Study On Preparation And Performance Of Waterborne Polyurethane

Polyurethane(PU)is a kind of unique polymer material.The designability of its structure enables it to show different characteristics and meet the needs of a variety of applications.With the improvement of environmental protection requirements of the industry,the research and industrialization of waterborne polyurethane gradually rise.Waterborne polyurethane(WPU)is a kind of green environmental protection material with excellent performance,which can be widely used in fiber sizing agent,adhesive,coating and other fields.However,as an O/W emulsion,the stability of waterborne polyurethane is easily affected by external conditions,resulting in flocculation,demulsification and other problems,which limits the application and development of waterborne polyurethane.In this paper,by designing the molecular structure of waterborne polyurethane,optimizing the formulation and process,waterborne polyurethane with excellent mechanical properties and good stability was prepared.The specific research contents are as follows:Firstly,anionic waterborne polyurethane was synthesized by acetone method using phthalic anhydride polyester polyol(PN)and polycarbonate polyol(PCD)as mixed soft segment,isophorone diisocyanate(IPDI)as hard segment,and2,2-dihydroxymethylpropionic acid(DMPA)as hydrophilic chain extender.Through the study on the properties of waterborne polyurethane emulsion and paint film,it was found that when the polyol PN:PCD was 2:1,the R value was 1.2,the DMPA content was 14%,and chain extension with EDA after emulsification,the performance of the anionic waterborne polyurethane was the best.The emulsion had good mechanical stability and dilution stability.The tensile strength of the paint film was 29.08 MPa,the elongation at break was 424.38%,and the water absorption rate was only 1.68%.In order to further improve the adaptability and stability of waterborne polyurethane in use,a micro cross-linking anionic/nonionic waterborne polyurethane was prepared by introducing ethoxy terminated polymer glycol(n-120)as a non-ionic hydrophilic chain extender and trimethylolpropane(TMP)as a cross-linking agent.Through the comprehensive analysis of the properties of emulsion and paint film,it is found that introducing N-120 into the non-ionic hydrophilic structure with long side chains can effectively improve the acid and alkali stability and electrolyte stability of waterborne polyurethane,and the mechanical properties of film will decrease with the increase of N-120 content.Moderate cross-linking can effectively improve the mechanical properties of waterborne polyurethane film while the emulsion is stable.The emulsification process of micro cross-linked anionic/non-ionic waterborne polyurethane prepolymer was studied.The results showed that the suitable emulsification conditions of micro cross-linked anionic/non-ionic waterborne polyurethane prepolymer were as follows: backward dispersion emulsification,diameter ratio of disperser disk 2:3,water drop acceleration 40 m L/min,rotating speed of dispersion disk 1200r/min,dispersion temperature 30?,dispersion time 10 min.Through the comprehensive analysis of emulsion particle size,mechanical properties of film and SEM,it is concluded that the waterborne polyurethane prepared after emulsification process optimization has better performance and the morphology of spherical colloid particles is more regular.