Frequently Asked Questions About 3M™ VHB™ Tapes

Engineers have been using 3M VHB double-sided tapes since 1980 to permanently bond and seal metals, plastics and other surfaces to increase productivity, durability and improve appearance. The strength and superior performance of 3M VHB Tapes mean they can often be used to replace mechanical fasteners for joining a wide range of materials. Common uses and applications are found in outdoor and indoor signs, construction, furniture manufacturing, automotive products, aerospace applications, and much more.

The exceptional performance of these tapes comes from the properties of the acrylic core. The core has the dual properties of behaving like a very viscous liquid and an elastic solid. This property is known as viscoelasticity. The “visco” properties allow the adhesive to flow into the microscopic irregularities of the surface to form very strong bonds. The elastic properties allow these tapes to absorb dynamic loads, accommodate differential expansion between surfaces and help distribute loads over the greatest possible area. The elastic properties are maintained between -40°C and 90°C.

The VHB tapes are viscoelastic in nature. The foam absorbs energy and relaxes stress which provides these tapes with their unique properties.

  

Viscoelastic means the tape has both solid-like and liquid-like characteristics.

  

- Solid-like: Elasticity, strength, form stability.
- Liquid-like: Flow depending on time, temperature, rate and amount of loading. 

  

Energy Absorption
The foam absorbs and dissipates energy to increase the effective strength of the surface bond. Absorbing energy in the foam is what provides the high level of strength, as well as the excellent fatigue resistance and sound and vibration damping properties.

  

Stress Relaxation
The foam relaxes stress through viscous flow, reducing the long term stress on the surface bond line. 3M™ VHB™ Tapes, because of their resilient stress relaxing nature, allow parts to move independently such as with thermal expansion/contraction, as compared with traditional fasteners that either fight or must compensate for the movement.

All 3M VHB Tapes are double-sided foam tapes that use closed cell technology, provide outstanding environmental resistance and durability. Acrylic is a very durable chemistry with excellent long-term ageing resistance. These tapes are able to form bonds of exceptional strength and have greater durability and elasticity than conventional double-sided foam tapes.

The performance of VHB Tapes is not significantly affected by exposure to sunlight and harsh environments. The long-term ageing resistance lies in the polymer comprising 3M™ VHB™ Tapes. The chemical bonds that make up the polymer chains consist of carbon-carbon single bonds that are highly resistant to energy in the form of heat, cold, or ultraviolet light, as well as chemical attack. Outdoor weathering decks around the world are used to collect data on the long-term performance of these tapes. These harsh tests typically show 100% bond strength retention after 2-5 years.

When stored in the original cartons in cool dry conditions (ideal 20°C, 50% relative humidity) the shelf life is 24 months from date of manufacture.

3M™ VHB™ Tapes bond most surfaces permanently, but if you have to separate the surfaces and remove residue, 3M also has the tools for a fast, effective job.

  

3M™ Smart Tool
Use by hand or in an air chisel to quickly separate such bonded assemblies as overlapped panels and stiffeners.

  

3M™ Stripe Off Wheel
Takes residue off faster and easier than solvents or adhesive cleaners. Resilient rounded edge follows contours and irregular surfaces and cleans without scratches or damage to acrylic enamel or urethane paint.

Special Feature products have special performance characteristics. Products are available for:
- Situations where high dynamic stresses are involved
- Applications to paints and plastics including plasticised vinyl
- Situations that require a transparent tape
- When the tape is applied between 0°C and 10°C
- Components that are bonded before powder coating or need to withstand higher temperatures

  

General Purpose products are ideal for many interior and exterior industrial applications. These tapes have softer cores and are especially suited for textured surfaces or where sealing is required.

- All VHB Tapes provide good adhesion to most metals, glass and high surface energy plastics.*
- For higher performance on paints and plastics** use 4941, 4991, 5925, 5952, 5962 or 4945. The liner side of 4618, 4622 and 4624 has good adhesion to paints and plastics.
- Use General Purpose VHB Tapes or 4941 or 4991 when the surface is textured to get a more complete bond or when sealing the joint is a critical requirement.
- On flexible vinyls use only plasticiser resistant 4941, 4945 or 4991 (Note: the liner side of 4618, 4622 and 4624 is also plasticiser resistant).

  

* High surface energy plastics include acrylic, ABS, polycarbonate, PVC, polyester, Polyamide, Polyimide, Phenolic, Noryl.
** Low surface energy plastics include PVA, EVA, polystyrene, acetal and some paints. They may require priming with 3M Tape Primer 94. Very low surface energy plastics such as polypropylene, polyethylene and EPDM are difficult surfaces to stick to. Primer 94 may improve the performance on these surfaces.

- The tape thickness required depends on the mismatch between the surfaces to be joined. The more closely the two surfaces fit together the thinner the tape can be. Generally, the tape can accommodate up to 50% of its thickness in a mismatch (i.e. the tape should be at least twice as thick as the mismatch). If in doubt, use a thicker tape to ensure a significant area of the tape forms a bond.
- When bonding sheets or large pieces, the thickness of the material should not be more than twice the tape thickness, e.g. 1.1mm thick tape is commonly used to bond sheets up to 2.2mm thick.
- Thermal expansion and contraction or movement in the joint should not exceed three times the tape thickness. Generally, a 2.4m length of plastic can be bonded to metal using a 1.1mm thick tape.

In shear (e.g. holding a sign or panel to a wall) the suggested amount of tape to hold up 1 kg is about 55cm^2 or for:

Standard Tape Widths	Tape Length
12.7 mm wide	430 mm
19.0 mm wide	290 mm
25.4 mm wide	215 mm

These amounts of tape include a significant factor of safety to allow for the different properties of the tapes in the VHB Tape range. These amounts can be reduced by up to 50% depending on the tape type if customer evaluation gives satisfactory results.

The desirable tape application temperature range is 20ºC - 40ºC. There are VHB Tapes with special properties that allow low temperature application.

  

The minimum suggested surface temperatures for tape application are:
16°C: 4936, 4941, 4945, 4991
10°C: 4611, 4618, 4622, 4624, 4905, 4910, 4915, 4918, 4930, 4950, 4959, 5925, 5952, 5962, 9473
0°C: 4951, 4957 (on high surface energy substrates only)

  

Once properly applied, low temperature holding is generally satisfactory down to -40°C