| Polyurea coating has excellent mechanical properties and good chemicalresistance,low temperature resistance,heat aging properties,can improve the service lifeof the structure,has been widely used in many domestic and international protectionengineering.In the field of metal protection,the adhesion properties of the polyureametal composite coatings is important,failure of protective coating is often due to thelow adhesion properties.But research about the polyurea metal composite coatingadhesion performance is little.So,to carry out research with polyurea protective metalcoating adhesion is very necessary.In this paper,we study the metal surface treatmentand service environment of polyurea metal composite coating adhesion effect,with theanalysis of scanning electron microscope(SEM),sandblasting roughness and QUVaccelerated aging effect on adhesion of coating, the main research conclusions are asfollows:(1)Conventional performance of polyurea metal composite coating on the adhesioneffect research shows:As primer viscosity increased,construction difficulties,the dryingtime and film thickness increases,polyurea metal composite coating adhesiondecreases;With the increase of polyurea coating gel time,coating increasedliquidity,reduce internal stress to improve adhesion;Polyurea coating thicknessincreases,the coating itself will produce different degrees of interface stress due todeformation,making it easier for the coating and metal substrate release,reduce thecomposite coating adhesion.(2)Different processing methods of metal surface for polyurea metal composite onthe coating adhesion effect research shows:In order to improve the metal surfaceroughness,sandblasting processing was carried out on the metal surface,thus increasethe polyurea coatings and substrate combination area,prevent coating crack,to resist thenegative impact of the tension of the coating to improve composite coatingadhesion.Corresponding composite coating adhesion of Q235steel plate and aluminium plate after sandblasting treatment were12.3MPa,10.2MPa.In addition,the metal surfacephosphate film was generated by phosphating,its internal pore capillary is advantageousto the primer infiltrating metal substrate,thereby enhance composite coatingadhesion.The existence of the phosphating film also make metal substrate surface to bea good conductor,inhibit the formation of surface micro batteries,not only can improvethe tolerance of metal, also can improve the adhesion of polyurea metal compositecoating. Corresponding composite coating adhesion after phosphating treatment ofQ235steel plate and aluminium plate were10.19MPa,8.79MPa.(3)Curing temperature on polyurea metal composite coating on the adhesion effectresearch shows: curing temperature can influence the internal reaction rate of polyureacoating,also can affect the chemical reactivity of half prepolymer and amino polyetherand amine chain extension agent,can also affect the required time of molecular chain ofchemical crosslinking,which influence the coating itself cohesion and the developmentof polyurea metal composite coating adhesion.Under the condition of low curingtemperature,the adhesion strength of polyurea metal composite coating rise slowly,andthere are different forms of destruction;Under the condition of high curingtemperature,the development of polyurea metal composite coating adhesion israpid,curing2d the adhesion can achieve stable adhesion strength of60.4%,curing5dthe adhesion has been basically reaches stable adhesion of the composite coating.(4)Dry-wet circulation,the freeze-thaw cycle and QUV accelerated aging onpolyurea metal composite coating adhesion effect research shows:Environmentaldegradation factors,oxygen, water molecules and temperature effect on the properties ofthe coating adhesion is serious,as the growth of the service time,the adhesion ofcomposite coating can also become lower,and the influence of three serviceenvironment effect on adhesion from large to small is:QUV acceleratedaging>freeze-thaw cycle>dry-wet cycle.After90times of dry-wet cycle,polyurea Q235steel composite coating adhesion decreased from11.36MPa to11.36MPa;Polyurea Q23aluminum coating adhesion decreased from10.13MPa to9.71MPa.After90times of freeze-thaw cycle,polyurea Q235steel composite coating adhesion decreased from11.25MPa to11.25MPa;Polyurea aluminum composite coating adhesion decreased from10.59MPa to6.46MPa.After7200h of QUV accelerated aging,polyurea Q235steelcomposite coating adhesion decreased from11.87MPa to11.87MPa;Polyurea aluminumcomposite coating adhesion decreased from8.01MPa to4.91MPa.In addition,threekinds of service condition all involve the change of temperature,can produce a largertemperature difference effect,since the linear expansion coefficient of the metalsubstrate and polyurea coating is larger,the slip is produced between the coating andthe metal interface, When the invasion of oxygen and water molecules interface to causecorrosion of the metal substrate,which affect polyurea metal composite coatingadhesion.Based on the above study,get metal protection with the changing rule of thepolyurea coating adhesion performance and its influencing factors,for polyureaapplication in the field of metal protection provide basic data and theoretical support. |
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