PurposeThe purpose of this paper is to synthesise environment friendly UV curable polyurethane acrylate resins for various industrial applications and study the performance properties of the cured coating films applied over metal surfaces.Design/methodology/approachThe polyurethane acrylate resin was synthesised using polyester polyol (synthesised using ethylene glycol, adipic acid and 1,6 hexane diol), isophorone diisocynate (IPDI) and 2‐hydroxy ethyl methacrylate (HEMA). The different formulations were developed using various reactive diluents viz. monofunctional, difunctional, trifunctional and tetrafunctional (ethoxylated phenol monoacrylate, 1, 6 hexane diol di acrylate, dipropylene glycol di acrylate, trimethylol propane triacrylate, propoxylated trimethylol propane triacrylate, pentaerythrol triacrylate – PETA). These samples were cured under UV radiation. For effective curing, various compositions of oligomers, photoinitiator and reactive diluents were used. The mechanical, optical, rheological, chemical and stain resistance properties were evaluated.FindingsThe designed polyurethane acrylate gave good performance properties when used with reactive diluents having different functionality in different ratios for application over metal surfaces as protective coatings for various industrial applications. While using reactive diluents, the coating compositions showed significant enhancement of mechanical, physical and chemical resistance properties. Owing to different functionality of reactive diluents used, highly cross‐linked structures are formed, which lead to excellent mechanical and chemical properties. The optimum results were obtained with PETA as reactive diluent.Research limitations/implicationsThe polyurethane resin has been synthesised from polyester polyol (made up of ethylene glycol, adipic acid and 1, 6 hexane diol), IPDI, 2‐HEMA. Besides, this, it can be synthesised from some other polyester polyol or polyether polyol. In addition to this, some other isocyanates such as TDI, MDI, HDI, HMDI, etc. may be used.Practical implicationsThe study has provided a better solution for developing low volatile organic compound (VOC) products by using UV radiations, which can be cured within a minimum period of time and can save significant application curing time for the end‐users. The developed product is also an environmentally friendly product.Originality/valueMetallic surfaces are widely used in packaging industry in rigid and semi‐rigid forms. One of the prime requirements of the surface is an attractive printing on it. Conventionally used coating system on metallic surfaces are not holding or retaining their decorative effect/gloss level to a large extent. For this purpose, an overprint varnish is normally used which is mostly solvent based. This paper has been able to suggest very good formulations for printing of metallic surfaces for packaging and for overprinting in particular, which is radiation curable and environment friendly.

A series of polyester polyol resin was synthesized by using 1,4-cyclohexanedimethanol (1,4-CHDM) and three different diacids: 1,3-cyclohexanedicarboxylic acid (1,3-CHDA), isophthalic acid (IPA) and adipic acid (AA). The solubility and viscosity of the polyester polyols were determined by using methyl ethyl ketone (MEK). All the polyester polyols were crosslinked with hexamethylene diisocyanate (HDI) isocyanurate to form polyurethane coating films. These films were evaluated for their mechanical and chemical resistance properties. Studies on the film characteristics revealed that the polyurethane films based on cycloaliphatic diacid generally showed comparatively better performance properties than the polyurethane film based on aromatic and linear aliphatic diacids in general.

A copolymer of styrene and maleic anhydride was synthesized by free radical polymerization at 80°C using N,N‐dimethylformamide (DMF) as solvent and benzoylperoxide as initiator. The monomer feed ratio of styrene to maleic anhydride was varied in the range of 1 : 1 : to 3 : 1. The polymer yield was found to decrease with increase in styrene in the feed. The molecular weight of copolymers which were formed by taking styrene to maleic anhydride ratio of 1 : 1, 2 : 1, and 3 : 1, as determined by Ostwald Viscometery were about 1862, 2015, and 2276 respectively. The acid values of abovementioned three copolymers were found to be 480, 357, and 295, respectively. The typical viscosity values of 20% solids in ammonical solution of copolymers formed by taking feed ratios of Sty : MAn as 1 : 1 and 2 : 1 were 26 and 136 cp, respectively. For the feed ratio 3 : 1, a gel was formed. The synthesized copolymers were hydrolyzed by alkalis, namely, NaOH, KOH, and NH4OH. The dispersing ability of hydrolyzed styrene‐maleic anhydride (SMA) copolymers for dispersion of titanium dioxide was studied. The modified SMA copolymers were found to be effective dispersants for TiO2. Among the three alkalis studied, the Sodium salts of SMA were found to give better dispersion. The copolymer having a 1 : 1 feed ratio showed the best dispersing ability for TiO2 particles among the three ratios studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3194–3205, 2007

Hydroxyl-terminated polyesters are the most common polyols that are crosslinked through an isocyanate group. In this study, the polyester polyol resins were synthesized by using 1,4-cyclohexanedimethanol (1,4-CHDM) with the mixture of different diacids as 1,3-cyclohexanedicarboxylicacid (1,3-CHDA), 1,4-cyclohexanedicarboxylicacid (1,4-CHDA), isophthalic acid (IPA), adipic acid (AA), and azelaic acid (AZA). The solubility and viscosity of these polyester polyol resins were determined by using suitable solvent. All the polyester polyols were crosslinked with HDI isocyanurate and IPDI trimer to form polyurethane coating films. These films were evaluated for their mechanical, thermal, and chemical resistance properties. The studies on film characteristics reveal that the cycloaliphatic diacids afforded polyurethane with greater performance properties than that of aromatic and linear aliphatic diacids.

PurposeThe purpose of this paper is to describe how to synthesise polyurethane resins by using different polyester polyols and HDI isocyanurate. The polyester polyols were prepared by reacting single diol with different diacids. The effects of these polyester polyols on the performance properties of the coating films are studied.Design/methodology/approachA series of hydroxyl‐terminated polyester polyols were synthesised by using 1,4‐cyclohexanedimethanol (1,4‐CHDM) with different diacids such as 1,3‐cyclohexanedicarboxylic acid (1,3‐CHDA), 1,4‐CHDA, adipic acid (AA), azelaic acid (AZA), and isophthalic acid (IPA). The general properties including acid number, hydroxyl number average molecular weight, polydispersity index, and viscosity of these polyester polyols were evaluated. Different coating formulations were developed by using polyester polyols and HDI isocyanurate. These coatings were applied on sand blasted mild steel panels and glass panels and were cured in hot air oven. Various mechanical, thermal and chemical resistance properties of the coating films were evaluated.FindingsThe paper shows that, the polyurethane coatings have good resistance to water and other chemicals and can be used safely in exterior applications. In polyester polyols for polyurethane coating, CHDA showed a good balance in mechanical properties, which may be attributed to its unique cycloaliphatic structure and 1,4‐substitution. The polyester polyol based on aromatic diacids provided polyurethane coatings with maximum hardness and high Tg.Research limitations/implicationsThe polyurethane resins were prepared from polyester polyol (made up of cyclohexanedimethanol (CHDM) and CHDA, IPA, AA, and AZA). Besides, this, it can be synthesised from some other polyester polyols (having different acids and alcohols) or polyether polyols. In addition to this, some other isocyanates such as TDI, MDI, HMDI, etc. can also be used.Practical implicationsThe paper has provided a better solution for developing high solid polyurethane coatings for exterior applications due to presence of cycloaliphatic compounds.Originality/valueIn this paper, cyclohexyl dibasic acids have been used as the replacement for the aromatic dibasic acids. In aromatic dibasic acids, the phenyl ring readily absorbs UV‐light limiting the photo‐oxidative stability of the polyesters. So, these studies will help to develop high‐solid polyurethane coatings which could find numerous industrial applications in surface coatings.