Adhesion performance of PSA–clay nano-composites by the in-situ polymerization and mechanical blending

The synthesis and characterization of acrylic polymer/Na-montmorillonite (Na-MMT) clay nano-composites pressure sensitive adhesives (PSA) are researched. The PSA/clay nano-composites were synthesized by in-situ emulsion polymerization and mechanical blending. And then, different amounts of nanoclay were dispersed in 2-ethylhexyl acrylate (2-EHA)/n-butyl acrylate (BA)/methyl methacylate (MMA)/acrylic acid (AA) monomer mixture, which was synthesized using in-situ emulsion polymerization technique. Morphological observation was carried out using X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). Viscoelastic properties of PSA/clay nano-composites were analyzed using advanced rheometric expansion system (ARES). The adhesion performances of synthesized PSA/clay nano-composites were determined by measurements of peel strength, probe tack and shear adhesion failure temperature.     

Characterization of antireflective coatings on poly(methyl methacrylate) substrate by different process parameters

The high/low refractive index organic/inorganic antireflective (AR) hybrid polymers were formed using the sol–gel process, in which TiO₂/2‐hydroxyethyl methacrylate (2‐HEMA) (high refractive index hybrid polymer) and SiO₂/2‐HEMA (low refractive index hybrid polymer) two‐layer thin films were formed on a hard coating deposited poly(methyl methacrylate) (HC‐PMMA) substrate by both spin coating and dip coating. The relationship between the process parameters and the optical properties, thickness, porosity, surface morphology, and adhesion was determined. The results show that the reflectance of the two‐layer thin films on HC‐PMMA substrate is less than 0.21% (λ = 550 nm), with good adhesion (5B) and a hardness of up to 4H. In addition, the thickness, porosity, and roughness of the films affect refractive index and the antireflection properties of the AR two‐layered thin film. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Relationship between degree of polymerization and optical and thermal properties of fluorene in polycarbonate polymers

The influences of average degree of polymerization (D_p) and terminal group on thermal and optical properties of high refractive indexed transparent polymers were investigated. In this study, 9,9‐bis[4–(2‐hydroxyethoxy) phenyl] fluorene (BPEF) homo polymer was selected because it has been used as a representative monomer in high refractive index polymers as well as its unique property. BPEF has stable amorphous phase and reacts like a polymer. Its unique reaction allows continuous investigation from monomer to polymer. For hydroxyl‐terminated polymer, the refractive index (n_d) decreased with increasing D_p. On the other hand, for a phenolic‐terminated group, n_d increased with increasing D_p, and both converged to same value in high D_p region. As for glass transition temperatures (T_g), both terminal group series were increased as D_p increased. Though T_g of hydroxyl‐terminated polymer was higher than that of phenolic‐terminated polymer in the low D_p region, both converged to the same value and the inverse number of T_g had linear correlation against the weight percentage of carbonyl groups (CO), which was calculated by D_p. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45042.     

Development of an aluminum/amorphous nano-SiO2 composite using powder metallurgy and hot extrusion processes

Ceramic nanoparticle reinforced aluminum matrix composites usually exhibit superior mechanical properties when compared to monolithic materials, particularly in severe working conditions such as elevated temperatures. Aluminum matrix nano-composites (AMNCs) are widely used for structural applications in aerospace and automotive industries due to their low density and high strength to weight ratio. The aim of this research was to study the effect of SiO₂ nanoparticles as the reinforcing phase on the mechanical properties of aluminum matrix composites. For this purpose, powder metallurgy and subsequent hot extrusion methods were used to prepare a reference sample and several Al-SiO₂ nano-composite rods, containing 1, 2 and 3 wt% nano-silica. Some sample preparation procedures for the manufacturing process, involved mixing, compaction, sintering, preheating and hot extrusion. Mechanical properties of the developed composites were investigated by macro- and micro-hardness, density measurement, tensile, cold compression and hot compression tests. A scanning electron microscope and an optical microscope were used for microstructural analysis of the composite and monolithic samples before and after the hot extrusion process. Experimental tests on aluminum matrix composites reinforced with nano SiO₂ particles revealed that adding just 1 wt% SiO₂ nanoparticle increases both hardness and tensile strength by 41.8% and 24.8%, respectively. In addition, the mechanical properties were seen to decrease with increases in the SiO₂ weight fraction. Density also decreased as the SiO₂ weight fraction increased. It can therefore be said that based on the findings of this study, the SiO₂ nanoparticle can be used as an effective reinforcing material for developing aluminum matrix nano-composites.     

Additive and free-volume effects on the refractive index of a thiol-ene polymer network

A series of hard, transparent, thermoset polymer samples containing tetravinylsilane (TVS) and 1,3-benzenedithiol (BDT) with varying loadings of zirconium oxide clusters Zr₆(OH)₄O₄(OMc)₁₂ (ZOC) were synthesized. Resulting polymers exhibited a higher refractive index (n) than the parent polymer containing only the monomers TVS and BDT. The refractive index reached a maximum value of 1.711 at a ZOC loading of 3 wt% and then decreased as the ZOC concentration in the polymer matrix increased. The refractive index of ZOC was determined to be 1.540 using the Becke line method. Because the refractive index of ZOC is lower than that of the TVS–BDT polymer matrix, the finding that the incorporation of small quantities of ZOC can increase the refractive index of the TVS–BDT polymer composite was unexpected and is accounted for by the effects of ZOC on the packing efficiency of the composite.     

Synthesis and characterization of flame retardant hyperbranched polyurethanes for nano-composite and nano-coating applications

Flame retardant hyperbranched polyurethanes were prepared by reacting phosphorous containing triol, tris(bisphenol-A) mono phosphate, castor oil, and polyethylene glycol with different diisocyanates like TDI, IPDI and HMDI via A₂+B₃ method. In this method A₂ reactants were diisocyanates along with castor oil and polyethylene glycol whereas phosphorous containing triol was used as B₃ reactant and dibutyltin dilaurate (DBTDL) was used as catalyst. Synthesized polyurethans were characterized by gel-permeation chromatography (GPC), elemental analysis, Fourier transform infrared spectroscopy (FTIR) and ¹H NMR spectroscopic techniques. Neat polyurethanes were used for preparing films. Nano-clay composites were prepared with various concentration of organomodified montmorillionite nano-clay. Flame retardant, Thermal and mechanical properties of these hyperbranched polyurethanes and their nano-composites were found out. The polyurethanes and their formulations with nano-clay were also used for the coating of mild steel panels. Scratch, pencil, and impact hardness, flexibility and adhesion properties of coated panels were also determined. Observations show an increase in the scratch hardness and flexibility with the introduction of clay. All the coatings show excellent chemical resistance properties compare to their linear counterpart.     

Sensing and surface morphological properties of a poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] liquid‐crystalline polymer for optoelectronic applications

The sensing properties of a poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] (F8T2) polymer were investigated at different concentrations and volume percentages. The effects of the concentrations and volume percentages on the sensing parameters were investigated. The sensitivities of F8T2 were found to be 3.190, 1.434, and 0.362 dB/vol % at 290, 580, and 940 nm, respectively. The response of the F8T2 increased with increasing concentration. F8T2 exhibited good sensitivity and response behaviors. Then, the optical parameters based on the refractive indices of the F8T2 at different molarities were calculated. The dispersion energy, moment of the dielectric constant optical spectrum (M_?1, M_?3), oscillator strength, and contrast of the F8T2 increased with increasing molarity, whereas the average excitation energy or single‐oscillator energy decreased with increasing molarity. The surface morphological properties of the F8T2 polymer film were investigated, and the roughness parameters were obtained. The F8T2 polymer could be used in the fabrication of various sensors because of the good solubility, sensitivity, and response behaviors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41659.     

Water absorption,residual mechanical and thermal properties of hydrothermally conditioned nano-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> enhanced glass fiber reinforced polymer composites

The durability of the nano-Al₂O₃ enhanced glass fiber reinforced polymer (GFRP) composites in hydrothermal environment is necessary for hydro/hygro thermal applications. The present investigation emphasizes the effect of nano-Al₂O₃ filler concentration on moisture absorption kinetics, residual mechanical and thermal properties of hydrothermally treated GFRP nano-composites. Nano-Al₂O₃ particles were mixed with epoxy matrix through temperature assisted magnetic stirrer and followed by ultrasonic treatment. It has been observed that, the addition of 0.1 wt% of nano-Al₂O₃ into the GFRP nano-composites reduces the moisture diffusion coefficient by 10%, as well as improves the flexural residual strength by 16% and interlaminar residual shear strength by 17% as compared to the neat epoxy GFRP composites. However, the glass transition temperature has not been improved by the addition of nano-Al₂O₃ filler. Weibull design parameters have been determined for dry and hydrothermally conditioned nano-composites. A good agreement between the experimental and the simulated stress–strain results has been observed. The interface failure mechanism has been evaluated by field emission scanning electron microscope to support the new findings.     

Evaluation of structural,optical and dielectric properties of MWCNT-BaTiO3/silica ceramic nanocomposites

In this research, MWCNT-BaTiO₃/silica nano-composites were synthesized and analyzed at different MWCNTs loadings (2, 4, 6, and 8% wt). Utilizing the different concentrations of MWCNTs, the optical responses of MWCNT-BaTiO₃/silica nanocomposite were investigated. For this purpose, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy were used. Using the Kramers-Kronig method, the refractive index and dielectric coefficient of MWCNT-BaTiO₃/silica nanocomposites were analyzed. Results clearly revealed that the higher incorporation of MWCNTs in nanocomposites led to more strong responses in the real parts of both refractive index and dielectric coefficient. Finally, the transversal (TO)/longitudinal (LO) phonon frequencies shifted to the blue wavenumbers by decreasing the amount of MWCNTs in MWCNT-BaTiO₃/silica nanocomposite.     

Thermal and optical properties of La2O3–Ga2O3– (Nb2O5 or Ta2O5) ternary glasses

La₂O₃–Ga₂O₃–M₂O₅ (M = Nb or Ta) ternary glasses were fabricated using an aerodynamic levitation technique, and their glass‐forming regions and thermal and optical properties were investigated. Incorporation of adequate amounts of Nb₂O₅ and Ta₂O₅ drastically improved the thermal stabilities of the glasses against crystallization. Optical transmittance measurements revealed that all the glasses were transparent over a wide wavelength range from the ultraviolet to the mid‐infrared. The refractive indices of the glasses increased and the Abbe number decreased upon substituting Ga₂O₃ with Nb₂O₅, and the decrease in the Abbe number was significantly suppressed when Ta₂O₅ was incorporated into the glass. As a result, excellent compatibility between high refractive index and lower wavelength dispersion was realized in La₂O₃–Ga₂O₃–Ta₂O₅ glasses. Analysis based on the single‐oscillator Drude–Voigt model provided more systematical information and revealed that this compatibility was due to an increase in the electron density of the glass.     

Room temperature deposition of XRD-amorphous TiO2 thin films: Investigation of device performance as a function of temperature

In this study, TiO₂ thin films were fabricated by radio frequency sputtering at room temperature in pure Ar atmosphere starting from a 6?in. TiO₂ target. The thickness of the films was controlled by deposition time and the effect of Ar sputtering pressure on the characteristics of TiO₂ thin films was evaluated. Surface morphology and optical properties of TiO₂ films were investigated using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and UV–Vis spectrophotometry. Also, the refractive index and extinction coefficient of films were inferred by fitting spectrophotometric data. Schottky diode were fabricated by evaporation of Ni on TiO₂ films. Current-voltage (I-V) measurements of Ni/TiO₂ films showed that the rectifying properties of the device improves with the increasing of TiO₂ film density and thickness. Therefore, the best I-V characteristic of the device was investigated depending on the temperature. Also, Ni/n-TiO₂/p-Si/Al devices were fabricated to understand their transport mechanism.     

The effect of refractive index on the friction coefficient of DLC coated polymer substrates

This paper describes the enhanced mechanical performance that can be achieved by the application of diamond-like carbon (DLC) coatings to polymer substrates. The polymers coated are silicone and polyethylene, and the effect on the friction coefficient is studied. Film adhesion is found to depend on the DLC film refractive index (n), whereas the friction is largely independent of n in the range studied. Films were deposited from a He/C₂H₂ mixture at 20 Pa (0.15 Torr) on to the polymer substrates placed on a 10-cm-diameter electrode driven at 13.56 MHz. Film growth was monitored by in-situ ellipsometry (at 675 nm), which was performed on a glass slide placed near the polymer substrate. Friction measurements were obtained using a pin-on-disk tribometer, and measurements were carried out using a stainless-steel pin at a linear speed of 6 cm s⁻¹. Film adhesion was evaluated using a pull-adhesion tester. It was found that DLC coatings adhere well to the polymer substrates and can significantly reduce the friction coefficient of polymers such as silicone. Higher refractive index films (which are harder and have a higher mechanical strength) were found to have a poorer adhesion and provide a slightly increased friction on the polymer surface when compared to lower-index films. This study indicates that DLC may be used to enhance the tribological properties of polymers with potential applications in the biomaterials and light-engineering industries.     

Preparation and characterization of TiO2 and polymer nanocomposite films with high refractive index

Novel nanocomposite films of TiO₂ nanoparticles and hydrophobic polymers having polar groups, poly (bisphenol‐A and epichlorohydrin) or copolymer of styrene and maleic anhydride, with high refractive indices, high transparency, no color, solvent‐resistance, good thermal stability, and mechanical properties were prepared by incorporating surface‐modified TiO₂ nanoparticles into polymer matrices. In the process of preparing colloidal solution of TiO₂ nanoparticles, severe aggregation of particles can be reduced by surface modification using carboxylic acids and long‐chain alkyl amines. These TiO₂ nanoparticles dispersed in solvents were found not to aggregate after mixing with polymer solutions. Transparent colorless free‐standing films were obtained by drying a mixture of TiO₂ nanoparticles colloidal solution and polymer solutions in vacuum. Transmission electronic microscopic studies of the films suggest that the TiO₂ nanoparticles of 3–6 nm in diameter were dispersed in polymer matrices while maintaining their original size. Thermogravimetric analysis results indicate that the nanocomposite film has good thermal stability and the weight fraction of observed TiO₂ nanoparticles in the film is in good accordance with that of theoretical calculations. The refractive index of nanocomposite films of TiO₂ and poly(bisphenol‐A and epichlorohydrin) was in the range of 1.58–1.81 at 589 nm, which linearly increased with the content of TiO₂ nanoparticles from 0 to 80 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

New effective process to fabricate fast switching and high contrast electrochromic device based on viologen and Prussian blue/antimony tin oxide nano-composites with dark colored state

We developed a new electrochromic device by using compact Prussian blue (PB)/antimony tin oxide (ATO) nano-composites as anodic electrode and viologen anchoring on titanium dioxide (TiO₂) nano-particles as cathodic electrode. The anodic electrode was based on a transparent nanostructured ATO nano-particle film and was electro-deposited by Prussian blue to form compact Prussian blue/ATO nano-composites by means of galvanostatic electrodeposition process. Nanocrystalline TiO₂ thin films on conducting glass were modified with a mono-layer of viologen with two anchoring groups, which were much strongly adsorbed onto the surface of TiO₂ nano-particles. A polymer gel electrolyte sandwiched between the anodic and cathodic layers is used as the ionic transport layer. The 2.5 cm × 2.5 cm electrochromic device shows high contrast (64.8%, at 600 nm) very low transmittance at colored stage (0.1%, at 600 nm), fast switching time (600 and 720 ms for coloration and bleaching, respectively), high coloration efficiency of 912 cm² C⁻¹ at 600 nm and good stability. The enhanced performance of the electrochromic device can be attributed to the ATO nano-particles as inter-conductive materials.     

Role of helium plasma pretreatment in the stability of the wettability,adhesion, and mechanical properties of ammonia plasma-treated polymers. Application to the Al-polypropylene system

The stability of a plasma-treated polymer surface is an important issue, but very often a surface rendered wettable by the treatment is found to revert to a less wettable state with time. The purpose of this work was to minimize the ageing phenomenon by stabilizing the surface layer via crosslinking using an inert gas discharge. The stability of the wettability, adhesion, and mechanical properties of treated polypropylene (PP) has been investigated by a comparative study of two different plasma treatments (i.e. an NH₃ plasma and a He plasma pretreatment carried out before the NH₃ plasma; He plasma is well known to crosslink polymer surfaces). The aluminium-polypropylene (Al-PP) interfaces present very different features depending on the gas treatment. The role of the treatment time has been pointed out and under our experimental conditions, a treatment time of the order of a few seconds seems to be an overtreatment leading to degradation of the adhesion and mechanical properties. A broad interphase was obtained for an NH₃-overtreated PP, in contrast to the abrupt one formed when pretreated with the helium gas followed by NH₃ treatment. Good correlations between wettability and mechanical properties with adhesion measurements were established.     

Effects of aluminium nitride silane-treatment on the mechanical and thermal properties of polybenzoxazine matrix

A new kind of polymer composite, produced from the typical polybenzoxazine and 0–30 wt-% native and silane-treated aluminium nitride (T-AlN), was investigated. The mechanical tests revealed a significant increase in the microhardness and flexural properties upon adding the T-AlN particles compared to that obtained from the untreated ones. By adding 0–30 wt-% T-AlN, the tensile moduli were accurately reproduced by the Halpin-Tsai and Nielsen models. At 30 wt-% T-AlN, dynamic mechanical analysis showed a significant increase in the storage moduli and the glass transition temperature (T_g), reaching 3.2?GPa and 217°C, respectively. The thermal stability of these materials was significantly improved upon the addition of the T-AlN fillers. These improvements are attributed to the high thermal and mechanical properties of the fillers and their good dispersion and adhesion in and to the matrix as revealed by a morphological analysis.     

Preparation and properties of polystyrene–γ‐methacryloxypropyl trimethoxy silane copolymer/zirconia nanohybrid materials

Polystyrene (PS)–γ‐methacryloxypropyl trimethoxy silane (MPTMS) copolymer/zirconia (ZrO₂) nanohybrid materials were successfully prepared by the combination of solvothermal and in situ synthesis methods, in which the comonomer was used as chemical bonding agent between the nanoparticles and the matrix, and acetylacetone (AcAc) was used as a size control agent of ZrO₂ in the PS matrix. Then, a new transparency film with a relatively high refractive index (1.72) was successfully obtained, in which ZrO₂ could be dispersed well in the PS–MPTMS matrix. Field emission scanning electron microscopy images indicated that AcAc was helpful in the dispersion of the nanoparticles, and smaller ZrO₂ particles with no aggregation were obtained in the PS–MPTMS matrix. The structure and thermal properties of the hybrid films were investigated by Fourier transform infrared spectroscopy and thermogravimetric analysis, and the surface properties were also examined. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2320–2327, 2013     

Nanocomposites of PVC/TiO2 nanorods: Surface tension and mechanical properties before and after UV exposure

In this study, nanocomposites of poly(vinyl chloride) (PVC), using the synthesized titanium dioxide (TiO₂) nanorods and commercial nanopowder of titanium dioxide (Degussa P25) were produced by melt blending. The presence of TiO₂ nanorods in PVC matrix led to an improvement in mechanical properties of PVC nanocomposites in comparison with unfilled PVC. The photocatalytic degradation behavior of PVC nanocomposites were investigated by measuring their structural change evaluations, surface tension, and mechanical properties before and after UV exposure for 500 h. It was found that mechanical and physical properties of PVC nanocomposites are not reduced significantly after UV exposure in the presence of TiO₂ nanorods in comparison with the presence of TiO₂ nanoparticles, which can be due to the amorphous structure of the synthesized nanorods. Therefore, it can be concluded that TiO₂ nanorods led to an improvement in photostability and mechanical properties of PVC nanocomposites. The interfacial adhesion between TiO₂ nanorods and PVC matrix was also investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Microwave dielectric and nonlinear optical studies on radio‐frequency sputtered Dy2O3‐doped KNN thin films

We report the effect of oxygen mixing percentage (OMP) on structural, microstructural, dielectric, linear, and nonlinear optical properties of Dy₂O₃‐doped (K_0.5Na_0.5)NbO₃ thin films. The (K_0.5Na_0.5)NbO₃ + 0.5 wt%Dy₂O₃ (KNN05D) ferroelectric thin films were deposited on to quartz and Pt/Ti/SiO₂/Si substrates by RF magnetron sputtering. An increase in the refractive index from 2.08 to 2.21 and a decrease in the optical bandgap from 4.30 to 4.28 eV indicate the improvement in crystallinity, which is also confirmed from Raman studies. A high relative permittivity (ε_r=281‐332) and low loss tangent (tanδ=1.2%‐1.9%) were obtained for the films deposited in 100% OMP, measured at microwave frequencies (5‐15 GHz). The leakage current of the films found to be as low as 9.90×10^?9 A/cm² at 150 kV/cm and Poole‐Frenkel emission is the dominant conduction mechanism in the films. The third order nonlinear optical properties of the KNN05D films were investigated using modified single beam z‐scan method. The third order nonlinear susceptibility (?χ⁽³⁾?) values of KNN05D films increased from 0.69×10^?3 esu to 1.40×10^?3 esu with an increase in OMP. The larger and positive nonlinear refractive index n₂=7.04×10^?6 cm²/W, and nonlinear absorption coefficient β=1.70 cm/W were obtained for the 100% OMP film, indicating that KNN05D films are good candidates for the applications in nonlinear photonics and high‐frequency devices.     

Preparation and properties of a high-entropy amorphous oxide with high refractive index by containerless solidification

A non-proportional high-entropy oxide glass disc: 25LaO_3/2-25TiO₂–25NbO_5/2-(25-x) WO₃-xZrO₂(x = 0, 5, 10) was formed using containerless solidification technology. In optical tests, the 25LaO_3/2-25TiO₂–25NbO_5/2-20WO₃–5ZrO₂(x = 5) disc had the highest refractive index (2.53) and the highest visible transmittance (84%). In addition, the refractive index of amorphous materials prepared from La₂O₃, TiO₂, Nb₂O₅, WO_3, and ZrO₂ were all greater than 2.1, which is considered as a high refractive index. The results suggest that these components can provide a specific reference for optical glass material selection in future research.Furthermore, based on the concept of performance synergy in high-entropy materials, our research group developed a high-entropy amorphous oxide in equal proportion, 20LaO_3/2-20TiO₂–20NbO_5/2-20WO₃–20ZrO₂ (Qi Xiwei, 2019). The structure has a high refractive index (2.22) and a high Abbe coefficient (61), which ensures that the lens has sufficient clarity when it is ultra-thin. By comparing the results of the two systems, we found that all non-proportional high-entropy systems are unable to simultaneously show both a high Abbe value and a high refractive index. This phenomenon further indicates the necessity of preparing high-entropy amorphous oxide in equal proportion.