Study On The Synthesis Of PEG/MDI Polyurethane Elastic Curing Agent And Coating Properties

There is an extensive application of polyurethane. As a kind of coating, and its good hardness, abrasion resistance and good chemical resistance make it in the paint industry developed rapidly. In this paper, based on the experimental analysis of the factors and had synthesis the polyurethane elastomer curing agent, then the prepared polyurethane varnish, to examine its overall performance.The curing agent is synthesized by diphenylmethane diisocyanate (MDI) and Polyether polyol(in this paper, mainly for PEG: polyethylene glycol) which dehydrated was completed. The optimal conditions for the synthesis the curing agent is: the ratio of -NCO and -OH is 2.4, thermal control in high-temperature about 110℃, reaction time is about 3h, Solvent mixture by Butyl acetate: xylene: ethyl acetate: cyclohexanone is 1:1:1:3.Under the conditions, the viscosity of curing agent is 10s or so, the -NCO% content is 3.15%, slightly lower than the theoretical value, but is better content. From the infrared spectrum analysis, we found that the characteristic peak of hydroxyl groups in the elastic curing agent is disappeared. At the same time, the peak of Urethane group is increased in response, There is a typical characteristic peak of -NCO, so it means that the final products was terminal isocyanate prepolymers. In the TG test we can seen that there are two weight loss steps in the TG curve,and have a good heat resistance.That the elastic curing agent which was prepared by process optimization direct curing at room temperature, by the experiment we found the performances of film is as follows: in the mechanical properties, the elastic modulus is 3144 kPa, tensile strength is 1605 kPa, and the elongation at break is 57.5%. In the physical properties of the coating, the adhesion level is 4, impact resistance to 70 kg·cm, the flexibility to reach the best.By the choice of Group B and additives can be appropriately increased the appearance of varnish and the properties. we use the curing agent applied to the prepare of polyurethane coatings, characterized and discussed its performance from the mechanical point of view. Been comparing experiment, 825 hydroxyl acrylic resin as a varnish Group B, and Choose the mass ratio of group A and B is 3.3, add the appropriate dose of defoamer BYK-141 and leveling agent deuchem 466. And after curing at 80℃for 1.5h, the obtained properties of the film such as the adhesion of the varnish film is good, the elastic modulus reached 5524 kPa. From the SEM graph of coating, we can find that in the coating surface is smooth and no bubbles. when the specimen under uniform tension and eventually pulled off, the fracture cross-section fracture is smooth, and there are some parallel and vertical cracks on the section. Also, the coating immersed in 30% H2SO4 and 10% NaOH solution for 120 hours can not see the bubble.We can add antioxidant in the product to delay yellowing.