Synthesis and characterization of PANI/PU/PMMA latexes

Abstract

Polyester polyol was synthesized by condensation polymerization of 1,6- hexanediol, adipic acid, and isophthalic acid at 5:3:1 mole ratio. The hydroxyl value and acid value of polyester polyol were found to be 140 mg KOH/g and 3.7, respectively. Polyester polyol was then reacted with 2,4-toluene diisocyanate and dimethylolpropionic acid to form polyurethane prepolymer containing pendant carboxylic acid group. After neutralizing with triethylamine, it was dispersed in water and ethylene diamine was added to obtain aqueous polyurethane dispersion. Then, aqueous polyurethane dispersion was used as medium in the synthesis of PMMA to generate PU/PMMA latexes at different weight ratios; 2:1, 1:1, and 1:2. At the first two ratios, the same average particle size of PU/PMMA was 182 nm, while at the last ratio larger particle size of 206 nm was resulted. PU/PMMA latex (1:1) was selected for preparing as PANI/PU/PMMA latex. The formation of PANI/PU/PMMA latex occurred by polymerization of aniline hydrochloride using ammonium peroxydisulfate as an oxidant and poly (N-vinylpyrrolidone) (PVP) as stabilizer in PU/PMMA latex. The concentration of aniline hydrochloried and PVP was varied in order to obtain stable PANI/PU/PMMA latex. These latexes were characterized by Fourier transform infrared spectroscopy (FTIR), particle size analyzer, and transmission electron microscopy. Finally, the corrosion protection performance of PANI/PU/PMMA latex was studied by immersion the tested samples, which were steel pieces coated with latex, in NaCl solution (3.5 wt. %) for 30 days and then investigated by scanning electron microscopy. PANI/PU/PMMA film was also subjected to the same test and its FTIR spectrum was analyzed. The results indicated that PANI/PU/PMMA latex prepared from aniline hydrochloride at a concentration of 0.4 mol L[superscript-1] gave good corrosion resistance.