Study On The Synthesis Of Waterborne Polyurethane Based On Polyacrylate Diols

With the gradually control of volatile organic compounds(VOCs),waterborne polyurethane(WPU)is favored by various industries,considered to be conducive to environment,increasingly.Various attempts have been made to develop WPU-based environmentally applied materials.However,WPU has general shortcomings in water resistance,heat resistance,gloss and so on.In order to expand its application range,Waterborne polyurethane resin should be modified by other resin.Polyacrylate has excellent properties in water resistance,chemical resistance and substrate adhesion.Therefore,the modification of WPU by poly-acrylate can prepare polyacrylate-based waterborne polyurethane(PUA)emulsion with excellent comprehensive performance.At present,methods of modified WPU by acrylate mainly have mechanical blending modification,composite emulsion copolymerization,graft copolymerization,etc.But for the structure of WPU,synthesized by soft segments were not polyacrylate,doesn't have good twophase structure,and is different from the general polyether-based waterborne polyurethane and polyester waterborne polyurethane structure.Polyacrylate diols are used as the soft segments of polyurethane,because it has hydroxyl groups at both ends,thus it can react with isocyanate.Polyacrylate segments are reacted as the main chain of polyurethane molecular,and the soft and hard segments of the polymers obtain nice compatibility.So,this is a new way of acrylic modified polyurethane.Based on this method,the types of acrylates and the copolymerization of different vinyl monomers were further studied to prepared polyols,and researched the performance of PUA synthesized by polyacrylates polyols.In this paper,degraded iodine transfer radical polymerization method(DITP)is used,with acrylate monomers as raw materials,4,4'-azobis(4-cyanopentanol)(ACPO)as the initiator,?,?'-di Iodine paraxylene(DIX)as a chain transfer agent and toluene as solvents to synthesize polyacrylate diols.The structures of the polymerized products were characterized by nuclear magnetic resonance spectroscopy(NMR),gel permeation chromatography(GPC),matrixassisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF MS),and Fourier infrared spectrometer(FI-IR).Polyacrylate diol as soft segment,reacts with toluene diisocyanate(TDI),then 1,4-butanediol(BDO)as molecule chain extenders,and dimethylolpropane acid(DMPA)as the hydrophilic chain extenders to prepare waterborne polyurethane.Malvern laser particle size analyzer,differential scanning calorimeter(DSC)and thermogravimetric analyzer(TG)were available to characterize the structure of the synthesized polyurethane.The research content is listed as follows:(1)Synthesis of four polyacrylate diols and preparation of waterborne polyurethane.Using methyl acrylate(MA),ethyl acrylate(EA),n-butyl acrylate(n-BA),and styrene(St)as raw materials,four polyacrylate diols were synthesized by the DITP.And then these four polyester diols were used as soft segment to prepare an aqueous polyurethane under the same other conditions.The four polyacrylate-based waterborne polyurethane emulsions were characterized by Malvern laser particle size analyzer,thermogravimetric analyzer,differential scanning calorimeter and so on.It was found that the properties of PUA were distinct by structure of soft segment.(2)Synthesis of polyethylene acrylate copolymer diols and preparation of waterborne polyurethane.Polyurethane film obtained by polyethylene acrylate(PEA)diol as soft segment become relatively soft.In order to improve the hardness of polyurethane film,the ethyl acrylate monomer was designed to be separately copolymerized with methyl methacrylate(MMA),styrene(St),and acrylonitrile(AN)to obtain a random copolymer diols,which was played as soft segment to of WPU.Results showed much better thermal stability and mechanical properties of hybrid films than pure waterborne polyurethane resin.The results show that the addition of hard monomers significantly increases the hardness of the WPU film.(3)Synthesis of polyethylene acrylate-polyacrylic acid(PEA-PAA)diol and preparation of waterborne polyurethaneSince the use of polyethylene acrylate as soft segment for the synthesis of aqueous polyurethane requires the addition of hydrophilic chain extender dimethylolpropionic acid(DMPA).While DMPA is not easily soluble in ketone solvents,so using acetone as solvent DMPA has more VOCs.While N,N-dimethylformamide(DMF)is used as solvent,the solubility of DMPA is just higher,but DMF is difficult to remove in the subsequent process.Therefore,the new polyethylene acrylate-polyacrylic acid diol with a certain amount of carboxyl groups is newly synthesized,so that it is not necessary to add DMPA in the process of preparing waterborne polyurethane.