question: How does that adhesive work that isn't sticky when you touch it, but can easily seal a bag of treats?
comment: I'm not sure about those cookie packages specifically, but usually it's a substance that stick to itself really well but not to other things. They use some process to bind it to the packaging, usually just a layer of the sticky stuff is put in between 2 layers of the regular packaging material. The regular material is shaped and cut in a way that you can pull the adhesive layer apart easily, and then you have a nice adhesive layer that won't stick to you but will still close the package.
passages: After degreasing, a good test to determine cleanliness of the surface is to use a drop of water. If the drop spreads on the surface, a low contact angle and good wettability has been achieved, which indicates the surface is clean and ready for application of the adhesive. If the drop beads up or retains its shape, the degreasing process should be repeated.
  
  Section::::Surface preparation of plastics.:Abrasion.
   Another factor determining the strength of an adhesive contact is its shape. Adhesive contacts of complex shape begin to detach at the "edges" of the contact area. The process of destruction of adhesive contacts can be seen in the film.
  
  Section::::Other effects.
  
  In concert with the primary surface forces described above, there are several circumstantial effects in play. While the forces themselves each contribute to the magnitude of the adhesion between the surfaces, the following play a crucial role in the overall strength and reliability of an adhesive device.
  
  Section::::Other effects.:Stringing.
   Section::::Composition.
   Section::::Surface preparation of plastics.:Plasma treatment.
   The adhesion promoter with a specific thickness is deposited, i.e. spin-coated or contact printed on the wafer to improve the bonding strength. Spray coating is preferable when the adhesive is deposited on free standing structures.
   Section::::Lifetime.
  
  A pressure-sensitive adhesive will experience a range of conditions throughout its lifetime. These conditions affect one of the following parts of the tape: the surface or the bulk. The surface is merely the part of the tape that is exposed to the environment through the whole of its lifetime. The bulk is everything under the surface of the tape, that is the interactions that occur between the substrate and the adhesive part of the tape.
  
  Section::::Lifetime.:Surface exposure conditions.
   BULLET::::- Fracture can also occur in the adherend if the adhesive is tougher than the adherend. In this case, the adhesive remains intact and is still bonded to one substrate and remnants of the other. For example, when one removes a price label, the adhesive usually remains on the label and the surface. This is cohesive failure. If, however, a layer of paper remains stuck to the surface, the adhesive has not failed. Another example is when someone tries to pull apart Oreo cookies and all the filling remains on one side; this is an adhesive failure, rather than a cohesive failure.
   Section::::Surface preparation of plastics.:Flame treatment.
   Section::::SU-8.:Procedural steps.
  
  The standard process (compare to figure "Schematic bonding process") consists of applying SU-8 on the top wafer by spin-on or spray-on of thin layers (3 to 100 µm).
   One method of degreasing is that of vapor degreasing, in which the adherend is dipped in a solvent. When removed from the solvent, the vapors condense on the surface of the adherend and dissolve any contaminants that had existed. These contaminants then drip off the adherend with the condensed vapors.
  
  Section::::Surface preparation of plastics.:Degreasing.:In lieu of vapor degreasing.
   Section::::Technical properties.
  
  HMG is advertised with a flash point, and a temperature resistance. It is insoluble in water and soluble in acetone, and is composed of 70% amyl acetate solvent, 25% cellulose nitrate, approximately 5% of the plasticizer dibutyl phthalate, and a small amount of a phenolic resin leveling agent. The adhesive is touch dry in five minutes, and hard dry in ten.
   Billy Bunter is glued into a chair with seccotine in The Magnet #100 (1910).
  
  In the C.S. Lewis novel "That Hideous Strength" (1945) a character is described as having a cigarette "seccotined" to her lip.
  
  In the E. Nesbit novel "The Story of the Amulet" (1906) a broken saucer would never be the same again even if bits were joined "with Seccotine or the white of an egg."
   If the BCB is hard-baked (far over 50%), it loses its adhesives properties and results in an increased amount of void formation. But also if the soft-curing is above 210 °C the adhesive cures too much, so that the material is not soft and sticky enough to achieve a high bonding strength.
   Section::::Surface preparation of plastics.:Peel ply.
  
  For a peel ply, a thin, woven piece of material is applied to the adherend during fabrication. Because the material is woven, it will leave a torturous surface when removed, which will improve bonding by mechanical interlocking. Prior to adhesive bonding, the woven material acts to protect the surface of the adherend from contaminates. When an adhesive is ready to be applied, the material can be peeled off, leaving a rough and clean surface for bonding.
  
  Section::::Surface preparation of plastics.:Corona discharge treatment.
   The adhesiveness of the tape does depend not only on the type of the tape but also on its macroscopic shape. Tapes with sharp corners start to detach at pointed corners. The adhesive strength can be sufficiently improved by cutting the edges as shown in the film
  
  Section::::Types.:Water activated tape.
  
  Water activated tape, gummed paper tape or gummed tape is starch- or sometimes animal glue-based adhesive on a kraft paper backing which becomes sticky when moistened.
   Section::::Application.:Substrate-adhesive conditions.
  
  Section::::Application.:Substrate-adhesive conditions.:Bonding strength.
   The intermediate layer is applied by spin-on, spray-on, screen-printing, embossing, dispensing or block printing on one or two substrate surfaces. The adhesive layer thickness depends on the viscosity, rotational speed and the applied tool pressure. The procedural steps of adhesive bonding are divided into the following:
  
  BULLET::::1. Cleaning and pre-treatment of substrates surfaces
  
  BULLET::::2. Application of adhesive, solvent or other intermediate layers
  
  BULLET::::3. Contacting substrates
  
  BULLET::::4. Hardening intermediate layer
   Section::::Application.:Environmental factors.
   Section::::SU-8.
  
  Section::::SU-8.:Overview.
   PSAs are designed for either permanent or removable applications. Examples of permanent applications include safety labels for power equipment, foil tape for HVAC duct work, automotive interior trim assembly, and sound/vibration damping films. Some high performance permanent PSAs exhibit high adhesion values and can support kilograms of weight per square centimeter of contact area, even at elevated temperatures. Permanent PSAs may initially be removable (for example to recover mislabeled goods) and build adhesion to a permanent bond after several hours or days.
   Section::::Surface preparation of plastics.:Chemical treatment.
   When preparing a surface for adhesive bonding, all oil and grease contamination must be removed in order to form a strong bond. Although the surface may appear to be clean, it is important to still use the degreasing process. Prior to performing the degreasing process, the compatibility of the solvent used and the adherend must be considered to prevent irreversible damage of the surface or part.
  
  Section::::Surface preparation of plastics.:Degreasing.:Vapor degreasing.
   The adhesive bonding of a tape or label can be affected by its shape. Tapes with pointed corners start to detach at those corners; adhesive strength can be improved by rounding the corners.
  
  Section::::Applications.
   Section::::Surface preparation of plastics.:Ultraviolet radiation treatment.
   Visy has won awards including the 2011 Australian Packaging Design Awards where it was named Overall Show Winner at the Packaging Council of Australia annual awards.
  