Hyperbranched Soya Alkyd Nanocomposite: A Sustainable Feedstock

Subscriber access provided by Binghamton University | Libraries

Article

Hyperbranched Soya Alkyd Nanocomposite: A Sustainable feedstock based Anticorrosive nanocomposite Coatings Obaid Ur Rahman, Shahidul Islam Bhat, Haibin Yu, and Sharif Ahmad ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b01513 • Publication Date (Web): 19 Sep 2017 Downloaded from http://pubs.acs.org on September 19, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Sustainable Chemistry & Engineering is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Hyperbranched Soya Alkyd Nanocomposite: A Sustainable feedstock based Anticorrosive nanocomposite Coatings Obaid ur Rahman1,2 Shahidul Islam Bhat1 Haibin Yu2 and Sharif Ahmad*1 1. Material Research Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi, India, 110025. 2. Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Division of surface engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, P. R. China *Corresponding author, E-mail: [email protected] Abstract Globular structured oleo alkyds possess low viscosity, good fluidity and play important role in the generation of volatile organic compound (VOC) free paints and coatings. Soya oil (SO), an abundant, inexpensive, renewable, and sustainable is one of the examples of such oleo alkyd precursor that meets the requirement of green chemistry. Present work reports the synthesis of hyperbranched soya alkyd based nanocomposite coatings and their corrosion inhibition efficiency. Hyperbranched alkyd (HBA) was synthesized using SO, pentaerythritol and phthalic anhydride. The magnetite (Fe3O4) nanoparticles were dispersed via sonication in butylated melamine formaldehyde (BMF) modified HBA (HBA-BMF) to formulate the nanocomposite (HBA-BMF-Fe3O4) anticorrosive coatings. The ASTM methods were used to evaluate structural, morphological, physico-mechanical, thermal, electrochemical and anticorrosive properties of these coatings. The HBA has a globular structure with the good degree of branching (DOB = 0.69). HBA-BMF and HBA-BMF-Fe3O4 nanocomposite coatings showed good flexibility and physico-mechanical properties. The inclusion of Fe3O4 nanoparticles enhanced the load bearing capacity of nanocomposite coatings by dissipating the instantaneous energy in scratch and impact

test.

Electrochemical

corrosion

studies

revealed

ACS Paragon Plus Environment

that

the

HBA-BMF-Fe3O4


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 27

nanocomposite coatings exhibit superior corrosion resistance performance (impedance=107 Ω and corrosion rate 1.0×10-4 mils per year (mpy) than that of HBA-BMF and other similar reported coating systems. Keywords: Hyperbranched Alkyd, nanocomposite, corrosion, EIS Introduction Corrosion is a serious everlasting industrial problem and poses significant economic threats to the society and infrastructure. Due to the unwanted corrosion of goods, items, and machinery, industries are losing billions of dollars every year in the form of deterioration and maintenance.1 In fact, corrosion is a nightmare which is creating a huge burden on the economy of a country as a large amount of gross domestic product (GDP) is being spent by both the developing (3-5%) and under-developed countries (5%) to circumvent this culprit.1,2 This, along with other factors, prompted researchers to understand the actual mechanism and develop new methods

of

corrosion protection to enhance service life of metallic devices, machines, infrastructures etc.2 Several methods and techniques were used to combat corrosion such as cleansing of environment, alloying, composites2,3 corrosion inhibitors4,5 various types of metallic, inorganic and polymeric coatings.6–8 Among these, polymeric coatings emerged as a smarter way to protect underlying materials from corrosion by providing strong adhesion and good anticorrosive performances.9 Epoxy coatings have been commonly used to protect the underlying metallic substrate, W. Brostow et al. used commercial epoxy on mild steel and studied their curing and cross linking behavior in view of their corrosion inhibition efficiency.10 Generally, epoxies and other polymeric coating materials are based on non-renewable precursors from petrochemicals sources containing VOC, and thus against the principles and regulations of green chemistry. Green chemistry principals urge


Page 3 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


extensive efforts to develop materials from biodegradable renewable resource to replace toxic petrobased materials.3-4 Nowadays, different types of biobased materials are being used for this purpose such as chitosan and chitin,5 furans,6 polysaccharides,7 and vegetable oil (VO).8-11 VO based alkyds are of low cost, abundant and ease of application on various substrates,11,12 with excellent transparency and hard film forming ability.12 However, literature reveals that coatings based on alkyds failed to provide satisfactory performance in stringent and extreme corrosive environment.12-13 To surpass this obstacle and enhance the anticorrosive properties of alkyd coatings, different types of modifications have been reported. For example, nanocomposite synthesis by dispersing nanofillers such as ZrO2,14 TiO2,15 ZnO,16 Fe2O3 nanoparticles,17 and conducting polymers, etc.18 It has been observed that the nanocomposites exhibit good mechanical, thermal, ultra violet (UV) protection and anticorrosive properties and thus offers promising, smart and economical way to develop new generation anticorrosive materials.19 Particularly, Fe3O4 nanoparticles are emerged as a potential

candidate to be used as

anticorrosive nanofillers due to its unique electrical and magnetic properties.20 Electrons transfer between ferrous (Fe+2) to ferric (Fe+3)21 on octahedral sites enhances the interaction between nanocomposite coatings and substrate surface resulting well-adhered nanocomposite coatings with superior physico-mechanical and anticorrosive properties.11,22 During the literature survey, we found that hyperbranched polymers induced more superior properties in the coating materials.22–26 The Hyperbranched alkyds have interesting physicochemical properties and similar molecular weight to the linear counterpart. The hyperbranched polymer with low viscosity and a large number of functional groups enables good solubility, compatibility and enhances adhesion to the metal substrate which facilitates better anticorrosive performance.22,24 As we know nanoparticles inclusion improve thermal,



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

mechanical, UV and corrosion protection of alkyds. Hence, in view of this, the present work describes the formulation, characterization and anticorrosive performance of BMF cured HBA and Fe3O4 nanoparticles dispersed HBA-BMF-Fe3O4 nanocomposite coatings. The results of physicomechanical, electrochemical corrosion, and salt mist studies depicted that the HBABMF-Fe3O4 nanocomposite coatings possess superior properties than those of other oleopolymer coating systems. Materials and Methods Materials Butylated melamine formaldehyde (BMF) and soya oil (SO) [specific gravity (1.10) and mol. Wt. (2603)], were procured from Shankar dyes & chemicals (Delhi, India). Ethanol (C2H5OH), ferrous sulfate heptahydrate (FeSO4.7H2O) were obtained from Merck (India). Ethylene glycol [HOC2H4OH, mol. wt. 62.07 gmol-1, Density 1.11gcm-3] and ammonium hydroxide (NH4OH) from SD fine chemicals Pvt. Ltd (Mumbai, India). Hydrogen peroxide (H2O2 30 wt. %) was procured from Fisher Scientific (Mumbai, India). Pentaerythritol [C5H12O4, mol. Wt. 136.15 gmol-1], phthalic anhydride (C6H4(CO)2O, mol. Wt. 148.1 gmol-1) purchased from Sigma Aldrich, Germany. P-Toluenesulfonic acid (p-TSA) were obtained from Loba Chemie Pvt Ltd and all the chemicals were used as such without further purification. Preparation of Fe3O4 nanoparticles, Hyperbranched Alkyd (HBA) and HBA-BMF-Fe3O4 nanocomposite Fe3O4 nanoparticles were synthesized via polyol method using ethylene glycol as solvent as well as a stabilizer as reported earlier.20 Ferrous sulfate heptahydrate (3.00 g, 0.1008 mol) was used as a precursor in 50 mL ethylene glycol and stirred for 30 min. to prepare a homogeneous solution.


Page 4 of 27

Page 5 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


20 mL 0.5% aqueous solution of 30% H2O2 were added dropwise, pH of the reaction mixture was maintained around 13.0 by mixing 25% aqueous ammonia solution and the reaction was proceeded at 50 °C for 4 h in a 250 mL three necked flat bottomed flask under nitrogen atmosphere. Synthesis of hyperbranched alkyd HBA-BMF resin As shown in scheme 1a, monoglyceride were synthesised by transesterification reaction of soy oil with pentaerythritol in presence of catalyst sodium hydroxide (in 1:2:0.01 molar ratios, respectively) at 240 °C for 3 h in a three necked round-bottomed flask under continuous stirring on magnetic stirrer in silicon oil bath in nitrogen atmosphere. The monoglyceride formation was monitored by the solubility in methanol (by mixing one part of the reaction product in three parts of methanol) and recording the Fourier transfer infrared (FT-IR) spectra at regular intervals of time.12,

27

Monoglyceride and phthalic anhydride were reacted (in 1:0.5 wt. % ratio) to

synthesised hyperbranched alkyd at 190 °C with continuous stirring for 2 h and the reaction was stopped on achieving the anticipated acid value (30 mg/KOH) and reaction was further confirmed by FT-IR (Scheme 1b).13 The HBA was crosslinked in an acid catalyzed (p-TSA) environment by the butylated melamine formaldehyde (in 1:0.5 weight ratio) at 120 °C for 2h to formulate the HBA-BMF coating system (Scheme 1c). Preparation of HBA-BMF-Fe3O4 nanocomposite coatings HBA-BMF-Fe3O4 nanocomposite was prepared by the dispersion of 0.5, 1.5 and 2.5 wt. % of the Fe3O4 nanoparticles in 10.0 g of HBA-BMF resin to formulate HBA-BMF-Fe3O4-0.5, HBABMF-Fe3O4-1.5, and HBA-BMF-Fe3O4-2.5 nanocomposites, respectively via sonication for 30 min. (using ultrasonic wave sonicator with the frequency 40 kHz) at 30 .11, 28 Nanocomposite coating materials were obtained as a homogeneous ferrite suspended colloidal solution as per



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Scheme 2. HBA-BMF and nanocomposite coating materials were applied to commercially available carbon steel (CS) for physico-mechanical as well as corrosion analysis (PDP, EIS and salt mist test) as reported earlier.11, 15 Results and discussion The synthesis of SO based hyper branched alkyd was achieved by the A2+B3 popular approach in which PA used as an A2 type of monomer while monoglyceride as B3. SO was reacted with the pentaerythritol at 240 °C in the presence of the sodium hydroxide to produce monoglyceride (B3 type monomer) through transesterification mechanism. PA was reacted at 190 °C with monoglyceride to form HBA (Scheme S1).26,27 Further, BMF was used to cross linked HBA to obtain a highly cross-linked network of HBA-BMF via the condensation reaction,11 which further increases the DOB as shown in Scheme 1c. Later, Fe3O4 was dispersed in the highly crosslinked HBA-BMF matrix where nanoparticles occupied the interstitial sites, voids and thus resulted in the formation of the HBA-BMF-Fe3O4 nanocomposite (Scheme 2).28,29 FT-IR spectroscopy of HBA, HBA-BMF, and HBA-BMF-Fe3O4 was performed to confirm and identify the functional groups present in the final product as shown in Fig. 1. Fig. 1a shows the FT-IR spectra of HBA, stretching vibration band of the hydroxyl group (−OH) observed at around 3389 cm-1, while ester linkages (−COO) show the prominent peak at 1725 cm-1. Peak associated with the −C−H asymmetric and symmetric stretching vibrations of the −CH3 and −CH2 group of the fatty acid can be seen at 2915 cm-1 and 2857 cm-1, respectively. The FT-IR spectrum of the HBA-BMF is shown in Fig. 1b, the presence of a band at 1553 cm-1 is due to the plane stretching vibration of the s-triazine ring which confirmed the introduction of BMF in HBA.30 Further, the reaction between BMF and HBA was also confirmed by the additional peaks present in the range 1125-1072 cm-1 due to different modes of vibration of the ether linkages


Page 6 of 27

Page 7 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(−C−O−C−).13 The peak at 1464 cm-1 can be correlated to the asymmetric -C-H deformations of methyl and methylene groups. The FTIR spectrum of the HBA-BMF-Fe3O4 shown in Fig. 1c shows the similar peaks with lower intensity as in case of HBA-BMF, an additional prominent peak at 576.30 cm-1 confirm the addition of nano Fe3O4 in HBA-BMF. Intensity lowering of the functional groups of HBA-BMF in the FT-IR of nanocomposite is may be due to the physical interaction of Fe3O4 nanoparticles, which present with in the skeleton of the matrix of nanocomposite at interstitial and voids position.17 Fig. 2 show the protons nuclear magnetic resonance (1H NMR) of HBA and HBA-BMF. In Fig. 2a, fatty acid terminal methyl group show the peak around δ

0.9 ppm.31 The proton of −CH2−

groups of the fatty acid backbone show the peak between δ

1.20−1.59 ppm.30 The peak at δ =

5.4 ppm is attributed to the protons attached to the olefinic carbon atom (−CH CH−) of the fatty acid,28 this peak provides the evidence of the presence of the fatty acid chain in the HBA resin. The peak in the range δ

7.3−7.5 ppm associated with the aromatic protons attached to the

benzene ring of the phthalic anhydride of HBA. The peak δ = 4.2 ppm associated with the proton attached to the ester group (−CH2−O−C O) confirmed the formation of the HBA by the reaction between PA and monoglyceride. The unreacted hydroxyl proton of pentaerythritol shows the peak at δ

4.4 ppm. The sandwiched methylene group in between two olefinic carbon atoms of

the fatty acid chain show the peak at δ linkages show a peak at δ

2.8 ppm. The proton of methylene group next to ester

2.3 ppm and proton of fatty acid chain next to methylene group of

ester linkages show a peak at δ

1.7 ppm. Fig. 2b shows the 1H NMR of HBA-BMF which

shows the peak at δ = 3.2−3.8 ppm, which corresponds to proton attached to ether group (−OCH2),30 and other peaks are similar as in case of HBA. Presence of the prominent peak of the proton of −OCH2 confirmed the formation of HBA-BMF resin by etherification reaction of HBA



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

with BMF. In the

13

Page 8 of 27

C NMR spectrum of HBA, carbonyl carbon atom of ester group present in

the polymeric skeleton show the peaks at δ 170 ppm (Fig. S2). Carbon Present in the aromatic ring of phthalic anhydride show the peak at δ 125−135 ppm.13, 32 Moreover; carbon attached to the oxygen atom directly shows the peak in the region of δ

30−70 ppm. The peaks at δ

0−35

ppm correspond to methyl and methylene carbon, the unsaturated carbon atom of fatty acid alkyl chain in the HBA show the peak at δ

127 ppm. The 13C NMR spectra of HBA-BMF show the

similar peaks as HBA with two additional peaks around δ

180 ppm and δ

90 ppm attributed

to the carbon atoms of the symmetrical s-triazine ring and carbon atom sandwiched between the oxygen of the ether group and the nitrogen of the BMF (−OCH2−N), respectively as shown in Fig. S3, providing an evidence for the reaction of BMF with HBA to form crosslinked HBABMF matrix.11 DOB was also determined with the help of the below given equation.22,26

DOB

0.69

(1)

The value of DOB confirms the hyper branching of the alkyd resin with DOB values equal to 0.69 and is considered to be polydisperse in nature,33 which leads to the introduction of branching with in the backbone of the alkyd resin resulting in the formation of HBA resin (scheme S1).34 Fig. 3 shows the morphological study HBA-BMF and HBA-BMF- Fe3O4 nanocomposite. Fe3O4 dispersion and its polydisperse nature were studied by the transmission electron microscopy (TEM) and it was found that Fe3O4 nanoparticles were uniformly dispersed in HBA-BMF matrix (Fig. 3 a). The black circle represents uniform dispersion of Fe3O4 nanoparticles ( 20–50 nm ) in HBA-BMF matrix (gray in color),11 and no agglomeration of Fe3O4 nanoparticles was


Page 9 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


observed.20 Fig 3 b and c show the SEM micrograph of HBA-BMF and HBA-BMF- Fe3O4 nanocomposite coatings respectively. From the scanning electron microscopy (SEM) analysis it was clear that there is no phase separation and both the coatings well-adhered to the metal substrate. Fig. 4 show the thermogravimetric analysis (TGA) thermograms of HBA, HBA-BMF, and HBABMF-Fe3O4 nanocomposite coatings and derivative thermogravimetric (DTG) thermograms are given in supporting information as Fig. S6. The trapped solvent molecule were evaporated in the temperature range 180-200

and causes 5 wt. % loss. In the first thermal degradation step, 30

wt. % weight loss occurs due to de-crosslinking of HBA-BMF around 250-350 °C. HBA-BMF show second thermal degradation step around 450 °C and show the weight loss of 80 wt. %. In this thermal decomposition process, functional groups such as ester, ether and melamine ring decompose showing major weight loss.13 After Fe3O4 nanoparticle dispersion, there is an increase in thermal stability and HBA-BMF-Fe3O4 nanocomposite show the second weight loss around 490 °C.11 In case of HBA-BMF-Fe3O4 coatings, initially there is lowering in thermal stability up to 366 °C due to the to the chain scission of HBA-BMF as reported by H.R. Ong et al.35 This behaviour may be due to the fact that polymers have much higher linear coefficient of thermal expansion than the metal oxides, therefore most of the heat absorbed by the HBA-BMF is used in increasing interatomic distance rather than increasing the temperature of the HBABMF. After 400 °C HBA-BMF-Fe3O4 show higher thermal stability than HBA and HBA-BMF. Further, at 750 °C 90% weight loss was observed in the case of the HBA-BMF coatings while higher residue remained for HBA-BMF-Fe3O4, confirmed the incorporation of thermally stable Fe3O4 nanoparticles in HBA-BMFmatrix.36 The improved thermal stability of HBA-BMF-Fe3O4 can also be attributed to the electrostatic interaction between the s-triazine ring of the polymer



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 27

matrix and Fe3O4 nanoparticles result in well dispersed uniform stable nanocomposite coatings. 16, 37

The glass transition temperature (Tg) for HBA, HBA-BMF, and HBA-BMF-Fe3O4 were in the range of 90-100 °C, 120-130 °C , 140-150 °C, respectively (Fig. S4). The higher Tg value of HBA-BMF as compare to HBA is due to the cross linked s-triazine ring which restricted the mobility of polymer. The HBA-BMF-Fe3O4 show the highest Tg value because of the uniform dispersion of polar Fe3O4 nanoparticles at interstitial and voids position of HBA-BMF crosslinked matrix which restrict its mobility and consequently resulted in high Tg value.11, 15, 38 Physico-mechanical behaviour of HBA-BMF and HBA-BMF-Fe3O4 nanocomposite coatings were studied and tabulated in Table S1. With the loading of Fe3O4 nanoparticles in HBA-BMF, there is a decrease in drying time behaviour (Table S1). HBA-BMF show refractive index (RI) value 1.48, which is well in accordance to the other reported hyper-branched polymer.39 On inclusion of the Fe3O4 nanoparticles, slight decrease in RI and gloss values were observed because of the dark colour and opaque nature of the Fe3O4 nanoparticles.11 On the other hand, the scratch hardness test (SHT) values increases from HBA-BMF to HBA-BMF-Fe3O4-0.5 and show the highest value for HBA-BMF-Fe3O4-2.5 (Table S1). The Fe3O4 nanoparticles fill the voids and provide electrostatic interaction with the matrix which resulted in high scratch hardness values for the nanocomposite coatings with satisfactory performance.40 From the optical images of the scratched surface of the coatings (Fig. 5) it was found that the coatings show strong adhesion and good plastic deformation which bear the weight stress during the SHT, large number of functional group in HBA and uniform Fe3O4 nanoparticles dispersion responsible for enhancement.41 The presence the Fe3O4 nanoparticles improve the impact resistance of the HBABMF-Fe3O4 coatings providing crack healing property by restricts the chain mobility of the


Page 11 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


nanocomposite coatings.42 Further, the adhesion of these coatings was tested by cross-hatch adhesion test and it was found that after the test no square peel out with the adhesion tap which revealed good adhesion of coatings with the metal substrate. All the coatings pass the bend test revealed that the coatings were flexible, as no damage or fracture was scrutinized Fig. 8b, due to flexible fatty acid chain acting as an internal plasticizer.43,44 Contact angles (CA) of these coatings were also measured to check the hydrophobic behavior of these coatings. Coatings with CA>90° are considered to have the hydrophobic surface which repels the corrosive ion to penetrate into the coatings. CA for HBA-BMF was found 95° (Fig. S5 e), and it is expected to increase after Fe3O4 nanoparticles dispersion as reported earlier.11,15 The potentiodynamic polarization (PDP) study for uncoated, HBA-BMF and HBA-BMF-Fe3O4 coated CS in 3.5 wt % NaCl at room temperature were performed as shown in Fig. 6 and tabulated in Table 1. Tafel parameters such as corrosion potential (Ecorr), corrosion current density (Icorr) corrosion rate and polarisation resistance (Rp) of coated and uncoated specimens were obtained by Tafel extrapolation method using the software Nova 1.8 (Table 1). The promising anticorrosive coatings generally exhibit lower Icorr and higher Ecorr values leading to the fairly low corrosion rates.33 The HBA-BMF-Fe3O4 coatings showed higher Ecorr values and lower Icorr values with respect to HBA-BMF coatings Ecorr (-0.811V) and Icorr (2.67× 10-7 Acm-2) values, while HBA-BMF has higher values as compared to the uncoated CS (Ecorr =-0.853V and Icorr=9.18× 10-5 Acm-2). The decrease in Icorr values of HBA-BMF-Fe3O4 coatings can be correlated to the presence of Fe3O4 nanoparticles which acts as a protective barrier layer which reduces corrosive ion interaction with the metal substrate.34 The corrosion inhibition resistance performance of coated sample has been resulted due to the formation of the well adhered film to the CS substrate. The different polar functional group such as ether and ester linkages present in



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 27

the HBA-BMF facilitate the good adhesion as discussed above in the SHT and cross-hatch adhesion test.45, 46 Well adhered oil based hydrophobic coatings further enhance the anticorrosive behaviour by preventing the corrosive ions penetration into the coatings.11 Fe3O4 nanoparticles dispersed nanocomposite coatings form a protective barrier layer which enhances the anticorrosive performance by obviating the penetration of the corrosive ions at the coatings-metal interface. Further, nanocomposite coatings show superior anticorrosive behaviour as evident from the Tafel parameters, showing higher Ecorr and Rp values, and lower Icorr and corrosion rate values (Table 1). Superior corrosion protection of HBA-BMF-Fe3O4 coatings governed by the uniform dispersion of Fe3O4 nanoparticles which provide torturous path and barrier to corrosive ion by filling coating artefacts at coating-metal interface. The electrochemical impedance spectroscopy (EIS) was applied to study protection behaviour and the influence of Fe3O4 nanoparticles loading in nanocomposite coatings. The impedance of the coated samples directly represent the corrosion protection behaviour, and in the Nyquist plots, impedance is directly proportional to the capacitive loop diameter of charge transfer resistance (Rct) at high frequency. Coatings with the larger diameter will show higher impedance hence better corrosion protection, The HBA-BMF-Fe3O4 nanocomposite coatings better corrosion protection ability as it is clearly visible from the diameter of the nanocomposite coatings in the Nyquist plot in comparison to HBA-BMF coatings as shown in Fig. S5. High impedance values at the lowest frequency (|Z|0.01Hz) is characteristics of good polymeric coating which protects metal substrate in the stringent corrosive environment.15 In the case of the nanocomposite coatings impedance values were found many fold (2-3) higher (Fig. 7 b-d) than those of virgin HBA-BMF (105 Ω) coatings (Fig. 7 a). The nanocomposite coatings show stable corrosion protection with the single time constant for a longer time period (seven days) providing


Page 13 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


evidence that there is no corrosion reaction is started and underlying material and are well protected. From the EIS result, it was revealed that the HBA-BMF-Fe3O4 nanocomposites coatings provide the superior corrosion inhibition as compared to the HBA-BMF coatings, due to the presence of Fe3O4 nanoparticles in HBA-BMF matrix. Fe3O4 nanoparticles act as a strong barrier and provide a torturous path to the corrosive ions which cause a delay in the corrosion initiation and resulted in the high impedance and Rp values of nanocomposite coatings. The HBA-BMF-Fe3O4-2.5 shows the best anticorrosive performance with no sign of corrosive ion diffusion into the coating material during the exposure of aggressive corrosive environment (3.5 wt. % NaCl solution), which is clearly visible by the higher impedance value (≈107 Ω) at lowest frequency and results were in accordance with the polarisation studies. To further confirm the corrosion inhibition performance, HBA-BMF and HBA-BMF-Fe3O4 nanocomposite coated samples were exposed to the salt mist test in the 5.0 wt. % NaCl solution under 90% humid environment for 240 h. The HBA-BMF coated samples show the sign of corrosion (Fig. 8 a) which may be due to penetration of corrosive ions. However, no sign of corrosion initiation was observed on nanocomposite coated surface except slight deposition of salt ions (Fig. 8b). Salt mist test also shows the similar corrosion protection as discussed above due to the uniformly dispersed Fe3O4 nanoparticles which protect the underlying metal substrate from the corrosive ions attack. The literature revealed that among various oil based polymer coatings, hyperbranched nanocomposite coatings with 2.5 wt. % Fe3O4 nanoparticles loading have superior corrosion protective performance, with high potential in the field of corrosion protection and have a good scope for their commercialization.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 27

From the physicomechanical, PDP, EIS, salt mist studies it is clear that the HBA-BMF-Fe3O4 nanocomposite provides good corrosion protection to the beneath CS substrate. The corrosion protection to the substrate governs by a large number of the polar group present in the hyperbranched polymer which enhances the adhesion by strong electrostatic interaction and formed the uniform anticorrosive coating. The HBA-BMF act as a hydrophobic surface which inhibits the penetration of corrosive ions into the coating and protects the substrate. Moreover, the Fe3O4 nanoparticles fill the voids and cavity of HBA-BMF matrix and enhance the corrosion protection by acting as a strong barrier, which provides a torturous path to corrosive ion and delays the corrosion initiation at the coating-metal interface. Hence, the HBA-BMF-Fe3O4 nanocomposite coatings show good corrosion-protection efficiency and protect the under laying CS substrate for the long period in sewer corrosive environment. Concluding remarks The HBA and HBA-BMF matrix was developed via green route using soya oil monoglyceride as the precursor. The hyperbranched structure of HBA was confirmed by 0.69 degrees of branching value, which was cross linked with BMF. The synthesized polymer matrix was further modified by the dispersion of various percentages of Fe3O4 nanoparticles resulting in the formation of nanocomposites. The nanocomposite coatings were tough, mechanically robust and yielded outstanding results as corrosion protective coatings. The results of these studies are well in agreement with the values derived from corrosion studies like PDP, EIS and salt spray test. The comparison of the present system with the earlier reported systems reveals that the present system can have a potential scope for its application as low cost, eco-friendly and VOC free coatings system. ASSOCIATED CONTENT


Page 15 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Supporting Information The Supporting Information is available free of charge on the ACS Publications website and it include characterization section, chemical structure of HBA, electrical circuit used in EIS,

13

C

NMR of HBA and HBA-BMF, Nyquist plot, DSC and DTG thermograms of HBA, HBA-BMF and HBA-BMF-Fe3O4 nanocomposite coatings and table of Physico-mechanical properties of HBA-BMF and HBA-BMF- Fe3O4 coatings. Author Information Corresponding Author Email: [email protected], Tel no. +91 11 26827508, Fax: +91 11 26840229 Notes (i) Obaid Ur Rahman currently working at Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Surface Department, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, P. R. China. (ii) The authors declare no competing financial interest. Acknowledgements One of the authors (i) (Obaid ur Rahman) is thankful to Chinese academy of science (CAS) for financial support in the form of CAS-PIFI post-doctoral research fellowship (UCAS: 20161963 dated: 4th January 2016) and Shahidul Islam Bhat is thankful to university grants commission (UGC) New Delhi, India for financial support. References 1. Jacobson, G. A., NACE International’s IMPACT Study Breaks New Ground in Corrosion Management Research and Practice. The Bridge 2016, 46. 2. Stewart, M. G.; Wang, X.; Nguyen, M. N., Climate change adaptation for corrosion control of concrete infrastructure. Struct. Saf. 2012, 35, 29-39, DOI: 10.1016/j.strusafe.2011.10.002. 3. Delidovich, I.; Hausoul, P. J.; Deng, L.; Pfützenreuter, R.; Rose, M.; Palkovits, R., Alternative Monomers Based on Lignocellulose and Their Use for Polymer Production. Chem. Rev. 2016, 116,1540– 1599, DOI: 10.1021/acs.chemrev.5b00354



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

4. Perlack, R. D.; Wright, L. L.; Turhollow, A. F.; Graham, R. L.; Stokes, B. J.; Erbach, D. C. Biomass as feedstock for a bioenergy and bioproducts industry: the technical feasibility of a billion-ton annual supply; DTIC Document: 2005. 5. Rinaudo, M., Chitin and chitosan: properties and applications. Prog. Polym. Sci. 2006, 31, 603632, DOI: 10.1016/j.progpolymsci.2006.06.001. 6. Mahmood, N.; Yuan, Z.; Schmidt, J.; Xu, C. C., Depolymerization of lignins and their applications for the preparation of polyols and rigid polyurethane foams: A review. Renewable Sustainable Energy Rev. 2016, 60, 317-329, DOI: 10.1016/j.rser.2016.01.037. 7. Gandini, A.; Lacerda, T. M.; Carvalho, A. J.; Trovatti, E., Progress of Polymers from Renewable Resources: Furans, Vegetable Oils, and Polysaccharides. Chem. Rev. 2016, 116, 1637–1669, DOI: 10.1021/acs.chemrev.5b00264. 8. Yeganeh, H.; Hojati-Talemi, P., Preparation and properties of novel biodegradable polyurethane networks based on castor oil and poly (ethylene glycol). Polym. Degrad. Stab. 2007, 92, 480-489, DOI: 10.1016/j.polymdegradstab.2006.10.011 9. Surface Behavior and Tribology. In Materials: Introduction and Applications, First ed.; Lobland, W. B. a. H. E. H., Ed. WILEY: October 2016, ©2017; Vol. 1, pp 391-426. 10. Brostow, W.; Dutta, M.; Rusek, P., Modified epoxy coatings on mild steel: tribology and surface energy. Eur. Polym. J. 2010, 46, 2181-2189, DOI: 10.1016/j.eurpolymj.2010.08.006. 11. Rahman, O. u.; Ahmad, S., Physico-mechanical and electrochemical corrosion behavior of soy alkyd/Fe3O4 nanocomposite coatings. RSC Adv.2014, 4 , 14936-14947, DOI: 10.1039/C3RA48068B. 12. Pathan, S.; Ahmad, S., Synergistic effects of linseed oil based waterborne alkyd and 3isocynatopropyl triethoxysilane: Highly Transparent, Mechanically robust, thermally stable, hydrophobic, anticorrosive coatings. ACS Sustainable Chem. Eng. 2016, 4, 3062-3075, DOI: 10.1021/acssuschemeng.6b00024. 13. Pathan, S.; Ahmad, S., s-Triazine ring modified waterborne alkyd: Synthesis, characterization, antibacterial and electrochemical corrosion studies. ACS Sustainable Chem. Eng. 2013, 1, 1246–1257, DOI: 10.1021/sc4001077. 14. Behzadnasab, M.; Mirabedini, S.; Kabiri, K.; Jamali, S., Corrosion performance of epoxy coatings containing silane treated ZrO 2 nanoparticles on mild steel in 3.5% NaCl solution. Corros. Sci. 2011, 53, 89-98, DOI: 10.1016/j.corsci.2010.09.026. 15. Rahman, O. u.; Ahmad, S., Soy polyester urethane/TiO2 and Ce-TiO2 nanocomposites: preparation, characterization and evaluation of electrochemical corrosion resistance performance. RSC Adv. 2016, 6 , 10584-10596, DOI: 10.1039/C5RA23928A. 16. Dhoke, S. K.; Bhandari, R.; Khanna, A., Effect of nano-ZnO addition on the silicone-modified alkyd-based waterborne coatings on its mechanical and heat-resistance properties. Prog. Org. Coat. 2009, 64, 39-46, DOI: 10.1016/j.porgcoat.2008.07.007. 17. Dhoke, S. K.; Khanna, A., Effect of nano-Fe< sub> 2 O< sub> 3 particles on the corrosion behavior of alkyd based waterborne coatings. Corros. Sci. 2009, 51 , 6-20, DOI:10.1016/j.corsci.2008.09.028. 18. Alam, J.; Riaz, U.; Ashraf, S.; Ahmad, S., Corrosion-protective performance of nano polyaniline/ferrite dispersed alkyd coatings. J. Coat. Technol. Res. 2008, 5 , 123-128, DOI: 10.1007/s11998-007-9058-4. 19. Riaz, U.; Nwaoha, C.; Ashraf, S., Recent advances in corrosion protective composite coatings based on conducting polymers and natural resource derived polymers. Prog. Org. Coat. 2014, 77, 743756, DOI: 10.1016/j.porgcoat.2014.01.004. 20. Rahman, O. u.; Mohapatra, S. C.; Ahmad, S., Fe3O4 inverse spinal super paramagnetic nanoparticles. Mater. Chem. Phys. 2012, 132, 196-202, DOI: 10.1016/j.matchemphys.2011.11.032. 21. Rahman, O. u.; Kashif, M.; Ahmad, S., Nanoferrite dispersed waterborne epoxy-acrylate: Anticorrosive nanocomposite coatings. Prog. Org. Coat. 2015, 80, 77-86, DOI: 10.1016/j.porgcoat.2014.11.023.


Page 16 of 27

Page 17 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


22. Murillo, E. A.; Lopez, B. L.; Brostow, W., Synthesis and characterization of novel alkyd–silicone hyperbranched nanoresins with high solid contents. Prog. Org. Coat. 2011, 72 , 292-298, DOI: 10.1016/j.porgcoat.2011.04.019. 23. Hult, A.; Johansson, M.; Malmström, E., Hyperbranched polymers. In Branched Polymers II, Springer: 1999; pp 1-34. 24. Chattopadhyay, D. K.; Raju, K., Structural engineering of polyurethane coatings for high performance applications. Prog. Polym. Sci. 2007, 32, 352-418, DOI: 10.1016/j.progpolymsci.2006.05.003. 25. Karak, N.; Roy, B.; Voit, B., s‐Triazine‐based hyperbranched polyethers: Synthesis, characterization, and properties. J. Polym. Sci. A Polym. Chem. 2010, 48, 3994-4004, DOI: 10.1002/pola.24183. 26. Karak, N., Vegetable oil-based polymers: properties, processing and applications. 1st ed.; Elsevier: 2012. 27. Pathan, S.; Ahmad, S., Synthesis, characterization and the effect of the s-triazine ring on physicomechanical and electrochemical corrosion resistance performance of waterborne castor oil alkyd. J. Mater. Chem. A 2013, 1 , 14227-14238, DOI: 10.1039/C3TA13126B. 28. Ahmad, S.; Ashraf, S. M.; Kumar, G. S.; Hasnat, A.; Sharmin, E., Studies on epoxy-butylated melamine formaldehyde-based anticorrosive coatings from a sustainable resource. Prog. Org. Coat. 2006, 56 , 207-213, DOI: 10.1016/j.porgcoat.2006.05.002. 29. Hahn, F. J., ALKYD-MELAMINE RESIN COATING. Google Patents: 1950. 30. Ahmad, S.; Ashraf, S.; Sharmin, E.; Nazir, M.; Alam, M., Studies on new polyetheramidebutylated melamine formaldehyde based anticorrosive coatings from a sustainable resource. Prog. Org. Coat. 2005, 52 , 85-91, DOI: 10.1016/j.porgcoat.2004.09.002. 31. Yudovin-Farber, I.; Beyth, N.; Weiss, E. I.; Domb, A. J., Antibacterial effect of composite resins containing quaternary ammonium polyethyleneimine nanoparticles. J. Nanopart. Res. 2010, 12 , 591-603, DOI: 10.1007/s11051-009-9628-8. 32. Kenawy, E.-R.; Worley, S. D.; Broughton, R., The Chemistry and Applications of Antimicrobial Polymers: A State-of-the-Art Review. Biomacromolecules 2007, 8 , 1359-1384, DOI: 10.1021/bm061150q. 33. Hazarika, D.; Karak, N., Waterborne Sustainable Tough Hyperbranched Aliphatic Polyester Thermosets. ACS Sustainable Chem. Eng. 2015, 3 , 2458-2468, DOI: 10.1021/acssuschemeng.5b00494. 34. Gurunathan, T.; Mohanty, S.; Nayak, S. K., Hyperbranched Polymers for Coating Applications: A Review. Polym Plast Technol Eng 2016, 55, 92-117, DOI: 10.1080/03602559.2015.1021482. 35. Ong, H. R.; Rahman Khan, M. M.; Ramli, R.; Yunus, R. M., Effect of CuO Nanoparticle on Mechanical and Thermal Properties of Palm Oil Based Alkyd/Epoxy Resin Blend. Procedia Chemistry 2015, 16, 623-631, DOI: 10.1016/j.proche.2015.12.101. 36. Chattopadhyay, D.; Webster, D. C., Thermal stability and flame retardancy of polyurethanes. Prog. Polym. Sci. 2009, 34 , 1068-1133, DOI: 10.1016/j.progpolymsci.2009.06.002. 37. Rengaraj, A.; Haldorai, Y.; Puthiaraj, P.; Hwang, S. K.; Ryu, T.; Shin, J.; Han, Y.-K.; Ahn, W.S.; Huh, Y. S., Covalent Triazine Polymer–Fe3O4 Nanocomposite for Strontium Ion Removal from Seawater. Ind. Eng. Chem. Res. 2017, 56, 4984-4992, DOI: 10.1021/acs.iecr.7b00052. 38. Pan, X.; Sengupta, P.; Webster, D. C., High Biobased Content Epoxy–Anhydride Thermosets from Epoxidized Sucrose Esters of Fatty Acids. Biomacromolecules 2011, 12 , 2416-2428, DOI: 10.1021/bm200549c. 39. Shi, J.; Jim, C. J. W.; Mahtab, F.; Liu, J.; Lam, J. W. Y.; Sung, H. H. Y.; Williams, I. D.; Dong, Y.; Tang, B. Z., Ferrocene-Functionalized Hyperbranched Polyphenylenes: Synthesis, Redox Activity, Light Refraction, Transition-Metal Complexation, and Precursors to Magnetic Ceramics. Macromolecules 2010, 43 , 680-690, DOI: 10.1021/ma9012658.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

40. Sanes, J.; Carrión, F.; Bermúdez, M., Effect of the addition of room temperature ionic liquid and ZnO nanoparticles on the wear and scratch resistance of epoxy resin. Wear 2010, 268 , 1295-1302, DOI: 10.1016/j.wear.2010.01.024. 41. Dhoke, S. K.; Bhandari, R.; Khanna, A. S., Effect of nano-ZnO addition on the silicone-modified alkyd-based waterborne coatings on its mechanical and heat-resistance properties. Prog. Org. Coat. 2009, 64 , 39-46, DOI: 10.1016/j.porgcoat.2008.07.007. 42. Wetzel, B.; Haupert, F.; Qiu Zhang, M., Epoxy nanocomposites with high mechanical and tribological performance. Compos. Sci. Technol. 2003, 63 (14), 2055-2067, DOI: 10.1016/S02663538(03)00115-5. 43. Sharmin, E.; Ashraf, S.; Ahmad, S., Synthesis, characterization, antibacterial and corrosion protective properties of epoxies, epoxy-polyols and epoxy-polyurethane coatings from linseed and< i> Pongamia glabra seed oils. Int. J. Biol. Macromol. 2007, 40 , 407-422, DOI: 10.1016/j.ijbiomac.2006.10.002. 44. De, B.; Karak, N., Novel high performance tough hyperbranched epoxy by an A2+ B3 polycondensation reaction. J. Mater. Chem. A 2013, 1 , 348-353, DOI: 10.1039/C2TA00011C. 45. Naik, R. B.; Ratna, D.; Singh, S. K., Synthesis and characterization of novel hyperbranched alkyd and isocyanate trimer based high solid polyurethane coatings. Prog. Org. Coat. 2014, 77, 369-379, DOI: 10.1016/j.porgcoat.2013.10.012. 46. Deka, H.; Karak, N., Bio-based hyperbranched polyurethanes for surface coating applications. Prog. Org. Coat. 2009, 66, 192-198, DOI: 10.1016/j.porgcoat.2009.07.005.

Figure caption Scheme 1. Synthesis of HBA-BMF and in inset 3D view of hyperbranch HBA. Scheme 2. Synthesis of HBA-BMF-Fe3O4 nanocomposite. Fig. 1. FT-IR spectra of HBA, HBA-BMF and HBA-BMF-Fe3O4 nanocomposite Fig. 2 (a) 1H NMR of HBA. Fig. 2 (b) 1H NMR of HBA-BMF. Fig. 3 TEM micrograph of (a) HBA-BMF- Fe3O4 nanocomposite, SEM micrograph of (b) HBABMF and (c) HBA-BMF- Fe3O4 nanocomposite coatings. Fig. 4 TGA thermograms of HBA, HBA-BMF and HBA-BMF-Fe3O4 nanocomposite. Fig. 5 Optical micrographs after the scratch test (a) HBA-BMF coatings, (b) HBA-BMF-Fe3O40.5 and (c) HBA-BMF-Fe3O4-2.5 Fig. 6 PDP curves in saline of coated and uncoated CS.


Page 18 of 27

Page 19 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig 7. Bode plot of (a) HbA-BMF, (b) HbA-BMF-Fe3O4-0.5, (c) HbA-BMF-Fe3O4-1.5 and (d) HbA-BMF-Fe3O4-2.5 Fig.8 SEM micrograph after salt mist exposure (a) HBA-BMF and (b) HBA-BMF-Fe3O4. Table 1. Electrochemical Parameters Obtained from PDP Studies for Uncoated, HBA-BMF and HBA-BMF-Fe3O4 Coated CS in 3.5 wt % NaCl at room temperature.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Scheme 1. Synthesis of (a) monoglyceride, (b) hyperbranched alkyd (HBA), (c) HBA-BMF and in inset 3D view of hyperbranched HBA.


Page 20 of 27

Page 21 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Scheme 2. Synthesis of HBA-BMF-Fe3O4 nanocomposite. HbA HbA-BMF HbA-BMF-Fe3O4 -1

2851cm

-1

1553cm 100

%T

-1

576cm -1

0

3389cm

4000

3500

-1

2929cm 3000

2500

-1 1075cm

-1 1725cm 2000

1500

1000

-1

Wave Number(cm )

Fig. 1. FT-IR spectra of HBA, HBA-BMF and HBA-BMF-Fe3O4 nanocomposite



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 2 (a) 1H NMR of HBA

Fig. 2 (b) 1H NMR of HBA-BMF.


Page 22 of 27

Page 23 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig.3 TEM micrograph of (a) HBA-BMF- Fe3O4 nanocomposite, SEM micrograph of (b) HBABMF and (c) HBA-BMF- Fe3O4 nanocomposite coatings. 0 HbA HbA-BMF HbA-BMF-Fe3O4-2.5

20

40

% wt loss 60

80

100 100

200

300

400

500

600

700

800

o

Temperature ( C)

Fig. 4 TGA thermograms of HBA, HBA-BMF and HBA-BMF-Fe3O4 nanocomposite

Fig. 5 Optical micrographs after the scratch test (a) HBA-BMF coatings, (b) HBA-BMF-Fe3O40.5 and (c) HBA-BMF-Fe3O4-2.5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 6 PDP curves in saline of coated and uncoated CS.


Page 24 of 27

Page 25 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig 7. Bode plot of (a) HbA-BMF, (b) HbA-BMF- Fe3O4-0.5, (c) HbA-BMF- Fe3O4-1.5 and (d) HbA-BMF- Fe3O4-2.5

Fig.8 SEM micrograph after salt mist exposure (a) HBA-BMF and (b) HBA-BMF-Fe3O4.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 27

Table 1. Electrochemical Parameters Obtained from PDP Studies for Uncoated, HBA-BMF and HBA-BMF-Fe3O4 Coated CS in 3.5 wt % NaCl at room temperature. Sample

Ecorr (V) Icorr(Acm-2) Rp ( )

CS HBA-BMF HBA-BMF-Fe3O4-0.5 HBA-BMF-Fe3O4-1.5 HBA-BMF-Fe3O4-2.5

-0.853 -0.811 -0.781 -0.752 -0.724

9.18 2.67 5.33 3.50 8.88

10-5 10-7 10-7 10-8 10-8

472 276230 324340 440080 528350


Corrosion (mpy) 1.0671 0.0031 0.0027 0.0011 0.0001

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Use Only

5 .0 4 .8 4 .6 4 .4 4 .2 4 .0

Log (impedance)

Page 27 of 27

3 .8 3 .6 3 .4 3 .2 3 .0 2 .8 2 .6 2 .4 2 .2 2 .0 -1

0

1

2

3

4

5

L o g ( f)

Ferrite dispersed hyperbranched soya alkyd nanocomposite anticorrosive coatings were synthesised via green route with promising physico-mechanical, thermal and anticorrosive performance.


Hyperbranched Soya Alkyd Nanocomposite: A Sustainable Feedstock

Recommend Documents