3M SJ3551CF Dual Lock Reclosable Fastener 25 mm x 45.7 m

What Is 3M™ Dual Lock™ SJ3551CF?

3M™ Dual Lock™ SJ3551CF is a reclosable mechanical fastening system designed for applications that require a secure connection with the option to separate and reattach components. Unlike conventional hook-and-loop tape, Dual Lock uses interlocking mushroom-shaped stems that engage when two compatible strips are pressed together.

SJ3551CF is the Type 400 version, featuring approximately 400 stems per square inch. Its black polyolefin fastening surface is combined with a clear acrylic pressure-sensitive adhesive that bonds to a range of suitable substrates, including metals, glass, acrylic, polycarbonate and ABS.

The adhesive-backed design can provide an alternative to screws, nuts, bolts and clips in suitable applications. This version is supplied in a 25 mm wide, 45.7 m roll, making it suitable for industrial assemblies, removable access panels, equipment covers and other components that may need to be opened for maintenance or inspection.

What Is the Difference Between Dual Lock Type 400 and Type 250?

The main difference between 3M™ Dual Lock™ SJ3551CF and 3M™ Dual Lock™ SJ3550CF is the density of the interlocking stems. SJ3551CF is Type 400, while SJ3550CF is Type 250.

A higher stem density does not automatically mean that one fastener is the best choice for every application. The overall fastening force depends on the combination of stem types, engaged area, substrate, loading direction and operating conditions. Select the fastener combination according to the requirements of the assembly.

How Does the 3M Dual Lock SJ3551CF Fastening System Work?

The fastening strips contain rows of flexible stems with mushroom-shaped heads. When compatible strips are pressed together, the heads interlock and create a mechanical connection. The assembly can subsequently be opened by separating the strips, allowing access to the attached components.

Dual Lock provides an audible snap when the strips engage correctly. This can help the user confirm that the fastening surfaces have connected.

SJ3551CF is Type 400 and is designed to mate with compatible Type 170 and Type 250 Dual Lock fasteners. The chosen combination affects the coupling and release forces, and the 400 type is the one that allows you to achieve the greatest force by combining it with the 250 type.

Please note: it is not recommended to pair two pieces of SJ3551CF (type 400) together, as the stems would be too densely packed to interlock properly without risking damage.

Key Industrial Advantages of 3M SJ3551CF

• Type 400 stem density: Approximately 400 interlocking mushroom-shaped stems per square inch provide a high-density fastening surface.
• Reusable connection: Components can be opened and reattached when maintenance, inspection or replacement is required.
• Acrylic adhesive backing: Allows the fastening strip to be bonded to suitable surfaces without drilling or conventional mechanical fixings.
• Concealed fastening: Offers a neat appearance where visible screws or clips are undesirable.
• Broad substrate compatibility: Designed for suitable metals, glass, painted surfaces and selected plastics.
• Industrial roll format: The 25 mm width and 45.7 m length suit applications requiring narrow fastening strips or multiple fastening points. However, it can also be die-cut into various shapes, ready for immediate application.
• Indoor and outdoor applications: Can be considered for suitable environments, subject to temperature, moisture, UV exposure, chemicals and other service conditions.

Which Materials Can 3M Dual Lock SJ3551CF Bond To?

The clear acrylic pressure-sensitive adhesive is designed to attach the fastener to various medium- and high-surface-energy materials. Surface condition and the exact substrate must be considered before use.

• Metals: such as aluminum or stainless steel.
• Glass: the surface must be thoroughly cleaned before application.
• Plastics: those with high surface energy, such as acrylic, PC, and ABS.

Powder-coated surfaces or surfaces with low surface energy (PP, PE) may require a different fastening solution, the use of a primer, and, in any case, appropriate testing.

Industrial Applications of 3M Dual Lock SJ3551CF

Removable Equipment Panels and Covers

Use Dual Lock for selected panels and covers that need to remain secure during operation but must be removable for servicing, cleaning or inspection.

Electronic Enclosures and Components

The system can be considered for compatible electronic enclosures and equipment components where a removable fastening method is required. 

Automotive and Special-Vehicle Interiors

SJ3551CF can be considered for selected interior trim, panels and accessories when the substrate, environmental conditions and required holding force are suitable.

Industrial Fixtures and Displays

Dual Lock can provide a concealed, reclosable connection for selected fixtures, displays and equipment assemblies that require occasional removal or repositioning. The product is suitable for the furniture, construction, electronics, automotive, transport and special vehicles sectors, as well as for general industry.

How to Apply 3M Dual Lock SJ3551CF

1. Prepare the substrate: Remove dust, oil, grease and other contaminants using a cleaning method compatible with the surface.
2. Check compatibility: Confirm that the acrylic adhesive is suitable for the substrate, finish and operating environment.
3. Cut the strip: Cut the 25 mm roll to the required length for the intended fastening area.
4. Apply the adhesive-backed fastener: Remove the release liner, position the strip accurately and apply firm, even pressure in accordance with the manufacturer's instructions.
5. Allow the adhesive to develop bond strength: Follow the current technical data sheet for the recommended dwell time before loading the assembly.
6. Engage the mating strip: Align the compatible Dual Lock surfaces and press them together until the stems engage.
7. Validate the connection: Test the assembly under representative service conditions before putting it into operation.

Do not assume that the adhesive reaches its full bond strength immediately after application. Surface preparation, pressure, temperature and dwell time all affect performance.

Technical Specifications of 3M Dual Lock SJ3551CF

These are typical manufacturer values, not guaranteed design specifications. Consult the current 3M technical data sheet for the applicable performance limits and installation requirements. Confirm the operating-temperature limit against the documentation relevant to the intended application.

Frequently Asked Questions About 3M Dual Lock SJ3551CF

What does Type 400 mean?

Type 400 refers to the approximate density of the interlocking stems: 400 stems per square inch. The density affects the fastening characteristics when combined with a compatible Dual Lock strip.

What is the difference between SJ3551CF and SJ3550CF?

SJ3551CF is Type 400, while SJ3550CF is Type 250. They use the same general mushroom-stem fastening principle, but the stem density and compatible mating combinations differ. Choose according to the required engagement force, application design and manufacturer guidance.

Which Dual Lock types can SJ3551CF connect to?

SJ3551CF is Type 400 and can be paired with compatible Type 170 or Type 250 fasteners (to achieve very high strength).

Does the adhesive bond to plastic?

It is designed to bond to selected plastics, including acrylic, polycarbonate and ABS, as well as suitable metals and glass. Adhesion varies with the exact grade, surface finish and preparation, so testing is recommended.

Can 3M Dual Lock SJ3551CF be used outdoors?

It can be considered for suitable indoor and outdoor applications. 

How should I prepare the surface before applying SJ3551CF?

Surfaces should be clean, dry and free from oil, grease, dust and other contaminants. Use a cleaning method suitable for the substrate and follow 3M's instructions for application pressure and adhesive dwell time.