Preparation and characterisation of polyurethane coatings based on polyester polyol

Abstract

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.

Effect of difunctional acids on the physicochemical, thermal, and mechanical properties of polyester polyol‐based polyurethane coatings

“…While 1,6‐AA can improve the flexibility, but it has an adverse effect on the outdoor durability because of the lack of hardness, thus 1,4‐CHDA was introduced to provide hardness and overcome this shortcoming. Likewise, Awasthi et al employed AA/isophthalic acid (IPA) to achieve a hardness/flexibility balance in coating films. Generally speaking, the sample PU‐6 has the better mechanical property than other samples.…”

Development of a flame retardant chemical for finishing of cotton, polyester, and CO/PET blends

“…DCDA was used owing to being a good blowing agent in intumescent FR system [41][42][43]. Hydroxyl-terminated polyesters are commonly used as modifiers in epoxy resins [44][45][46] and polyurethane-based coatings [47][48][49] due to effective molecular weight build-up by a chain extension reaction. They are the most common polyols, which are cross-linked through isocyanate groups [50,51].…”

Advancements in polyurethane coating: Synthesis and characterization of a novel hyper branched polyester polyol

“…The synthesis of polyester polyol for polyurethane coating has been reported in several studies [1][2][3][4][5][6][7] . Polyester resins are widely used due to their versatile applications such as elastomers [8][9] , coatings 10 , polyurethane foam [11][12] and sealants and adhesive 13 . The demand for polyurethane coatings has led to the importance of manufacturing polyester polyols [14][15][16] .…”