Adhesives are attractively increasing important in prevailing businesses. Adhesive also called Glue is a mixture that sticks two items strongly.

  Adhesives are used for various different purposes and industries like in textiles for apparel and industrial fabrics, in automotive used for headlamps, in building components: lumber, wood and furniture used for furniture/cabinet assembly, decorative laminate etc. in Engineered wood products used for windows, doors, floor beams, plywood, finger joints, millwork, edge gluing or laminating, in Food and Consumer Packaging used for packaging and labeling foods, beverages, household products, soaps and detergents, in Paper Industry used for manufacturing of envelopes, perfect binding of paperback and edition-bound books, magazines, catalogs and manuals, tube winding, tissues, towels, bags, paperboard laminating, folding cartons, corrugating and general converting, Modified carrier starches, liquid performance additives and resins used in the manufacture of corrugated boxes. Water-based, solvent-based and hot melt adhesives used in Footwear industries for stock fitting and shoe assembly. Also used to combine flexible films for food and pharmaceutical packaging, electrical insulation, textiles and graphics arts, in the production of trans dermal drug delivery systems, wound closures, bandages, medical and cosmetic applications, construct disposable diapers, feminine hygiene and adult incontinence products and surgical gowns.

 

There are various categories of adhesives

 

Natural adhesives made from non-living mineral sources, biological sources like vegetable substance, animal skin, natural resins and these are known as bioadhesives.

 

Drying adhesives are a mixture of ingredients like polymers dissolved in a solvent. As the solvent fades away, the adhesive gets harder. Depending on the chemical composition of the adhesive, they will adhere to different materials to greater or lesser degrees. These adhesives are typically weak and are used for household applications.

 

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 before the surfaces are to be held together. Once the surfaces are pushed together, the bond forms very quickly, hence, it is usually not necessary to apply pressure for a long time. So there is no need to use clamps. Natural rubber and poly chloroprene are commonly used contact adhesives. Both of these plasterers undergo strain crystallization. Contact adhesives find use in laminates, such as bonding Formica to a wooden counter, and in footwear, such as attaching an outsole to an upper.

 

Hot adhesives (thermoplastic adhesives) also known as "hot melt" adhesives, are thermoplastics; they are applied hot and simply allowed to harden as they cool. These adhesives are being used for crafts because of their ease of use and the wide range of common materials to which they can bond fast.

 

Light Curing Adhesives also referred to as Light Curing Materials (LCMs) have become popular within the manufacturing sector due to their rapid curing time and strong bond strength. Light curing adhesives can cure in as little as a second and many formulations can bond dissimilar substrates and withstand harsh temperatures. These qualities make LCMs curing adhesives essential to the manufacturing of items in many industrial markets such as electronics, telecommunications, medical, aerospace, glass, and optical. Unlike traditional adhesives, LCM light curing adhesives not only bond materials together but they can also be used to seal and coat products.

 

Pressure sensitive adhesives (PSAs) form a bond by the application of light pressure to marry the adhesive with the adherend. They are designed with a balance between flow and resistance to flow. The bond forms because the adhesive is soft enough to flow (i.e. "wet") 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 forces, become involved in the bond, contributing significantly to its ultimate strength. Pressure sensitive adhesives (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 temperature. Permanent PSAs may be initially 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 tapes, bookmark and note papers, price marking labels, promotional graphics materials, and for skin contact (wound care dressings, EKG electrodes, athletic tape, analgesic and transdermal drug patches, etc.). Some removable adhesives are designed to repeatedly stick and unstick. They have low adhesion and generally can not support much weight. 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 linking reaction and increase 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.