Acrylic, also known as Plexiglas, Lucite, or PMMA (polymethyl methacrylate), is a versatile transparent thermoplastic often used as an alternative to glass. With its shatter-resistant properties and sleek appearance, acrylic sheets have become a popular choice for applications ranging from aquariums to furniture to scientific equipment.
However, working with acrylic can be tricky. Unlike other plastics, acrylic cannot be effectively bonded using hot glue guns or standard super glues. Properly gluing acrylic requires using the right adhesive to create strong, long-lasting bonds.
What Is Acrylic and Why Is It Difficult to Glue?
Acrylic is a transparent, thermoplastic polymer material that resembles glass but has properties that make it superior for certain applications. Some key facts about acrylic:
- Acrylic is half the weight of glass but has up to 17 times more impact resistance. This makes it safer and easier to work with.
- It has high optical clarity and light transmission, maintaining 92% of its light transmission over 10 years. This makes it ideal for applications like aquarium tanks, windows, and display cases.
- Acrylic sheets can be heat formed into complex shapes and designs that would be difficult or impossible with glass.
- Acrylic is weather and UV resistant. It does not yellow or fade over time like other plastics.
These beneficial properties come from acrylic’s chemical structure. Each acrylic molecule contains strong polar bonding groups that allow acrylic chains to pack together tightly, creating a rigid, uniform material.
However, these same properties also make acrylic difficult to glue. Acrylic has a very smooth, non-porous surface. Most standard adhesives cannot penetrate the surface to create a strong mechanical or chemical bond. Using the wrong adhesive can result in bonds that appear to stick initially but fail over time.
Best Adhesives for Bonding Acrylic
Choosing the right adhesive is the most critical step in gluing acrylic. Here are the top options:
Acrylic Solvent Cements
Solvent cements are the preferred adhesive for gluing acrylic to itself. They work by partially dissolving the surface of the acrylic and fusing the pieces together. The bond forms as the solvent evaporates, leaving the acrylic molecules fused into one continuous piece.
Acrylic solvent cements contain solvents like chloroform, dichloromethane, acetone, or methyl ethyl ketone (MEK). These active solvent ingredients soften the acrylic surface to allow the fusion process to occur. Popular name brand solvent cements include Weld-On, SciGrip, Christy’s Red Hot Blue Glue, and IPS.
Solvent cements have several advantages:
- Provide the strongest possible bond between acrylic pieces
- Cure fully at room temperature
- Result in clear, invisible joints
- Can be used for bonds under high stress and load
- Allow repositioning during initial assembly
However, solvent cements also have some limitations:
- Long cure times, sometimes over 24 hours
- Strong solvent fumes during application
- Bond is permanent – pieces cannot be separated after curing
- Only useful for acrylic-to-acrylic joints, not other materials
Overall, acrylic solvent cements are the best choice for permanently bonding acrylic parts like display cases, aquariums, plastic furniture, and exhibit displays.
Two-Part Acrylic Adhesives
Two-part acrylic adhesives provide another option for strongly bonding acrylic. They consist of two components – an acrylic resin and a hardener – that are mixed together before application.
Popular brands of two-part acrylic adhesives include Devcon Plastic Welder, 3M Scotch-Weld DP810, and Loctite AA 330. Some products come in dual syringe tubes that mix the resin and hardener together automatically.
Two-part acrylic adhesives offer some advantages compared to solvent cements:
- Lower odor and fewer fumes during application
- Can bond dissimilar materials like acrylic to wood or metal
- Provide impact and vibration resistance
- Waterproof bonds suitable for outdoor use
The main downsides of two-part adhesives are longer clamp times and potential for yellowing over time. They also lack the exceptionally high strength of solvent cement on acrylic-to-acrylic joints. However, two-part adhesives remain an excellent choice for working with acrylic and are safer to use than solvents.
Cyanoacrylate Adhesives
Cyanoacrylate adhesives, better known as “super glues”, can also be used to bond acrylic effectively in certain situations. Popular brands like Loctite Super Glue Gel and Krazy Glue are readily available from hardware and hobby stores.
The main benefit of cyanoacrylate glue is the incredibly fast cure time. Bonds form within seconds, allowing for quick repairs and fabrication. Cyanoacrylates also give clear bonds and can adhere to plastics, wood, fiberglass, leather, rubber, and more.
However, cyanoacrylate adhesives have lower strength compared to other options and may fail under high stress loads. They are best for temporary bonds rather than permanent fabrication. The fast cure time also makes repositioning difficult.
Overall, cyanoacrylate glue can be handy for quick acrylic projects but is not recommended for structural applications like large aquariums or display cases.
Epoxy Adhesives
Two-part epoxy adhesives, such as Gorilla Epoxy or J-B Weld, can create effective bonds with acrylic. They offer very high strength and are useful for bonding acrylic to materials like metal, wood, and fiberglass.
However, epoxies tend to cure to an opaque yellow color that can detract from acrylic’s clarity. The long cure time of many epoxies also makes them impractical for bonding large acrylic pieces.
UV-Curing Acrylic Adhesives
UV-curing adhesives represent an interesting alternative for gluing acrylic. These adhesives cure in seconds when exposed to UV light, allowing for incredibly fast fabrication and repairs. Most UV-curing adhesives also create clear, non-yellowing bonds.
The downside is that UV-curing requires investing in a UV lamp if you don’t already have access to one. But for applications where fast cure and high optical clarity are critical, UV-curing adhesives are worth considering.
How To Prepare Acrylic Surfaces for Gluing
To achieve reliably strong acrylic bonds, proper surface preparation is a must. Follow these steps before gluing:
Clean With Solvent
Wipe down the acrylic bonding surfaces with isopropyl alcohol, acetone, or another solvent. This removes any oils, dust, or contamination that could interfere with adhesion. Avoid using soapy water, as the residual film can compromise the bond.
Lightly Abrade The Surface
Using fine grit sandpaper (320+ grit), lightly scuff the surface. This helps the adhesive penetrate and mechanically adhere to the acrylic. Take care not to over-sand, as excessive scratching can weaken the acrylic.
Apply Primer If Needed
For cyanoacrylate or epoxy adhesives, using a primer/activator can improve their bonding capability on acrylic. Products like Loctite 770 or 7239 plastic primer are recommended for cyanoacrylates. Follow the manufacturer’s instructions for proper primer application.
Clamp Securely
Clamp the acrylic pieces together while gluing to prevent slippage and create consistent contact between surfaces. Use foam or rubber pads to protect from clamp marks. Maintain even clamping pressure across the entire bond area.
Proper surface prep goes a long way towards creating durable acrylic bonds. It allows the adhesive to penetrate the surface and makes a strong connection.
Step-By-Step Directions for Gluing Acrylic
Here are step-by-step instructions for applying the most common acrylic adhesives:
Acrylic Solvent Cement
Supplies Needed:
- Acrylic solvent cement
- Applicator brush / syringe
- Acrylic scraps or cloth
- Foam pads
- Clamps or jig
Directions:
- Clean bonding surfaces with solvent and abrade lightly with sandpaper.
- Apply solvent cement evenly to both surfaces using brush or syringe applicator. Use scrap acrylic to prevent oozing.
- Assemble pieces and clamp securely with even pressure. Foam pads help prevent marring.
- Maintain clamp pressure for at least 12 hours to allow full cure. Longer times up to 72 hours are recommended for load-bearing bonds.
- Avoid moving or stressing joint for 24 hours minimum after curing.
Two-Part Acrylic Adhesive
Supplies Needed:
- 2-part acrylic adhesive (resin + hardener)
- Mixing sticks / syringe
- Foam pads
- Clamps or jig
Directions:
- Clean bonding surfaces with solvent and abrade lightly with sandpaper.
- Mix resin and hardener according to manufacturer’s instructions, using precise ratio. Mix thoroughly for 1-2 minutes.
- Apply mixed adhesive evenly to both bonding surfaces.
- Clamp pieces together with firm, even pressure. Use foam pads to prevent marring.
- Allow adhesive to cure for recommended time, usually 24-72 hrs before stressing joint.
Cyanoacrylate Adhesive
Supplies Needed:
- Cyanoacrylate adhesive (super glue)
- Primer/activator
- Clamps or jig
Directions:
- Clean surfaces with solvent and abrade lightly with sandpaper.
- Apply primer/activator to both surfaces according to directions and let dry.
- Apply small drop of cyanoacrylate glue to one surface. Avoid using too much.
- Quickly assemble pieces with clamping pressure. Bond will start curing immediately.
- Hold clamping pressure for 30-60 seconds until bond is fully set. Do not disturb joint for several minutes after gluing.
Epoxy Adhesive
Supplies Needed:
- 2-part epoxy adhesive
- Mixing sticks
- Foam pads
- Clamps or jig
Directions:
- Clean bonding surfaces with solvent and abrade lightly with sandpaper.
- Mix epoxy resin and hardener according to manufacturer’s instructions using precise ratio. Mix thoroughly for 2-3 minutes.
- Apply mixed epoxy evenly to both bonding surfaces.
- Clamp parts together with firm, even pressure. Use foam pads to prevent marring.
- Allow epoxy to fully cure for the recommended time before stressing joint (usually 24+ hours).
Tips for Gluing Acrylic to Other Materials
While solvent cements only work for acrylic-to-acrylic bonds, other adhesives can be used to bond acrylic to various substrates:
Wood – Use two-part adhesives like epoxy or acrylic resin mixed with hardener. Ensure the wood surface is clean and sanded. Clamp securely while curing.
Metal – Epoxy adhesives provide high-strength bonds for acrylic-to-metal joints. Roughen the metal surface slightly with sandpaper to improve adhesion.
Glass – Use a clear-drying cyanoacrylate, epoxy, or two-part acrylic adhesive. Prepare the glass by cleaning with solvent and lightly abrading with sandpaper.
Plastics – Bond acrylic to plastics like PVC, ABS, polycarbonate, etc using two-part adhesives or cyanoacrylate glue. Test compatibility first.
Fabrics/Leather – Transparent cyanoacrylate adhesives work well for adhering acrylic to fabric or leather. The flexible bond prevents cracking under flexing or vibration.
For load-bearing applications, epoxy or two-part adhesives are the best choice to give a high-strength cross-material bond. Always check the manufacturer’s guidelines for the adhesive’s suitability for the materials being joined.
Common Mistakes to Avoid
Gluing acrylic may seem straightforward, but there are some common mistakes that can compromise your bonds:
- Using too much adhesive: Excess adhesive results in weak, porous bonds prone to failure. A thin, consistent layer is best.
- Clamping too tightly: Over-tightening clamps can crack the acrylic. Use just enough pressure to create consistent contact.
- Moving joints too soon: Acrylic bonds need substantial cure time to reach full strength. Moving or stressing the joint too early can break the bond.
- Inadequate surface prep: Skipping steps like sanding or solvent cleaning prevents adhesives from properly penetrating the acrylic surface.
- Using expired adhesives: Solvent cements and two-part adhesives have relatively short shelf lives once opened. Always check freshness.
- Mixing two-part adhesives improperly: Failing to precisely mix the resin and hardener at the specified ratio negatively impacts curing and strength.
By being aware of these potential pitfalls, you can take steps to avoid them and ensure successful bonds every time.
Conclusion
Gluing acrylic may require more care than bonding other materials, but following the recommendations in this guide will set you up for success. Match your acrylic project to the right adhesive, properly prepare the bonding surfaces, and apply the adhesive correctly.
Acrylic’s optical clarity and versatility make it an ideal material for applications ranging from retail displays to custom aquariums to scientific tools. With the right adhesive and bonding technique, you can take advantage of acrylic’s potential for your projects and designs.