Linseed polyurethane/tetraethoxyorthosilane/fumed silica hybrid nanocomposite coatings: Physico-mechanical and potentiodynamic polarization measurements studies

The work presents the physico-mechanical properties and potentiodynamic polarization measurements studies of linseed oil based polyurethane/tetraethoxyorthosilane [LPU/TEOS] hybrid and polyurethane/tetraethoxyorthosilane/fumed silica NC [LPU/TEOS/FS] hybrid nanocomposite coatings. The best coating performance was obtained by the inclusion of 2 wt% FS in 2-LPU/TEOS hybrid. 2-LPU/TEOS/FS produced glossy, transparent, flexibility retentive, scratch-resistant and impact resistant coatings at ambient temperature relative to LPU/TEOS coatings. 2-LPU/TEOS/FS showed good scratch hardness (5.5 kg), impact resistance (250 lb/in.), flexibility (1/8 in.) as investigated by standard methods with corrosion rate obtained as 3.567 × 10⁻⁴ mm/year and 4.05 × 10⁻⁴ mm/year and inhibition efficiency as 99.816% and 99.710% in 3.5% NaOH and 3.5% HCl, respectively.     

Pyridine-poly(urethane ester amide) coatings from linseed oil

A novel attempt has been made to develop the room temperature cured polyesteramide resin by condensation polymerization reaction between fatty amide diol (N,N-bis 2-hydroxy ethyl linseed oil fatty amide) obtained from oil of linseed (Linum ussitatissimum seeds) and pyridine dicarboxylic acid (PyA) to develop pyridine polyesteramide (Py-PEA), which was further treated with toluylene-2,4-diisocyanate (TDI), in different weight percentages to develop a series of pyridine poly(urethane esteramide) resins (Py-UPEA). The structural elucidation of Py-PEA and Py-UPEA were carried out by FT-IR, ¹H-NMR and ¹³C-NMR spectroscopic techniques. Physico-chemical characterizations of these resins were performed by standard laboratory methods. Thermal analyses of these resins were accomplished by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Coatings of Py-UPEA were prepared on mild steel strips to evaluate their physico-mechanical and chemical/corrosion resistance performances under various corrosive environments. It was found that among all these systems, the sample having 14 wt% loading of TDI showed the best physico-mechanical and corrosion resistance performances. Thermal stability performance suggest that the system could be safely used up to 200 °C.     

Bio-degradable vegetable oil based hyperbranched poly(ester amide) as an advanced surface coating material

Vegetable oil based hyperbranched poly(ester amide) (HBPEA) has enormous importance because of its unique characteristics. Thus the synthesis of HBPEA using N,N′-bis(2-hydroxy ethyl) castor oil fatty amide, maleic anhydride, phthalic anhydride and isophthalic acid as A₂ monomers and diethanol amine, as B₃ monomer was reported for the first time. The chemical structure of the synthesized resin was characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (¹H NMR and ¹³C NMR) spectroscopic techniques. The degree of branching (DB) (as vouched by ¹H NMR analysis) and initial degradation temperature were found to increase with the increment in B₃ monomer content. Resins with 5 and 10 wt% of B₃ monomer showed shear thinning behavior while rheopectic nature of HBPEA with 15 wt% of B₃ content was observed. The evaluation of tensile strength, elongation at break, abrasion resistance, adhesion strength, scratch hardness, gloss, impact strength and chemical resistance complemented by microbial and lipolytic degradation forward the epoxy cured thermosets as advanced biodegradable surface coating materials.     

Synthesis,characterization and corrosion protective properties of boron-modified polyurethane from natural polyol

A novel attempt has been made to incorporate boron in the backbone of castor oil to develop boron-modified polyester (BCPE) and polyurethane (BPU). The overall reaction strategy involved “single pot multiple reactions” in minimum solvent achieving about 50% reduction in the use of volatile organic compounds (VOCs) during the synthetic procedure. Spectral (I.R., ¹H NMR and ¹³C NMR), physicochemical and thermal (TGA and DSC) analyses of BCPE and BPU were carried out by standard methods. The physico-mechanical and corrosion/chemical resistance performances (in various corrosive media) tests of BPU coatings were also conducted to evaluate their coating properties. These studies revealed that (i) the incorporation of boron has a significant influence on structural and physico-chemical aspects, thermal stability as well as on coating properties of BPUs, (ii) interestingly, BPUs showed very good performance in alkaline media (unaffected in 5 wt% NaOH for 50 h) as compared to their other previously reported oil-based counterparts, (iii) boron, here, acts both as a modifier and crosslinker and (iv) BPUs serve as novel and promising candidates for use as corrosion protective coating material, which can be safely employed up to 220 °C.     

Synthesis,Characterization and Performance of Amine Modified Linseed Oil Fatty Amide Coatings

A novel attempt has been made to develop ambient cured polyamine amide (PAA) resins by the condensation polymerization reaction of oil fatty amide diol (N,N-bis 2-hydroxy ethyl linseed oil fatty amide) (HELA) and o-phenylene diamine, which was further modified by poly(styrene-co-maleic anhydride) (SMA) at different phr (parts per hundred part of resin) to get a series of PAA–SMA resins. The structural elucidation of HELA, PAA and PAA–SMA were carried out by FT-IR, ¹H-NMR and ¹³C-NMR spectroscopic techniques. The physico-chemical and physico-mechanical analyses were carried out by standard laboratory methods. Thermal analyses of these resins were accomplished by thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) techniques. Coatings of PAA–SMA were prepared on mild steel strips to evaluate their physico-mechanical and chemical/corrosion resistance performance under various corrosive environments. It was found that among the PAA–SMA systems, PAA-35 showed the best physico-mechanical and corrosion resistance performance. Thermal studies reveal that the coatings can be safely used up to 305 °C.     

Synthesis and characterization of corrosion protective polyurethanefattyamide/silica hybrid coating material

For the first time, polyurethanefattyamide/silica [PULFAS] based organic-inorganic hybrid coatings were prepared at ambient temperature to combat the corrosion of mild steel. The coating material was synthesized in situ by the reaction of Linseed diol fattyamide (HELA) and tetraethoxy orthosilicate (TEOS, 20-30 phr) at 80 °C, followed by the addition of calculated amount of toluene-2,4-diisocyanate (TDI) in the reaction setup at room temperature. The formation of PULFAS was confirmed by FTIR spectral technique while morphology of the same was observed by optical micrography. The physico-mechanical properties of PULFAS coatings such as scratch hardness, impact resistance, bend test and gloss along with coating thickness were evaluated by standard methods. Thermal stability of PULFAS was investigated by thermogravimetric analysis (TGA). Curing behavior of PULFS was studied by differential scanning calorimetry (DSC). Corrosion resistance performance of the hybrid coatings was evaluated by potentio dynamic polarization (PDP) measurements in different corrosive environments at room temperature. Salt spray test of PULFAS coatings was carried out in 3.5 wt% NaCl solution. The corrosion protection mechanism of the same was also investigated. The results showed that PULFAS coatings exhibit good physico-mechanical properties with excellent performance against the corrosive environments.     

Synthesis and self-assembly of amphiphilic maleic anhydride-stearyl methacrylate copolymer

Amphiphilic maleic anhydride-stearyl methacrylate (MA-SMA) random copolymer was synthesized via the free radical copolymerization and its amide was prepared through the MA moieties being reacted with morpholine. Polymers obtained were characterized by GPC and ¹H NMR. The aggregating behaviors of copolymers were investigated by first dissolving them in tetrahydrofuran (THF) and then adding water to induce association of the long alkyl chains and observed over the range of copolymer concentrations from 0.028 to 0.22 wt% and water content from 5.32 to 34.85 wt%. Resultant aggregates show new potential application in the fields of drug delivery systems, microcapsules and so on.     

Electropolymerized polyaniline coatings on aluminum alloy 3004 and their corrosion protection performance

Homogeneous and adherent polyaniline coatings were electrosynthesized on aluminum (Al) alloy 3004 (AA 3004) from an aqueous solution containing aniline and oxalic acid by using the galvanostatic polarization method. A higher applied current density in the polymerization stage proved to be the best condition to adopt for the synthesis of more compact and strongly adherent polyaniline coatings on Al. The corrosion performances of polyaniline coatings were investigated in 3.5% NaCl solution by the potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS).Potentiodynamic polarization and electrochemical impedance spectroscopy studies reveal that the polyaniline acts as a protective layer on Al against corrosion in 3.5% NaCl solution. The current corrosion decreases significantly from 6.55 μA cm⁻² for uncoated Al to 0.158 μA cm⁻² for polyaniline-coated Al. The corrosion rate of the polyaniline-coated Al is found to be 5.17 × 10⁻⁴ mm year⁻¹, which is ∼40 times lower than that observed for bare Al. The potential corrosion increases from −1.015 V versus SCE for uncoated Al to ∼−0.9 V versus SCE for polyaniline-coated Al electrodes. The positive shift of ∼0.11 V in potential corrosion indicates the protection of the Al surface by the polyaniline coatings.The synthesized coatings were characterized by UV-visible absorption spectrometry, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Optical absorption spectroscopy reveals the formation of the emeraldine form of polyaniline. The results of this study clearly ascertain that the polyaniline has outstanding potential to protect the AA 3004 alloy against corrosion in a chloride environment.     

Cd and Zn-incorporated polyesteramide coating materials from seed oil—A renewable resource

Cd and Zn metal (with completely filled ‘d’ orbital) incorporated linseed oil polyesteramides [Zn-LPEA and Cd-LPEA] were synthesized by in situ condensation polymerization reaction between linseed fattyamide diol (HELA), phthalic anhydride and divalent cadmium/zinc acetate (different mole ratios) obviating the use of any solvent. The structures of these resins were confirmed by FT-IR, ¹H NMR and ¹³C NMR spectral studies. The solubility of the resin was checked in different polar and non-polar solvents. The physico-chemical and physico-mechanical properties were studied by standard methods. Curing and thermal behavior were investigated by DSC and TGA techniques. The corrosion protective performance of coatings on mild steel strips was investigated by standard methods. Agar diffusion method was used to determine the antibacterial activities of these polymers. The studies revealed that the minor incorporation of divalent cadmium and zinc in virgin linseed oil based polyesteramide [LPEA] enhances the physico-mechanical and anticorrosive properties as well as reduces the curing temperature. Besides these properties they also show effective antibacterial behaviour against the Escherichia coli and Staphylococcus aureus. The Zn-LPEA and Cd-LPEA resins are, therefore, inexpensive coatings material, developed from renewable resource, for anti-corrosive and antibacterial applications.     

Studies on self cured zinc-containing Pongamia glabra oil based polyesteramide

Efforts have been made for the development of high performance protective coating materials from non drying oil such as Pongamia glabra oil and their commercialization. Zn-containing self cured Pongamia glabra oil based polyesteramide [Zn-APGPEA] resin was synthesized in situ by the reaction of Pongamia glabra fatty amide diol [HEPGA], poly(styrene-co-maleic anhydride) [SMA] and zinc acetate (different ratios) at 100 ± 5 °C in the presence of an acid catalyst. The physico-chemical characterizations of the resin were carried out by standard laboratory methods. The structural elucidation of the prepared resin was carried out by FTIR, ¹H NMR and ¹³C NMR spectral techniques. The thermal behavior was studied by TGA technique. Antibacterial activity was measured by agar diffusion method against Escherichia coli and Staphylococcus aureus. The effect of the loading of zinc on properties of Zn-APGPEA film was also investigated. The properties of Zn-APGPEA compared with reported self cured Pongamia glabra polyesteramide [APGPEA]. Physico-mechanical and chemical/corrosion resistance test of Zn-APGPEA coatings showed that the presence of zinc metal in APGPEA considerably enhances the overall film performance and also improves antibacterial activity. Therefore, Zn-APGPEA can be used as an anti-corrosive and antibacterial coatings material which may substitute polymers obtained from petroleum.     

Oxidation of methyl linoleate in the presence of lignin

The overall aim of this study is to develop new wood modifications using vegetable oils to obtain improved durability of wood materials in an environmentally friendly way. Nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopies were used to study oxidation and possible chemical coupling reactions between polyunsaturated fatty acids and model lignin compounds in order to better understand the interactions between oxidatively drying systems such as vegetable oils or alkyds with the lignin part in wood. This was done by studying mixtures of different model lignin compounds and methyl linoleate. The oxidation process was analyzed at 70 °C both in methyl linoleate alone and in combination with 20 wt% of lignin model compounds. The effects of those compounds on the oil polymerization processes were monitored by NMR (both ¹³C and ¹H experiments) and the domain specific reactivity and patterning were then combined with FT-IR data. No covalent bonds having formed between the oil and the model compounds were detected by combination of several ¹³C/¹H 2D NMR methods. From the spectra, the oxidation degrees of model compounds were calculated, and for some lignin model compounds alcohols were oxidized to carbonyls during the process. Those results were in excellent agreement with FT-IR data and oxidation mechanisms were proposed. The combination of both analytical techniques was necessary to have a better understanding of these systems: NMR demonstrated the absence of chemical bond and quantified oxidation degree of model lignin molecules while FT-IR focused on oil oxidation.     

Poly (urethane fatty amide) resin from linseed oil—A renewable resource

Poly (urethane fatty amide) [PULFA] resin was synthesized by using a one-shot technique at room temperature from diol linseed fatty amide [DLFA; a monomer obtained from the aminolysis of renewable resource, such as linseed oil with diethanolamine and sodium methoxide used as a catalyst], 1.0 moles, and varying ratio of toluylene-2,4(6)-diisocyanate [TDI, 0.08–1.5 moles] in minimum amount of xylene without any chain extender and catalyst. In this process phthalic acid/anhydride which is normally used in the synthesis of polyesteramide was completely replaced by TDI as in case of uralkyd. The reaction mechanism of the same has been discussed here. The mode of reaction and structure of the resin was confirmed by physico-chemical tests and spectral analysis. The performance of the coatings on mild steel strips was tested by physico-mechanical and chemical/corrosion resistance tests. Thermo gravimetric analysis [TGA] and differential scanning calorimetry [DSC] techniques were used to investigate the thermal stability and curing behavior of the resin. The aforementioned properties of newly synthesized resin were compared with those of reported linseed oil-based polyesteramide urethane [Ur-LPEA, synthesized by partial replacement of phthalic anhydride by TDI] and uralkyd. The newly synthesized resin has shown improved physico-mechanical and corrosion resistance performance to Ur-LPEA and alkyd, whereas to those of uralkyd has comparable results. The PULFA resin exhibits not only superior properties to some of the reported resins, but also helps in the conservation of energy by being synthesized at room temperature as compared to other similar reported systems which were synthesized at reasonably high temperatures. The present study reveals that the PULFA resin can be used as a substitute to Ur-LPEA, alkyd and uralkyd in the field of corrosion protective paints and coatings.     

Synthesis and characterization of new modified anti-corrosive polyesteramide resins incorporated pyromellitimide ring for surface coating

In this paper new modified anti-corrosive polyesteramide resins were obtained by means of a condensation polymerization reaction between N,N-bis (2-hydroxyethyl) linseed oil fatty acid amide (HELA) and phthalic anhydride (PA), which was partially replaced with pyromellitimide acetic acid (PAA) as a new dibasic acid source. The structure of the resin was confirmed by FT-IR and ¹H NMR spectral studies. The coatings of 50 ± 5 μm thickness were applied to the surface of glass panels and mild steel strips by means of a brush. The coating performance of the resins was evaluated using international standard test methods and involved the measurement of phyisco-mechanical properties such as viscosity, drying time, specular gloss, pencil hardness, adhesion, flexibility and impact resistance. Chemical resistance of the resins to water, acid, alkali and solvent was also evaluated to ascertain their suitability as a surface coatings vehicle. The results show that the modification enhances both phyisco-mechanical and chemical properties. The resins were incorporated within primer formulations and evaluated as anti-corrosive single coatings. The results illustrate that the introduction of pyromellitimide acetic acid, containing a pyromellitimide ring, within the resin structure, enhances the corrosion resistance performance of polyesteramide resins.     

Synthesis, characterization and thermal properties of soluble aromatic poly(amide imide)s

Novel diamines such as N,N′-bis(aminoaryl)terephthalamido-2-carboxylic acids (BATCA), which contain primary amine, amide and carboxylic acid groups and are soluble in dilute aqueous NaOH solution, were synthesized by reacting aromatic diamines with trimellitic anhydride chloride in dimethylformamide. Poly(amide imide)s containing 3:1 ratio of amide:imide groups in the polymer chain were prepared by low temperature solution polymerization of BATCAs with isophthaloyl chloride or terephthaloyl chloride in dimethylformamide at 5-10 °C to form poly(amide amic acid)s, and followed by treating with a mixture of triethylamine and acetic anhydride. The PAIs were soluble in polar aprotic solvents like dimethylformamide, dimethylacetamide, dimethylsulphoxide and N-methylpyrrolidone, and have inherent viscosities in the range of 0.30-0.66 dL/g. The PAIs were characterized by IR, ¹H NMR and ¹³C NMR techniques. Thermogravimetric analysis (TGA) has shown that the initial decomposition temperatures of the polymers are in the range of 250-440 °C, depending upon the structures of diamine and diacid chloride. The glass transition temperatures of the PAIs are in the range of 128-320 °C. The IDT and T_g values of the polymers containing terephthaloyl unit are higher by about 20-40 °C than those of the polymers with isophthaloyl unit. BATCA could be utilized for the preparation of thin film composite membranes having PAA/PAI barrier layer on PES by in situ interfacial polymerization with IPC/TPC/TMC.     

Corrosive inhibition behavior of well-dispersible aniline/p-phenylenediamine copolymers

Well-dispersible aniline/p-phenylenediamine copolymer [P(ANI-co-p-PDA)-F] was synthesized by chemical oxidative polymerization in the presence of nonylphenol ethoxylate (TX-8) with the hydrophilic lipophilic balance (HLB) value of 10–11. The FTIR and ¹H NMR spectra proved that there was TX-8 composition in P(ANI-co-p-PDA)-F copolymer. And the P(ANI-co-p-PDA)-F had the smaller particle diameter and better dispersion stability in toluene than that of P(ANI-co-p-PDA) copolymer without TX-8. The anti-corrosion performance of carbon steel samples coated by P(ANI-co-p-PDA)-F/epoxy composite coatings in 5 wt% NaCl and 0.1 M HCl aqueous solution were evaluated by the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the P(ANI-co-p-PDA)-F/epoxy coatings on carbon steel possessed good corrosion resistance, and composite coating containing 7 wt% P(ANI-co-p-PDA)-F exhibited best anti-corrosive performance.     

Conducting polyaniline-nano-TiO2 composites for smart corrosion resistant coatings

Coatings prepared from polyaniline-nano-TiO₂ particles synthesized by in situ polymerization were found to exhibit excellent corrosion resistance much superior to polyaniline (PANI) in aggressive environments. The corrosion studies were carried out on steel plates coated with these formulations containing 10 wt% polyaniline prepared with different concentrations of nano-TiO₂. The electrochemical impedance spectroscopy was studied at periodic intervals during exposure to hot saline (65 °C) conditions for prolonged durations over a period of 90 h. The open circuit potential (OCP) was found to shift with time from −0.38 V SCE to more anodic side (−0.2 V SCE) much above that of bare steel (−0.5 V SCE). The presence of nano-TiO₂ was found to be vital in the prevention of corrosion and the shift of OCP to anodic side. From these data, one could envisage more than 100 times improvement in the corrosion resistance especially for polyaniline prepared with 4.18 wt% nano-TiO₂. The exceptional improvement of performance of these coatings has been associated with the increase in barrier to diffusion, prevention of charge transport by the nano-size TiO₂, redox properties of polyaniline as well as very large surface area available for the liberation of dopant due to nano-size additive.     

Investigation of co-combustion of coal and olive cake in a bubbling fluidized bed with secondary air injection

In this study, a bubbling fluidized bed of 102 mm inside diameter and 900 mm height was used to burn olive cake and coal mixtures. Tunçbilek lignite coal was used together with olive cake for the co-combustion tests. Combustion performances and emission characteristics of olive cake and coal mixtures were investigated. Various co-combustion tests of coal with olive cake were conducted with mixing ratios of 25%, 50%, and 75% of olive cake by weight in the mixture. Operational parameters (excess air ratio, secondary air injection) were changed and variation of pollutant concentrations and combustion efficiency with these operational parameters were studied. The results were compared with that of the combustion of olive cake and coal. Flue gas concentrations of O₂, CO, SO₂, NO_x, and total hydrocarbons (C_mH_n) were measured during combustion tests.For the setup used in this study, the optimum operating conditions with respect to NO_x and SO₂ emissions were found to be 1.35 for excess air ratio, and 30 L/min for secondary air flowrate for the combustion of 75 wt% olive cake and 25 wt% coal mixture. The highest combustion efficiency of 99.8% was obtained with an excess air ratio of 1.7, secondary air flow rate of 40 L/min for the combustion of 25 wt% olive cake and 75 wt% coal mixture.     

An experimental study of oil recovery from sewage sludge by low-temperature pyrolysis in a fluidised-bed

Pyrolysis of activated sewage sludge was investigated under inert conditions in a fluidised-bed to study the effects of temperature and gas residence time on the product distribution and composition with an aim to maximise the oil yield. The temperature was varied from 300 to 600 °C and the gas residence time from 1.5 to 3.5 s. Three groups of products were produced, namely, a non-condensable gas (NCG) phase, a solid phase (char) and a liquid phase (oil). A maximum of 30% oil yield (wt% daf of sludge fed) was achieved at a pyrolysis temperature of 525 °C and a gas residence time of 1.5 s. Higher temperatures and longer gas residence times favoured the formation of NCG, suggesting that secondary cracking reactions had occurred. The oil obtained was analysed using GC-MS and H NMR to determine the oil's composition and structure, a unit structure of the oil was proposed which consisted of aromatic rings connected by hydrocarbons with -OH functional groups attached.     

Utilization of muscovite granite waste in the manufacture of ceramic tiles

Granite waste is by-product from a decorative rock industry. The present study aims to investigate the effect of muscovite granite waste on the physico-mechanical properties of ceramic tiles to demonstrate its suitability for industrial production. A series of flooring- and facing ceramic tiles were prepared by adding 20, 25, and 30 wt% muscovite granite waste into the batch compositions. The sintering behavior and degrees of densification of two kinds of ceramic tiles were evaluated by determining their physico-mechanical properties and characterizing them by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. As expected, the facing ceramic tile (FacCT1) sample, containing wollastonite, hematite, anorthite, quartz, and cristobalite, with 20 wt% muscovite granite waste showed lower physico-mechanical properties than those of the flooring ceramic tile (FloCT3) sample, containing mullite, calcium aluminosilicate, quartz, and cristobalite, with 30 wt% muscovite granite waste. The reason is that lower firing temperatures cannot accelerate a complete fusion of the granite waste which behaves like an inert non-plastic material similar to quartz. These results illustrate the prospects of utilizing muscovite granite waste in ceramic tile production.     

Co γ-irradiation-initiated RAFT polymerization of VAc at room temperature

In this work, the reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc) was successfully performed at room temperature using ⁶⁰Co γ-irradiation as the initiation source. Under the dose rate of 10 Gy/min irradiation, the polymerization proceeded smoothly and converted approximately 90% of the monomer within 7 h. The molecular weight distribution (M_w/M_n) remained narrow (M_w/M_n < 1.35) up to 90% conversion. Compared to AIBN-initiated RAFT polymerization at 60 °C, ⁶⁰Co γ-irradiation-initiated RAFT polymerization is a technique that can better control the molecular weight, especially at high conversion. The ¹H NMR spectra and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry confirmed that most of the chain ends of poly(VAc) (PVAc) from γ-irradiated RAFT polymerization were living and can be reactivated for chain-extension reactions. The microstructures of PVAc from ⁶⁰Co γ-irradiated RAFT polymerization (almost head-to-tail addition) and AIBN-initiated RAFT polymerization (5% tail-to-tail addition) were different, as revealed by the ¹³C NMR spectra. For the first time, ⁶⁰Co γ-irradiation was used as an initiation source for RAFT polymerization of VAc at room temperature.