagosei’s Aron Alpha® products. Our versatile product line consists of high-performance cyanoacrylate adhesives, primers, accelerators, and applicators manufactured to fulfill the permanent bonding requirements of demanding industries. To best support our customers, we also offer services such as on-site consultations, prototype testing, lab testing, and custom formulation development.

For more information on our plastic bonding adhesive technologies for PC, ABS, rigid PVC, acrylic, nylon, and more, contact us today.