Synthesis and evaluation of new hyperbranched alkyds for coatings

Progress in Organic Coatings 89 (2015) 252–259

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Synthesis and evaluation of new hyperbranched alkyds for coatings Nawal E. Ikladious a , Samia H. Mansour a,∗ , Jeannette N. Asaad a , Hassan S. Emira a , Michael Hilt b a

Department of Polymers and Pigments, National Research Center, 33 El Bohouth st. (former El Tahrir st.) Dokki, P.O. 12622, Giza, Egypt Fraunhofer Institute for Manufacturing Engineering and Automation IPA, Coating Systems and Painting Technology, Allmandring 37, 70569 Stuttgart, Germany b

a r t i c l e

i n f o

Article history: Received 4 April 2015 Received in revised form 11 August 2015 Accepted 10 September 2015 Keywords: Coatings Hyperbranched alkyds Oil fatty acids Rheological properties 1,3,5-tris (2-hydroxyethyl) cyanuric acid

a b s t r a c t Novel hyperbranched alkyd resins (HBAs) were synthesized by reacting the hydroxyl end-groups of the prepared hyperbranched polyesters, based on 1,3,5-tris(2-hydroxyethyl) cyanuric acid (THECA) as a trifunctional core, with different oil fatty acids, namely, linseed, soya and sunflower oil fatty acids. Resins of different compositions of HBAs were prepared by changing either the fatty acid or the generation of the hyperbranched polyester. Their molecular structures were identified using IR and 1 H and 13 C NMR spectroscopy. The thermal stability, glass transition temperatures and rheological properties were investigated. All of the alkyd resins exhibited initial decomposition temperature at values >300 ◦ C. The decreased Tg values of LG3, SG3 and SFG3 render them suitable for use as coatings that are applied at ambient temperature. All HBAs show Newtonian behaviour and the viscosity was ranging between 1.2 and 5.2 Pa s. Film properties of the prepared alkyd resins using different driers were determined and it has been found that all samples exhibited good adhesion, bending, impact, ductility, and high gloss, but show low hardness. © 2015 Elsevier B.V. All rights reserved.

1. Introduction The negative impacts of volatile organic compounds (VOCs) to both the atmosphere and the human health have resulted in increasing research activity focusing on the reduction of VOC levels in coatings and paints. Recently, Europe-wide legislation has placed an upper level of VOC in paint products of 300 g/L. This legislation has effectively eliminated many solvent-borne coatings from the market place and accelerated research work for developing eco-friendly coating formulations, i.e. increased demand for new air-drying solvent-borne coatings, to replace the previous generation of alkyd resin coating technologies [1,2]. Hyperbranched polymers are a class of polymeric materials belonging to the group of macromolecules having highly branched structures and a large number of end groups. The structure of these polymers has a great influence on their physical and chemical properties. Many commercially available chemicals can be used as the monomers in these systems, which should extend the availability and accessibility of hyperbranched polymers with various new end groups, architectures and properties. Macromolecular architectures including comb-like polymers have been synthesized by Cheng et al. [3] and used to produce

∗ Corresponding author. E-mail address: [email protected] (S.H. Mansour). http://dx.doi.org/10.1016/j.porgcoat.2015.09.008 0300-9440/© 2015 Elsevier B.V. All rights reserved.

low viscosity coatings. They reported that model paint formulations containing up to 40 wt% of the linoleyl-based comb polymers exhibited a dramatic reduction in viscosity (from 35 to 13 Poise at 25 ◦ C) with increasing quantities of polymer added. Because of their unique behaviour, when compared to linear polymers, hyperbranched polymers contain a greater number of surface functional groups and exhibit lower viscosities rendering them suitable for a wide range of applications, especially for low VOC eco-friendly coatings [4–6]. Reduced coating viscosity lowers the quantity of VOC thinners that are required, whereas curing rates can be increased as a consequence of the high number of surface functional groups present in hyperbranched polymers [7]. Recently, Cheng et al. [1,3,8] synthesized novel hyperbranched polymers featuring oxazoline linear units and studied their application in fast-drying solvent-borne coating formulations. They reported that paint formulations based either on the new hyperbranched polymers or on the blends of them with a commercial alkyd resin resulted in new coatings that cured more rapidly than the control formulation which incorporated only the commercial alkyd resin. Hyperbranched polyesters are among the most widely studied of the class of hyperbranched polymers [5,9–13]. Their rheological properties, combined with a broad range of possible functional end groups in high amounts, enable good flow, efficient cross-linking, excellent chemical resistance, and good mechanical properties for many different film-forming systems. They are

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being used in a variety of coatings applications, some examples are hydroxyl-functional polymers for coil coatings, powder coatings, and car refinish applications. In addition, hyperbranched polyesters found applications as flow and levelling agents in powder coatings for UV curable coatings and in blends with epoxy resins which enhance the mechanical properties of the cured films [14]. Hyperbranched polyesters modified with caprolactone and with methacrylic anhydride-functional chain ends have been used for the coating of wood and plastic substrates [4]. Alkyd resins are the most widely used polymers for paint and coatings applications [15]. They have good wetting, mechanical properties and durability. One of the factors affecting coating properties is the type of fatty acid or oil used in the alkyd production [16]. Meeting the requirements for high solids and low volatile organic compounds without compromising on the quality of the coating has always been a challenge for scientists. Hyperbranched alkyds provide a solution with their low viscosity at high molecular weights, meeting the stringent requirements of volatile organic contents [7,17–19]. Hyperbranched alkyd resins are hydroxylated hyperbranched polyester modified with fatty acids [15]. Highly branched chains have several advantages compared to the conventional alkyd resins with the same molecular weight, such as lower viscosity, higher gloss, better chemical resistance, and less chemical drying time [20]. Bat et al. [21] studied the synthesis of hyperbranched alkyd resins based on a hydroxylated hyperbranched polyester obtained from dipentaerythritol and 2,2-bis(hydroxymethyl) propanoic acid. The synthesized polyester was first reacted with castor oil fatty acids, then with different amounts of linseed oil fatty acids and benzoic acid. The authors reported that the hardness of the resins increased with fatty acids contents but did not change with benzoic acid content. Hyperbranched alkyds of different generations based on tall oil fatty acids have been synthesized and characterized by Murillo et al. [22,23]. All synthesized alkyd resins have shown excellent adhesion, flexibility, drying time, gloss, and chemical resistance. In a previous work [24] we synthesized and characterized some aromatic hyperbranched polyesters based on 1,3,5-tris(2hydroxyethyl) cyanuric acid as multifunctional core. The work was extended [25] and a detailed study on synthesis, identification and modification of some new aliphatic hyperbranched polyesters based on 1,3,5-tris(2-hydroxyethyl) cyanuric acid (THECA) as multifunctional core and 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) as an AB2 type monomer was performed. Modification and methacrylation [26] and evaluation [27] of these aliphatic hyperbranched polyesters as binding agents for heavy metals were also investigated. Our work with hyperbranched polyesters based on 1,3,5-tris (2hydroxy- ethyl) cyanuric acid (THECA) as a core is still in progress and represents the objective of this study. Synthesis of low viscosity air drying hyperbranched alkyd resins by modifying the aforementioned hyperbranched polyesters, with different oil fatty acids has been carried out. These prepared resins, which are of interest to the coating industry, will be investigated with respect to methods of preparation, their physical and mechanical properties and advantages over conventional counter parts. Such hyperbranched alkyd resins can be of great potential for different applications.

2. Experimental 2.1. Materials 2,2-Bis(hydroxymethyl) propionic acid (bis-MPA), 1,3,5-tris(2hydroxyethyl) cyanuric acid (THECA), and p-toluene sulfonic acid (PTSA) were purchased from Sigma–Aldrich, Germany. All driers

253

including Octa-Soligen 155, Borchers Dry 0133 and Borchers Dry 0411 HS were kindly provided as a gift by OMG Borchers GmbH OM Group, Schönebeck, Germany. The oil fatty acids were also kindly supplied as a gift by Oleon GmbH, Emmerich, Germany. All materials in this study were used as received without further purification. 2.2. Methods 2.2.1. Synthesis of hyperbranched polyesters (HBPs) A series of new aliphatic hyperbranched polyesters was synthesized by the polycondensation of stoichiometric amounts of the monomer bis-MPA, corresponding to each generation with 1 mol of THECA as a trifunctional core [25]. The monomer to core ratio was varied between 3 and 21. The polymerization reaction was carried out in bulk at a maximum temperature of 160 ◦ C. p-Toluene sulfonic acid (PTSA), 0.5 wt% based on bis-MPA monomer, was used as an acid catalyst in all reactions. To obtain several generations of growth, (G1–G3), the procedure was repeated with a stepwise addition of stoichiometric amounts of monomers to the core molecule. The yield of all obtained polymers was found to be above 97%. The first generation G1 was synthesized according to the following method. THECA (26.124 g, 0.1 mol), bis-MPA (40.239 g, 0.3 mol), (molar ratio 1:3), and a catalytic amount of PTSA (0.2 g) were placed in a three-necked flask equipped with argon inlet. The reaction vessel was evacuated for 10 min, flushed with argon, and then immersed in a preheated oil bath with magnetic stirrer at 160 ◦ C. The reaction mixture was left to react for 2 h under stream of argon. After that a vacuum was applied for another 1 h. The resulting product was collected and identified by 1 H and 13 C NMR. Yield: 59.6 g (98%); 1 H NMR (250 MHz, CDCl3 , ı): 1.01–1.16 (CH3 -bis-MPA), 3.44 (CH2 -OH), 3.82 (CH2 -N), 4.1 (CH2 -OR), 4.64 (OH-terminal), 4.94(OH-linear). 13 C NMR (62.5 MHz, CDCl3 , ı): 17.6 (CH3 ), 46.8–50.8 (quaternary C), 58.3–66.1 (CH2 ), 149.1 (N C O), 172–175 (C O). 2.2.2. Synthesis of hyperbranched alkyd resins (HBAs) Novel hyperbranched alkyd resins (HBAs) were synthesized by reacting the hydroxyl end-groups of the prepared hyperbranched polyesters with different oil fatty acids, namely, linseed, soya and sunflower oil fatty acids. The reaction was carried out in bulk at a maximum temperature of 220 ◦ C. PTSA, 0.5 wt% based on fatty acid, was used as an acid catalyst in all reactions. The reaction of the first generation (G1) of the hyperbranched polyester with linseed oil fatty acids (in molar ratio of 1:5) is presented as an example: Linseed oil fatty acids (41.1 g, 0.1476 mole), G1 (18.0 g, 0.03 mole) and a catalytic amount of PTSA (0.2055 g) were placed in a three necked flask, equipped with a condenser, thermometer and an argon inlet. The reaction vessel was evacuated for 10 min, flushed with argon, and then immersed in a preheated oil bath with magnetic stirrer at 180 ◦ C. The reaction mixture was further heated to 220 ± 5 ◦ C and maintained at this temperature until the acid value decreased to the desired one (7–17 mg KOH/g). A stream of argon was applied to continuously remove the water formed during the reaction. The acid value was monitored during the reaction and determined by end-group analysis of samples collected at different time intervals. Yield: 48.4 g (86%); 1 H NMR (250 MHz, CDCl3 , ı): 0.85–1.2 (CH3 fatty acid and -bis-MPA), 1.5–2.8 (CH2 and CH-fatty acid), 4.2 (CH2 OR), 3.82 (CH2 -N), 5.30 ( CH CH ). 13 C NMR (62.5 MHz, CDCl3 , ı): 14.3 (CH3 ), 22.5–31.9 (CH3 CH2 , CH3 (CH2 )2 and CH3 (CH2 )3 – methylene carbons), 34 (CH2 COOR), 128–130 ( C C ). In a similar manner, resins of different compositions of HBAs were prepared by changing either the fatty acid or the generation of the hyperbranched polyester. The yield of all obtained alkyd resins

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HO OH O

HO

OH O

O O

O

O

O

O O

HO

HO

O

O

O

O

OH

OH O

O

OH

O

O OH

HO

O

HO O

O HO

N

O O

O

O

N

N O

O

HO O

O O

O

O

O

O O

O HO

O

O OH

OH OH

OH

O O OH

HO

O

O

O

HO O

O

OH O

OH

+ Linseedoil fatty acids

CH3 CH3 CH3 CH3 O HO O O O O O O O O O O O O O O O O O O O O O O HO O OH O O OH H O O O O O OH O O O O N O O N N O O O O O O O O O O O O O O O O OH O O O O O HO O OH O O O O HO O O O O O O O O O O O

H3 C H3 C

CH3

CH3

CH3

H3 C H3 C

H3 C H3 C

H3 C

Scheme 1. Modification of hyperbranched polyester (G3) with the linseed oil fatty acids (LG3).

was found to be above 90%. The resulting products were identified by IR, 1 H and 13 C NMR. 2.2.3. Characterization Infrared (IR) spectra of the prepared hyperbranched alkyds were recorded on ATR-FTIR Perkin Elmer Spectrum One. The 1 H NMR (250 MHz) and 13 C NMR (62.5 MHz) spectra were recorded on a

Bruker 250 MHz NMR using CDCl3 as solvent. Differential scanning calorimetry (DSC) was performed on a Perkin-Elmer DSC-7, at a heating/cooling rate of 10 ◦ C/min under nitrogen atmosphere. The second heating scans were used for the glass-transition temperature (Tg) determination; Tg was defined as the halfway point of transition heat flow. Thermogravimetric analysis (TGA) was performed using a Pyris 1 TGA (Perkin Elmer, California, USA)

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instrument. The samples were heated up to 650 ◦ C under nitrogen atmosphere, at a programmed rate of 40 K/min. The rheological properties were determined using a cone-plate viscometer Paar UDS 200 from Paar Physica Messtechnik GmbH. 2.2.4. Film properties In order to analyze film properties, the resin samples (80 wt%) were mixed with 20 wt% of turpentine and toluene (1:1) and the desired amount of the drier. The content of driers (by wt%) in the formulated coatings was based on the resin content. The resulted mixtures were stirred to give homogeneous solutions and then stored overnight prior to their application either on glass or metal plates. The films were cast on the test panels with a 120 ␮m applicator. In order to accelerate curing, they were left in an oven at 90 ◦ C for 3 h followed by 2 days at room temperature. Hardness was determined using a pendulum hardness tester according to ASTM D 4366-14. Adhesion was measured using a cross-hatch cutter according to ASTM D 3359-2009. Cupping test was used to determine the ductility according to ISO 1520-2006. It consists of measuring the minimum depth at which the coating cracks and/or becomes detached from the substrate. Gloss measurements according to ASTM D 523-2008 were performed at incidence angle of 20◦ . Bending and impact resistance were determined according to ASTM D 522 and ASTM D 2794-2010 respectively. 3. Results and discussion Detailed description of the preparation and characterization of different generations (first to third generation, G1–G3) of the new aliphatic hyperbranched polyesters, based on the polycondensation of 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) as a monomer and 1,3,5-tris(2-hydroxyethyl) cyanuric acid (THECA) as a core is given elsewhere [25]. The number of hydroxyl endgroups calculated via 1 H NMR was 6, 11 and 17 for G1, G2 and G3, respectively. The modification of the hydroxyl end-groups of the prepared HBPs, to synthesize HBAs, was carried out via esterification with different oil fatty acids. The abbreviations LG3, SG3 and SFG3 denote the third generation modified with linseed, soya and sunflower oil fatty acids and their acid numbers were 15.2, 16.7 and 16.2 mg KOH/g, respectively. The abbreviations, LG1–LG3 correspond to the first–third generation of the hyperbranched polyester modified with linseed oil fatty acids. The acid number of LG2 and LG1 were 7.3 and 12.2 mg KOH/g respectively. The modification of the hydroxyl-terminated hyperbranched polyester, G3, is outlined in Scheme 1. 3.1. Structural characterization To elucidate the structural units in the prepared hyperbranched alkyds all samples were identified using IR, 1 H and 13 C NMR techniques. The IR spectra of all polymers (Fig. 1) were quite similar and showed the band characteristic of the stretching frequencies of the ester carbonyl group at 1739 cm−1 and the hydroxyl group at 3500 cm−1 , respectively. However, a decrease of the intensity of the OH band of the HBAs was observed indicating the esterification with the oil fatty acids. The bands at 2855, 2925, 1462 and 1375 cm−1 are assigned to symmetrical, asymmetrical, stretching and bending frequencies of the CH2 group, respectively. The appearance of a band at about 3010 cm−1 , attributed to the unconjugated cis-unsaturations due to fatty acids, strongly suggests the formation of the hyperbranched alkyd resins, whereas its complete disappearance in the spectrum of the LG3 dry film (Fig. 1) suggests the curing of the sample. 1 H and 13 C NMR spectra of the different samples shown in Figs. 2 and 3, exhibit well resolved signals and indicate that all

Fig. 1. The FTIR spectra of hyperbranched alkyd resins.

prepared HBAs have similar features. From the 1 H NMR spectra, it is possible to distinguish the CH CH protons of the fatty acid at 5.30 ppm. The CH2 -N signal of the core appears at 3.82 ppm. The intense signals around 4.2 ppm are due to the methylene groups in the vicinity of reacted hydroxyl groups CH2 -OR. The signals between 1.5 and 2.8 ppm are most probably due to aliphatic protons of CH2 and CH groups of the fatty acid. The signals at 1.2 and 0.85 ppm are the CH3 protons of bis-MPA and fatty acid residues, respectively. The presence of CH CH signals is an indication of the formation of the hyperbranched alkyd resins. In 13 C NMR spectra, the methyl groups appear at 14.3 ppm. The groups of the signals between 22.5 and 31.9 ppm are most probably due to methylene carbons (CH3 CH2 , CH3 (CH2 )2 and CH3 (CH2 )3 ). The signal at 34 ppm can be related to CH2 COOR.

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Fig. 2.

1

Fig. 3.

H NMR spectra of hyperbranched alkyd resins.

The signals, that can be assigned to the olefinic C C , are located in the region between 128 and 130 ppm. Results of 1 H and 13 C NMR reveal that the LG3 possessed the expected structure illustrated in Scheme 1. 3.2. Thermal properties of the hyperbranched alkyd resins TGA and DSC were employed to investigate the thermal properties of the hyperbranched alkyd resins (Figs. 4, 5 and Table 1). The TGA thermograms have almost similar degradation patterns which indicate that the molecular structure of all samples is similar, as well as the mechanism of degradation. All of the alkyd resins exhibited initial decomposition temperature at values >300 ◦ C which is far above the processing requirements for most conventional coating applications. In order to evaluate the effect of the type

13

C NMR spectra of hyperbranched alkyd resins.

Table 1 Thermal behaviour data of G3 modified with different oil fatty acids. Samples

T50 [◦ C]

Residue [%] at 520 ◦ C

Tg [◦ C]

LG3 SG3 SFG3 Cured LG3 film

458 454 462 428

1.38 2.56 0 11.44

−4.98 −30.75 −22.93 –

of oil fatty acids on the thermal stability of the prepared alkyds, the degradation temperature at 50% weight loss (T50 ), and the residues at 520 ◦ C of LG3, SG3, SFG3 and the cured LG3 film are summarized in Table 1. As can be deduced, the 50% weight loss of the SFG3 sample took place at 462 ◦ C whereas, LG3, SG3 and the cured LG3 weight losses displayed at 458, 454 and 428 ◦ C, respectively. The lower stability of the cured film can be related to some

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Fig. 4. TGA curves of LG1, LG2 and LG3.

Fig. 6. Viscosity of hyperbranched alkyd resins as a function of shear rate.

Fig. 5. TGA curves of LG3, SG3, SFG3 and the cured LG3 film.

intramolecular degradation reactions that occurred during the drying process. Stenberg et al. [28] reported that the increased concentration of radicals formed using a drier, increases the overall reaction rate and, to some extent, the possibility for chain scission. The reaction rates were influenced by both desired intermolecular cross-linking reactions building up the polymer matrix, and undesired intramolecular degradation reactions, leading to volatile emission of low molecular species as well as photon emission from the auto-oxidation process. It has also been observed that the degradation for all samples is practically completed at 520 ◦ C, except that of the cured LG3, this is attributed to its cross-linking structure. Moreover, the decreased Tg values of LG3, SG3 and SFG3 illustrated in Table 1 render these hyperbranched alkyd resins suitable for use as coatings that are applied at ambient temperature. 3.3. Rheological properties It is well known that the rheological behaviour of alkyd resin plays an important role in coating applications. Lower viscosity of the resin means lower volatile organic compounds and easier application and coating formation. The diagrams of viscosity as a function of shear rate and of time at constant shear rate (200 s−1 ) for the different prepared HBAs are presented in Figs. 6 and 7 respectively. It is quite evident that all HBAs show Newtonian behaviour. Such behaviour has also been observed by Murillo et al. [22] for other hyperbranched

Fig. 7. Viscosity of hyperbranched alkyd resins as a function of time at 200 s−1 shear rate.

alkyd resins. These authors reported that this Newtonian behaviour can be explained by the high packing of the material due to its low hydrodynamic volume and absence of entanglements. It was also found that LG3 exhibits a higher viscosity (3.55 Pa s) than LG1 (1.2 Pa s), which is logically a result of the increased molecular weight. The diagrams of viscosity against time at 200 s−1 shear rate (Fig. 7) indicate that all samples show high stability as a consequence of lack of entanglement or molecular interaction. It should be noted that the HBAs described here possess much lower viscosity ((1.2, 2.7, 3.55, 4.15 and 5.2 Pa s) for LG1, LG2, LG3, SFG3 and SG3 respectively) than those of the conventional high solid alkyd resin (26 Pa s) and commercial conventional resin (1000 Pa s) and are quite comparable to other reported hyperbranched resins (2.5–5 Pa s) [3,7,18,21]. 3.4. Film properties Film properties of the alkyd resins using different driers, namely 0.7 wt% and 2 wt% Octa-Soligen 155, 0.2 wt% Borchers Dry 0411 HS and 2 wt% Borchers Dry 0133, are depicted in Table 2. It is obvious

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Table 2 Film properties of hyperbranched alkyd resins using different driers. Properties

Dryers LG1

Adhesion Bending Ductility Hardness Impact Gloss 20◦

LG2

LG3

SG3

a

b

c

d

a

b

c

d

a

b

5B

5B

5B

5B

5B

5B

5B

5B

4B

5B

5.3 10 25 102

Pass 6.0 5.7 9 11 25 25 89 88

Pass 5.2 8 25 88

5.8 8 25 96

5.7 11 30 89

5.1 12 25 92

5.0 12 25 80

5.2 11 25 91

c

5B Pass 6.0 5.7 12 12 25 25 92 79

SFG3

d

a

b

c

d

a

b

5B

3B

5B

5B

5B

2B

5B

5.7 14 25 88

4.9 14 25 95

5.5 18 25 93

Pass 5.7 12 25 105

5.3 13 25 89

5.8 13 25 108

c

5B Pass 6.0 5.6 15 16 25 40 103 96

d 5B 5.3 15 25 94

Dryers: a – 0.7 wt% Octa-Soligen 155, b – 2 wt% Octa-Soligen 155, c – 0.2 wt% Borchers Dry 0411 HS, d – 2 wt% Borchers Dry 0133.

that all samples exhibit good adhesion, bending, impact and ductility, but show low hardness. It is important to note that the film properties of the samples did not change substantially when different dryers are used. Some wrinkles were observed for LG3 sample using 0.2 wt% Borchers Dry 0411 HS. This implies that the drier promotes slight fast rapid surface curing as a result of the high content of linolenic acid (about 52%) in linseed oil fatty acids, which creates diffusion barriers towards atmospheric oxygen and consequently lower hardness. Our results are in accordance with Stenberg et al. [28] who reported, that it is difficult to increase the drying rate above a certain limit for oils with high content of linolenic acid, without the risk of poor through drying and skin formation, generating wrinkles in the dried film. The results also indicate an inversely proportional relationship between linolenic acid content of the fatty acids and hardness of the samples. The gloss values of all samples measured at incidence angle of 20◦ were higher than 70, indicating that all HBRA resins exhibit high gloss. In view of the above results, it may be argued that these new HBAs, based on inexpensive and renewable materials, are good candidates for the production of eco-friendly industrial coatings. 4. Conclusions • Hyperbranched alkyds were prepared by modifying aliphatic hyperbranched polyesters, based on 1,3,5-tris(2-hydroxyethyl) cyanuric acid (THECA) as a core, with different oil fatty acids, namely, linseed, soya and sunflower oil fatty acids. • Their molecular structures were identified using IR and 1 H and 13 C NMR spectroscopy. • The TGA thermograms of all alkyd resin samples exhibited similar degradation patterns which indicate that the molecular structure of all samples is similar, as well as the mechanism of degradation. • The decreased Tg values of LG3, SG3 and SFG3 render these hyperbranched alkyd resins suitable for use as coatings that are applied at ambient temperature. • All prepared HBAs show Newtonian behaviour and possess much lower viscosity than those of the conventional high solid alkyd resins and commercial conventional resins. • All HBAs films exhibit good adhesion, bending, impact, ductility and high gloss values, but show low hardness. • It could be concluded that that these new HBAs, based on inexpensive and renewable materials, are good candidates for the production of eco-friendly industrial coatings. Acknowledgements The authors thank the National Research Center, German Academic Exchange Program (DAAD), Fraunhofer Institute for Manufacturing Engineering and Automation IPA, especially Dipl. Chem. H. Greisiger and Dr. K. Dirnberger, Institute of polymer chemistry (IPOC), Stuttgart, Germany, for the facilities and help provided.

References [1] G. Cheng, B.W. Greenland, C. Lampard, N. William, M.S. Bahra, W. Hayes, Synthesis of novel hyperbranched polymers featuring oxazoline linear units and their application in fast-drying solvent-borne coating formulations, J. Polym. Sci. Part A: Polym. Chem. 51 (2013) 3964–3974. [2] U. Konwar, N. Karak, T. Jana, Vegetable oil-based highly branched polyester modified epoxy based low VOC high solid industrial paint, J. Appl. Polym. Sci. 125 (S2) (2012) E2–E9. [3] G. Cheng, B.W. Greenland, C. Lampard, N. Williams, M.S. Barhra, W. Hayes, Lightly branched comb polyesters: application in fast drying solvent-borne coating formulations, J. React. Funct. Polym. 73 (2013) 619–623. [4] P.N. Mehta, Hyperbranched polymers: unique design tool for coatings, Surf. Coat. Int. Part B: Coat. Trans. 89 (2006) 333–342. [5] C. Gao, D. Yan, Hyperbranched polymers: from synthesis to applications, Prog. Polym. Sci. 29 (2004) 183–275. [6] B. Voit, D. Beyerlein, K.-J. Eichhorn, K. Grundke, D. Schmaljohann, T. Loontjens, Functional hyper-branched polyesters for application in blends, coatings, and thin films, Chem. Eng. Technol. 25 (2002) 704–707. [7] K. Manczyk, P. Szewczyk, Highly branched high solids alkyd resins, Prog. Org. Coat. 44 (2002) 99–109. [8] G. Cheng, B.W. Greenland, C. Lampard, N. Williams, M.S. Bahra, W. Hayes, Hyperbranched polymers containing oxazoline monomers and succinic anhydride: applications in fast drying, low solvent coating formulations, Prog. Org. Coat. 77 (2014) 1516–1522. [9] X. Hong, Q. Chen, Y. Zhang, G. Liu, Characterization of a hyperbranched polyol with long flexible chains and its application in cationic UV curing, J. Appl. Polym. Sci. 77 (2000) 1353–1356. [10] B.R. Frings, M. Wend, New Hyperbranched Polyesters for UV-Curing, DIC Technical Review, No. 9, 2003, pp. 43–51. [11] M. Johansson, M. Malmstrom, A. Jansson, A. Hults, A novel concept for low-temperature curing powder coatings based on hyperbranched polyesters, J. Coat. Technol. 72 (2000) 49–54. [12] J. Lange, E. Stenroos, M. Johansson, E. Malmström, Barrier coatings for flexible packaging based on hyperbranched resins, Polymer 42 (2001) 7403–7410. [13] K. Johansson, T. Bergman, M. Johansson, Hyperbranched aliphatic polyesters and reactive diluents in thermally cured coil coatings, ACS Appl. Mater. Interfaces 1 (2009) 211–217. [14] A. Hult, M. Johansson, E. Malmström, Hyperbranched polymers, Adv. Polym. Sci. 143 (1999) 1–34. [15] A.D. Hofland, Alkyd resins: from down and out to alive and kicking, Prog. Org. Coat. 73 (2012) 274–282. [16] V. Atimuttigul, S. Damrongsakkul, W. Tanthapanichakoon, Effect of oil type on the properties of short oil alkyd coatings materials, Korean J. Chem. Eng. 23 (2006) 672–677. [17] C. Karakaya, G. Gündüz, L. Aras, I.A. Mecido˘glu, Synthesis of oil based hyperbranched resins and their modification with melamine-formaldehyde resin, Prog. Org. Coat. 59 (2007) 265–327. [18] R.A.T.M. van Benthem, Novel hyperbranched resins for coating applications, Prog. Org. Coat. 40 (2000) 203–214. [19] M. Johansson, T. Glauser, A. Jansson, A. Hult, E. Malmström, H. Claesson, Design of coating resins by changing the macromolecular architecture: solid and liquid coating systems, Prog. Org. Coat. 48 (2003) 194–200. [20] J. Lindeboom, Air-drying high solids alkyd pants for decorative coatings, Prog. Org. Coat. 34 (1998) 147–151. [21] A. Bat, G. Gunduz, D. Kisakurek, I.M. Akhmedov, Synthesis and characterization of hyperbranched and air drying fatty acid based resins, Prog. Org. Coat. 55 (2006) 330–336. [22] E.A. Murillo, P.P. Vallejo, B.L. López, Synthesis and characterization of hyperbranched alkyd resins based on tall oil fatty acids, Prog. Org. Coat. 69 (2010) 235–240. [23] E.A. Murillo, P.P. Vallejo, B.L. López, Effect of tall oil fatty acids content on the properties of novel hyperbranched alkyd resins, J. Appl. Polym. Sci. 120 (2011) 3151–3158. [24] S.H. Mansour, N.N. Rozik, K. Dirnberger, N.E. Ikladious, Hyperbranched polyesters based on polycondensation of 1,3,5-tris(2-hydroxyethyl) cyanuric acid and 3,5-dihydroxybenzoic acid, J. Polym. Sci. Part A: Polym. Chem. 43 (2005) 3278–3288.

N.E. Ikladious et al. / Progress in Organic Coatings 89 (2015) 252–259 [25] N.E. Ikladious, S.H. Mansour, N.N. Rozik, K. Dirnberger, C.D. Eisenbach, New aliphatic hyperbranched polyester polyols based on 1,3,5-tris(2-hydroxyethyl) cyanuric acid as a core, J. Polym. Sci. Part A: Polym. Chem. 46 (2008) 5568–5579. [26] N.E. Ikladious, J.N. Asaad, N.N. Rozik, Modification and methacrylation of some new aliphatic hyperbranched polyester polyols based on 1,3,5-tris(2-hydroxyethyl) cyanuric acid (THECA) as a core, Des. Monomers Polym. 12 (2009) 469–481.

259

[27] J.N. Asaad, N.E. Ikladious, F. Awad, T. Müller, Evaluation of some new hyperbranched polyesters as binding agents for heavy metals, Can. J. Chem. Eng. 91 (2013) 257–263. [28] C. Stenberg, M. Svensson, M. Johansson, A study of the drying of linseed oils with different fatty acid patterns using RTIR-spectroscopy and chemiluminescence (CL), Ind. Crops Prod. 21 (2005) 263–272.