Bonding Polycarbonate Polycarbonate Adhesive Bonding

Polycarbonate adhesive bonding is one of several ways to join polycarbonate pieces. The first requirement is that the pieces fit together well and are free of any oil or grease.  Sand the surfaces with 220 grit sandpaper and clean with isopropyl alcohol. SciGrip (Weld-on) recommends their 55/58 2-part polyurethane adhesive which dries clear. Henkel H5004 is a clear 2-part acrylic cement. Selecting the right adhesive for the application is the most important step in the polycarbonate adhesive bonding process. Environmental factors are critical. These include both upper and lower temperature, the environment such as the presence of hydrogen gas, moisture, and solvents.  The  user also needs to define if the cement must be suitable for food or medical products.  Without a full picture of all the requirements the polycarbonate adhesive bonding process is likely to fail prematurely.  If the adhesive bonding process appears to have problems, other choices are polycarbonate solvent bonding and polycarbonate hot air welding.

Polycarbonate Adhesive Bonding

Polycarbonate solvent bonding involves moistening the surface of the polycarbonate on each side of the bond with a solvent, waiting for the solvent to penetrate the surface and soften the polycarbonate, and then forcing the two pieces together and clamping then until the solvent evaporates. The solvents can be the same ones used to solvent bond acrylic. SciGrip Weld-0n 3 Polycarbonate Adhesive Bonding is frequently used. This method is not recommended for food products. Also the fit of the parts must be very good because there is not material to fill gaps.

It is a much slower process. The welding rod and the polycarbonate workpieces must first be free of internal moisture. This involves drying the materials in a 250F oven for several hours. The Polycarbonate Adhesive Bonding welding process heats both sides of the joint with hot air and the softened rod is forced into the weld joint. There is extra material added so the joint is obvious on the finished product. Crazing of the weld is also a problem that requires annealing the finished piece by heating it slowly to 276F, holding it there for 1 hour and then cooling back to 120F over 4 hours.  Although a slow process, no other materials are introduced because the welding rod is also polycarbonate so it is FDA approved.

Adhesive bonding for polycarbonate water baths

The joints used to bond polycarbonate or acrylic water baths need to be both structurally strong and completely water tight. The joints we use are actually tee joints which are finished to make a rectangular box. The bonding is done using jigs to keep the pieces at right angles while the cement hardens.

The figure below shows a typical bond using ½” sheet. Prior to bonding, one edge is beveled at 12 degrees using a router or table saw, and the adjacent side is cut 1/8” larger than the final dimension. The pieces are clamped together in the jig and the cement is injected between the pieces with a full fillet. The cement shrinks as it hardens so it is important to overfill the gap as shown. After about 4 hours the excess material can be removed with a router.

The cement we use for polycarbonate bonding is IPS Weld-On 55, a slow curing, clear, colorless 2 component, 100% reactive polyurethane adhesive.