Study On Synthesis And Properties Of Linear And Hyperbranched Fluorinated Polyesters

Fluorinated materials have excellent performance such as chemical stability, water resistance, oil resistance and pollution resistance etc. However, the high fluorine content (76 % fluorine content for PTFE) results into the traditional fluorinated polymers high cost and poor processability. Fluorinated polymers possessing both low fluorine content and low surface energy are desirable for broadening their application field. In an effort to overcome the above drawbacks, the present work was carried out to synthesize a series of polyesters with different fluorine content. Their chemical structure and surface properties were investigated.Fluorinated monomer N-hydroxyethyl perfluorooctanamide (HPFOA) was synthesized from perfluorooctanoic acid (PFOA) and ethanolmine. Its chemical structure was confirmed by FTIR, Mass spectroscopy and metling measurement methods.Fluorinated Polybutylene terephthalates (FPBT) containing different content from 0% to 10% were synthesized from dimethyl terephthalate, 1,4-Butanediol and N-hydroxyethyl perfluorooctanamide(HPFOA), using tetrabutyl titanate as catalyst. Their chemical structures and surface properties were examined through FTIR, DSC and water contact angle measurement etc. The effects of fluorine content on surface properties of FFPBT films were discussed. The results showed that surface energies of FPBT decreased evidently with the increase of fluorine content.Fluorinated polybutylene isophthalates (FPBI) containing different fluorine content were synthesized from dimethylisophthalate, 1,4-Butanediol and N-hydroxyethyl perfluorooctanamide, using tetrabutyl titanate (TBT) as the catalyst. Their chemical structures and surface properties were investigated by FTIR spectroscopy, attenuated total reflection FTIR spectra (ATR-FTIR), X ray photoelectron spectroscopy (XPS) as well as water and hexadecane contact angle measurement methods. The results showed that the fluorine-containing groups could migrate and enrich on the surfaces. When the fluorine content was 10 mol%, the calculated surface energy was 15.07 mJ/m² which was lower than polytetrafluorethylene (22 mJ/m²), exhibiting excellent water and oil repellency.A series of hyperbranched fluoropolymer(HBFP) which contained different fluorine content were synthesized from pentaerythritol, dimethylisophthalate, 1,4-butanediol, N-hydroxyethyl perfluorooctanamide, using tetrabutyl titanate as the catalyst. The hydroxyl values of HBFPs, which was determined by acetic anhydride-pyridine method, were 27-107mg/g. The chemical structures were confirmed by FTIR spectroscopy. The degree of branch was regulated by the pentaerythritol content and determined by ^13C-NMR. Their curing kinetics was studied by DSC using diisocyanate as curing agent. The curing kinetics parameters, including the activation energy, frequency factor and reaction order were calculated with Kissinger and Crane methods. Their values were 158.67 kJ /mol, 2.25×10¹⁵ and 0.95, respectively. The results show that the curing reaction was complex reaction, closing to the first order reaction. The experiment provides reference to curing process of identical polyhydroxy hyperbranched polyester.