4926 datasheet(7/9 Pages) 3M

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3M™ VHB™ Tapes

- 7 -

Design and Tape Selection Considerations

Choose the right tape for the substrate: Adhesives must flow onto the substrate surfaces in order to achieve intimate contact area

and allow the molecular force of attraction to develop. The degree of flow of the adhesive on the substrate is largely determined by the

surface energy of the substrate.

This illustration demonstrates the effect of surface energy on adhesive interfacial contact. High surface energy materials draw the adhesive closer

for high bond strength.

Aluminum

Polyimide

ABS

PVA

EVA

Stainless Steel

Phenolic

Polycarbonate

Polystyrene

Polyethylene

Copper

Nylon

PVC

Acetal

Polypropylene

Zinc

Alkyd Enamel

PPE

PVDF Paint

PVF

Tin

Polyester

Acrylic

Powder Paint

Silicone

Lead

Epoxy Paint

PU Enamel

PTFE

Anodized Aluminum

Polyurethane

Powder Paint

Glass

NOTES: There are a wide variety of formulations, surfaces finishes and surface treatments available on substrate materials which can affect adhesion.

This chart is intended to provide only a rough estimate of the adhesion levels which can be expected on some common materials relative to a

reference surface such as aluminum.

Foam type can affect and/or limit maximum adhesive strength.

u Use the right tape thickness: The necessary thickness of tape depends on the rigidity of substrates and their flatness irregularity. While the 3M™ VHB™ Tapes will conform to a

certain amount of irregularity, they will not flow to fill gaps between the materials. For bonding rigid materials with normal flatness, consider use of tapes with thickness of 45 mils

(1.1 mm) or greater. As the substrate flexibility increases thinner tapes can be considered.

u Use the right amount of tape: Because 3M™ VHB™ Tapes are viscoelastic by nature their strength and stiffness is a function of the rate at which they are stressed. They

behave stronger with relatively faster rate of stress load (dynamic stresses) and will tend to show creep behavior with stress load acting over a long period of time (static

stresses). As a general rule, for

static loads, approximately four square inches of tape should be used for each pound (57 cm2 of tape per kg) of weight to be supported in order to

prevent excessive creep. For

dynamic loads, the dynamic performance characteristics provided on page 4 should be useful, factoring in the appropriate safety factors.

u Allow for thermal expansion/contraction: 3M™ VHB™ Tapes can perform well in applications where two bonded surfaces may expand and contract differentially. Assuming

good adhesion to the substrates, the tapes can typically tolerate differential movement in the shear plane up to 3 times their thickness.

u Bond Flexibility: While an advantage for many applications where allowing differential movement is a benefit, the tape bonds are typically more flexible than alternative bonding

methods. Suitable design modifications or periodic use of rigid fasteners or adhesives may be needed if additional stiffness is required.

u Severe Cold Temperature: Applications which require performance at severe cold temperatures must be thoroughly evaluated by the user if the intended use will subject the tape

product to high impact stresses. A technical bulletin “3M™ VHB™ Tape Cold Temperature Performance” (70-0707-3991-0) is available for additional information.

Adhesive

High surface energy

— Substrate

Adhesive

Low surface energy

— Substrate

4941 Family

5952 Family

RP Family

1100-400

50-42

39-38

37-36

33-18

(High)

(Medium)

(Low)

Surface Energy (Dynes/cm)

Relationship of Adhesion and Surface Energy for 3M™ VHB™ Tape Adhesive Families

Generally good

adhesion

Primer may be

needed for good

adhesion

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