Development Of New Organic Wood Paints With Lignin As Additive
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Date
2011-07
Authors
Mustapha, Asniza
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
Lignin has been used as additive in preparation of the new organic paints. Soda lignin was extracted from black liquor of soda-AQ (anthraquinone) pulping of oil palm empty fruit bunch (EFB) fibers by 20% sulfuric acid precipitation. Two different types of azo pigment namely, phenyl-azo-2-naphthol and 4-Hydroxyphenylazo-3-N-(4-hydroxyphenyl)maleimide were synthesized by azo coupling reaction. Phenyl-azo-2-naphthol which was represented as aromatic azo pigment was produced from the reaction of diazonium salt (phenyldiazonium chloride) with pure 2-naphthol as the coupling agent whereas a new heterocyclic coupling agent namely, N-(4-hydroxy-phenyl)maleimide was synthesized by the reaction of maleic anhydride and p-aminophenol in the presence of di-phosphorus pentoxide (P2O5) as a catalyst. The coupling agent was then undergone a reaction with aromatic amine (p-aminophenol) to produce a new heterocyclic azo pigment, 4-Hydroxyphenylazo-3-N-(4-hydroxyphenyl)maleimide. Alkyd resin, as the binder was obtained from the reaction of soya oil, phthalic anhydride and glycerol by alcoholysis process. The characteristics and structural features of these compounds were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR), CHN elemental analysis, Nuclear Magnetic Resonance Spectroscopy (1H-NMR, 13C-NMR), Ultraviolet/Visible (UV/Vis) Spectroscopy, and single crystal X-ray analysis. A comparison study between lignin-based paint and non-lignin paint films on wood for both aromatic and heterocyclic system was then performed through paint testing
to examine their physical and mechanical performance. Testing prior to application includes viscosity, solid content, degree of dispersion, gloss, opacity and surface drying time whereas adhesion, SEM, contact angle, water absorption and weathering were determined after application of the paints on the substrates. Furthermore, the hardness and flexibility of the paints were also studied by pendulum hardness, pencil hardness and impact test, respectively. Results indicated that the degree of dispersion of all paint systems were suitable for use as an undercoat or primer. Studies on wooden test panels proved that the incorporation of lignin as additive led to significant improvements in the drying time, adhesion, as well as better hiding and obliteration. Notably, the presence of lignin in the paint has reduced the water uptake of wood substrates in total immersion tests and also possessed good resistance when exposed to outdoor. In addition, the lignin-based paints also showed superior results than that of lignin-free paints for both hardness and flexibility tests.
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Keywords
Lignin has been used as additive , preparation of the new organic paints