Contents lists available at ScienceDirect Progress in Organic Coatings journal homepage: www.elsevier.com/locate/porgcoat Improving self-healing performance of polyurethane coatings using PU microcapsules containing bulky-IPDI-BA and nano-clay Farhad Alizadegan a , S. Mojtaba Mirabedini a,b, ⁎ , Shahla Pazokifard a , Saba Goharshenas Moghadam a , Ramin Farnood b a Iran Polymer and Petrochemical Institute, P.O. Box 14965-115, Tehran, Iran b Department of Chemical Engineering and Applied Chemistry, University of Toronto, Canada ARTICLE INFO Keywords: Microencapsulation Self-healing Polyurethane Butyl acetate Nanoclay ABSTRACT In this study, polyurethane-based microcapsules filled with bulky isophorone diisocyanate, IPDI, were prepared via interfacial polymerization method in an oil-in-water emulsion. For this purpose, at first, 2,4-toluene diiso- cyanate, TDI, based pre-polymer was synthesized and used for the preparation of microcapsules shell compound. n-Butyl acetate solvent was used in the synthesis of both pre-polymer and microcapsules as a low toxic solvent. Various techniques and methods were used to characterized pre-polymer and microcapsules. Mechanical properties of microcapsule-embedded polyurethane, PU, coating was studied using tensile strength measurement under three different conditions (intact, scratched and healed). The standard salt spray test method was used to analyze the healing ability of microcapsules within the PU coatings. The crack healing properties of the PU coatings was defined using SEM micrographs. The results showed increasing healing efficiency by increasing microcapsule content. The best healing and corrosion performance was achieved for the coating with 1 wt % nanoclay and 5 or 10 wt % microcapsules as a result of barrier properties of intercalated and/or exfoliated clay platelets within the coating formulation. 1. Introduction Self-healing coatings are smart materials which can intrinsically repair damages such as nano- and micro-sized scratches and cracks, and improving coating lifetime and efficiency. Self-healing properties are usually achieved through either intrinsic or extrinsic mechanism. In intrinsic self-healing, the polymer matrix itself contains a latent func- tionality that triggers repairing damage via thermally reversible reac- tions, hydrogen bonding, ionomeric arrangements, or molecular diffu- sion and entanglement [1,2]. In extrinsic mechanism, healing agent materials are introduced or pre-embedded into a polymeric matrix, through different careers such as fibers [3,4], capillaries [5–7], or mi- crocapsules [8–11]. The healing agent is released from the careers into the damaged area and mends the crack via different mechanisms. The idea of using microcapsules containing reactive healing agent is a well- known approach to design self-healing coatings. Over the last decade, anticorrosion coatings containing microcapsules have been developed for the protection of metallic substrates from the corrosive environ- ments (i.e. oxygen, water, acids and gases) [12,13]. An early example of this technology is the microencapsulation of endo-dicyclopentadiene (endo-DCPD) as a healing agent in poly (urea-formaldehyde) shell used along with a dispersed Grubb’s catalyst [14]. In other work, hydroxyl end-functionalized polydimethylsiloxane (HOPDMS) was used as a healing agent via phase separation method in vinyl ester matrix while the di-n-butyltin dilaurate (DBTL) as catalyst was encapsulated in polyurethane microcapsules and embedded in the matrix [15]. How- ever, toxicity, high cost and sensitivity of catalysts have led researchers to work on catalyst free system, more eco-friendly and cheaper alter- natives. Jin et al. [16] introduced the first dual-capsule self-healing system with appropriate thermal stability of 91% healing efficiency by separate encapsulation of epoxy in polyurethane (PU) – poly(urea-for- maldehyde) (UF) double-shell wall and polyoxypropylenetriamine (POPTA) curing agent in poly(urea-formaldehyde) (UF) microcapsules. The encapsulation of air-drying healing agents such as linseed and Tung oils are among such examples reported in the literature [17]. Mir- abedini et al. [18] described the preparation of linseed oil-filled ethyl cellulose microcapsules and the improvement of interfacial interaction between microcapsules and a water-based acrylic matrix via micro- capsules surface treatment using three different trimethoxysilane. In this regard, Yang et al. [19] introduced the microencapsulation of https://doi.org/10.1016/j.porgcoat.2018.07.024 Received 22 May 2018; Received in revised form 7 July 2018; Accepted 17 July 2018 ⁎ Corresponding author at: Iran Polymer and Petrochemical Institute, P.O. Box 14965-115, Tehran, Iran. E-mail addresses: sm.mirabedini@ippi.ac.ir, m.mirabedini@utoronto.ca (S.M. Mirabedini). Progress in Organic Coatings 123 (2018) 350–361 0300-9440/ © 2018 Elsevier B.V. All rights reserved. T