Linseed oil derived terpolymer/silica nanocomposite materials for anticorrosive coatings

Formulation of sustainable resource-based organic–inorganic hybrid protective coatings have been achieved using Linseed oil-based silica hybrid with terpolymer (TP) as basic skeletal matrix. The fabrication of TP system was performed by using systematic one pot multi-facile steps (diol fatty amide–linseed oil-based polyester amide TP) synthesis route. The conversion of ester amide functional ends of TP to urethane was initiated to enhance adhesiveness, impermeability, and corrosion resistivity of the processed hybrid material. FT-IR and NMR (¹H, ¹³C, and ²⁹Si) studies help in verifying the chemical structure and progress of the reaction. The formulation of smooth corrosion resistive coating was further analyzed by transmission electron microscopy, scanning electron microscope, and electrochemical corrosion studies. The in-situ tethering and homogeneous dispersion of inorganic moiety in nanoregime throughout the TP system further enhances the stability, wettability, and corrosion protection ability of the nanohybrid vegetable oil-based coating under corrosive environment. High phase angle value at higher frequency end indicates the stability of the coating system. Such coating systems composed of sustainable resource with improved mechanical, thermal, and corrosion protective properties have great potential in future applications.     

Microstructural features, diffusion and molecular relaxations in polyimide/silica hybrids

FTIR spectroscopy has been used to investigate the microstructure of the inorganic phase in polyimide/silica hybrids obtained by the sol-gel route. It has been shown that the presence of a coupling agent (GOTMS) strongly influences the silica phase by favoring the formation of linear, branched chains which make the structure loosely interconnected. The morphological changes induced by GOTMS are reflected in the water sorption properties of the investigated systems. Due to the hydrophilic nature of the silica phase, the amount of sorbed water increases in the hybrid systems in comparison to the pristine polyimide, and among the two hybrids, increases more in the two-phase system than in the co-continuous. Molecular interactions of the hydrogen-bonding type have been identified between the imide units and the H₂O molecules, both in the polyimide and in the hybrid systems. Finally, the sub-T_g relaxation processes have been investigated in detail by dynamic-mechanical analysis coupled with molecular mechanics simulations. Considerable effects of the inorganic phase on these processes were observed, especially for the case of the co-continuous systems, and were accounted for by molecular scale contiguity among the phases.     

Preparation and characterization of phosphine oxide based polyurethane/silica nanocomposite via non-isocyanate route

A novel carbonate-modified bis(4-glycidyloxy phenyl) phenyl phosphine oxide (CBGPPO) was synthesized to prepare phosphine oxide based polyurethane/silica nanocomposites. Spherical silica particles were prepared according to Stöber method and modified with cyclic carbonate functional silane coupling agent (CPS) to improve the compatibility of silica particles and organic phase. The cyclic carbonate-modified epoxy resins and silica particles were used to prepare hybrid coatings using hexamethylene diamine as a curing agent. The cupping, impact and gloss measurements were performed on aluminum panels, and the tensile test, gel content, thermal and morphological analyses were conducted on the free films. No damage was observed in the impact strength of the coatings. Incorporation of silica and CBGPPO into formulations increased modulus and hardness of the coating making the material more brittle. It was also observed that, the thermal stability of hybrid coatings enhanced with the addition of silica and CBGPPO.     

A new strategy to improve alkyd/acrylic compatibilization in waterborne hybrid dispersions

Grafting of alkyd resin to the acrylic polymer is needed to fully exploit the possibilities of these hybrids; but in the current technology, grafting is accompanied by an important reduction of the unsaturated groups of the alkyds, which adversely affects the curing of the film and its properties. A novel strategy that overcomes these limitations is presented. The strategy is based on the use of alkyd resin functionalized with methacrylic groups, that substantially improved the incorporation of the resin to the growing acrylic polymer chain, and the polymer particle homogeneity, without decreasing the degree of unsaturation in the alkyd resin.     

Corrosion protection evaluation of silica/epoxy hybrid nanocomposite coatings to AA2024

Silica-based organic–inorganic hybrid nanocomposite films have been developed by sol–gel method for corrosion protection of AA2024 alloy. The sol–gel films have been synthesized from 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) precursors. Interlinked organic–inorganic networks can be formed because of the presence of both epoxy and silicon alkoxide functionalities in the precursor molecules. In order to investigate the effective factors on the properties of organically modified silicates films (Ormosils), different coatings with different organic and hydrolysis water content were developed. The films were prepared by dip-coating technique. The chemical composition and the structure of the hybrid sol–gel films were studied by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM), respectively. The corrosion protection properties of the films were studied by potentiodynamic scanning (PDS) and salt spray tests. The results indicate that the hybrid films provided exceptional barrier and corrosion protection in comparison with untreated aluminium alloy substrate.     

Morphology and thermo-mechanical properties of new hybrid coatings based on polyester/melamine resin and pyrogenic silica

Polyester/melamine (PM)-based formulations used in coil-coating applications were modified with pyrogenic silicas of different types. The influence of the chemical modification of the silica surface on various properties was investigated. The viscosity of filled PM formulations was measured. Transmission electron microscopy and dynamic mechanical measurements were used to characterize nanocomposite films. Roughness and gloss measurements were done on nanocomposite coatings. The results show that the viscosity and morphology observed are directly linked to the balance and nature of the interactions developed between the silica surface and the organic medium. Both hydrophilic and hydrophobic silica lead to too high viscosity of the filled formulation, to different silica dispersion and, as a consequence, to low gloss coatings. However with an adequate organo-modification of the silica, formulations compatible with the process and having a high gloss can be obtained. Additionally, the surface modification of silica has no obvious influence on the dynamic mechanical properties.     

Wear,thermal, and physical properties of fluorine-containing polyimide/silica hybrid nanocomposite coatings

This study prepared fluorine and SiO₂ particles containing organic–inorganic hybrid polyimide nanocomposite coatings (PISFs) with inorganic content in the range of 5–20% in pure polyimide solutions via the sol–gel process. Polyimide hybrid structures containing fluorine and SiO₂ particles were synthesized by using perfluorooctyltriethoxysilane and tetraethyl orthosilicate. These formulations were applied on aluminum sheets by using a 75 μm wire wound applicator, and the coatings were cured for 8 h at room temperature and then 24 h at 100 °C. Increased inorganic contents caused slight decreases in the initial decomposition temperatures, but the char yield values increased for PISF15 and PISF20. All samples exhibited hydrophobic properties. When all samples were compared, PISF5 and PISF10 exhibited hydrophobicity, high wear resistance and thermal properties. Additionally, PISF5 and PISF10 showed high adhesion, hardness, and methyl ethyl ketone solvent resistance. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47399.     

Preparation and characterization of polyurethane/silica aerogel nanocomposite materials

In this investigation, silica aerogel (SA)/Rigid Polyurethane (PUR) foam composites and silica aerogel/Polyurethane (PU) composites were prepared by dry mixing of granular and grinded silica aerogels with polyol part. They were then combined with diisocyanate part. Three different types of PUR foams and an elastomeric coating grade of PU were studied as well. Results show that thermal conductivity of foams did not decrease by adding silica aerogel. It even increased for some grades which is assumed to be due to the change in cell configuration of these foams. It was also found that sound insulation performance of these cellular composites did not improve significantly. Unlike foam composites, addition of silica aerogel into elastomeric PU improved its thermal and acoustic insulation properties. Because of the more promising properties of elastomeric PU composites, further examinations including measurements of compression strength and water contact angle of silica aerogel/PU composites were also taken. Final results showed a significant improvement in general properties of PU coatings by adding little amounts of silica aerogel (1–4 wt %). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44521.     

PMMA/silica nanocomposite studies: Synthesis and properties

Polymethylmethacrylate (PMMA)/silica nanocomposites are prepared by solution polymerization in this project and the resulting materials are subjected to characterization to evaluate thermal, mechanical, and fire properties. IR results show that both (3‐acryloxypropyl)methydimethoxy‐silane (APMDMOS) and (3‐acryloxypropyl)trimethoxysilane (APTMOS) can serve as reagents for the surface modification of silica, while APTMOS performed better than APMDMOS for the modification of the silica surface. Mechanical properties of PMMA/silica nanocomposites prepared by solution blending showed decreased tensile strength and elongation at break, while materials from solution polymerization performed better than PMMA itself. Moreover, all prepared samples have shown improved thermal stabilities versus PMMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3844–3850, 2004     

Preparation and characterization of UV-curable epoxy/silica nanocomposite coatings

To enhance the interfacial interaction in silica nanoparticles filled polymer composites, the silica surface was firstly treated with glycidoxypropyl trimethoxysilane (GPTMS), and its structure was analyzed by ¹³C NMR and FTIR spectrophotometry. Then a series of GPTMS-modified silica/cycloaliphatic epoxy nanocomposite coatings with 0–6 wt% silica content were prepared by UV-induced cationic polymerization in the presence of a diaryliodonium photoinitiator and thioxanthone photosensitizer. The physical and mechanical properties such as hardness, adhesion, gloss, impact as well as tensile strength were examined. As a result, these composites demonstrated superior tensile strength and tensile modulus with increasing proportion of modified silica up to a certain level. An increase in abrasion resistance of nanocomposites with the addition of modified silica was observed. The thermal stability of nanocomposites was not enhanced with the addition of silica particles. SEM studies indicate that silica particles were dispersed homogenously through the polymer matrix.     

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.     

Linseed amide diol/DGEBA epoxy blends for coating applications: Preparation,characterization, ageing studies and coating properties

Linseed amide diol [HELA] was used as modifier for conventionally available epoxy resin [DGEBA] by blending in different ratio. Blends [DGEBA/HELA] were subjected to spectral, physico-chemical, ageing and antibacterial studies. Interesting features of the blends were complete miscibility of HELA with DGEBA, principally due to hydrogen bonding and chemical reaction between the two constituents, and their moderate antibacterial activity against S. aureus. DGEBA/HELA blends were further treated with triethylenetetramine [TETA-A] [DGEBA/HELA/A] as curing agent to evaluate their performance as corrosion protective coating materials. DGEBA/HELA/A coatings showed good physico-mechanical and chemical resistance behavior, in particular against alkaline media. Thermal analysis of DGEBA/HELA/A revealed their single to multi-step degradation behavior with safe usage upto 220 °C. Our investigations confirm the dual role of HELA as environment-friendly, reactive-modifier and mild curing agent for epoxy resins. Besides, DGEBA/HELA/A may find potential applications as “solvent free”, ambient temperature cured antibacterial coating materials.     

Polyamide-6,6/in situ silica hybrid nanocomposites by sol-gel technique: synthesis, characterization and properties

The organic-inorganic hybrid nanocomposites comprising of poly(iminohexamethyleneiminoadipoyl), better known as Polyamide-6,6 (abbreviated henceforth as PA66), and silica (SiO₂) were synthesized through sol-gel technique at ambient temperature. The inorganic phase was generated in situ by hydrolysis-condensation of tetraethoxysilane (TEOS) in different concentrations, under acid catalysis, in presence of the organic phase, PA66, dissolved in formic acid. Infrared (IR) spectroscopy was used to monitor the microstructural evolution of the silica phase in the PA66 matrix. Wide angle X-ray scattering (WAXS) studies showed that the crystallinity in PA66 phase decreased with increasing silica content. Atomic force microscopy (AFM) of the nanocomposite films revealed the dispersion of SiO₂ particle with dimensions of <100 nm in the form of network as well as linear structure. X-ray silicon mapping further confirmed the homogeneous dispersion of the silica phase in the bulk of the organic phase. The melting peak temperatures slightly decreased compared to neat PA66, while an improvement in thermal stability by about 20 °C was achieved with hybrid nanocomposite films, as indicated by thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) exhibited significant improvement in storage modulus (E′) for the hybrid nanocomposites over the control specimen. An increase in Young's modulus and tensile strength of the hybrid films was also observed with an increase in silica content, indicating significant reinforcement of the matrix in the presence of nanoparticles. Some properties of the in situ prepared PA66-silica nanocomposites were compared with those of conventional composites prepared using precipitated silica as the filler by solution casting from formic acid.     

Air-drying bio-based polyurethane dispersion from cardanol: Synthesis and characterization of coatings

Exploring bio-renewable materials to replace petroleum-based building blocks for advanced coatings has been a major thrust area for researchers for the development of eco-friendly and sustainable products. For the last few decades, there has been significant interest among coating researchers around the world to design water-based polyurethane dispersions (PUDs) that can be cured at ambient conditions. In the present work we synthesized auto-oxidizable PUDs based on cardanol as sustainable material that also provides self-crosslinking attribute to the PUDs. Such types of PUDs are expected to be suitable for water-based industrial protective primers. The cardanol-based intermediates and final products are characterized by FTIR spectroscopy for conformation of synthesis reaction and their structures. The dried films of the coatings, formulated using a suitable drier catalyst, exhibited improvement in mechanical properties and solvent resistance. The oxidative curing has also been investigated by FTIR and differential scanning calorimetry (DSC). The corrosion resistance properties of the coatings on steel substrate, as studied by using electrochemical impedance spectroscopy (EIS) technique also showed better performance for cross-linked films.     

Role of fumed silica on ion conduction and rheology in nanocomposite polymeric electrolytes

The electrochemical, rheological, calorimetric, spectroscopic and morphological investigations have been used to examine poly(methyl methacrylate), PMMA based electrolytes dispersed with nano-sized fumed silica (SiO₂). The observed ionic conductivity was one of the highest and is of the order ∼mS/cm at ambient temperature which was studied as a function of concentration of fumed silica nano-particles. It was further found that the fumed silica acted as a passive filler and played a predominant role in controlling the rheological properties while ion transport properties were least effected. The differential calorimetry studies revealed single glass transition temperature pointing towards homogeneous nature of the composite polymeric electrolytes (CPEs). At an optimum concentration of fumed silica (2 wt%) the observed maximum conductivity and morphology was attributed to the presence of a strong network structure, while at a higher concentration the elastic behavior was more pronounced which impeded ion transport. This contention was supported by spectroscopic data.     

Effect of organoclays on the properties of polyurethane/clay nanocomposite coatings

Linear, one‐binding‐site or two‐binding‐site (N⁺) organifiers with two hydroxyl end groups were synthesized, and novel organoclays were prepared through a cation‐exchange reaction between pristine sodium montmorillonite and the synthesized organifiers. After sonication of the as‐prepared organoclay in N,N′‐dimethylformamide for 10 min, the average size of the clay decreased to about 1 μm. The X‐ray diffraction patterns confirmed that the d‐spacing of the silicate layers of the organoclay expanded from 1.1 to about 1.9 nm and the peak intensity decreased with the molecular weight of the organifier increasing. Polyurethane/clay nanocomposites were synthesized by a one‐shot polymerization method. Both intercalated and exfoliated structures of the layered silicates in the polyurethane matrix were observed from transmission electron microscopy micrographs, and the d‐spacing ranged from 4 to 10 nm. The thermal and mechanical properties of the nanocomposite were enhanced by the introduction of the organoclay into the polyurethane matrix. An approximately 40–46°C increase in the onset decomposition temperature, a 200% increase in the tensile strength with a 0.5 wt % clay loading, and a 49% increase in Young's modulus with a 3 wt % clay loading were achieved. The effects of the molecular weight and the number of binding sites of the organifier on the properties of the nanocomposites were also evaluated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Sound absorption properties of polyurethane/nano‐silica nanocomposite foams

In this study, polyurethane (PU)/nano‐silica nancomposite foams were prepared. The effects of isocyanate index, cell size, density, and molecular weight of polyols on the sound absorption ratio of PU/nano‐silica foams were investigated. With increasing nano‐silica content, the sound absorption ratio of PU/nano‐silica foams increases over the entire frequency range investigated in this study. Decrease of isocyanate index, cell size, and increase of density leads to the increase of sound absorption ratio of PU/nano‐silica foams. PU/nano‐silica foams have a broad T_g centered around room temperature by decreasing molecular weight of polyol resulting in good sound absorbing ability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polymer/layered clay nanocomposites: 2 polyurethane nanocomposites

A kind of novel polyurethane/Na⁺-montmorillonite nanocomposites has been synthesised using modified 4,4′-di-phenymethylate diisocyanate (M-MDI), modified polyether polyol (MPP) and Na⁺-montmorillonite (layered clay). Here, MPP was used as a swelling agent to treat the layered clay. Experimental results indicated that with increasing the amount of layered clay, the strength and strain-at-break increased. The storage modulus below the glass transition temperature of the soft segments in the polyurethane was increased by more than 350%. With increased loading of layered clay, the thermal conductivity decreased slightly rather than increased. This finding will provide valuable information for polyurethane industry.     

Preparation and characterization of water reducible alkyd resin/colloidal silica nanocomposite coatings

In this study, water reducible alkyd resins containing different amounts of colloidal silica were synthesized for the first time. In order to achieve this, alkyd resin, which has an oil content of 35%, was prepared with tall oil fatty acid, isophthalic acid, trimellitic anhydride, and trimethylolpropane. The alkyd resin was neutralized with triethylamine, and was dissolved in an isobutyl alcohol-isopropyl alcohol-butyl glycol mixture to produce 75% (wt.) solution, which was called stock alkyd resin. The stock alkyd resin was diluted with water to 50% (wt.) concentration with water and colloidal silica mixture in order to prepare an alkyd solution containing 0%, 5%, 10%, 15% and 20% colloidal silica. Then the effect of the silica nanoparticle addition on the surface coating properties, thermal behaviors and surface morphologies of water reducible alkyd resins was investigated. As a result, the addition of colloidal silica has improved surface coating properties and thermal behaviors of nanocomposite water reducible alkyd resin.     

Preparation and characterization of phosphine oxide based polyurethane/silica nanocomposite via non-isocyanate route

A novel carbonate-modified bis(4-glycidyloxy phenyl) phenyl phosphine oxide (CBGPPO) was synthesized to prepare phosphine oxide based polyurethane/silica nanocomposites. Spherical silica particles were prepared according to Stöber method and modified with cyclic carbonate functional silane coupling agent (CPS) to improve the compatibility of silica particles and organic phase. The cyclic carbonate-modified epoxy resins and silica particles were used to prepare hybrid coatings using hexamethylene diamine as a curing agent. The cupping, impact and gloss measurements were performed on aluminum panels, and the tensile test, gel content, thermal and morphological analyses were conducted on the free films. No damage was observed in the impact strength of the coatings. Incorporation of silica and CBGPPO into formulations increased modulus and hardness of the coating making the material more brittle. It was also observed that, the thermal stability of hybrid coatings enhanced with the addition of silica and CBGPPO.