The utilization of carbon nitride to reinforce the mechanical and thermal properties of UV-curable waterborne polyurethane acrylate coatings

The waterborne polyurethane-acrylate (WPUA and Wsi-PUA) oligomers were prepared by anionic self-emulsifying method, using isophorone diisocyanate (IPDI), polyethylene glycol (PEG), dimethylol propionic acid (DMPA), vinyl hydroxyl silicone oil (VHSO) and hydroxyethyl methyl acrylate (HEMA) as raw materials. Then, a series of UV-curable waterborne Wsi-PUA–C₃N₄ composites containing different content of g-C₃N₄ were obtained with oligomer and photoinitiator Darocur 1173. FTIR, XRD, TEM, SEM, and TGA were employed to investigate the structure, morphology and thermal property of the Wsi-PUA–C₃N₄ composite films. The effect of g-C₃N₄ content on the performance was also investigated. The mechanical performance, water resistance and gel content of UV-PUA films were measured. It was found that with g-C₃N₄ particle was introduced into Wsi-PUA oligomer, the hardness, tensile strength, gel content, water resistance and thermal stability of composite films were significantly augmented. Moreover, when the content of g-C₃N₄ was 1.0 wt.%, the UV-curable film had the best mechanical property. The obtained composite is promising for a number of applications, e.g., for protecting the surfaces of metal and wood.     

Effect of clay on the corrosion inhibition and dynamic mechanical properties of epoxy ester–polyurea–polysiloxane hybrid coatings

The corrosion resistance of polymeric coatings containing epoxy ester, polyurea, and polymethylhydrosiloxane was significantly improved by the addition of cloisite 15A organoclay. The weight percent of organoclay was varied from 0.5 to 10%. The presence of organoclay in the coatings was confirmed using the Fourier transformed infrared spectroscopy. The effect of organoclay on the surface energy of the coatings was analyzed by measuring contact angle with a video contact angle analyzer and using water and iodomethane as the probing liquids. The surface energy of the coatings increased with increasing organoclay concentration. The corrosion resistant properties were measured by direct current polarization technique. The addition of organoclay enhanced the corrosion resistance of the coatings, and the best corrosion resistance was shown by coating containing 1% organoclay. The dynamic mechanical property of the coatings was determined using the dynamic mechanical spectrometer. The glass transition temperature of the films decreased significantly with the addition of organoclay up to 1% after which it increased with additional increase in the wt% of organoclay. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

The effect of donor-acceptor interactions on the mechanical properties of wood

This paper explores the empirical correlations between the mechanical properties of solvent-treated wood and solvent parameters. Wood beams (10 inch x 0.7 inch x 0.4 inch) of lauan, birch, and Douglas fir were soaked in five solvents (benzene, dioxane, methanol, dimethyl sulfoxide, and distilled water) for 4 months at room temperature (23°C) and then mechanically tested in bending. The acoustic emission (AE) energy (related to failure energy), the modulus of rupture (MOR), and the modulus of elasticity (MOE) of the specimens were determined. It was found that all of these properties of the specimens decreased with the solvent strength parameter which was related to acceptor number (AN), donor number (DN) and molecular volume (MV ). The linear correlation of the AE energy of the specimens with the solvent parameter (AN + DN)^1/2 was verified. Alternative relationships between the AE energy, MOR or NIOE of the specimens and the modified solvent strength parameters, 2.5 DN + AN or DN/MV^1/3, were explored. The microstructures of fracture surfaces of lauan specimens were examined by scanning electron microscopy (SEM) and showed dramatic changes when the solvent strength increased, such as microfibril pull-out and a decrease in roughness of the fracture surfaces of cell walls. All these observations reflected the changes in mechanical properties and the mean AE energy qualities of the specimens.     

Preparation and properties of novel high performance UV-curable epoxy acrylate/hyperbranched polysiloxane coatings

Novel high performance UV-curable coatings based on epoxy acrylate (EA) oligomer and hyperbranched polysiloxane (HPSi) were prepared, the effect of HPSi on the processing of uncured EA/HPSi system and integrated performance of cured resins is evaluated. Results show that a small addition of HPSi can greatly decrease the viscosity of EA oliogmer, while the viscosity almost does not reduces as the content of HPSi continuously increases owing to the interaction between HPSi and EA oligomer. The integrated performance of cured resins is closely related with the content of HPSi, those resins with suitable contents of HPSi have significantly improved toughness and stiffness as well as thermal and moisture resistance. The origin of all these changes in macro-performance are investigated and proved to be resulted from the variety in the chemical structure and crosslinking density induced by the addition of HPSi. These attractive features of EA/HPSi resins suggest that HPSi is an effective multi-functional diluent for UV-curable EA resin, and the method proposed herein is a new approach to develop high performance UV-curable coatings, solvent-free resins, etc., for cutting-edge industries.     

Functionalized graphene-reinforced polysiloxane nanocomposite with improved mechanical performance and efficient healing properties

It is a challenge to design nanofiller reinforced self-healing nanocomposites with both improved mechanical properties and highly efficient self-healing properties. In this work, we report a self-healing polysiloxane nanocomposite using furan-functionalized graphene (G-FA) as reinforcement based on Diels−Alder (DA) chemistry. The formed interactions between G-FA and polysiloxane chains were reversible DA bonds, which negligibly affected the nanocomposites healing efficiency. The self-healing polysiloxane nanocomposite with 6% G-FA has a tensile strength of 0.25 MPa that was improved by 140% when compared to an elastomer without G-FA. The healable polysiloxane nanocomposite recovered more than 90% of its tensile strength and 98% of its elongation-at-break, demonstrating that the nanocomposite exhibited highly efficient self-healing properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47725.     

Optimization of the mechanical properties of magnetron sputtered diamond-like carbon coatings

Diamond-like carbon coatings containing hydrogen, a-C:H, were deposited by use of reactive DC magnetron sputtering with an industrial deposition system. The reactive gas C₂H₂ was used in combination with carbon targets. Using Raman spectroscopy, nanoindentation and Rockwell C indentation, the mechanical properties of the coatings were optimized. Excessively high compressive stresses, which were measured with Raman spectroscopy, were found in the coatings with high hardness, resulting in poor adhesion to the substrates. By thermal annealing, these compressive stresses were reduced without altering the hardness, resulting in diamond-like carbon coatings with good adhesion.     

Conversion behaviour and resulting mechanical properties of polysilazane-based coatings

Polymer-derived ceramics exhibit a convenient route for the processing of low-dimensional ceramics like coatings or fibres. In previous investigations unfilled and composite coatings have been developed using ammonolysed bis(dichloromethylsilyl)ethane (ABSE) or perhydropolysilazane (PHPS) as precursors and BN, ZrO₂ or glass particles as filler materials. The coating systems provide excellent corrosion and oxidation resistance to underlying metals. This paper reports on the effect of the precursor system and the pyrolysis parameters on the conversion behaviour, shrinkage and mechanical properties, including hardness and Young's modulus, of ABSE- and PHPS-based coatings. Therefore the crosslinking and pyrolysis behaviour as well as the mechanical properties of the coatings were investigated up to pyrolysis temperatures of 1000 °C in nitrogen and in air by ATR-IR, SEM, profilometry and nanoindentation measurements. The coatings pyrolysed at 1000 °C in nitrogen, have hardness values of 13 GPa and Young's moduli up to 155 GPa.     

The effect of morphology on the corrosion inhibition and mechanical properties of hybrid polymer coatings

The durability and mechanical properties of epoxy ester coatings and films has been improved by blending with rigid aromatic polyurea (PU). The interaction of PU and epoxy ester was enhanced by coupling the polymers with polymethylhydrosiloxane. The reactions between various entities are analyzed by Fourier transform infrared spectroscopy and the change in physical and mechanical properties are studied by a dynamic mechanical analyzer. The corrosion resistance of the hybrid coatings was measured by direct current polarization method, direct current polarization (DCP). The addition of polymethylhydrosiloxane enhances the corrosion properties in the hybrid coatings. The surface morphology was analyzed by scanning electron microscopy. The glass transition temperature of the films increases with increasing PU concentration and a wide glass rubber transition range for hybrid coatings was achieved which confirms the higher impact strength of the hybrid coatings and films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The influence of ultra-fine glass fibers on the mechanical and anticorrosion properties of epoxy coatings

The effects of different contents of ultra-fine glass fiber on mechanical and anticorrosion properties of epoxy coatings have been investigated. The FTIR and SEM have been used to analyze the surface nature and microstructure of the coatings. Electrochemical impedance spectroscopy (EIS) and a salt spray test have also been used to characterize the contents of ultra-fine glass fibers on the impedance of the coatings. When 10%, 20%, 30% of ultra-fine glass fibers are added to the coatings, their hardness and adhesion increases by 67%, 67%, 200% and 21.6%, 39%, 40%, respectively, compared with the properties of the pure coating. But the anticorrosion properties of the coatings containing high ultra-fine glass fiber content decreased with respect to the pure coatings properties.     

Effect of pigmentation on polyurethane/polysiloxane hybrid coatings

Rutile TiO₂ was formulated into polyurethane/polysiloxane hybrid coatings in order to investigate the influence of pigmentation on the inorganic phase of the hybrid coatings. Two urethanes were prepared from the isocyanurate of hexane diisocyanate (HDI), alkoxysilane modified HDI, and tetraethyl orthosilicate (TEOS) oligomers, with oligoesters derived from either cyclohexane diacids (CHDA) and 2‐butyl‐2‐ethyl‐1,3‐propanediol (BEPD) or adipic acid (AA), isophthalic acid (IPA), 1,6‐hexanediol (HD), and trimethylol propane (TMP). The oligoesters were spectroscopically characterized using GPC, FT‐IR, and NMR. Chemical interaction between the TiO₂ and the sol–gel precursor was investigated using solid‐state ²⁹Si NMR and XPS. The morphology, mechanical, viscoelastic, thermal properties of the pigmented coatings are evaluated as a function of pigmentation volume concentration (PVC). Using AFM and SEM, the pigment was observed to be well dispersed in the polymer binder. The thermal stability, the tensile modulus, and strength of the coatings were enhanced with increasing PVC, whereas the pull‐off adhesion and flexibility (elongation‐at‐break) were reduced with increasing PVC. Finally, the pigmented coatings were evaluated by electrochemical impedance spectroscopy (EIS) and the results showed that 10 wt % of the pigment improved the corrosion resistance of the entire coating system. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42947.     

Effects of thickness and substrate on the mechanical properties of hard coatings

Nanoindentation technique was employed to characterize the mechanical properties of TiN coatings deposited on high-speed steel and stainless steel substrates. Effects of thickness and substrate on-the mechanical properties were investigated. The results show that TiN coatings exhibit different mechanical properties corresponding to the variation in thickness and substrate.     

Relation between chip resistance and mechanical properties of automotive coatings

This work addresses the correlation between stone-chip resistance and mechanical properties of automotive solid colour coating systems. Single-impact tests, which are believed to realistically simulate chipping due to stone impact, were performed to investigate eight different coating systems. Additionally, conventional tests on chip resistance currently used in automotive industry were performed. Results were related to mechanical properties of the coatings, measured by dynamic mechanical thermal analysis and double cantilever adhesion test. It is found that coating systems with a low glass transition temperature for the primer have better stone-chip resistance.     

Investigations on the mechanical properties of hybrid nanocomposite hard coatings on polycarbonate

Hybrid nanocomposite coatings derived from titanium tetraisopropoxide and epoxy or acrylic modified silanes were deposited on polycarbonate (PC) by dip coating employing various withdrawal speeds followed by ultraviolet and thermal curing. The effect of different organic functional groups in the precursors and ageing effect of these sols were systematically studied with respect to thickness, abrasion resistance, pencil scratch test, nanoindentation hardness and transmittance. The gels derived from the freshly prepared and aged sols were structurally characterized by FT-IR and TEM analysis. The viscosities of the sols were monitored with time. The change in viscosity is rapid for sol from epoxy modified silane. The thickness of the coatings increases with increase in viscosity in case of both the silane precursors. The scratch as well as abrasion resistance increases as a function of coating thickness. The pencil scratch hardness improves from 2B for the bare PC to a maximum of 3H for the coating obtained from an aged sol derived from epoxy modified silane. Also, the abrasion resistance of the coatings from same sol was maximum as evidenced by a <6% change in haze after 500 cycles, vis-a-vis 40% for the bare PC. The coatings from a freshly prepared sol of acrylic modified silane and titania showed the maximum nanoindentation hardness of 0.52 GPa, when compared to 0.23 GPa for the bare PC.     

Thermal and mechanical properties of crack-designed thick lanthanum zirconate coatings

Vertical cracks are beneficial in thermal barrier coatings due to enhanced thermo-mechanical compliance. Accordingly, an aqueous nitrate based precursor solution was atomized on stainless steel substrates by spray pyrolysis to deposit thick crack-designed lanthanum zirconate coatings. Coatings with designed crack patterns were deposited and characterized by electron microscopy, tribology, Vickers indentation, and thermal diffusivity. The crystallization of the coatings was investigated by in situ high temperature X-ray diffraction. The green coatings crystallized from 600 °C and the pyrochlore structure was formed after heat treatment at 1000 °C. Crystalline lanthanum zirconate multilayered coatings with small crack spacing and crack opening exhibited a higher density, a higher hardness, lower thermal diffusivities, and higher thermal conductivities compared to crystalline monolayered coatings of similar thickness with large crack spacing and crack opening. The thermal diffusivity of the coatings, ∼28 mm²/s at room temperature, was similar to the values reported for yttria-stabilized zirconia plasma sprayed coatings.     

Tuning the mechanical properties of UV coatings towards hard and flexible systems

The standard resins of radiation-curable coatings provide either hard or flexible coatings dependent on the type of chemistry used. Whereas aromatic epoxide acrylates usually give hard and brittle coatings, urethane acrylates are known for their flexibility. Since the radiation curable systems should not contain solvents, the desired low viscosity for the specific application is adjusted with reactive monomers. This normally prevents the use of flexible high-molecular-weight polymers. On the other hand, the viscosity of dispersions is determined by the solid content only and not by the molecular weight of the polymers used. Thus, waterbased UV-curable coatings are one strategy out of this dilemma in order to combine the flexibility of higher-molecular-weight polymers with the hardness of highly crosslinked acrylates. The mechanical data of conventional and waterbased UV coatings are discussed in dependency on glass transition temperature and elastically effective chain length between crosslinks.