Synthesis And Properties Of Hydroxylated Tung Oils Based Zwitterionic Polyurethane Dispersion

In the present thesis, a series of novel hydroxylated tung oil (HTO) based zwitterionic polyurethanedispersion (HTO-ZPUDs) containing both anionic/cationic ions and three conjugated double bonds havebeen, for the first time, prepared based on HTO, polyethylene glycol (PEG, MW=800),N-methyldiethanolamine (MDEA), dimethylol propionic acid (DMPA) and4,4methylene dicyclohexyldiisocyanate(HMDI). Either alkali or acidic agent was used to carry out the neutralization, respectively.FTIR, NMR, GPC, dynamic laser particle size analyzer (DLS), viscosity meter, conductivity meter,thermal gravimetric analysis (TG), dynamic mechanical analyzer (DMA) and Instron tester etc were usedto examine the structure, particle size, viscosity, pH stability, thermal stability and mechanical properties ofthe HTO-ZPUD; and the effect of HTO content, neutralizing method and the alkali/acidic group ratio onproperties of HTO-ZPUD was also studied. In addition, blending HTO-ZPUD was used to compare withchemically synthetic ZPUD. And their anti-water and anti-solvent abilities among four types ofrepresentitive solvents from aromatics, aliphatics, alcohols and ketones were especially investigated. Themain research results are as follows:Due to the incorporation of both ionizable tertiary amine and-COOH groups, the polymer in aqueousmediums could be stable at pH=1-5.6as well as pH=8.5-14. DLS measurement indicated that theHTO-ZPUDs have particle size ranging from90to200nm whereas their surface tension could be as low as40mN/m. The viscosity of HTO-ZPUD decreased initially and increased afterwards with increasing ofHTO content at low solid content, while the viscosity of HTO-ZPUD increased with HTO at high solidcontent. The viscosity of HTO-ZPUD with the solid content of22%could be up to10320mPa·s.The paticle size of HTO-ZPUD with acetic acid as neutralizer was smaller than that withtriethylamine and the former was preferably solvent resistance and had better mechanical properties. Inaddition, the solvent tests showed that solvent resistance of chemically synthetic HTO-ZPUD was muchstronger than those of both blending HTO-ZPUD and commercially available anionic waterbornepolyurethane, and the HTO-ZPUD with acetic acid as neutralizer was even N-methyl pyrrolidone (NMP)resistance. When the ratio of-COOH and tertiary amine group was close to1:1, the HTO-ZPUD could beapplied under acidic and alkali conditions with good pH reversibility, and when the ratio was1:2, theemulsion was only stable in acidic conditions, not completely dissolving under alkali conditions.The thermal stability and mechanical properties of the crosslinking HTO-ZPUD were studied by TG,DMA and instron tester. After the conjugated double bonds were crosslinked, thermal stability, especiallyhigh-temperature stability was significantly increased. The oxidative crosslinking of polymer film wasobtained at the different temperatures. The results showed that the content of double bonds in HTO-ZPUDfilm decreased and crosslinking density gradually increased by increasing heat treatment temperature.Within a certain time at the heat treatment temperature60-150oC, the crosslinking density of the filmcould rise from9.97×102mol/m3to25.31×102mol/m3. While decreasing in elongation at break, thebreaking strength increased from5.15MPa to24.34MPa. The crosslinking density of HTO-ZPUD filmwas increased with increasing the content of HTO and/or the temperature of crosslinking. Thecrystallization of PEG was easily disturbed by the crosslinking of three conjugated double bonds, therefore,the modulus of HTO-ZPUD decreased at low temperature but increased at high temperature by increasingthe crosslinking density.In short, the heat treatment for HTO-ZPUD containing conjugated double bonds was a significantlyeffective method for improving water and solvent resistance and mechanical properties of film prepared byHTO-ZPUD. Simultaneously, the mechanical and dynamic mechanical properties of such film could becontrolled and adjusted by changing the oxidation crosslinking degree of the three conjugated doublebonds in HTO-ZPUD.