Structural Design,preparation And Properties Research Of Waterborne Polyurethane Modified By Composite Hydrophilic Units

The preparation process of waterborne polyurethane(WPU)is eco-friendly,its molecular structure can be designed,and its function can be controlled.Therefore,the application of WPU in the leather finishing,coatings,inks and biomaterials has been relatively well developed.At present,the preparation of traditional WPU usually selects a single hydrophilic monomer,such as anionic hydrophilic monomer,cationic hydrophilic monomer or non-ionic hydrophilic monomer.This formula is easy to concentrate the hydrophilic groups in the soft or hard segment of the WPU,resulting in excessive microphase separation between the soft and hard segments,which seriously affects the properties of the WPU.In order to overcome the above shortcomings,composite hydrophilic units were used to prepare the WPU with excellent properties and different functions through molecular structure design in this thesis,which could be applied to leather finishing agent,ink binder,and degradable and biomedical materials.In the work,carboxylate/sulfonate compound,carboxylate/non-ionic hydrophilic monomer compound and carboxylate/sulfonate/non-ionic hydrophilic monomer compound were used respectively,which could not only play the synergistic effect of different hydrophilic monomers,but also regulate their uniform distribution in the soft and hard microphases of WPU,thereby improving the comprehensive properties of the WPU.The specific research contents of this thesis include the following four parts.Carboxylate/sulfonate was used as the composite hydrophilic unit to prepare a waterborne polyurethane(SWPU)without any organic solvent addition.The2,2-dimethylolpropionic acid(DMPA)and the sulfonate N-[(2-amino)-amino]ethane sulfonate(A950)were used as hydrophilic chain extenders and internal emulsifiers to prepare the SWPU.As a post-chain extender,A950 could easily make the SWPU dispersion form a large number of stereoregular spherical particles,and make the colloidal film have a natural gloss during the drying process.By adjusting the content of A950 and polyols,the molar ratio of NCO/OH and other factors to control the viscosity of the SWPU prepolymer,the degree of microphase separation between the soft and hard segments,and the solid content,the preparation process did not need to add any organic solvents,thus avoiding the environmental pollution and human injury.The results showed that when the molar ratio of NCO/(OH+NH₂)was 1.3,and the molar percentages of A950 and polyol were 6%and 15.5%,respectively,the comprehensive properties of SWPU was the best.At this time,the SWPU had the smallest particle size of 59 nm,the best thermal stability with the temperature for the initial maximum thermal degradation rate up to 307°C,the tensile properties were significantly improved,and the tensile strength and elongation at break reached 42.45 MPa and 1165%,respectively.This kind of SWPU could be used for the surface finishing of artificial and synthetic leathers.The application experiments showed that,compared with the traditional waterborne polyurethane coatings,the SWPU was safe and environmentally friendly,with natural gloss and better adhesion properties,bending resistance,and hand feeling.A one-component cross-linking modified synthetic method was used.Three kinds of WPU dispersions were prepared by using N-[(2-amino)-amino]ethane sulfonated sodium(AAS)with two functional groups and diethylenetriamine(DETA)and triethylenetetramine(TETA)with multiple functional groups as post-chain extension crosslinking modifiers,respectively.The effects of three modifiers on the properties of WPU dispersion and colloidal film were investigated.The research results showed that compared with the WPU prepared by the other two chain extenders,the WPU prepared by DETA with three functional groups had the best comprehensive properties.The number average molecular weight and weight average molecular weight of the WPU were the highest,reaching 47200 g/mol and 81000 g/mol,respectively.Its peel strength was the highest,2.89 N/15mm,and the water absorption rate was the lowest,reaching 8%.These results indicated that compared with AAS and TETA,DETA,as a crosslinking modifier,was the most effective in improving the properties of WPU.In addition,when the AAS/DETA compound was used to prepare WPU,when the molar ratio of AAS/DETA was2:3,the WPU had excellent adhesion and steaming and boiling resistance;and when the molar ratio of NCO/OH was 1.6,the WPU had good emulsion stability and high solid content up to 42.8%.Carboxylate/sulfonate was used as the composite hydrophilic unit,and a very small amount of organic solvent(less than 4%of the total mass of the dispersion)needed to be added during the preparation of WPU by the method of one-component post-chain extension cross-linking modification.Therefore,as the ink binder for food packaging,it is convenient and effective to use.Using carboxylate/sulfonate/non-ionic hydrophilic monomer as a composite hydrophilic unit,non-ionic hydrophilic monomer polyethylene glycol(PEG)(PEG200,PEG400,PEG1000,and PEG2000)and hydrophobic and biodegradable polycaprolactone glycol(PCL)(PCL2000)were used as the mixed soft segments to prepare a series of novel non-toxic amphiphilic biodegradable waterborne polyurethane(WBPU).The preparation process did not add any organic solvent,catalyst or crosslinking agent,so it was“green”and sustainable.As a 3D printing ink,this WBPU overcame the shortcomings of the traditional 3D printing materials such as high toxicity,poor degradability,and poor biocompatibility,and could be used to make soft tissue engineering scaffolds.The combination of ester and ether groups made WBPU amphiphilic,which was of great significance to the regeneration and maintenance of human tissues.In order to meet the requirements of 3D printing for WBPU,the solid content,viscosity,and average particle size of the WBPU dispersions were adjusted separately.The WBPU dispersions had a solid content of 30%,a viscosity range of 0.4-2.5 Pa·s,and a particle size range of 81-109 nm.The research results showed that these properties could meet the requirements of 3D printing.At the same time,the effects of PEG segment length and soft segment content on the phase separation,thermal properties,biodegradability,and cytotoxicity of the WBPU were also investigated.The results showed that when the soft segment content was 72.6%,the WBPU containing PEG1000 could achieve ideal properties and was a promising 3D printed material for tissue-engineered scaffolds.A high-solid and biodegradable waterborne polyurethane dispersion(BHPU)was prepared by changing the connection relationship of the hydrophilic segments in the polyurethane.A carboxylate/non-ionic hydrophilic monomer compound was used as the hydrophilic unit of BHPU,and PEG was introduced into the molecular chain of the PCL-based waterborne polyurethane.The BHPU prepared by PCL as soft segment had not only biodegradability,but also excellent mechanical properties for its colloidal film.The BHPU was prepared by two synthetic methods:all non-ionic hydrophilic monomer PEG was directly connected with ionic hydrophilic monomer DMPA and part of PEG was connected with DMPA.The effects of different connection relationships of two hydrophilic monomers on the solid content,average particle size,crystallization performance,mechanical properties,water absorption,surface energy,and biodegradation properties of BHPU were investigated by means of various characterization methods such as differential scanning calorimeter,dynamic mechanics tester,and laser particle size tester.The results showed that the synthesis method with all the PEG molecules directly connected with DMPA improved the crystallization performance,tensile properties,water resistance and antifouling performance of the BHPU,and increased the solid content of BHPU dispersions from 41%to 52.7%.The introduction of PEG400 increased the crystallinity of BHPU from 20.2%to 24.2%and the tensile strength from 40 MPa to 49 MPa.The BHPU had relatively good biodegradability.