Synthesis And Application Of Hyperbranched Polyester

The synthesis of hyperbranched polyester (HBPE) with Trimethanol propane (TMP) as a core and 2, 2 - Dimethylol propionic acid (DMPA) as AB₂ monomer was studied in detail. Carboxyl-terminated hyperbranched polyester (CHBP) and acrylic-terminated hyperbranched polyester (AHBP) were synthesized by end group modification, and excellent properties were obtained when they were used in modification of epoxy resin and acrylic latex.Hyperbranched polyesters from second generation (G-2) to fifth generation (G-5) were obtained by changing the TMP:DMPA molar ratio. The kinetics of formation of hyperbranched polyester was observed and the effects of catalyst, temperature and core monomer were discussed. The characteristics of hyperbranched polyester were determined by nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared (FTIR). The degree of branching was calculated from ¹³C NMR. The molecular weight was measured by gel permeation chromatography (GPC). Moreover, the molecular weight, the glass transition temperature (Tg) and heat-resistant stability of hyperbranched polyesters were detected. The results showed the optimum reaction conditions were that p-toluence sulfonic acid was used as catalyst and its amount used was 0.5 1 wt%;the reaction mixture was stirred under a stream of argon at atmospheric pressure followed by a further reaction time under reduced pressure;the reaction temperature was 140℃;the reaction time was more than 4h. The molecular weight of hyperbranched polyester was between 1024g/mol and 3265g/mol, and the degree of branching was between 0.3 and 0.4. The acid catalyzed esterification reaction follows a second-order rate equation and determined by the concerntration of carboxyl group and hydroxyl group, -d[COOH]/dt=K[COOH][OH]. The molecular weight detected by GPC was different with the theoretical value especially at higher generation, and only the molecular weights of the second and third generation detected by GPC were close to thetheoretical value. The Tg of hyperbranched polyester was about 60 °C, and its decomposition temperature was above 300°C.Carboxyl-terminated hyperbranched polyester (CHBP) and acrylic-terminated hyperbranched polyester (AHBP) were synthesized by using succinic anhydride and maleic anhydride as modification monomers. The characteristics of CHBP and AHBP were determined by IR and NMR, and the reaction degree was pursued by acid value titration.The effect of HBPE on the modification of epoxy resins (EP) cured with tetrahydrophthalic anhydride (THPA) was mainly discussed. The impact strength, thermal properties and morphologies of cured system were studied, and the toughening mechanism was proposed. The investigation showed that HBPE could improve the toughness significantly, especially HBPE of second generation. When the amount of HBPE (G-2) was 5 wt%, the value of impact strength was twice that of unmodified epoxy resin, and the thermal property was not affected at the same time. The smooth glassy fractured surface in unmodified epoxy resin indicated brittle fracture, and many volute cracks in modified epoxy resin illustrated tough fracture had taken place. The toughening mechanism of HBPE/EP/THPA system was that hyperbranched polymer bridged epoxy resin and stopped the cracks with nail and anchor.The effect of CHBP on the modification of epoxy resins cured with tetrahydrophthalic anhydride (THPA) was mainly discussed. The impact strength, thermal properties and morphologies of cured system with different ratios of CHBP.THPA (weight ratio) were studied. The investigation showed that CHBP could improve the toughness significantly. When the amount of CHBP was 10 wt%, the value of impact strength was twice that of unmodified epoxy resin, and the Tg was increased 5 °C. The rough fractured surface in modified epoxy resin illustrated tough fracture had taken place when the amount of CHBP used was less than 30 wt%, and CHBP could not act as toughening agent when its amount used was more than 30 wt%. The toughening mechanism of CHBP/EP/THPA system was that hyperbranched polymer bridged epoxy resin and stopped the cracks with nail and anchor.The effects of acrylic-terminated hyperbranched polyester (AHBP) used as reactive monomer on the modification of acrylic latex were mainly studied. The latexes were synthesized by semi-continuous emulsion polymerization of methyl methacrylate (MMA), butyl acrylate (BA), acrylic acid (MAA) and AHBP. The investigation showed that good latex was obtained when the amount of AHBP (G-2 or G-3) was between 2³ wt% (based on all monomers). The particle diameter of latex was between 105¹20nm, and polydispersity index (PDI) was between 0.07 and 0.2. The introduction of AHBP could improve the hardness of latex film, and the hardness increased from 2B to HB when the amount of AHBP used was 2⁴ wt%. The introduction of AHBP could also improve the stability of latex, and Ca2+ stability increased twice than before according to the "hair" function of AHBP.The latex based on miniemulsion polymerization of butyl acrylate (BA), methyl methacrylate (MMA), acrylic acid (AA) and AHBP was discussed. The investigation showed that good latex was obtained by using miniemulsion polymerization. The particle diameter of latex was between 70¹00nm, and PDI was between 0.16 and 0.23. The AHBP of higher generation (G-4 or G-5) could not be used in miniemulsion polymerization. The hardness of latex film increased from 2B to HB when the amount of AHBP (G-2) was 3 wt%.