H12MDI와 IPDI의 혼합비율에 따른 폴리우레탄 수지의 물성 연구

Abstract

Typically, polyurethane materials are classified into polyol, diisocyanate, chain extender, blocking agent, solvent and additive. More than anything else, properties of polyurethane depend on the types of diisocyanate to a great extent. Accordingly, it is important to select suitable types of diisocyanate for usage. At present, as coating materials for nonferrous metals are weak in terms of processability, they are subject to pre-processing and post-coating. Also, for improvement of adhesion, coating materials undergo a range of production processes ranging from the first primer processing, intermediate coat to top coat. Thus, coating materials would save production cost significantly with simplified steps in production based on pre-coating, post-processing and 1-bake if they assume similar properties to the existing coating materials. Hence, the present study performed a comparative experiment regarding the properties of H12MDI and IPDI, both of which diisocyanate are typically used for polyurethane resin, by injecting different ratios in polymerization of polyurethane (100:0, 75:25, 50:50, 25:75 and 0:100). As the result, machinability improved, as IPDI's mixing ratio increased, and it showed thermal stability in the TGA test, corrosion property in the impedance test, shock resistance in the impact test, and good wear resistance and solvent resistance. Whereas room temperature stability, hardness, stain resistance and alkali resistance improved in the IR and viscosity measurement test, as H12MDI's mixing ratio went up. In particular, machinability displayed remarkably big differences. It is because H12MDI has a symmetrical structure to NCO groups and thus two NCOs have the same reactivity. Unlike H12MDI, IPDI has an asymmetrical structure to NCO groups. Based on this molecular structure, polyurethane resin using H12MDI was hard and a serious crack occurred in it, when banding it in the machinability test. Also, it appears that IPDI didn't cause any crack in the machinability test, because it has an asymmetrical structure and polyurethane resin's structure is entangled to make it flexible.