(2) Basis and the Latest Developments in Polyurethane Adhesive

Polyurethane materials have been widely utilized as the essential adhesives, owing to their many advantages of flexibility, low-cost, easy to produce and modification with variety of curing style such as moisture cure, emulsion, and two-component mixing style and so on. In this review, basis of polyurethane technology to make adhesive materials by using isocyanates and polyols are introduced and some important points to note are summarized. There have been substantial demands for inventing materials having better physical strength, mechanical and thermal properties which is generally difficult to achieve. In this context, hard-segment size and distribution states in soft-segment are controlled by hybridization of different types of polyols to form nanolevel-mixed structure. This structure enhanced mechanical strength with excellent elasticity and thermal properties, in a much wider range, compared to conventional polyurethane elastomers. Additionally, since the physical properties are strongly reflected by this structure, adjusting the physical properties as required can be achieved by changing the mixing ratio.