Characterization of structure and corrosion resistivity of polyurethane/organoclay nanocomposite coatings prepared through an ultrasonication assisted process

In this study, a series of castor oil based polyurethane/organically modified montmorillonite (OMMT) clay nanocomposite coatings have been successfully prepared by effective dispersing of OMMT nano-layers in polyurethane matrix through an ultrasonication assisted process. Effectiveness of ultrasonication process in de-agglomeration of clay stacks in castor oil dispersions was evaluated by optical microscopy and sedimentation test. Structure of nanocomposite coatings was investigated by wide angle X-ray diffraction (WAXD) and Fourier-transform infrared spectroscopy (FT-IR). The anticorrosive properties of nanocomposite coatings were characterized by electrochemical impedance spectroscopy (EIS), Tafel polarization study, water absorption and pull-off adhesion tests. The experimental results showed that PU/OMMT nanocomposite coatings were superior to the neat PU in corrosion protection effects. Also, it was observed that the corrosion protection of polyurethane organoclay nanocomposite coatings is improved as the clay loading is increased up to 3 wt.%.     

SiAlON–epoxy nanocomposite coatings: Corrosion and wear behavior

In this study, epoxy powder as a matrix was combined with different contents of silicon–aluminum–oxygen–nitrogen (SiAlON) nanoparticles using a planetary ball mill. Pure epoxy and nanocomposite powders were applied on the surface of plain carbon steel components by the electrostatic spraying method. Curing of the coatings was done in an oven or microwave for the appropriate time. The coating structure and morphology of the SiAlON nanoparticles were studied by scanning electron microscopy and transmission electron microscopy, respectively. The corrosion properties of the coatings were assessed by immersion, Tafel polarization, and electrochemical impedance spectroscopy tests in 3.5% NaCl solution. The results show that addition of 10 wt % SiAlON nanoparticles markedly increases the corrosion resistance of epoxy coatings. Thus, it can be inferred that the corrosion rate of these coatings is 15 to 18 times lower than that of pure epoxy samples and 8 to 11 times lower than coatings with 20 wt % SiAlON. The higher corrosion resistance of nanocomposite coatings can be attributed to the barrier properties of SiAlON nanoparticles. The tribological performance of the coatings was studied with the pin‐on‐disk test. The results of wear testing show that the samples containing 10 wt % SiAlON provide about five times more wear resistance than pure ones and about two times more than coatings with 20 wt % SiAlON. However, the coefficient of friction for nanocomposite coatings is reduced about 50% compared to the pure sample. Also, the curing process in either regime (oven or microwave) has the same effect on the corrosion and wear properties, and the coatings are completely crosslinked. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43855.     

Synthesis and characterization of elastomeric polyurethane and PU/clay nanocomposites based on an aliphatic diisocyanate

This investigation reports preparation of polyurethane and polyurethane/clay nanocomposites based on polyethylene glycol, isophorone diisocyanate (IPDI), an aliphatic diisocyanate and 1,4‐ Butanediol as chain extender by solution polymerization. In this case PU/clay nanocomposites were prepared via ex‐situ method using 1, 3, and 5 wt % of Cloisite 30B. Thermogravimetric analysis showed that the maximum decomposition temperature (T_max) of the PU/clay nanocomposite is much higher than the pristine PU. The tensile properties improved upon increasing the organoclay (Cloisite 30B) content upto 3 wt %, and then decreased to some extent upon further increasing the nanoparticle loading to 5 wt %. Optical properties of the nanocomposites were studied by UV‐vis spectrophotometer. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the morphology of the nanocomposites. It was observed that with the incorporation of 3 wt % nanoclay the crystallinity in PU nanocomposite increases, then diminishes with further loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3328–3334, 2013     

Characterization and anticorrosive properties of poly(2,3‐dimethylaniline)/Na+‐montmorillonite composite prepared by emulsion polymerization

Composites of Poly(2,3‐dimethylaniline) and inorganic Na⁺‐montmorillonite clay were synthesized by emulsion polymerization. The as‐synthesized composites (PDMA) were characterized by Fourier Transform Infrared Spectroscopy, X‐ray diffraction, and scanning electron microscopy. The protective performance against corrosion of the samples was evaluated by Tafel and electrochemical impedance spectroscopy measurements. The results showed that the composite containing 5 wt. % of clay loading (PDMA‐5%) displayed a better anticorrosive performance than other samples. The Epoxy(E) blend with PDMA‐5% (EPM5) coating was founded to have a higher corrosion potential and a lower current density than that of Epoxy blend P(2,3‐DMA) (EP) coating. The impedance value of EPM5 coating was about 6.68×10⁶Ω·cm² in 5 wt. % NaCl solution even after 288 h, compared to EP (4.26×10⁵Ω·cm²) coating, which went to show that the corrosion inhibition of P(2,3‐DMA) could be effectively enhanced by incorporating MMT into the P(2,3‐DMA) matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4528–4533, 2013     

Designing of polyamidoamine-based polyurea microcapsules containing tung oil for anticorrosive coating applications

A novel method for the fabrication of robust polyurea microcapsules containing tung oil as a core material was developed for self-healing anticorrosive coating application. Well-distinct microcapsules with polyurea as a shell were prepared by reacting hexamethylene diisocyanate trimer with 0.0 G polyamidoamine (PAMAM) via interfacial polymerization technique. Fourier transform infrared spectroscopic analysis was performed to elucidate the chemical structure of microcapsules as well as to confirm successful encapsulation of core by the polyurea shell. Surface morphology, particle size, distribution of particle size, thermal, and mechanical properties of the prepared PAMAM-based polyurea microcapsules were compared with microcapsules that were prepared using diethylenetriamine (DETA) and triethylenetetramine (TETA). The prepared microcapsules were embedded with acrylic polyol-based polyurethane (PU) coatings to ensure anticorrosive performance. The immersion study of self-healing PU coatings loaded with 5% PAMAM-based polyurea microcapsules possesses satisfactory anticorrosive property under an accelerated corrosion process in 5% NaCl salt solution.     

Subsurface mechanical properties of polyurethane/organoclay nanocomposite thin films studied by nanoindentation

A series of the exfoliated or intercalated PU/organoclay nanocomposite thin films were prepared by in situ polymerization of polyol/organoclay mixture, chain extender and diisocyanate. The surface mechanical properties of the PU/organoclay nanocomposite films were investigated by means of nanoindentation. The results show that the hardness, elastic modulus and scratch resistant of the nanocomposites dramatically improved with the incorporation of organoclay. This improvement was dependent on the clay content as well as the formation structure of clay in the PU matrix. At 3% clay content, the hardness and elastic modulus of intercalated nanocomposites increased by approximately 16% and 44%, respectively, compare to pure PU. For exfoliated nanocomposite, the improvements in these properties were about 3.5 and 1.6 times higher than the intercalated ones. The exfoliated PU nanocomposites also had greater hardness and showed better scratch resistance compared to the intercalated ones.     

Thermal and surface characterization of polyurethane–urea clay nanocomposite coatings

This paper reports synthesis and characterization of polyurethane–urea (PU‐urea) and the nanocomposites derived from the PU‐urea with silicate clays. Organophilic montmorillonite cotreated by cetyl trimethyl ammonium bromide (CTAB) was synthesized and used to prepare PU‐urea/montmorillonite nanocomposites coatings. PU‐ureas were prepared from polyethylene glycol (PEG), polypropylene glycol (PPG), trimethylol propane (TMP), and 4,4′‐diphenylmethane diisocyanate (MDI) by reacting excess diisocyanate with polyether glycols. The excess isocyanate of the prepolymers was cured with atmospheric moisture. The synthesized moisture cured PU‐urea and nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetric (DSC), and angle resolved X‐ray photoelectron spectroscopy (AR‐XPS). The thermal stability of the PU‐urea nanocomposites was higher relative to the mother PU‐urea films. DSC results showed a slight enhancement in the soft segment glass transition temperature after 3 wt % clay loading. The surface properties showed an enrichment of the soft segment toward the surface. An enhancement in the hard segment composition in the nanocomposite coatings has resulted in enhancing the phase mixing process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2393–2401, 2006     

Synergistic Effects of Montmorillonite/Cerium Nitrate Additives on the Corrosion Performance of Epoxy-Clay Nanocomposite Coatings

In this work, different amounts of montmorillonite were added to cerium nitrate epoxy mixture. Nanocomposite coatings containing cerium nitrate were applied on cold rolled steel panels. The state of dispersion and incorporation were characterized by transmission electron microscopy and atomic force microscopy. To investigate anticorrosive properties of nanocomposites, electrochemical impedance spectroscopy, polarization measurement and salt spray tests were employed. Results showed that epoxy cerium nanocomposite coatings were superior to the neat epoxy in corrosion protection properties. Also, it was observed that the best corrosion protection was achieved with nanocomposite coatings containing 4 wt.% and 2 wt.% cerium nitrate.     

Investigation of the corrosion protection behavior of natural montmorillonite clay/bitumen nanocomposite coatings

The influence of clay particles on the corrosion properties of bituminous coating was studied. Different percentages of natural montmorillonite clay (Cloisite Na⁺) were added to emulsified bitumen in water to make 2 wt.%, 3 wt.% and 4 wt.% of clay/bitumen nanocomposite coatings. The coatings were applied on steel 37. Optical microscopy and transmission electron microscopy (TEM) were employed to study the structure of nanocomposite. To investigate the anti-corrosion properties of the coated panels, electrochemical impedance spectroscopy (EIS) was used. The findings indicated that the addition of clay nanolayers improved corrosion resistance of the coatings. Moreover, increasing clay loading up to 4 wt.%, increased the corrosion resistance.     

Preparation of epoxy–clay nanocomposite and investigation on its anti-corrosive behavior in epoxy coating

An epoxy–clay nanocomposite was synthesized using a quaternary ammonium-modified montmorillonite clay and diglycidyl ether of bisphenol A (DGEBA) type epoxy resin, in order to produce anti-corrosive epoxy coating. Anti-corrosive properties of the nanocomposite were investigated using salt spray and electrochemical impedance spectroscopy (EIS) methods. The results showed an improvement in the barrier and anti-corrosive characteristics of epoxy-based nanocomposite coating and a decrease in water uptake in comparison with pure epoxy coating. Wide-angle X-ray diffraction (WAXD) patterns and transmission electron microscopy (TEM) analysis showed that the interlayer spacing of clays increased after addition of epoxy resin along with applying shear force and ultrasound sonicator. The best performance of this coating was achieved at 3 and 5 wt.% clay concentration.     

Synthesis and characterization of elastomeric polyurethane/clay nanocomposites

An elastomeric polyurethane/clay (PU/clay) nanocomposite based on poly(propylene glycol) (PPG), glycerol propoxylate, and toluene‐diisocyanate (TDI) was synthesized by intercalative polymerization technology. The results of wide angle X‐ray diffraction (WAXD) studies showed that the gallery distance of the clay in the hybrid was enlarged from 1.9 to 4.5nm or more. Introducing clay in the PU matrix resulted in an increase in both the tensile strength and elongation at beak. When the clay content reached about 8%, the tensile strength and elongation at break were two times and five times respectively to that of the pure PU. In addition, the clay intercalative route to the nanocomposite synthesis also effected the thermal properties of the nanocomposites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1444–1448, 2001     

Polyimide/substituted polyaniline–copolymer–nanoclay composite thin films with high damping abilities

Polyimide (PI)/poly(N‐ethyl aniline‐co‐aniline‐2‐sulfonic acid)–clay (SPNEAC) nanocomposite films containing water‐soluble SPNEAC were successfully synthesized. Atomic force microscopy studies showed a homogeneous distribution of coated clay particles in the PI matrix. The particle sizes varied between about 50 nm and about 220 nm in height and 6–7 μm in length in the nanocomposite containing 5 wt % SPNEAC. Average surface roughnesses of 0.253 and 34.9 nm were obtained for neat PI and the 5 wt % SPNEAC–PI nanocomposite, respectively. Dynamic mechanical spectrometry was used to study the viscoelastic transitions and their temperatures. The dynamic mechanical spectrometry results show a decreasing glass‐transition temperature of the nanocomposites with increasing SPNEAC weight fraction. The area under the α‐transition peak, which is associated with damping and impact energy, increased with increasing SPNEAC weight fraction. The impact energy of the nanocomposites was estimated with a viscoelastic model. It increased with increasing SPNEAC weight fraction, and a maximum value of 84.9 mJ was obtained. The viscoelastic model was based on the area under the α‐transition peak, rubbery plateau modulus, and sample volume. A 5 wt % addition of SPNEAC improved the impact energy of neat PI films by 300%. Scanning electron micrographs of the nanocomposite films showed a less compact cross‐sectional morphology. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanism of corrosion protection of aluminum alloy substrate by hybrid polymer nanocomposite coatings

The corrosion protection of polymer clay nanocomposite, PCN coatings consisting of polyurea, siloxanes, epoxy ester and montmorillonite clay was determined. Corrosion resistance of the coating, was assessed by monitoring the polarization resistance and impedance of coated aluminum alloy, Al 2024-T3, coupons immersed in 3.5 wt.% of sodium chloride, NaCl, solution. Direct current polarization and electrochemical impedance spectroscopic techniques were used to measure polarization resistance and impedance of the samples, respectively. Diffusion of saturated salt solution into free-standing PCN films was measured gravimetrically and diffusivity of the nanocomposites was determined. The presence of clay decreases diffusivity and increases corrosion resistance of the non-scribed coatings containing up to 10 wt.% of clay. A correlation between polarization resistance and diffusivity was made. It was shown that for non-scribed coatings, polarization resistance increases with decreasing diffusivity. A relationship between coating's diffusivity and weight fraction of clay was established. Increasing clay concentration also resulted in decreasing diffusivity. The scribed nanocomposite coatings show slightly decreasing polarization resistance with increasing weight fraction, however, the polarization resistance of scribed coatings containing low clay weight fraction in the range between 0.5 and 2.0 wt.% was higher than that for the matrix. A barrier mechanism of corrosion prevention of the coated substrate is proposed for non-scribed coatings. The viscoelastic property of the nanocomposites was determined by using dynamic mechanical spectrometer. A correlation between polarization resistance of the coatings and the rubbery plateau modulus on the one hand and polarization resistance and tan δ peak area for α-transition of the nanocomposites is made. Decreasing tan δ peak area for α-transition and increasing rubbery plateau modulus resulted in increasing coatings polarization resistance.     

Synthesis and properties of polyurethane/clay nanocomposite by clay modified with polymeric methane diisocyanate

A polyurethane (PU)/clay nanocomposite was synthesized from polyol, polymeric 4,4′‐diphenyl methane diisocyanate (PMDI), and modified clay with PMDI. To achieve the modified clay with PMDI, the silanol group of the clay and the NCO group of the PMDI were reacted for 24 h at 50°C to form urethane linkage. Fourier transform IR analysis of the clay modified with the PMDI demonstrated that the NCO characteristic peak was observed in the clay after a modification reaction with PMDI. The results of the X‐ray pattern suggested that the clay layers were exfoliated from the PU/clay nanocomposite. From the results of the mechanical properties, the maximum values of the flexural and tensile strength were observed when 3 wt % clay based on PMDI was added into the PU/clay nanocomposites. The glass‐transition temperature and change in the heat capacity at glass transition temperature (ΔC_p) of the PU/clay nanocomposite decreased with an increase in the modified clay content. We suggested that the decrease in the ΔC_p with the modified clay content might be due to the increase of steric hindrance by the exfoliated clay layers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2879–2883, 2006     

Thermal and anticorrosive properties of polyurethane/clay nanocomposites

A montmorillonite clay has been modified with two different quaternary ammonium salts, dilauryldimethylammonium bromide (LD) and 4,4-diaminodiphenylmethane (AP), to form the corresponding organophilic clays, LDM and APM. Two series of PU/clay nanocomposite materials, PU/LDM and PU/APM, were then prepared by the reaction of appropriate amounts of PPG, TDI and 1,4 butandiol, followed by addition of the various amounts of LDM or APM. The X-ray diffraction patterns and transmission electron micrographs of the nanocomposites revealed that the modified clay galleries were exfoliated or intercalated in the polyurethane matrix. In comparison with the corresponding pure PU, the results of the TGA and LOI measurements showed that the thermal stability and the flame retardancy of the PU/clay nanocomposites were significantly enhanced due to the presence of the dispersed nanolayers of the organophilic clay in the PU matrix. Using the Tafel method, the results of the electrochemical measurements, which included the corrosion potential, polarization resistance and corrosion current, showed that all the PU/clay nanocomposites, even with low clay loading, in the form of coating on stainless steel disk (SSD) exhibited better corrosion protection over the pure PU. The SSD coated with the composite containing 2 wt% of APM showed the lowest corrosion rate, which was one order lower than that of the SSD coated with the pure PU.     

Flame retardancy and char microstructure of nylon‐6/layered silicate nanocomposites

We investigated the effect of organically modified clay alone and in combination with zinc borate on the thermal/flammability behavior of nylon‐6 nanocomposites. Differential thermogravimetric analysis indicated that the peak decomposition temperature was not affected by the addition of clay, but the rate of weight loss decreased with increase in clay concentration. Nanocomposite films of approximately 0.5 mm thickness with 2.5 and 5 wt % clay burned for almost the same duration as neat nylon‐6 but with reduced dripping in horizontal flame test. The 10 wt % clay nanocomposite sample burned without any dripping and the flame spread rate was reduced by 25–30%. Zinc borate/clay containing nanocomposite developed into a very good intumescent system in cone calorimeter test, swelling about 10–13 mm height prior to ignition forming a cellular char structure. This was found to be an effective composition in reducing the heat release and mass loss rate of nylon‐6 by about 65% and at par with 10 wt % clay nanocomposite. Flame retardant behavior could be attributed to distinct char morphologies observed through scanning electron microscopy. Fourier transform infrared spectroscopy of the 10 wt % clay nanocomposite char showed the presence of amides, indicating possible residual polymer within the shielded char. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1540–1550, 2007     

Novel polyether polyurethane/clay nanocomposites synthesized with organicly modified montmorillonite as chain extenders

A kind of novel polyether polyurethane (PU)/clay nanocomposite was synthesized using poly(tetramethylene glycol), 4,4′‐diphenylmethane diisocyanate (MDI), 1,6‐hexamethylenediamine, and modified Na⁺‐montmorillonite (MMT). Here, organicly modified MMT (O‐MMT) was formed by applying 1,6‐hexamethylenediamine as a swelling agent to treat the Na⁺‐MMT. The X‐ray analysis showed that exfoliation occurred for the higher O‐MMT content (40 wt %) in the polymer matrix. The mechanical analysis indicated that, when the O‐MMT was used as a chain extender to replace a part of the 1,2‐diaminopropane to form PU/clay nanocomposites, the strength and strain at break of the polymer was enhanced when increasing the content of O‐MMT in the matrix. When the O‐MMT content reached about 5%, the tensile strength and elongation at break were over 2 times that of the pure PU. The thermal stability and the glass transition of the O‐MMT/PU nanocomposites also increased with increasing O‐MMT content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 6–13, 2006     

Corrosion and wear behavior of alumina‐polyester nanocomposite coatings

The corrosion and wear behavior of powder coatings fabricated by the electrostatic method was investigated in this study. Pure polyester coating and fabricated nanocomposite powder coating with 10 and 20 mass.% alumina nanoparticles were coated with electrostatic spraying method on the surfaces of carbon steel substrate. Coatings were cured in two regimes by oven and microwave for the appropriate time. The effects of alumina nanoparticles on the corrosion resistance of coated samples were studied by immersion and electrochemical impedance spectroscopy (EIS) tests. Also, pin‐on‐disk test was applied to evaluate the wear properties and coefficient of friction (COF) of the coatings. The results of the corrosion test reveal that the samples with 10 mass.% alumina show the best corrosion resistance and cause a reduction in corrosion rates which is about 36 times to that of the pure sample. The wear rate of nanocomposite coatings is 10 times lower than that of pure ones and also the coefficient of friction of nanocomposite samples is almost half of the pure samples. Furthermore, the nanocomposite coatings cured in the microwave show better protection properties and wear resistance than that of ones cured in an oven. POLYM. ENG. SCI., 57:846–856, 2017. © 2016 Society of Plastics Engineers     

Positive‐working aqueous base developable photosensitive polybenzoxazole precursor/organoclay nanocomposites

Positive‐working aqueous base developable photosensitive polybenzoxazole (PBO) precursor/organoclay nanocomposites have been prepared through the addition of an organoclay to a PBO precursor. The organoclay was formed by a cation exchange reaction between a Na⁺‐montmorillonite clay and an ammonium salt of dodecylamine. The PBO precursor used in this study was a polyhydroxyamide that was prepared from a low‐temperature polymerization of 2′2′‐bis(3‐amino‐4‐hydroxyphenyl) hexafluoropropane and 4,4′‐oxydibenzoyl chloride with an inherent viscosity of 0.3 dL/g. The photosensitive resin/clay formulations were prepared from the precursor with 2,3,4‐tris(1‐oxo‐2‐diazonaphthoquinone‐5‐sulfonyloxy)‐benzophenone photosensitive compound and 3–5 wt % organoclay. The PBO precursor/clay was subsequently thermally cured to PBO/clay at 350°C. Both X‐ray diffraction and transmission electron microscope analyses showed that the organoclay was dispersed in the PBO matrix in a nanometer scale. The thermal expansion coefficient of PBO/clay film, which contained 5 wt % organoclay, was decreased 33% compared to the pure PBO film. The PBO/clay nanocomposite films also displayed higher thermal stability, glass transition temperature, and water resistance than the pure PBO film. The photosensitive PBO precursor/clay nanocomposite showed a line/space pattern with a resolution of 5 μm and its sensitivity and contrast were not affected by the organoclay. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2350–2356, 2005     

Comparative effect of metallocene and Ziegler‐Natta polypropylene on the exfoliation of montmorillonite and hectorite clays to obtain nanocomposites

The present study was carried out on the effect of molecular weight and polydispersity of polypropylene (PP) obtained via Ziegler‐Natta or metallocene catalysis on the formation of nanocomposites with montmorillonite and mineral and synthetic hectorite. The formation of the nanocomposites was achieved by the melt‐mix method. X‐ray diffraction, transmission electron microscopy, and analysis of mechanical properties showed that, using PP obtained via metallocene catalysis (polydispersity ～ 2), it is possible to achieve improved formation of nanocomposites compared with PP obtained via Ziegler‐Natta catalysis (polydispersity ～ 4). It was also found that the molecular weight of the PP affects the tendency toward clay exfoliation and consequently the properties of the nanocomposites. Montmorillonite type clay was evaluated at 1%, 3%, and 5% by weight in the nanocomposite. The nanocomposite with 1 wt % clay was found to have better mechanical properties compared with the nanocomposite containing 3 wt % and 5 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 698–706, 2007