The Structure and Physical -Chemical Properties of Polymers in Pressure-sensitive Adhesives (PSA)

The term «pressure-sensitive adhesive» represents a group of adhesives that makes strong contact between the substrates by hand، in dry state، using the finger pressure at room temperature. This study focuses on the chemical structure of different pressure sensitive adhesives. The base polymers، used in a pressure sensitive adhesive، usually include acrylic polymers، silicones، polyurethanes and polyesters. Acrylic polymers، in pressure sensitive adhesives، can be either water or solvent-based and or free of organic solvent. Acrylic polymers are inherently sensitive to pressure. The adhesion properties of an acrylic pressure sensitive adhesive، containing monomers with high or low glass temperature، can be altered by changing the monomer content. The pressure adhesives based on silicon or other rubbers are generally used in tapes. Acrylic pressure sensitive adhesive can be used in temperature range of 40 to 300°C. The rubber-based pressure adhesive makes contact with a high and low energy level. Polyurethane-based pressure sensitive adhesive، stable at 40 to 100°C، shows a high flexibility after drying. The great adherence of polyestersbased pressure sensitive adhesive can be only achieved using aliphatic polyesters with a molecular weight of 5000 to 10000 Dalton and a glass temperature between 25 and 47 C.