Effect of nanodiamond surface functionalization using oleylamine on the scratch behavior of polyacrylic/nanodiamond nanocomposite

Addition of hard particles such as nanodiamonds to polymers to improve their physical and mechanical properties is very common. However, nanodiamonds are usually hydrophilic so their tendency to form agglomerates in a polymeric matrix is quite strong. In this study, the effect of nanodiamond surface modification on its uniform dispersion in a polymeric matrix such as polyacrylic-base polymer clear coat was investigated. For this purpose, detonation nanodiamond (DND) with an average particle diameter of 4–6 nm was used. To improve dispersion of as-received DND (AR-DND) in the polymeric matrix, the surfaces of the particles were modified by heat treatment (oxidation) in air and followed by functionalization using oleylamine (OLA) as surfactant. So, nanocomposites with different contents of AR-DND, HT-DND and OLA treated HT- DND (OLA-HT-DND) particles were produced. Their characterizations were investigated by employing many analytical methods such as: Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermo-gravimetry analysis (TGA). Scratch resistance test and study of coating surfaces, using scanning tunneling microscopy (STM), were carried out on the polymeric nanocomposites. The results showed that the surface-functionalized nanodiamonds are highly dispersive and stable in the polymeric matrix. In addition, scratch resistance was increased with the addition of nanoparticles.     

Surface texture effect on scratch behavior of injection molded plastics

The influence of surface texture pattern, i.e. distance between spherical bumps on the scratch behavior of injection molded polypropylene and polycarbonate has been investigated using a progressive load scratch test according to ISO 19252. The results show that the scratch properties can be enhanced when the distance between spherical bumps decreased. To understand the influence of distance between spherical bumps, polarizing optical microscope was used to observe the subsurface deformation. It was found that the size and depth of the deformation zone become smaller and shallower when the distance between spherical bumps decreased. This is the evidence that less stress concentration was generated under a scratch tip when the distance became shorter. POLYM. ENG. SCI., 52:1862–1867, 2012. © 2012 Society of Plastics Engineers     

Effect of heat treatment of nanodiamonds on the scratch behavior of polyacrylic/nanodiamond nanocomposite clear coats

In the current paper, effects of heat treatment of nanodiamond particles on the scratch behavior of polyacrylic/diamond nanocomposite coatings were studied. Two types of nanodiamond, i.e. one produced by detonation synthesis (DND) and the other produced by nondetonation synthesis (NDND) were used as reinforcement phase to increase scratch resistance of polyacrylic base polymeric clear coat. Heat treatment was used as the surface modification route. Coatings containing both types of particles in two surface conditions (as-received and heat treated) were compared to each other and also to the neat polyacrylic coating. The results showed strong effect of heat treatment on scratch resistance of coatings based on the scratch width criterion. The effect of heat treatment was more pronounced on DND particles than on NDNDs. However the pendulum hardness showed a reverse trend.     

Effect of graphene and CNT reinforcement on mechanical and thermomechanical behavior of epoxy—A comparative study

Graphene‐nanoplateles (Gr) and multiwalled carbon nanotubes (CNTs) reinforced epoxy based composites were fabricated using ultrasonication, a strong tool for effective dispersion of Gr/CNTs in epoxy. The effect of individual addition of two different nanofillers (Gr and CNT) in epoxy matrix, for a range of nanofiller content (0.1–1 wt %), has been investigated in this study. This study compares mechanical and thermomechanical behavior of Gr and CNT reinforced epoxy. Gr reinforcement offers higher improvement in strength, Young's modulus, and hardness than CNT, at ≤0.2 wt %. However, mode‐I fracture toughness shows different trend. The maximum improvement in fracture toughness observed for epoxy‐Gr composite was 102% (with 0.3 wt % loading of Gr) and the same for epoxy‐CNT composite was 152% (with 0.5 wt % loading of CNT). Thorough microstructural studies are performed to evaluate dispersion, strengthening, and toughening mechanisms, active with different nanofillers. The results obtained from all the studies are thoroughly analyzed to comprehend the effect of nanofillers, individually, on the performance of the composites in structural applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46101.     

A comparative study on effect of aromatic polyimide chain conformation on reinforcement of carbon nanotube/polyimide nanocomposites

Two kinds of polyimides (PIs) were selected as matrices for multiwalled carbon nanotubes (CNTs)‐based nanocomposites. The two PIs were initially synthesized through reactions of a same benzoxazole‐containing diamine with two different dianhydrids. A linear PI was formed from the ether bond‐containing dianhydride, while a nonlinear PI was formed from the ? C(CF3)_2? groups containing dianhydride. Optimized dispersion of nanotubes in both kinds of PIs was found to be at a concentration with 0.5 wt % COOH‐CNT, where great enhancement was achieved for both PIs. It was also found that introducing nanotubes into PI matrices aroused more significant increase of Young's modulus and break stress in linear PI than that in nonlinear PI. To determine the key parameters involved in design of PIs for maximum reinforcement efficiency using CNT as the nanofiller, the nanoscopic dispersion state of the nanotubes in diamine solution and their reaction were investigated via morphological and spectroscopic studies. The interfacial interactions between nanotubes and two PI chains were characterized by FT‐IR and Raman spectroscopy. The fracture surface characteristics of two series of CNT/PI nanocomposites were further investigated using SEM. Our findings show that the diamine plays a double role for the in‐situ polymerization, a dispersant to disentangle the CNT agglomerates and a monomer for PI synthesis with dianhydrides. It was also found that geometry and flexibility of PI chains are crucial to determine the interfacial interactions between nanotubes and PI chains. For elucidating the different interfacial characteristics of the two PIs on the surface of CNT, we proposed a model for preferred conformation adopted by a single PI chain on a single CNT. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40479.     

Effect of scratch velocity on scratch behavior of injection-molded polypropylene

Scratch tests of polypropylene injection moldings were conducted with a progressive load scratch test according to ISO 19252. Effect of scratch velocity on scratch visibility and damage initiation was investigated. The results showed that the critical normal load for onset of scratch visibility was independent of scratch velocity in the range from 1 to 10 mm/s. However, the critical normal load decreased with increase of scratch velocity higher than 10 mm/s. The other scratch damage transitions such as onset of fish-scale and cutting pattern, the critical normal load also decreased with increase of scratch velocity. A correlation between scratch behavior and subsurface deformation was observed by polarized optical microscope. The formation of yielded zone under scratch groove was clearly observed at onset of scratch visibility. It was found that the yielded zone size becomes shallower at higher scratch velocity. The results suggested that localized stress was generated near the surface at higher scratch velocity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Studies of reinforcement behavior of unique elastomer‐based nanocomposite gels

Unique nanocomposite (NC) gels were prepared by blending water swollen unmodified montmorillonite clay suspension with natural rubber (NR) and styrene‐butadiene rubber (SBR) latices followed by prevulcanization. These were extensively characterized by dynamic light scattering, solvent swelling, tensile, and dynamic mechanical measurements. Reinforcement behavior of NC gels was investigated by adding NC gels into virgin NR and SBR matrices at various loadings. The distribution and morphology of NC gels in the elastomer matrices was studied by X‐ray dot mapping and high‐resolution transmission electron microscopy. Experimental results indicated tremendous improvement of tensile strength (TS) and modulus of the NC gel‐filled matrices along with noticeable changes in dynamic mechanical and rheological properties. Compared with virgin NR, the TS of 16 phr NC gel‐filled NR system increased by 117%. Similar level of enhancement of TS was also registered for the NC gel‐filled SBR systems. NC gel‐filled systems showed higher shear viscosities and lower die‐swell values compared with their virgin counterparts. Contemporary particulate composite and nanofiller reinforcement models were used to understand the reinforcing behavior of these NC gels. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

A comparative investigation of the tribological behavior and scratch response of polyester powder coatings filled with different solid lubricants

Employing coatings is one of the most effective methods to reduce friction and protect contacting surfaces from wear. The deposition of protective coatings from thermosetting polymer powders has witnessed a rapid growth as an ecological, economic and energy efficient technology. During the last few decades, many new deposition techniques have been developed, and more and more tribological coatings have been made available. In this context, our present investigation tried, firstly to analyze the friction and wear behavior of electrostatically sprayed polyester powder coatings deposited on an aluminum substrate and secondly to focus on the response of these thermosetting coatings to micromechanical deformation under scratch test loading. The effect of graphite and hexagonal boron nitride (hBN) solid lubricant fillers on the friction and wear behavior of polyester composite coatings was evaluated using a reciprocating tribometer under dry friction condition. The experimental findings show that the additions of graphite or hBN are effective in enhancing the wear life of polyester powder coatings. Meanwhile, under the same sliding conditions, the wear results revealed that the polyester coating filled with only 10 wt.% of graphite has a higher anti-wear ability compared to the polyester coating filled with the same weight fraction of hBN. Thus, the two reinforcing polyester matrix fillers play an important role in reducing the plastic deformation of the coatings and enhance the formation of thick third body between the sliding parts as the fraction of solid lubricant increases from 0 wt.% to 10 wt.%. From the scratch analyses, we deduced that coatings scratch behavior is severely affected by the kind and amount of fillers inside the polyester matrix. In fact, the best friction characteristic and scratch resistance are observed in the case of polyester coatings filled with very low amount of hBN (5 wt.%).     

纳米复合水性外墙涂料的研究

采用表面改性方法制备了纳米复合水性外墙涂料,并对其耐候性,耐碱性、耐水性,耐擦洗等性能进行了研究.结果表明,纳米复合水性外墙涂料的综合性能比改性苯丙外墙涂料有明显提高,尤其在耐候性和耐擦洗性方面提高得更多.     

Spray impact resistance of a superhydrophobic nanocomposite coating

The performance of a polyurethane/organoclay superhydrophobic nanocomposite modified with perfluoroalkyl methacrylic copolymer in the presence of a high‐pressure air‐water spray which mimics an icing cloud impact is investigated in this study. To quantify the average velocites of droplets impacting the superhydrophobic samples, a computational study was performed. Such a study is important to understand the interaction between the jet and surface. Impacting velocities for three different testing conditions were estimated to be 14.5, 4.5, and 3.4 m/s. Liquid saturation did not occur immediately, but over time, the high mass flow rate of water led to antiwetting performance degradation. Upon evaporation, contact angle returned to pretest values, indicating little mechanical erosion. This was consistent with scanning electron microscopy which showed that the nano and microstructure was preserved, and with energy‐dispersive X‐ray spectroscopy, which showed no surface chemistry change after testing. However, sliding angle showed stronger degradation, especially at higher impact velocities. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3025–3032, 2014     

PANI-chitosan-TiO2 ternary nanocomposite and its effectiveness on antibacterial and antistatic behavior of epoxy coating

A straightforward approach has been developed for fabricating antibacterial and antistatic epoxy coatings by using polyaniline-chitosan modified TiO₂ ternary nanocomposite. This nanocomposite was synthesized through the following steps. First, chitosan was grafted onto the TiO₂ nanoparticles and then final nanocomposite was prepared via solution polymerization of aniline. Electrical conductivity measurement revealed that nanocomposite with 7.5 wt % of the modified TiO₂ nanoparticles has noticeably higher conductivity compared to polyaniline. Evaluating the coatings' antibacterial property indicated epoxy coatings with the content of ternary nanocomposite show significant bactericidal activity against Gram-positive bacteria and have acceptable antibacterial action against Gram-negative ones. Also, obtained results showed that the ternary nanocomposite would greatly decrease coatings' surface resistivity and when nanocomposite content is about 2 wt % surface resistivity is about 3 × 10⁷ Ω sq⁻¹. On the contrary, the coating with nanocomposite loading exhibits improved thermal and mechanical performance compared to the coating made of neat epoxy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47629.     

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.     

新型顺酐型聚酰亚胺耐高温涂膜材料的研究

以新型二元胺和顺丁烯二酸酐为原料,用直接法和间接法合成顺酐型聚酰亚胺树脂（溶液）。该树脂（溶液）可形成坚韧的涂膜,是一种优良的高温涂料,可在军工、电子电气工业中作电机电器、金属制件和电子元件的涂料。着重研究了涂膜的热稳定性、化学稳定性、电性能及粘结力。结果表明,该涂料可在180℃长期使用,对一般有机溶剂和稀酸抗性好,电绝缘性及粘结力优良。     

Computational design of thermoset nanocomposite coatings: Methodological study on coating development and testing

Thermoset nanocomposites (TSNCs) may offer significantly improved performance over conventional thermoset materials, and thus are attractive for wide industrial applications, especially in the coating industry. Design of TSNCs via experiment, however, faces various technical challenges due to design complexity. Computational design can provide deep insights and identify superior design solutions through exploring opportunities in a usually huge design space. This paper introduces a generic computational methodology for the design, characterization, and testing of TSNC-based coatings. A distinct feature of the methodology is its capability of generating quantitative correlations among material formulation, processing condition, coating microstructure and property, coating performance, and processing efficiency. The correlations can enable a comprehensive analysis for optimal TSNC coating design. Case studies will demonstrate the methodological efficacy and attractiveness.     

Rubber content effect on scratch behavior in acrylonitrile‐styrene‐acrylate copolymers

The scratch behavior of butyl‐acrylate rubber‐modified styrene‐acrylonitrile thermoplastics is investigated following the ASTM D7027 linearly increasing normal load test methodology. The critical normal loads at the onset of the major transitions along the scratch path, such as groove formation, scratch visibility, microcrack formation, and plowing, are reported and quantitatively analyzed. It is found that the scratch resistance generally deteriorates with increasing butyl‐acrylate rubber content, and is strongly related to the tensile and compressive yield stresses of the blends. Microscopy investigation indicates that a rubber content of up to 30 wt % in a styrene‐acrylonitrile copolymer (SAN) does not alter the scratch‐induced damage mechanisms, but only reduces the critical onset loads for the observed damage transitions. The present finding suggests that addition of rubber causes reductions in modulus, tensile, and compressive yield stresses, thus leading to deterioration in scratch resistance. It appears that the improvement in ductility for SAN after the rubber toughening does not benefit scratch resistance. Implication of rubber toughening on scratch behavior of polymers is discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polypropylene nanocomposite film: A critical evaluation on the effect of nanoclay on the mechanical,thermal, and morphological behavior

Polypropylene (PP)/clay nanocomposites prepared by melt blending technique using different percentages of clay with and without maleic anhydride grafted PP (MA‐PP) were studied. The intercalated and exfoliated structure of nanocomposites was characterized by X‐Ray Diffraction (XRD) and transmission electron microscopy (TEM). Because of the typical intercalated and exfoliated structure, the tensile modulus of the nanocomposites were improved significantly as compared to virgin PP. The viscoelastic behavior of the nanocomposites was studied by dynamical mechanical analysis (DMA) and the results showed that with the addition of treated clay to PP there was substantial improvement in storage modulus increases. The thermal stability and crystallization of the PP nanocomposites as studied by differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA) were also improved significantly compared to PP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of zirconia-magnesia nanocomposite powders and coating by a sucrose mediated sol-gel method and investigation of its corrosion behavior

The zirconia-magnesia nanocomposite powders and coating were prepared using a new sucrose- mediated sol-gel method. The effect of sucrose content to metal ions and calcination temperature on the morphologies and phase of the products were investigated. The samples were characterized by XRD, FTIR and FE-SEM analysis. The results showed that the cubic phase of ZrO₂-MgO with an average size of 30 nm was formed in the presence of sucrose as a gel agents. Finally, the corrosion behavior of optimized sample has been evaluated.     

A comparative study of the catalytic behavior of aluminum chloride and sulfated zirconia

At low conversion, isomerization of methylcyclopentane (MCP) to cyclohexane (CH) at 65°C is faster on sulfated zirconia (SZ) than on AlCl₃ containing traces of water, but the latter reaction reaches equilibrium much quicker because the former deactivates rapidly. Dimer formation (C₁₂H₂₂) occurs on SZ faster in the early stages and continues throughout the reaction, whereas AlCl₃ forms essentially no dimers at first, but in late stages of reactions, when a ``sludge' is expected to be formed on AlCl₃, some dimers are observed, but always much less than on SZ. This difference was predicted, because on SZ the dimers are formed by two pathways, dimerization of free radicals formed in the oxidative initiation step and alkene alkylation by carbocations later on, whereas only the latter mechanism is available for AlCl₃. Pretreatment with SO₂, which is a good solvent for carbocationscreases substantially the activity of AlCl₃ (which retains up to 30% SO₂) most likely by generation of a liquid film which contains carbocations in solution. By contrast, SZ is completely deactivated by this treatment, possibly from a combination of traces of water and loss of oxidizing ability. Dimer formation on AlCl₃ increases appreciably after pretreatment with SO₂, as expected for the reaction in a liquid film where a higher concentration of carbocations facilitates bimolecular reaction. Dimer formation on SZ is much reduced, but not entirely suppressed by pretreatment with SO₂ and the distribution of isomers is different for the two catalysts after pretreatment, showing that some oxidizing ability is retained by SZ, even though the further conversion of hydrocarbon is inhibited. All these results provide further support for the bifunctional nature (initiation by one-electron oxidation followed by acid-catalyzed, carbocationic, reaction of intermediates like surface esters and alkenes formed in the first step) advanced earlier by the authors for the sulfated metal oxides.     

A silanol-based nanocomposite coating for protection of AA-2024 aluminium alloy

A new hybrid sol–gel type film, composed of tetraethylorthosilicate (TEOS) and tetraocthylorthosilicate (TEOCS), and modified with different nanoparticle systems, has been investigated as a coating for protection of AA-2024-T3 aluminium alloy. The nanoparticle systems considered were either ZrO₂ or CeO₂ or their combination_. The zirconia nanoparticles were prepared from a Zr (IV) propoxide sol (TPOZ), using an organic stabilizer, and the CeO₂ nanoparticles were developed spontaneously after adding cerium nitrate solution to the hybrid sol. The chemical composition and the structure of the hybrid sol–gel films were examined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The corrosion resistance of the coated AA-2024 alloy was examined by potentiodynamic polarization. The results revealed that, for short exposure times in the electrolyte, incorporation of ZrO₂ or CeO₂ nanoparticles in the hybrid film does not provide an increase in the corrosion resistance of the coated AA-2024 alloy. Further, the resistance was significantly reduced by increasing the nanoparticle content. Conversely, by incorporating both nanoparticles (ZrO₂ and CeO₂), the corrosion resistance of the resulting hybrid films increased slightly. The behavior changed significantly when the coated alloy was exposed to the electrolyte for 5 days. The corrosion resistance of the coatings, unmodified and modified with CeO₂ or ZrO₂ nanoparticles, decreased by two or three orders of magnitude, while the film modified with both nanoparticles (CrO₂ and ZrO₂) showed a relatively high corrosion resistance and responsiveness to activation processes during anodic polarization.     

Determination of epoxy coating wet-adhesive strength using a standardized ASTM/ISO scratch test

A new approach for evaluating the wet-adhesive strength of epoxy-based coatings was carried out based on a recently standardized ASTM/ISO scratch test. A linearly increasing scratch normal load was applied during scratch to induce progressively increased delamination stress at the coating and steel substrate interface. Thus, the applied critical load to cause coating debonding can be experimentally determined. To find out the corresponding stress magnitude to incur coating debonding, finite element methods (FEM) modeling was conducted to analyze the stress fields around the scratch tip during scratching. The wet-adhesive strength is then quantitatively determined. Based on the above methodology, investigation on a set of model coating systems suggests that the critical load for coating delamination is significantly influenced by water exposure time, coating thickness, and substrate surface roughness. By combining the standardized scratch tests and FEM modeling, the proposed approach is found to be effective for quantitative assessment of epoxy coating wet-adhesive strength and for the development of high performance protective coatings for various industrial applications.