Study On Synthesis And Modification Of Castor Oil-based Waterborne Polyurethane Nanoemulsion

Due to its environmental protection,easy operation,safe use,good compatibility,and compatibility with most resins,water-based polyurethane has developed rapidly in industrial production and is widely used in various fields.However,a single waterborne polyurethane contains more hydrophilic groups,and it has shortcomings in terms of hydrophobicity,heat resistance and mechanical properties.In addition,polyester or polyether polyols are also one of the indispensable raw materials for the synthesis of waterborne polyurethane,and they are all derived from non-renewable petroleum resources.Therefore,finding suitable modified raw materials and improving the comprehensive performance of waterborne polyurethane has become an urgent problem to be solved.The main research contents of this paper are as follows:(1)Adjust the ratio of two hydrophilic chain extenders,dimethylolpropionic acid(DMPA)and ethoxylated polymer diol(N120),to synthesize a series of waterborne polyurethane nanoemulsions.Through research and analysis,WPU3(the molar ratio of DMPA to N120 is 5)has good dispersibility;in terms of solid content,WPU3 is better than other emulsions;in terms of water absorption,WPU3 has the lowest water absorption among the samples with N120.Therefore,WPU3 was chosen as the synthesis route of waterborne polyurethane nanoemulsion.(2)On the basis of WPU3 synthetic formula,adjust the ratio of polybutylene adipate(PBA)and castor oil(CO)soft segment to obtain castor oil-based waterborne polyurethane(CWPU)nanoemulsion,and systematically study the performance of CWPU nano emulsion and film.Studies have shown that the emulsion has a small particle size and good stability;the maximum contact angle of the CWPU2(PBA/CO molar ratio is 7/3)film is 75.51°.The tensile strength of CWPU1(PBA/CO molar ratio is 9/1)film is 23.2 MPa,and the elongation at break is1460.7%;the thermal performance test shows that the thermal performance of the film is improved due to the increase of CO content,and the glass transition the temperature(T_g)increases.The surface morphology of the film was analyzed by AFM,and the surface roughness of the CWPU film was improved.(3)Use silane coupling agent(KH550)to modify castor oil-based waterborne polyurethane(PBA/CO molar ratio is 7/3).Studies have shown that the particle size of the emulsion is increased to 60.48 nm,and the stability is good;the analysis of mechanical properties shows that the mechanical properties of the modified film have been improved;the maximum contact angle of the CWPU2-3%(KH550 content is 3%)film is 92.39°.Through the thermal performance test,it is concluded that the thermal stability of the film is improved by the increase of KH550,and the glass transition temperature(T_g)is increased by about 10°C.The surface morphology of the film was analyzed by SEM,and the surface roughness of the CWPU film was improved.Based on the shortcomings of water-based polyurethane containing hydrophilic groups in terms of hydrophobicity,heat resistance,etc.,the comprehensive performance of water-based polyurethane is improved by the modification of castor oil and silane coupling agent,which provides a way for bio-based water-based polyurethane synthesis an easy way.