Bonding Acrylic with Industrial Adhesive
Acrylic or PMMA (poly methyl methacrylate) is a popular thermoplastic (most commonly referred to PlexiglasTM). It is often clear / transparent and is used for a wide variety of common everyday items such as display racks, menu stands, windows and skylights, signs, displays etc. It is a lightweight and easy to handle alternative to glass.
Acrylic is a great substrate for bonding with industrial adhesive. Its surface is receptive to adhesive bonding and bond strength normally exceeds the actual substrate strength (meaning that when you try to pull the joint apart the substrate breaks before the adhesive joint).
Surface Preparation for Bonding Acrylic with Industrial Adhesive
Normally acrylic can be bonded in its “as received” condition. Harsh solvents such as acetone should not be used for cleaning as they can damage the plastic. In fact, until recently solvent welding was a very popular method of joining acrylic. Due to health and safety in the workplace and some of the harsh chemicals and handling precautions of solvent cements, many goods manufacturers are looking to solvent-free adhesives as a safer alternative. Another benefit many are finding is that the appearance of the bonded goods and the bonding strength is actually higher with industrial adhesives than acrylic bonded with solvent cement.
Selecting a Suitable Industrial Adhesive for Bonding Acrylic
Most applications involve clear acrylic so normally a crystal clear, non-yellowing adhesive is preferred. There are a number of industrial adhesive options:
–Cyanoacrylates: these 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.
–Two-part epoxy: There are clear epoxies available which bond well to acrylic; they can achieve a larger gap fill than structural acrylics and have a longer cure time. They can yellow very slightly which could be noticeable if used in a thick layer.
–UV-curable adhesives: Most commercial acrylic is 100% UV stabilised. Grades available without the stabiliser are generally used in medical device applications or other applications where sunlight isn’t a factor. When using UV stabilised acrylic, it is important to select a UV adhesive with visible light cure (a longer wavelength photoinitiator) this is because acrylic is UV-stabilised to prevent it being destroyed by sunlight. This means it blocks UV light rays getting to the adhesive to cure it! Specialist UV adhesives for bonding acrylic are available and offer excellent strength performance, perfect aesthetic appearance, good gap fill, fast cure speed (cures on demand with a lamp) and excellent environmental durability.
Two-part structural acrylic adhesives: acrylic adhesives bonding acrylic substrate is a match made in heaven! For a clear / colourless and non-yellowing finished appearance, new crystal clear MMA structural adhesives can be considered.
For more information on bonding acrylic with industrial adhesive please contact us.