Hot melt adhesive is solid glue at room temperature which is heated until it reaches the consistency of honey (about 10,000 cp) and coated onto various materials.  While there are a variety of hot melt adhesive chemistries and tackiness quality, it is useful to categorize them as pressure sensitive adhesive (PSA) or permanent adhesive.

  Permanent adhesives are generally used for permanent laminations or to be reactivated with heat for later bonding. Typical uses are closing card board boxes and bonding Formica sheeting to cabinets and counter tops. At room temperatures, permanent adhesives are not tacky. Most are hard to the touch, but some can be rubbery such as the traction strips on the bottom of some socks or gloves.

  More commonly used in the converting industry are PSAs. These remain tacky at room temperature and will form a bond to a variety of materials when applied with pressure. These are coated onto materials which will be processed further and bonded to some surface in its final use.

  There is no clear demarcation between permanent adhesives and PSA, rather, there is a continuum from the simpler permanent adhesives to which various plasticizers and tackifier can be added to enable bonding at room temperature.