Preparation And Modification Of Moisture Curing Polyurethane Hot Melt Adhesive

In this paper, Moisture curing polyurethane hot melt adhesive (PUR) was prepared by reacting diols with excessive diisocyanates. Bis(2-morpholinoethyl)ether (DMDEE) was chosen as catalyst. Then PUR prepolymer was added into additives including thermoplastic resin, antifoaming agent and antioxidant. Technological conditions of polyurethane prepolymer was studied. Factors such as polyol, isocyanate, catalyst, index of isocyanate and thermoplastic resin, which affected the properties of PUR, were discussed. The results showed that the optimum temperature was at about80℃and the optimum reaction time was160min. When the molar ratio of polyester/polyether was60/40, index of isocyanate was2.0, the mass fraction of catalyst was1.0%, the mass fraction of TPU was10%, the PUR showed a better performance.To improve bonding strength, water resistance and heat resistance, silanized moisture-curing polyurethane hot-melt adhesive (SPUR) was studied. Effect of structure of silane and effect of silane end-capped ratio on SPUR properties was discussed. In comparison with KH560and KH550, Y9669was proved as a better end-capping agent to modify PUR. Shear strength of SPUR with Y9669had a37.23%increase than PUR and the failure mode was cohesive. With an increasing end-capped ratio, hardness was improved, track free time was reduced, water resistance was improved, water absorption was decreased. With an increasing end-capped ratio, shear strength first rose, then declined, reaching at the maximum at end-capped ratio of20%. Differential thermal analysis (DSC) and thermogravimetry (TG) showed that heat resistance of system can be improved by silane. Glass transition temperature (Tg), melting temperature (Tm) and thermal decomposition temperature(Td) were increased with an increase of end-capped ratio.PUR modified with hydroxy acrylic resin which was prepared by reacting methyl methacrylate(MMA), butyl acrylate(BA) and hydroxyethyl acrylate (HEA)was studied. Effect of content of initiator, content of hydroxy acrylic resin and content of HEA on properties of PUR were discussed. FT-IR showed that a grafted compund PUR/hydroxy acrylic resin was prepared sucessfully. The results showed that hydroxy acrylic resin had a lower number-average molecular weight and lower vicosity when the content of initiator was increased. With an increasing content of hydroxy acrylic resin in PUR, shear strength first rose, then declined, reaching at the maximal shear strength (17.54MPa) at content of20%. With an increasing content of HEA in acrylic monomer mixtures, track free time was reduced, viscosity was increaed and shear strength was improved. The optimal molar ratio of MMA/BA/HEA is40/40/20. DSC showed that Tg of system can be improved slightly by hydroxy acrylic resin.