Aliphatic polyurethane–montmorillonite nanocomposite coatings: Preparation,characterization, and anticorrosive properties

Polyurethane (PU)–clay nanocomposite coatings were prepared by a sonication method. The stability and morphology of these coatings was characterized by turbidometry, X‐ray diffraction, and transmission electron microscopy. The anticorrosive properties of these coatings were investigated by salt‐spray and electrochemical impedance spectroscopy methods. According to the results, dispersed nanoclay layers in the matrix of the nanocomposite coating compositions led to superior anticorrosive characteristics compared to those of pure PU coatings. The best results were obtained with coatings containing about 5 wt % clay. The resistance of the coating containing 5% clay was about 9.002 GΩ after 225 days of immersion in a 3.5 wt % NaCl solution, whereas it was only 97 kΩ for the pure PU coating. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fire‐resistant effect of nanoclay on intumescent nanocomposite coatings

The aim of the study is the development of an intumescent nanocomposite coating to provide fire protection for the metallic substrate. Acrylic nanocomposites containing nanoclay and relative intumescent nanocoatings are prepared. The effect of nanoclay on the thermal degradation of an intumescent nanocomposite coating is analyzed by using differential thermal analysis, thermogravimetry, and X‐ray diffraction. The influence of the added content of nanoclay on fire performance is studied by a fire protection test and measurements of the limiting oxygen index and effective thermal conductivity. The distribution of nanoparticles in the acrylic nanocomposite is characterized by transmission electron microscopy. The flame‐retardant efficiency of the intumescent nanocomposite coating is improved by 1.5% well‐distributed nanoclay particles. However, 3% nanoclay produces a negative effect on the fire performance of the coating. Fire protection tests and scanning electron microscopy observations reveal that the fire‐retardant property of a conventional intumescent coating is destroyed by aging, whereas the nanocomposite coating modified with 1.5% nanoclay demonstrates good aging and fire resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1681–1689, 2007     

Ultraviolet‐curable epoxidized sunflower oil/organoclay nanocomposite coatings

Hybrid nanocomposite coating films, prepared by the incorporation of epoxidized sunflower oil into organoclay, can be cured by ultraviolet radiation with either cationic or hybrid initiation. The organoclay used in this study was prepared by a cationic exchange process in which sodium ions were replaced by alkyl ammonium ions. The effects of types of photoinitiators on energy consumption in the curing process were studied. Formulations with a hybrid photoinitiator required less energy in the curing process than those with a cationic photoinitiator. Moreover, the physical properties of dried films were examined as a function of the organoclay incorporation, and it was found that the hardness of the films increased as the amount of organoclay in the formulation increased. The X‐ray diffraction patterns of an ultraviolet‐curable organoclay‐incorporated film showed an exfoliated structure of the organoclay in the ultraviolet‐curable coating film. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Enhanced corrosion protection coatings prepared from soluble electronically conductive polypyrrole‐clay nanocomposite materials

A series of electronically conductive nanocomposite materials that consisted of soluble polypyrrole (PPY) and layered montmorillonite (MMT) clay platelets were prepared by effectively dispersing the inorganic nanolayers of MMT clay in organic PPY matrix via an in situ oxidative polymerization with dodecylbenzene sulfonic acid (DBSA) as dopant. Organic pyrrole monomers were first intercalated into the interlayer regions of organophilic clay hosts and followed by a one‐step oxidative polymerization. The as‐synthesized electronically conductive polypyrrole–clay nanocomposite (PCN) materials were then characterized by Fourier transformation infrared (FTIR) spectroscopy, wide‐angle powder X‐ray diffraction (XRD), and transmission electron microscopy (TEM). PCNs in the form of coatings with low clay loading (e.g., 1.0 wt %) on cold‐rolled steel (CRS) were found to exhibit much better in corrosion protection over those of pristine PPY based on a series of electrochemical measurements including corrosion potential, polarization resistance, and corrosion current in 5 wt % aqueous NaCl electrolyte. Effects of the material composition on the thermal stability, optical properties, and electrical conductivity of pristine PPY along with PCN materials, in the form of fine powder, powder‐pressed pellet, and solution, were also studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), UV‐visible absorption spectra, and four‐point probe technique, respectively. The viscosity of PPY existed in PCN materials and pristine PPY were determined by viscometric analysis with m‐cresol as solvent. The heterogeneous nucleating effect of MMT clay platelets in PPY matrix was studied by wide‐angle powder XRD. The corresponding morphological images of the nucleating behavior of clay platelets in PPY matrix were investigated by scanning electron microscopy (SEM). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3264–3272, 2003     

CO2 gas barrier properties in polymer nanocomposite coatings containing Li‐hectorite clays

This is a study of the addition of hydrophilic Li‐hectorite nanoplatelets in waterborne acrylic resin emulsions and the resulting nanocomposite coatings. The mechanism of the dispersion of the nanoplatelets during film formation and curing from aqueous suspensions is described. The morphological features of the coating and the state of delamination is examined via X‐ray diffraction for three different clay treatment procedures. The influence of the shape of the nanosized objects and their dispersion level on the transport characteristics of the nanocomposite film are measured and their effect on the polymer free volume is discussed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40805.     

Organo‐soluble polyimde (ODA–BSAA)/montmorillonite nanocomposite materials prepared by solution dispersion technique

A series of polymer–clay nanocomposite materials, consisting of organo‐soluble polyimide (ODA‐BSAA) matrix and dispersed nanolayers of inorganic montmorillonite clay, were successfully prepared by solution dispersion technique and subsequently characterized by FTIR, powder X‐ray diffraction patterns, transmission electron microscopy, and atomic force microscopy. Effects of the materials composition on the corrosion protection performance, gas barrier, and optical properties, in the form of both coating and film, were also studied by electrochemical corrosion measurements (e.g., corrosion potential, polarization resistance, corrosion current, impedance spectroscopy), gas permeability analysis, and UV–visible transmission spectroscopy, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1082–1090, 2005     

Bio‐nanocomposite films based on cellulose nanocrystals filled polyvinyl alcohol/chitosan polymer blend

Bio‐nanocomposite films based on polyvinyl alcohol/chitosan (PVA/CS) polymeric blend and cellulose nanocrystals (CNC) were prepared by casting a homogenous and stable aqueous mixture of the three components. CNC used as nanoreinforcing agents were extracted at the nanometric scale from sugarcane bagasse via sulfuric acid hydrolysis; then they were characterized and successfully dispersed into a PVA/CS (50/50, w/w) blend to produce PVA/CS–CNC bio‐nanocomposite films at different CNC contents (0.5, 2.5, 5 wt %). Viscosity measurement of the film‐forming solutions and structural and morphological characterizations of the solid films showed that the CNC are well dispersed into PVA/CS blend forming strong interfacial interactions that provide an enhanced load transfer between polymer chains and CNC, thus improving their properties. The obtained bio‐nanocomposite films are mechanically strong and exhibit improved thermal properties. The addition of 5 wt % CNC within a PVA/CS blend increased the Young's modulus by 105%, the tensile strength by 77%, and the toughness by 68%. Herein, the utilization of Moroccan sugarcane bagasse as raw material to produce high quality CNC has been explored. Additionally, the ability of the as‐isolated CNC to reinforce polymer blends was studied, resulting in the production of the aforementioned bio‐nanocomposite films with improved properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42004.     

Preparation and characterization of acrylic resin/titania hybrid nanocomposite coatings by photopolymerization and sol–gel process

Titania‐containing coatings were prepared through a dual‐cure process involving radical photopolymerization of a polysiloxane diacrylate and subsequent condensation of alkyltitanate groups. The kinetics of photopolymerization and condensation reaction was investigated as a function of the inorganic phase precursor (titanium tetraisopropoxide) content. AFM analysis gave evidence of a strong interaction between the organic and inorganic phase with the formation of titania domains in the nanoscale region. An increase of hydrophilicity in the coatings surface with increasing TiO₂ content was evidenced. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4659–4664, 2006     

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     

Effect of shear rate on structural,mechanical, and barrier properties of chitosan/montmorillonite nanocomposite film

The dispersion of MMT‐Na⁺ (montmorillonite) layers in a chitosan polymer matrix, using the homogenization, was performed. The effect of shear rate was characterized on the mechanical, barrier, and structural properties of nanocomposites. Elongation at break (EAB) was unaffected by shear rate, which decreased after homogenization, increased above 13,000 rpm, however, tensile strength (TS) dramatically increased up to 59 MPa at 16,000 rpm. Water vapor permeability (WVP) and oxygen permeability (OP) of the homogenized nanocomposite decreased more than that of untreated nanocomposite and OP was not significantly changed above 16,000 rpm of shear rate. XRD result and TEM images indicated that three types of tactoids, exfoliation, and intercalation were generated and the largest distance of 18.87 Å between MMT‐Na⁺ layers was produced at 16,000 rpm. The results indicate that homogenization was a beneficial method for effectively dispersing MMT‐Na⁺ layers in a chitosan polymer matrix and that a shear rate of 16,000 rpm was the effective condition. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The characterization of organic modified clay and clay‐filled PMMA nanocomposite

Recently, polymer–clay hybrid materials have received considerable attention from both a fundamental research and application point of view. 1 - 3 This organic–inorganic hybrid, which contains a nanoscale dispersion of the layered silicates, is a material with greatly improved physical and mechanical characteristics. These nanocomposites are synthesized through in situ polymerization or direct intercalation of the organically modified layered silicate (OLS) into the polymer matrix. Thus, understanding the relationship between the molecular structure and the thermal stability (decomposition temperature, rate, and the degradation products) of the OLS is critical. In this study, modern thermal analysis techniques combined with infrared spectroscopy and mass spectrometry (TGA‐FTIR‐MS) were used to obtain information on the thermal stability and degradation products of organic modified clay. Furthermore, the thermal and mechanical properties of clay‐filled PMMA nanocomposites were determined by using TGA and DSC. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1702–1710, 2002     

Thermal,mechanical, and gas barrier properties of ethylene–vinyl alcohol copolymer‐based nanocomposites for food packaging films: Effects of nanoclay loading

For the application of single‐layer food packaging films with improved barrier properties, an attempt was made to prepare ethylene‐vinyl alcohol (EVOH) copolymer‐based nanocomposite films by incorporation of organically modified montmorillonite nanoclays via a two‐step mixing process and solvent cast method. The highly intercalated tactoids coexisted with exfoliated clay nanosheets, and the extent of intercalation and exfoliation depended significantly on the level of clay loadings, which were confirmed from both XRD measurements and TEM observations. It was revealed that the inclusion of nanoclay up to an appropriate level of content resulted in a remarkable enhancement in the thermal, mechanical (tensile strength/modulus), optical, and barrier properties of the prepared EVOH/clay nanocomposite films. However, excess clay loadings gave rise to a reduction in the tensile properties (strength/modulus/elongation) and optical transparency due to the formation of clay tactoids with a larger domain size. With the addition of only 3 wt % clay, the oxygen and water vapor barrier performances of the nanocomposite films were substantially improved by 59 and 90%, respectively, compared to the performances of the neat EVOH film. In addition, the presence of clay nanosheets in the EVOH matrix was found to significantly suppress the moisture‐derived deterioration in the oxygen barrier performance, implying the feasibility of applying the nanocomposite films to single‐layer food packaging films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40289.     

Effects of preparation method on microstructure and properties of UV‐curable nanocomposite coatings containing silica

UV‐curable nanocomposites were prepared by the blending method or the in situ method with nanosilica obtained from a sol–gel process. The microstructure and properties of the nanocomposite coatings were investigated using ²⁹Si‐NMR cross‐polarization/magic‐angle spinning, transmission electron microscopy (TEM), Fourier transform IR (FTIR), differential scanning calorimetry (DSC), and UV–visible (UV–vis) spectra, respectively. The NMR and TEM showed that during the blending method, tetraethyl orthosilicate (TEOS) completely hydrolyzed to form nanosilica particles, which were evenly dispersed in the polymer matrix. However, for the in situ method, TEOS partially hydrolyzed to form some kind of microstructure and morphology of inorganic phases intertwisted with organic molecules. FTIR analysis indicated that the nanocomposites prepared from the in situ method had much higher curing rates than those from the blending method. DSC and UV–vis measurements showed that the blending method caused higher glass‐transition temperatures and UV absorbance than the in situ method. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1119–1124, 2005     

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     

Enhancing the thermo‐oxidative stability of PLA through the use of hybrid organic–inorganic coatings

PLA samples have been coated with organic–inorganic hybrid films containing SiO₂ as inorganic phase and two different types of organic phase PEO or PCL. Sol–gel solutions, spin coating deposition, and mild thermal treatments have been used to form thin protective coatings. Coated and uncoated PLA samples have been submitted to accelerated thermo‐oxidative stresses at 120 °C in air up to about 400 h. The extent of the damage induced by this treatment has been evaluated by different techniques. Coated samples of both compositions are able to increase the resistance to thermo‐oxidation of PLA as proved by the smaller reduction of molecular weight. This effect is probably deriving from the reduced oxygen permeability, as well as from the constrained outward diffusion and recombination of the cyclic oligomers produced by intramolecular transesterification reactions of polyester chains. Data so far collected underline also a long‐term stability and adherence of the hybrid coatings during the entire aging process and hint at the possibility of using PLA in more demanding applications than that of packaging (i.e., electric industry, automotive field, or housewares). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43897.     

A novel method to prepare chitosan/montmorillonite nanocomposites

We are proposing a novel method to prepare chitosan/montmorillonite nanocomposites. The montmorillonite (MMT) clay was excavated from the mountainside of eastern Taiwan. After being purified, it was incorporated with potassium persulfate (KPS) through the intercalation process. As the KPS‐incorporated MMT was dispersed in the acidified aqueous solution of chitosan, the KPS instantly reacted with the chitosan, resulting in the cleavage of polymer chains and exfoliation of MMT as well. After removing the unexfoliated MMT, solutions were cast to form a film of chitosan/MMT nanocomposite. Interestingly, the exfoliated MMT layers were found to flatten out in parallel with the surface, which not only increased the tensile strength of the chitosan film but also hindered degradation in the vitro test. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2042–2047, 2005     

Transparent low‐density polyethylene/starch nanocomposite films

Low‐density polyethylene (LDPE)/starch nanocomposite films were prepared by melt extrusion process. The first step includes the preparation of starch–clay nanocomposite by solution intercalation method. The resultant product was then melt mixed with the main matrix, which is LDPE. Maleic anhydride‐grafted polyethylene (MAgPE), produced by reactive extrusion, was used as a compatibilizer between starch and LDPE phases. The effects of using compatibilizer, clay, and plasticizers on physico‐mechanical properties were investigated. The results indicated that the initial intercalation reaction of clay layers with starch molecules, the conversion of starch into thermoplastic starch (TPS) by plasticizers, and using MAgPE as a compatibilizer provided uniform distribution of both starch particles and clay layers, without any need of alkyl ammonium treatment, in LDPE matrix. The nanocomposite films exhibited better tensile properties compared to clay‐free ones. In addition, the transparency of LDPE film did not significantly change in the presence of TPS and clay particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Adhesion and permeability of polyimide–clay nanocomposite films for protective coatings

A polyimide (PI)–clay nanocomposite was prepared from a solution of poly(amic acid), a precursor of 2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and p‐phenylenediamine, and dodecylamine–montmorillonite. Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, and atomic absorption spectroscopy were used to verify the incorporation of the modifying agents into the clay structure and the intercalation of the modified clay into the PI matrix. Both PI and PI–clay films were subsequently prepared by solution casting. The gas permeability, resistivity, and adhesion properties were determined. In the case of gas permeability, only a 3 wt % addition of clay reduced oxygen permeability to less than half that of unfilled PI. Furthermore, this hybrid showed an improvement in electrical resistivity because of the prevention of electrical tree growth by clay particles. More importantly, adhesion between the films and silicon increased with increasing clay content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2875–2881, 2003     

Synthesis,characterization and properties of clay‐polyacrylate hybrid materials

A new type of hybrid material of clay with poly (butyl acrylate) (PBA) has been prepared successfully using intercalation‐polymerization process. The structure of the composite was investigated by X‐ray diffraction (XRD), Fourier transform infrared (FTIR), Transmission electron microscope (TEM), and Thermogravimetric analysis (TGA). The results show that the hybrid material prepared has a decomposition central temperature of 485.6°C, 83°C higher than that of pure PBA (402.0°C). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 796–801, 2000