Adhesive

These include the ability to bind different materials together, the more efficient distribution of stress across a joint, the cost-effectiveness of an easily mechanized process, and greater flexibility in design.

The earliest human use of adhesive-like substances was approximately 200,000 years ago,[4] when Neanderthals produced tar from the dry distillation of birch bark for use in binding stone tools to wooden handles.

[4] An experimental archeology study published in 2019 demonstrated how birch bark tar can be produced in an easier, more discoverable process.

[8] A study of material from Le Moustier indicates that Middle Paleolithic people, possibly Neanderthals, used glue made from a mixture of ocher and bitumen to make hand grips for cutting and scraping stone tools.

[10] Another investigation by archaeologists uncovered the use of bituminous cements to fasten ivory eyeballs to statues in Babylonian temples dating to approximately 4000 BC.

[11] In 2000, a paper revealed the discovery of a 5,200-year-old man nicknamed the "Tyrolean Iceman" or "Ötzi", who was preserved in a glacier near the Austria-Italy border.

Several of his belongings were found with him including two arrows with flint arrowheads and a copper hatchet, each with evidence of organic glue used to connect the stone or metal parts to the wooden shafts.

Such lamination of wood for bows and furniture is thought to have extended their life and was accomplished using casein (milk protein)-based glues.

The ancient Egyptians also developed starch-based pastes for the bonding of papyrus to clothing and a plaster of Paris-like material made of calcined gypsum.

Wood veneering and marquetry were developed, the production of animal and fish glues refined, and other materials utilized.

Egg-based pastes were used to bond gold leaves, and incorporated various natural ingredients such as blood, bone, hide, milk, cheese, vegetables, and grains.

[13] The Romans were also the first people known to have used tar and beeswax as caulk and sealant between the wooden planks of their boats and ships.

[10] In Central Asia, the rise of the Mongols in approximately AD 1000 can be partially attributed to the good range and power of the bows of Genghis Khan's hordes.

These bows were made of a bamboo core, with horn on the belly (facing towards the archer) and sinew on the back, bound together with animal glue.

[15] At this time, world-renowned cabinet and furniture makers such as Thomas Chippendale and Duncan Phyfe began to use adhesives to hold their products together.

[19] In 1862, a British patent (number 3288) was issued for the plating of metal with brass by electrodeposition to obtain a stronger bond to rubber.

[23] The 1920s, 1930s, and 1940s witnessed great advances in the development and production of new plastics and resins due to the First and Second World Wars.

Once the adhesive and the adherend are in close proximity, molecular interactions, such as van der Waals forces, become involved in the bond, contributing significantly to its ultimate strength.

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.

Removable adhesives are used in applications such as surface protection films, masking tapes, 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.).

They are often applied in thin layers for use with laminates, such as bonding Formica to countertops, and in footwear, as in attaching outsoles to uppers.

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.

The glue gun melts the solid adhesive, then allows the liquid to pass through its barrel onto the material, where it solidifies.

[34] PMF adhesives eliminate mixing mistakes by the end user and reduce exposure of curing agents that can contain irritants or toxins.

[36] One-part adhesives harden via a chemical reaction with an external energy source, such as radiation, heat, and moisture.

These qualities make UV curing adhesives essential to the manufacturing of items in many industrial markets such as electronics, telecommunications, medical, aerospace, glass, and optical.

Thiolated polymers, for example, form chemical bonds with endogenous proteins such as mucus glycoproteins, integrins or keratins via disulfide bridges.

Other types of fracture include: As a general design rule, the material properties of the object need to be greater than the forces anticipated during its use.

As the loads are usually fixed, an acceptable design will result from combination of a material selection procedure and geometry modifications, if possible.

Increasing the joint resistance is usually obtained by designing its geometry so that: Some glues and adhesives have a limited shelf life.