Synthesis And Functional Modification Of Biodegradable Waterborne Polyurethane

With the increase in the application of waterborne polyurethane(WPU)in daily life,the environmental protection performance of WPU waste must be considered.Therefore,the biodegradability of WPU becomes more important,and related research has become a hot spot.As a hydrophilic colloid,cold water fish skin gelatin is a product obtained by partial hydrolysis of the polypeptide chain in macromolecular collagen,and has high-quality biodegradability.Taking into account the environmental protection and biodegradability of WPU,WPU modified with cold water fish skin gelatin and ultraviolet light(UV)curing technology has a large market.The research work of this thesis mainly focuses on the following two parts.Study on the preparation and performance of soft segment modified biodegradable WPU:the article selects polyester lactone diol(PCL),poly-1,4-butanediol adipate diol(PBA),polytetrahydrofuran diol(PTMG)and polycarbonate diol(PCDL)four kinds of polyester and poly ether diols with molecular weight of 1000 as soft segment materials,and a series of WPUs with R values(-NCO/-OH)of 1.3 were synthesized through the prepolymer method.By comparing the surface properties,thermal properties and mechanical properties of PCL-WPU,PBA-WPU,PCDL-WPU,and PTMG-WPU,it was found that the PCL-WPU film has the highest hydrophilicity,the smallest water contact angle,which was 71.7°,the water absorption rate was as high as 26.7%,and the hardness was 91.5 HD,the Young's modulus reached 22.9 MPa,the tensile strength was 58.3 MPa,the elongation at break reaches 857.9%,the maximum thermal weight loss rate temperature Tmax reached 333.7?,and the soft segment Tg was-52.3?.In addition,the structure of polyester PCL-WPU was more easily destroyed by enzyme and water molecules,and the acid products produced after hydrolysis further promoted the degradation of polyester.The best biodegradation effect was achieved,with the degradation rate of 41.7%in lipase PBS solution and 32.0%in soil microorganisms.Study on the preparation of modified gelatin(GH)and the properties of WPU/GH composite materials:WPU prepolymers with acrylate group at the end of the molecular chain were prepared by using PCL as the soft segment dialcohol and HEA as the end capping agent.Due to the good biodegradability and mechanical properties of cold-water fish skin gelatin,modified gelatin(GH)was prepared by grafting vinyltrimethoxysilane(VTMS)into gelatin molecular chain by sol-gel method.Then,WPU/GH composites were prepared by covalent bonding after UV curing by mixing GH and WPU prepolymer with acrylate terminal.The test results showed that when the mass ratio of GH was 10 wt%,the amount of photoinitiator(Irgacure1173)reached 0.16 wt%,and the UV curing time was 5 minutes,the surface properties,mechanical properties,thermal properties,and dynamic mechanical properties of the WPU/GH film were all reached the highest,the water contact angle reached the maximum 96.5°,the hardness reached 95.0 HD,the Young's modulus was 280.57 MPa,the tensile strength reaches 13.83 MPa,and the elongation at break was 150.39%;the maximum thermal weight loss rate temperature Tmax increased from 342.1? for pure WPU to 417.5?,and the soft segment Tg increased from-27? gradually reduced to-53?.In addition,the degradation rate of WPU/GH membrane in lipase PBS solution was increased to 68%,and the degradation rate in soil microorganisms is 56%.