3M™ Dual Lock™ Reclosable Fastener SJ3731, Black, Pop-in Piece Part, Stem Density 400, 20 mm x 20 mm, 5000 Each/Case

3M™ Dual Lock™ Reclosable Fastener SJ3731 is a black, polypropylene reclosable fastener with a pop-in single disk base, and a square top with a stem density of 400 stems per square inch. Pop-in parts attach without the use of pressure sensitive adhesive, and come with a variety of bases that can be inserted into holes of precise dimension. They are easy to install and require no special equipment or skills.

This fastener overcomes the often difficult alignment and installation problems of screws and hidden fasteners, offering simple installation with no special tools required. 3M™ Dual Lock™ Reclosable Fasteners are positive-locking, blind fasteners designed for attaching automotive trim components. The products feature mushroom-shaped polyolefin stems that snap together, forming a high tensile closure. Dual Lock fasteners are used primarily to secure rigid and semi-rigid surfaces such as trim or door panels, instrument panel bezels, headliners and other automotive interior and exterior trim.

How It Works
This pop-in fastener is designed to be inserted into a slot of a specific dimension where attachment is desired. The polypropylene disk base grips the inside of the hole and holds tight. The fastener can then be mated and engaged to a second Dual Lock fastener attached to a piece of trim or other part to firmly secure the parts together.

When two pieces of 3M™ Dual Lock™ Reclosable Fasteners are pressed together, the stems flex and the mushroom heads slide past each other. After passing the opposing mating piece, the stems snap back into their original position and the opposing mushroom heads interlock. These fasteners can provide high tensile strength but can be opened by simply cleaving or peeling open the closure.

Alignment and re-alignment are easy and no special tools are required. This means that they can be used to attach components before they enter the final assembly plant, helping to reduce the number of parts and assembly time.

Stem Densities

Combinations of stem densities and the engaged area provide adjustable and proportional engagement and disengagement force to meet application needs. Dual Lock fasteners are offered in three different densities (stems per square inch): 170, 250 and 400. Dual Lock fastener SJ3731 has 400 stems per square inch, offering the tightest hold, and can be mated to Type 170 or 250. It should not be mated with another Type 400 fastener because the engagement would be so tight that detachment would likely result in damage to the parts.

Applications
3M™ Dual Lock™ Reclosable Fasteners can replace conventional mechanical fasteners in a wide range of assembly and attachment applications where reclosability or serviceability is desired. Dual Lock fasteners are used primarily to secure rigid and semi-rigid surfaces such as trim or door panels, instrument panel bezels, headliners and other automotive interior and exterior trim. Some examples of applications include:

• Vehicle headliners
• Attaching accessories and equipment
• Attaching window and door trim panels
• Vibration and sound damping control
• CHMSL cover plates
• Center console flanges
• Interior trim
• Sunroof rings