Editing Adhesive (section)

====Non-reactive====
=====Drying=====
There are two types of adhesives that harden by drying: ''solvent-based adhesives'' and ''polymer dispersion adhesives'', also known as ''emulsion adhesives''. Solvent-based adhesives are a mixture of ingredients (typically [[polymer]]s) dissolved in a [[solvent]]. [[Polyvinyl acetate|White glue]], contact adhesives and [[rubber cement]]s are members of the ''drying adhesive'' family. As the solvent evaporates, the adhesive hardens. Depending on the chemical composition of the adhesive, they will adhere to different materials to greater or lesser degrees.

Polymer dispersion adhesives are milky-white dispersions often based on [[polyvinyl acetate]] (PVAc). They are used extensively in the woodworking and packaging industries. They are also used with fabrics and fabric-based components, and in engineered products such as loudspeaker cones.

=====Pressure-sensitive=====
{{Main|Pressure-sensitive adhesive}}
''Pressure-sensitive adhesives'' (PSA) form a bond by the application of light pressure to bind the adhesive with the adherend. They are designed to have a balance between flow and resistance to flow. The bond forms because the adhesive is soft enough to flow (i.e., "wet") to the adherend. The bond has strength because the adhesive is hard enough to resist flow when stress is applied to the bond. Once the adhesive and the adherend are in close proximity, molecular interactions, such as [[van der Waals force]]s, become involved in the bond, contributing significantly to its ultimate strength.

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.

Removable adhesives are designed to form a temporary bond, and ideally can be removed after months or years without leaving residue on the adherend. Removable adhesives are used in applications such as surface protection films, [[masking tape]]s, bookmark and note papers, barcode labels, price marking labels, promotional graphics materials, and for skin contact (wound care dressings, EKG electrodes, athletic tape, analgesic and trans-dermal drug patches, etc.). Some removable adhesives are designed to repeatedly stick and unstick.<ref>{{cite web|last1=Barcode|first1=Barry|title=Rubber Acrylic Adhesive Labels|url=http://www.midcomdata.com/rubber-acrylic-adhesive-labels/|website=Midcomdata|date=23 July 2014|access-date=6 August 2014|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304085930/http://www.midcomdata.com/rubber-acrylic-adhesive-labels/|url-status=live}}</ref> They have low adhesion, and generally cannot support much weight. [[Pressure-sensitive adhesive]] is used in [[Post-it note]]s.

Pressure-sensitive adhesives are manufactured with either a liquid carrier or in 100% solid form. Articles are made from liquid PSAs by coating the adhesive and drying off the solvent or water carrier. They may be further heated to initiate a [[cross-link]]ing reaction and increase [[molecular mass|molecular weight]]. 100% solid PSAs may be low viscosity polymers that are coated and then reacted with radiation to increase molecular weight and form the adhesive, or they may be high viscosity materials that are heated to reduce viscosity enough to allow coating, and then cooled to their final form. Major raw material for PSA's are [[acrylate]]-based polymers.

=====Contact =====
{{See also|Contact adhesives}}
''Contact adhesives'' form high shear-resistance bonds with a rapid cure time. They are often applied in thin layers for use with [[laminate]]s, such as bonding [[Formica (plastic)|Formica]] to countertops, and in footwear, as in attaching outsoles to uppers. [[Natural rubber]] and [[polychloroprene]] (Neoprene) are commonly used contact adhesives. Both of these elastomers undergo [[strain crystallization]].

Contact adhesives must be applied to both surfaces and allowed some time to dry before the two surfaces are pushed together. Some contact adhesives require as long as 24 hours to dry completely before the surfaces are to be held together.<ref>{{cite web|url=http://www.thistothat.com/glue/contact.shtml|title=Contact Adhesives|website=www.thistothat.com|access-date=25 September 2006|archive-date=12 September 2006|archive-url=https://web.archive.org/web/20060912043858/http://www.thistothat.com/glue/contact.shtml|url-status=live}}</ref> Once the surfaces are pushed together, the bond forms very quickly.<ref>{{cite web| url = http://composite.about.com/library/glossary/c/bldef-c1257.htm| title = Definition of ''contact adhesive'' on About.com| access-date = 25 September 2006| archive-date = 24 October 2006| archive-url = https://web.archive.org/web/20061024171339/http://composite.about.com/library/glossary/c/bldef-c1257.htm| url-status = dead}}</ref> [[Clamp (tool)|Clamps]] are typically not needed due to the rapid bond formation.<ref>{{Cite web |title=Contact Adhesive |url=http://www.woodworkbasics.com/contact-adhesive.html |access-date=4 January 2024 |website=woodworkbasics.com}}</ref>

=====Hot=====
[[File:Stanley-Hot-Glue-Gun-GR35K.jpg|right|thumbnail|A glue gun, an example of a hot adhesive]]
{{Main|Hot-melt adhesive}}

''Hot adhesives'', also known as ''hot melt adhesives'', are [[thermoplastic]]s applied in molten form (in the 65–180&nbsp;°C range) which solidify on cooling to form strong bonds between a wide range of materials. [[Ethylene-vinyl acetate]]-based hot-melts are particularly popular for crafts because of their ease of use and the wide range of common materials they can join. A glue gun (shown at right) is one method of applying hot adhesives. The glue gun melts the solid adhesive, then allows the liquid to pass through its barrel onto the material, where it solidifies.

Thermoplastic glue may have been invented around 1940 by [[Procter & Gamble]] as a solution to the problem that water-based adhesives, commonly used in packaging at that time, failed in humid climates, causing packages to open.  However, water-based adhesives are still of strong interest as they typically do not contain volatile solvents.<ref>{{Cite journal |last1=Bhakare |first1=Madhuri A. |last2=Lokhande |first2=Kshama D. |last3=Bondarde |first3=Mahesh P. |last4=Dhumal |first4=Pratik S. |last5=Some |first5=Surajit |date=2023-02-15 |title=Dual functions of bioinspired, water-based, reusable composite as a highly efficient flame retardant and strong adhesive |url=https://www.sciencedirect.com/science/article/pii/S1385894722059010 |journal=Chemical Engineering Journal |volume=454 |pages=140421 |doi=10.1016/j.cej.2022.140421 |bibcode=2023ChEnJ.45440421B |issn=1385-8947}}</ref>