The shoe industry demands an impressive array of adhesives due to variations in materials, processes, types of footwear, and seasonal design changes. Equally impressive is the performance demands placed on adhesives in this industry. These include a high degree of bond strength to resist numerous repetitions of bending, straightening, compressing, recovering, rubbing, and friction. The bond strength must also not be affected by rain, snow, wind, ultraviolet light, temperature changes, and whatever other elements to which the shoe will be exposed. In this review identify the adhesives bonding failure reasons in footwear processing. Failure reasons such as poor adhesive selection for processing, adhesive application problems, upper bottom poor skiving, poor lasing. Improper buffing process, adhesives improper applying methods , hot oven temperature control , improper sole attaching and sole pressing. In addition to providing high performance properties and durability, the adhesives and bonding processes that are used in the footwear industry must also offer good early strength and workability for fast and efficient production. The adhesive bond must be invisible or at least aesthetically pleasing to the shoe's design. And more recently, an additional imposing set of requirements has been placed on the shoe manufacturers - formulations and processes must be environmentally friendly and hazard free. Now days all footwear industry used for Water based adhesives use water as the carrier fluid, with the adhesive particles suspended in water, reducing the adhesive’s viscosity so that it can be applied to various substrates at varying thicknesses. Evaporation of the carrier fluid during the set and cure stages typically occurs in large ovens. Evaporation and cure also can take place in the open under ambient, non-thermal conditions. It is important to note that not all water based adhesives are 100% solvent-free, but may contain some VOCs as assistants to the water base for proper viscosity or fluid control. Water based adhesives have been available since the 1970s. They are formulated from rubber compounds (as the base material), with various additives such as synthetic hydrocarbon resins or pine sap derivatives to increase strength characteristics. The performance of solvent-based adhesives is largely determined by the polymer system in the formulation. The choice of adhesive type depends on the specific substrates and environmental resistance needed – temperature resistance, oil and plasticizer resistance, etc. Most solvent based adhesives contain flammable solvents which require proper precautions for safe handling. In addition, many organic solvents are regulated due to environmental concerns with emissions. Within each type of solvent based adhesive, formulations are available to match the application requirements of the process – brush, roll, bead or ribbon, spray. Once the adhesive is applied, solvent evaporates relatively quickly causing an increase in viscosity of the adhesive film. Bonds can be made immediately after adhesive application or after some solvent has evaporated but before the adhesive has dried to the point.
