The Modification Of Polyurcthane On Epoxy Resin

With the development of technology of chip manufacturing, light-emitting diode (LED)has been more and more widely used in various fields. However, in accordance with therequirements, LED package with epoxy resin has a lot of problems to be solved:(1)It is verybrittle, and it is difficult to cast to the big size of the component;(2)Under certaincircumstances, LED has a very good heat resistance in order to maintain a long service life.The main purpose of this paper is to form a polyurethane/epoxy resin composite material byadding PU to epoxy resin. The mechanical properties, thermal properties, micro-structure ofthe modified epoxy resin are examined.Polyurethane prepolymer with isocyanate-terminated group(-NCO) and polyurethaneprepolymer with Hydroxy-terminated group(-OH) have been synthesized by using PEG andTDI, according to the ratio of n-NCO/n-OH.-NCO content of polyurethane prepolymer andInfrared characterization is analysised through Di-n-butylamine method and the method ofInfrared spectra. The optimum reaction conditions is: temperature60℃, reaction timebetween2-3h. The result of the study on the effect of the catalyst, solvent on synthesisreaction, and the best conditions is that the amount of DBTDL0.2%;the solvent formulation is amount of ethyl acetate30%, amount of xylene70%.In the Preparation of modified epoxy resin, polyurethane prepolymer withisocyanate-terminated is added into epoxy resin in order to inspect the mechanical andthermal properties of modified materials. The best condition is polyurethane prepolymer withisocyanate-terminated was synthesized by using PEG(Mn=1500) and TDI. When the amountof it is10%and rate of n-NCO/n-OH is2.5, mechanical properties of modified epoxy resin isthe best.The result of thermal gravimetric analysis shows that the toughness and the thermalstability of epoxy resin can be improved by PU. The result of SEM shows that the modifiedmaterial has obvious shell morphology stripes. The aggregates of soft segment of thepolyurethane exist in the fringes of strip, and form irregular particles. When the material is forced, these particles have played a role in energy absorption, the increase of the toughnessof epoxy resin.