Study On New High Performance Polyurea Adhesive From Preparation And Properties

Polyurea adhesive excellent performance and convenient in construction features draws more and more attention.However, the rapid response of polyurea will lead to the poor wettability of the substrate, meanwhile polyurea molecules has strong polarity and high surface tension which resulting the low adhesion to metal substrates, limiting the applications of polyurea in some construction area, thereby increasing adhesion is the key to expanding polyurea applications.This paper systematically studied the factors affecting the adhesion of polyurea and effective means to improve adhesion. First of all, a new type of polyurea adhesive was prepared by grafting epoxy resin on to the HDI trimer to be the A component, the aromatic amine terminated polyether made in our laboratory as the R component, also studied the influence on adhesive properties of changing the ratio of activity prepolymer and HDI trimer, the study found that through the using of activity prepolymer the reaction time can be slow down, which by the way increasing its wettability process of the substrate, while the reaction process can generate reactive hydroxyl which solved the problem of the decreasing of the number of reactive binding sites between the coating and the substrate which lead to the low adhesion of the polyurea adhesive, for the polarity of the adhesive system could easily form intermolecular hydrogen bonds. With appropriate epoxy resin grafting with HDI trimer there will be an epoxy resin-polyurea interpenetrating networks, solving the problem of low adhesion, which greatly improved the polyurea adhesive by increasing its cross-linked density, resistance to environmental performance, when add excessive epoxy resin, there will be a large number of unreacted epoxy resin in the system so that the cross-linking density of the whole system will decrease, also the mechanical properties decrease,When the content is 15%, show the best performance, attach adhesion was 19.6 MPa, the peel strength was 57.56 Ncm-1,the best flexibility＜1 mm and the high impact strength＞50 kg·cm.This paper also take it under consideration that the various type of epoxy resin grafted to HDI trimer will have a different adhesive properties. Secondly, a steric-type curing agent-polyaspartic acid ester-polyether was prepared by Michael Synthesis, and a polyurea adhesive was prepared by the reaction with HDI trimer, the adhesive properties was studied with different types of maleate and the length of poly ether segment and epoxy resin grafted HDI trimer was introduced into the system to study the changes of the adhesive. At last, by using the terminated aromatic amino ether to react with single-ended epoxy compounds, a novel polyurea curing agent was prepared. Through this way, the primary amine with higher activity could transmit into a secondary amino which lower amino hydrogen reaction activity, and at the same time introducing the active groups, so under the premise of reducing the reaction rate, the number of active groups in the system was increased which greatly improve the mechanical properties of adhesives; meanwhile, the influence of curing agent prepared by various epoxy compounds and single-ended side of aromatic and aliphatic amino polyether ether and different chain length aliphatic polyether on the adhesive properties was studied,we found that through the reaction, the reactivity apparently reduced, increased the adhesion and the longer the chains the lower the activity of amino.Based on above studies, we can find the using of epoxy resin grafted HDI trimer, a lot of favorable characteristics of epoxy resin were introduced into the polyurea system. Applied to the radar absorbing coating, due to the prepolymerization prepared by epoxy resin grafted HDI trimer have greater free volume, thus it has a relatively larger filling ratio and larger mechanical strength than the un-grafted ones. Comparing with traditional adhesives, the polyurea adhesives prepared by the addition of epoxy resin grafted HDI trimer or the new type of polyurea curing agent delaying the gel time and increase the wettability of the substrate, so that all kinds of mechanical properties was improved.