Synthesis Of Doubly Modified Waterborne Polyurethane Curing Agent And Its Curing Properties

The two-pack waterborne polyurethane,which are eco-friendly,low deposion temperature and its gloss,abrasion resistance,water resistance,solvent resistance are good,has become a research hotspot in recent years.The two-pack waterborne polyurethane should be well-mixed before coating,which include curing agents component and polyol component.The NCO groups from curing agent will react with OH groups from polyol component while film forms,which can form the crosslinking coating and result in effective improvement in the film properties.In this paper,the waterborne polyurethane curing agent is synthesized and the curing properties of two-pack waterborne polyurethane system are studied by mixed with polyol dispersion component.With hexamethylene diisocyanate(HDI)and trimethylolpropane(TMP)as main materials,polyethylene glycol 400(PEG400)as nonionic modifier,sodium hydroxyer--thyl sulfonate as ionic modifier,doubly modified waterborne polyurethane curing agent was synthesized.Some composition factors such as-NCO/-OH,PEG400 content,sodium hydroxyerthyl sulfonate content effects on curing agent and films have been studied.The influences of curing temperature and curing time on the two-pack waterborne polyurethane film performance have also been investigated.The higher the temperatue,the better the performance of the films in the range of 25?~55?.With the extension of the curing time,the gel fraction of the coating film increases.When curing time is 75 h,the gel rate has almost no change,and the crosslinking reaction between the polyol component and the curing agent component was substantially completed.The influences of the molar ratio NCO/OH of curing agents to dispersions on the films is studied.The films performance such as gloss,abrasion resistance,water resistance,solvent resistance are excellent when the molar ratio is 1.4~1.6,and it is provedby scanning electron microscopy(SEM).The synthesis process of curing agent is traced and the film properties of two-pack polyurenthane are tested,characterized and analyzed.Fourier transform infrared(FTIR)is used for tracing synthetic process and characterizing structures of the curing agent.The FTIR contrastive analysis of the curing agent and the final film prove that during the curing stage,the cross-linking reaction occurs between the polyol and the curing agent.The changes of surface crack spacing and regularity of the film with the molar ratio of two components was observed by scanning electron microscopy(SEM).The thermogravimetry-differential scanning calorimetry(TG-DSC)curves indicate that the final film has good heat resistance.