Successfully Bonding Acrylic with Industrial Adhesives
What is Acrylic? (PMMA) – polymethyl methacrylate – Several types of industrial adhesive bond acrylic. Because its surface is receptive to adhesive bonding, bond strength normally exceeds the actual substrate strength (meaning that when the joint is pulled apart, the substrate breaks before the adhesive joint). Most applications involve clear acrylic, so normally, a crystal clear, non-yellowing adhesive is preferred. There are a number of industrial adhesive options.
How to Bond Acrylic?
Cyanoacrylate – All grades adhere well to acrylic. Due to acrylics susceptibility, to bond acrylic with cyanoacrylate, it is important to use cyanoacrylate adhesive sparingly. When operators try to wipe excess adhesive outside the joint away it will fog the acrylic. Cyanoacrylates offer a rapid cure in seconds, do not require any mixing or curing equipment. These adhesives are particularly suited to high-speed production lines. Limitations – maximum gap fill is 0.5mm. Using alkoxy-ethyl cyanoacrylates will reduce visible powdery residue on the surface and is less pungent than a regular ethyl cyanoacrylate.
Epoxy adhesive – single component epoxies are not suitable as the heat required to cure the adhesive will damage acrylic. However, two-component epoxies will bond acrylic. Many grades will bond; however, often clear grades such as ET500, ET515 are preferred over black or other opaque products.
MS Polymer – For a flexible bonding solution MS Polymers can be considered. Since most acrylic is clear, MS359 CLEAR will provide a good finished appearance.
UV Curable adhesives. Permabond UV632, UV639, and UV645 UV/Visible light cure adhesives are recommended. Many grades of acrylic are UV stabilized – which means some or all of the UV light is blocked. Consequently, the UV/Visible light cure is recommended to ensure cure. All three of these products will produce a bond which is stronger than the substrate.
Structural acrylics – several grades are available. MMA’s provide very good bond strength but are flammable and have a very strong odor. As a result, they are often not acceptable, so Permabond formulated low odor toughened acrylic adhesives.
To determine the best specific adhesive to bond acetal in your application, please provide some detail to our technical team and our adhesive advisors will get back to you with a recommendation.
In addition to adhesion to acrylic, several other parameters are generally involved in selecting the best adhesive. Understanding the solvent and temperature resistance of the adhesives is especially relevant in selecting the best type of product.
Note: Products can withstand higher temperatures for brief periods providing the joint is not unduly stressed.
Tips for surface preparation:
1. Providing the surface is clean and dry and free from contamination, acrylic can generally be bonded “As Received”.
2. Engineers often choose to do a solvent wipe before bonding or for clean up afterwards and use isopropanol or Permabond Cleaner A. Many solvents, notably acetone, are too aggressive and as a result, will attack the plastic.
Properties of Acrylic:
- Surface energy: 38 mJ/m²
- Maximum service temperature: 85°C
- Softening temperature: 120°C
- Coloured, opaque, transparent, clear or metalized
It seems like acrylic is found in every industy. A few examples of acrylic uses follow:
- Point of sale displays
- Windows and skylights
- Medical devices
- Shop fitting
- Automotive lenses and instrument panels