SJ-3220 Series NonAdhesive Back Dual Lock Fastener

3M™ Dual Lock Reclosable Fasteners offer advanced closure alternatives to zippers, screws, snaps, hooks, bolts, and more, on items that require periodic opening and closing.

The Dual Lock system consists of continuous strips of plastic mushrooms protruding up from a backing which is typically coated with a high strength pressure sensitive adhesive covered with a peel-off liner.
When 2 strips are pressed together, the mushroom heads interlock, forming a releasable mechanical bond.

There are three Types of these fasteners 170, 250, and 400 — referring to the approximate number of mushrooms per square inch.
They can be mated in the following combinations of increasing closure strength —
Type 170 to Type 250
Type 250 to Type 250
Type 170 to Type 400
Type 250 to Type 400
(Type 170 will not stick to itself, and Type 400 to Type 400 is essentially a permanent bond.)
The "release strength" is a function of the Type(s) selected as well as the surface area of the fastener.

Note that unlike Hook & Loop Fastenings, there is no "male" or "female" side.
Both "sides" are identical - so you only buy one strip; but as noted above, different Types can be mixed to achieve the correct release strength.

• Approximately five times stronger in tensile than typical hook-and-loop fasteners
• No dirt catching fuzz, like hook and loop closure systems
• Can be opened and closed 1,000 times before losing 50% of its original strength
• High strength pressure sensitive adhesive is either general purpose, or specialized for difficult to adhere to plastics
• Solvent resistant
• Series with no adhesive backing, and those with acryilic adhesive backing can tolerate temperatures as high as 200°F
• Color in table is fastener color/foam backing color
• Clear fastener/backing combination allows for substrate color to show through the fastener
• Engaged thickness is approximately 1/4"

Series Properties:
• 354x Series is available in all 3 types and has a conformable backing with a black rubber-based low surface energy adhesive - good for difficult to adhere to plastics; see Related Products, below
• 355x Series is available in all 3 types and has a black high strength general purpose acrylic adhesive - good for textured and high surface energy (adhesive friendly) surfaces
• 356x Series is available in all 3 types and has a clear, very high bond general purpose acrylic adhesive, and has the best UV resistance - good for medium and high surface energy surfaces
• 3223 Series (shown here) is available in all 3 types (although we list only the Type 250), and has a non-adhesive, non-woven backing for user supplied adhesives. Use it where the normal pressure sensitive adhesive backing on these tapes is inappropriate