Flaky polyacrylic acid/aluminium composite particles prepared using in-situ polymerization Hongwei Zhu, Zhenxing Chen * , Yong Sheng, Thu Thuy Luong Thi School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, PR China article info Article history: Received 29 June 2009 Received in revised form 28 November 2009 Accepted 28 December 2009 Available online 6 January 2010 Keywords: Acrylic acid In-situ polymerization Coating Flaky aluminium particle Composite particle abstract In order to prevent corrosion of flaky aluminium particles, flaky polyacrylic acid/aluminium composite particles were prepared using in-situ polymerization. The influences of dosage of acrylic acid, ammonium persulphate, isopropanol and water, as well as reaction temperature and reaction time, on corrosion inhibition efficiency and gloss were investigated. Maximum corrosion inhibition efficiency was 99.7% and the gloss was 88.3 Gs. Using TGA, SEM, laser particle size analysis, FTIR and XPS, polyacrylic acid was found to be coated on the surface of clear aluminium particles. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Flaky aluminium pigments have been widely used as solvent- borne automotive coatings, printing inks, and roof coatings for many years [1]. From an environmental perspective, water-borne paints and inks are being developed to reduce the emission of organic solvents [2,3]. However, aluminium can react with water and form H 2 , resulting in loss of gloss as well as separation of the coating from substrates [4,5]. Much research has been carried out to inhibit such corrosion by surface modification of aluminium pigments. Nitro- and aminophenols were found to be effective inhibitors for aluminium pigments [6] as was a coating of aluminium pigments with SiO 2 via the solegel method using tetraethyl orthosilicate [7,8]. The anticorrosion property of aluminium pigments can be enhanced by the adsorption of corrosion inhibitors [9] as reported by Müller [10] in the case of styrene-maleic anhydride copolymers. Further- more, flake aluminium particles coated with Fe 2 O 3 or Cr 2 O 3 have been synthesized as colored aluminium pigment [11]. As a means of securing cost-effective, high corrosion inhibition efficiency, water-borne aluminium pigments, flaky polyacrylic acid/ aluminium (PAA/Al) composite particles were prepared using in- situ polymerization. 2. Experimental 2.1. Materials Clear aluminium particles were prepared through washing flaky solvent-borne aluminium pigment by acetone for 6 h and then drying under vacuum at 105  C for 6 h to remove organic compounds before encapsulation reaction and its average diameter (d 50 ) was 16.65 mm. Acrylic acid (99.5%), ammonium persulphate (>98%), isopropanol (99.7%) and hydrochloric acid (37%) were used without further purification. 2.2. Experimental process Clear aluminium particles (2 g), acrylic acid (0.1e0.4 g), ammonium persulphate (0.1e0.4 g), isopropanol (0.5e4 g) and distilled water (50e250 g) were mixed and poured into a reactor equipped with a condenser. The mixture was heated at 65e95  C for 0.5e2 h and then filtered and washed with water. The flaky polyacrylic acid/aluminium composite particles were dried under vacuum at 105  C for 6 h. 2.3. Characterization To evaluate corrosion inhibiting efficiency of PAA/Al composite particles, stability test was carried out, in which 0.5 g of composite particles and clear aluminium particles was dispersed in 0.1 M HCl * Corresponding author. Tel./fax: þ86 20 84113159. E-mail address: chenzx65@mail.sysu.edu.cn (Z. Chen). Contents lists available at ScienceDirect Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig 0143-7208/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.dyepig.2009.12.012 Dyes and Pigments 86 (2010) 155e160