Study Of The Synthesis And Application Of Polyurethane Sealant

Polyurethane has unique properties due to its special structure combining softand hard segment. The products of polyurethane mainly include coatings, fibers,elastomer etc. The polyurethane adhesive is widely used in automobile manufacturing,shipbuilding and aerospace fields.The one-component polyurethane sealant was prepared with polyether anddiphenylmethane diisocyanate as raw materials. The structure, composition andproperties of the sealant were studied. This study puts forward new ideas and datasupport for the structural design of one-component polyurethane sealant and play apositive role to further expand the application of polyurethane materials. The mainfindings are as follows:1) With polyether2000as bifunctional monomer, polyether330and360astrifunctional monomer, we synthesized one-component polyurethane sealant. We havestudied the effect of different polyether compound on the properties ofone-component sealant. The results show that, compared with the commonly usedone-component polyurethane sealant synthesized by polyether330, the tensilestrength of one-component polyurethane sealant synthesized by polyether360decreased slightly. But after adding the appropriate bifunctional polyether2000,one-component polyurethane sealant showed good elongation and peel strength, thebase material can meet the requirements of application.2) We further improved the performance of the polyether type one-componentpolyurethane sealant by adding the epoxy resin to the polyurethane. The resultsshowed that a small amount of epoxy resin can effectively improve the mechanicalproperties of polyether urethane/epoxy interpenetrating polymer network, and noserious phase separation occurs. Scanning electron micrograph showed that the epoxyresin as the dispersed phase uniformly dispersed in the rubbery continuous polyetherurethane phase.3) Adding the silane coupling agent in polyurethane sealant systems would furtherimproves its performance. The results show that the polyurethane modified by ND-42 silane coupling agent exhibits the good mechanical property. The tensile strength ofpolyether type polyurethane increased with the increase of mass fraction of ND-42,but the elongation at break decreased. The composite materials exhibit positivesynergies, which indicates that ND-42improved the compatibility of the polyurethanecomposites and enhanced the adhesion of polyurethane composites.4) Finally, by using atomic force microscopy based single molecule forcespectroscopy, we studied the mechanism of adhesion and adsorption of polyurethane.We found that the polyurethane chain adsorbs as a “train-like” conformation onamino-silanized substrate, OH-group terminated silicon (or glass) substrate, silversurface, and clean silicon and glass surface. And the polyurethane has a strongerinteraction with amino-silane functionalized substrate than other substrates. While onthe gold surface, the polyurethane chain adsorbs as a “tail-like” structure.