Synthesis and surface analysis of self-matt coating based on waterborne polyurethane resin and study on the matt mechanism

Self-matt coating of waterborne polyurethane (WBPU) was synthesized by combining prepolymer and self-emulsification methods. The emulsion was fabricated from both hydroxy carboxylic acid and aminosulfonic acid types of hydrophilic chain-extending agents, in which the 2-[(2-aminoethyl) amino] ethane sulphonate sodium (AAS salt) was produced in laboratory. This emulsion demonstrated an excellent matt performance without the addition of extra matting agents after filming. Four different kinds of surface properties were measured on the film: the specular gloss (60° gloss meter), the contact angle (CA), the surface roughness degree (3D Surface Profilometer), and the topography of the coatings surface (SEM). The results showed that tons of spherical particles with diameter in a few micrometers were aggregated on the film surface. The effect of the roughness parameters (R _a and R _q ) and the average particle size of the emulsions on the specular gloss degree were probed. The research indicated that the emulsion with average particle size in the range of 2.5–3.0 µm and, meanwhile, the film with roughness parameters R _a and R _q both greater than 1 µm could attain the best matt effect. The WBPU emulsions showed good physical and mechanical properties, and were introduced into wood varnish for matting purpose.     

Probing the Structural,Electronic, and Magnetic Properties of Ag<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>V (<Emphasis Type="Italic">n</Emphasis> = 1–12) Clusters

The structural, electronic, and magnetic properties of Ag _n V (n?=?1–12) clusters have been studied using density functional theory and CALYPSO structure searching method. Geometry optimizations manifest that a vanadium atom in low-energy Ag_nV clusters favors the most highly coordinated location. The substitution of one V atom for an Ag atom in Ag _n?+?1 (n ≥ 5) cluster modifies the lowest energy structure of the host cluster. The infrared spectra, Raman spectra, and photoelectron spectra of Ag _n V (n?=?1–12) clusters are simulated and can be used to determine the most stable structure in the future. The relative stability, dissociation channel, and chemical activity of the ground states are analyzed through atomic averaged binding energy, dissociation energy, and energy gap. It is found that V atom can improve the stability of the host cluster, Ag₂ excepted. The most possible dissociation channels are Ag _n V?=?Ag?+?Ag _n???1V for n?=?1 and 4–12 and Ag _n V?=?Ag₂?+?Ag _n???2V for n?=?2 and 3. The energy gap of Ag _n V cluster with odd n is much smaller than that of Ag _n?+?1 cluster. Analyses of magnetic property indicate that the total magnetic moment of Ag _n V cluster mostly comes from V atom and varies from 1 to 5 μ _B. The charge transfer between V and Ag atoms should be responsible for the change of magnetic moment.     

Sol-Gel Synthesis,Thermal Behavior of Nanopowders and Chemical Stability of La<Subscript>1 – <Emphasis Type="Italic">x</Emphasis></Subscript>Ho<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript> Ceramic Matrices

Nanosized powders of orthophosphates in the LaPO₄–HoPO₄–H₂O system have been synthesized to determine the mutual solubility of LaPO₄ · nH₂O and HoPO₄ · nH₂O initial components and to obtain ceramic matrices by sintering them. Formation of hexagonal, monoclinic or tetragonal solid solutions was revealed, and their limits and thermal stability were determined. A series of limited hexagonal LaPO₄ · nH₂O-based solid solutions was observed within the 0 ≤ x ≤ 0.6 concentration range up to 600°C. Further they transformed to monoclinic LaPO₄-based form within the 0 ≤ x ≤ 0.3 concentration range. Solubility of LaPO₄ · nH₂O and LaPO₄ in tetragonal HoPO₄(· nH₂O) is lower (≤10 mol %). Specific surface area of La_1–xHo_xPO₄ · nH₂O powders was in the range of 90.5–165.0 m²/g depending on x. Leaching rate of La³⁺ and Ho³⁺ from La_1–xHo_xPO₄ matrices in nitric acid solution (pH 1–2) was determined to be 10^–5–10^–2 g/(cm² day) for both ions.     

Partition of <Emphasis Type="Italic">n</Emphasis>-Butanol Among Phases and Solubilization Ability of Winsor type III Microemulsions

The partition of n-butanol in Winsor type III (W-III) microemulsions was investigated in this work. Three kinds of anionic surfactants (sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (DSS), and sodium dodecyl benzene sulfonate (SDBS)) and two kinds of anionic/cationic surfactant mixtures (SDS/octadecyl trimethyl ammonium chloride (OTAC) mixtures and DSS/OTAC mixtures) were studied. Internal standard gas chromatography was employed in n-butanol content analysis. The results showed that no water exists in the excess oil (EO) phase and no oil exists in the excess water (EW) phase. For the W-III microemulsions obtained by salinity scanning, relatively constant n-butanol content in the EO (11–12 v%) and EW (1–4 v%) was found under different salinities. Accurate measurement of n-butanol content in each phase is important for those systems having low solubilization ability. For the W-III microemulsions prepared using SDS/OTAC surfactant mixture, the percentage of n-butanol distributed into the interfacial layer decreased while the fraction of n-butanol in the interfacial layer first increased sharply and then tended to be stable with the addition of n-butanol. For the different optimum W-III microemulsion systems tested, most of the surfactant-to-alcohol molar ratio data are near 1:3, but obvious deviation could be observed for some data. On the basis of the accurate measurement of n-butanol content in the EO and EW phases, the standard free energy, ΔG _o→in ^* (T = 298.15 K) of n-butanol transferring from the EO phase to the interfacial region was calculated. The results show negative ΔG _o→in ^* values. For microemulsions with the same components, n-butanol content is an important factor influencing the ΔG _o→in ^* value, and a high absolute value of ΔG _o→in ^* leads to high solubilization ability.     

Supramolecular Architectures in Three Metal(II) Coordination Polymers with 2,5-Dichloroterephthalate and Flexible Bis(Benzimidazole) Ligands

Three supramolecular coordination polymers, namely [Ni(L1)(DCTP)(H₂O)] _n (1), [Cu(L2)(DCTP)] _n (2), [Co(L3)(DCTP)] _n (3) (L1?=?1,5-bis(5,6-dimethylbenzimidazole)pentane, L2?=?1,4-bis(5,6-dimethylbenzimidazole)butane, L3?=?1,4-bis(benzimidazole)-2-butylene) have been hydrothermally synthesized and characterized by single crystal X-ray structure determination, FT-IR, elemental analysis, X-ray powder diffraction (XPD), and thermogravimetric analysis (TGA). CP 1 exhibits 2D 6³ honeycombed network structure, which is further extended into a 3D Moganite (mog) supramolecular framework by classical O–H?O hydrogen-bonding interaction. CPs 2 –3 present 2D (4,4) layers, and 3D supramolecular frameworks that are formed by π–π stacking interactions. Furthermore, the catalytic activities of CPs 1–3 for the degradation of methyl orange in a Fenton-like process has been investigated, and CPs 1–3 show strong photoluminescence properties at room temperature in solid state.     

Polysiloxanes with Quaternary Ammonium and Polyether Groups for Silyl-Terminated Polypropylene Oxide Waterborne Emulsions

In this paper, polysiloxanes with pendant quaternary ammonium and polyether segments (EQAPS, nonionic–cationic silicone surfactant) were synthesized through hydrosilylation of poly(dimethylhydro)siloxane with allyl poly(ethylene glycol) acetic ester (M _n  = 540) and allyl glycidyl ether, followed by a ring-opening reaction of epoxide groups with diethyl amine and quaternization with benzyl chloride. The chemical structures of EQAPS and intermediate products were characterized by ¹H-NMR and FT-IR spectra. The surface activity and thermal properties of EQAPS were studied with surface tension measurement and differential scanning calorimetry analysis, respectively. The results showed that the EQAPS had a much smaller critical micelle concentration value (118 mg/L) and lower glass-transition temperature (T _g: ?57 °C). The silyl-terminated polypropylene oxide waterborne emulsions, which were substantially free from organic solvent, were prepared via a phase-inversion emulsification technique using EQAPS as single emulsifier and/or poly(ethylene glycol) (\(\bar{M}\) _n  = 400) as cosolvent. The electrical properties of the system indicated that the phase inversion was completely accomplished. The viscosity of the emulsions with different solid contents was measured, and the results showed that the most suitable solid content was about 50 wt%. The emulsions with smaller particle size (12 μm) had better storage stability (48 days at 50 °C) and freeze–thaw stability.     

Synthesis and Physicochemical Properties of Alanine-Based Surfactants

The synthesis of a homologous series of alanine-based surfactants, namely sodium salts of n-alkanesulfonamido-2-propanoic acids in which n-alkane is n-dodecane, n-tetradecane, n–hexadecane, and n-octadecane having the formula RSO₂NHCH (CH₃)COO^?Na⁺, is described. The starting materials used were a mixture of secondary positional isomers of n-alkanesulfonyl chlorides obtained by photosulfochlorination reaction using sulfuryl chloride and a catalyst. Surface properties of the aqueous solutions of the synthesized surfactants, including the critical micelle concentration and minimal surface tension δ_min, were determined using surface tension measurements at 25 °C. The surface excess Γ and minimum area per molecule (A _min) where calculated using the Gibbs equation. The foaming power was also determined by the Bartsh method, and the R ₅ parameter was calculated to estimate the stability of the foam formed. The results obtained were compared to those of a commercial surfactant, sodium dodecylsulfate, and a series of synthesized glycine-based surfactants. The results obtained clearly show that the alanine-based surfactants possess good surface properties. The investigations highlight the influence on the surface properties of the addition of a methyl group in the hydrophilic part.     

A Comprehensive Study on the Synthesis and Micellization of Disymmetric Gemini Imidazolium Surfactants

Two groups of disymmetric Gemini imidazolium surfactants, [C₁₄C₄C _m im]Br₂ (m = 10, 12, 14) and [C _m C₄C _n im]Br₂ (m + n = 24, m = 12, 14, 16, 18) surfactants, were synthesized and their structures were confirmed by ¹H NMR and ESI–MS spectroscopy. Their adsorption at the air/water interface, thermodynamic parameters and aggregation behavior were explored by means of surface tension, electrical conductivity and steady-state fluorescence. A series of surface activity parameters, including cmc, γ _cmc, π _cmc, pC ₂₀, cmc/C ₂₀, Γ _max and A _min, were obtained from surface tension measurements. The results revealed that the overall hydrophobic chain length (N _c) for [C₁₄C₄C _m im]Br₂ and the disymmetry (m/n) for [C _m C₄C _n im]Br₂ had a significant effect on the surface activity. The cmc values decreased with an increase of N _c or m/n. The thermodynamic parameters of micellization (ΔG _m ^θ , ΔH _m ^θ , ΔS _m ^θ ) derived from the electrical conductivity indicated that the micellization process of [C₁₄C₄C _m im]Br₂ and [C _m C₄C _n im]Br₂ was entropy-driven at different temperatures, but the contribution of ΔH _m ^θ to ΔG _m ^θ was enhanced by increasing N _c or m/n. The micropolarity and micellar aggregation number (N _agg) were estimated by steady-state fluorescence measurements. The results showed that the surfactant with higher N _c or m/n can form larger micelles, due to a tighter micellar structure.     

Nanoindentation as an alternative to mechanical abrasion for assessing wear of polymeric automotive coatings

Mechanical abrasion followed by transmission delta-haze measurement is a standard means to assess wear in polymeric silicone automotive hard coatings. However, the drawbacks of this abrasion–transmission (A–T) technique (drift, variability, sample size, and test time) make an alternative measurement method desirable. Literature reports have shown that the ratio of hardness to modulus can successfully predict wear performance in ceramic and metallic nanocomposite coatings. This work studied measures from both nanoindentation and nanoscratch testing to determine which could be a viable alternative to the historical A–T test for a specific polymeric coating system. Both nanoindentation measures of hardness (H) and the ratio of hardness to modulus (H/E _r) showed high repeatability compared with the other measures evaluated in this study and compared with the historical test. Of these two measures, the ratio H/E _r with an exponential fit showed the strongest correlation with A–T delta-haze measurements. Key formulation and process factors affecting abrasion resistance in automotive coatings were analyzed in a designed experiment with historical A–T delta-haze and nanoindentation H/E _r as responses. Analysis showed significant benefits to the use of the H/E _r measure of abrasion resistance in modeling coating performance.     

Conformational analyses for alanine oligomer during hydration by quantum chemical calculation (QCC)

The structure and association energy of hydrated l-alanine pentamers at the hydration rate (h) of 0–1 were calculated by quantum chemical calculation (QCC) using the density functional theory [B3LYP/6-31G(d, p)] method for three kinds of stable conformers (β-extended: t?/t+, PP_II-like: g?/g+, α-helix: g?/g?) converged by convergent calculations from l-alanine pentamers in gas phase. Water molecules are mainly inserted between intramolecular hydrogen bond of CO–HN in PP_II-like and α-helix conformers and attached to the CO group in β-extended conformer. α-Helix conformer turns to PP_II-like conformer at higher hydration rate. The association energy decreased with the increase of the hydration rate, indicating that the conformers were stabilized by the hydration. It was found that PP_II-like conformer, which was the most stable in the anhydrate state, was also the most stable in the hydrate state. This structure corresponds to a middle structure of PP_II (g?/t+) and β-extended (t?/t+) structures. These results obtained by energy calculation using QCC support the experimental results by Eker et al. and Graf et al., who reported that alanine oligomer exhibited a mixture of PP_II and β-extended structure in aqueous solution.     

A Functional Material Based Heterojunction Diode

In this study, the phosphotungstic acid /p-Si diode was fabricated by a drop coating method. The fabricated diode had excellent rectifying properties. The electrical properties of the diode were investigated in the temperature range of 50-400 K. The optical band gap of the phosphotungstic acid film was determined and found to be 3.66 eV. The electrical and photoresponse properties of an Al/p-Si-phosphotungstic acid/Al photodiode were studied. The electronic parameters such as ideality factor (n), barrier height (Φ _B ) and series resistance (R _s ) were found to be strongly temperature dependent.     

β-SiAlON-TiN/TiB<Subscript>2</Subscript>-BN composites by infiltration-mediated SHS under high pressure of nitrogen gas

Infiltration-mediated SHS of β-Si_6–z Al _z O _z N_8–z –TiN/TiB₂–BN composites was explored upon variation in applied nitrogen pressure, amount of combustible and inert components in green mixture, sample size, and BN content of resultant composites. Synthesized ceramics of different density and phase composition were characterized by their strength parameters, tribological behavior, electrical resistance, and thermal shock resistance.     

Effect of functionalized multiwalled carbon nanotubes on weather degradation and corrosion of waterborne polyurethane coatings

A series of waterborne polyurethane/functionalized multiwalled carbon nanotube (WBPU/f-MWCNT) nanocomposite dispersions was prepared using three defined concentrations of 0.5, 1.0 and 2.0 wt% carboxyl functionalized multiwalled carbon nanotubes (f-MWCNTs). All dispersions were coated on mild steel and exposed under natural weather condition for a maximum of 365 days. Both exposed and unexposed coatings were characterized by potentiodynamic polarization (PDP) and X-ray photoelectron spectroscopy (XPS) analyses. The pristine WBPU coating showed slight degradation and corrosion protection. Inclusion of a higher content of f-MWCNTs significantly improved both the degradation and corrosion protection efficiencies of the coatings. Maximal degradation and corrosion protection was observed when 2.0 wt% f-MWCNT was mixed with WBPU for all of the coatings.     

Physicochemical Properties of Nanosized Powders of the LaPO<Subscript>4</Subscript>–DyPO<Subscript>4</Subscript>–H<Subscript>2</Subscript>O System

Nanosized La_1–xDy_xPO₄ · nH₂O powders are synthesized by the sol-gel method using direct and reverse precipitation. The formation of a continuous series of hexagonal solid solutions based on LaPO₄ · nH₂O is confirmed by the XRD and DSC/TG methods. A continuous series of monoclinic solid solutions based on LaPO4 is formed at temperatures higher than 600°C. A reflex corresponding to a tetragonal form of DyPO₄ is formed during the calcination of DyPO₄ powder at 850°C. Two types of solid solutions are observed at temperatures of 1000–1200°C, namely, monoclinic solutions based on LaPO₄ (to x ≈ 0.7) and tetragonal solutions based on DyPO₄ (0.90 ≤ x ≤ 1.0). The results are compared depending on the methods of nanopowder synthesis.     

The role of molecular structure on impact resistance and bending strength of photocured urethane-dimethacrylate polymer networks

The objective of this study was to investigate the influence of molecular structure on impact resistance (a _n) and bending strength (σ) of photocured urethane-dimethacrylate polymer networks. Urethane-dimethacrylate (UDMA) monomers were synthesized through reaction of oligoethylene glycol monomethacrylate (OEGMMA) with diisocyanate (DI). OEGMMA varied within the length of the oligooxyethylene chain, which consisted of one to four oxyethylene units. DI varied in chemical character: aliphatic, cycloaliphatic or aromatic. The molecular structure of UDMA polymers was characterized by X-ray powder diffraction, which allowed the calculation of the d-spacing (d) and dimensions of microgel agglomerates (D). The measurements of the polymerization shrinkage were used for the determination of the degree of conversion (DC), whereas the concentration of double bonds was used as a measure of the crosslink density (q). It was found that all structural parameters depend on the UDMA chemical structure. The increasing length of the oligooxyethylene chains caused the decrease in d and q, in contrast to the increase in D and DC. The DI chemical character caused the increase in the DC and q accordingly: symmetrical cycloaliphatic or aromatic < asymmetrical cycloaliphatic and aromatic < substituted aliphatic < linear aliphatic. The compact packing and high DC in polymers derived from aliphatic DIs gave rise to the decrease in d and the increase in D. The non-planar conformation of cycloaliphatic DIs emerged in high d as well as D. The planar conformation of aromatic DIs resulted in the decrease in d as well as D. The study indicated that mechanical behavior of UDMA polymer networks can be explained in terms of the structural parameters. DC and q appeared to be the main factors determining both mechanical properties of poly(UDMA)s. The a _n was also shown to be affected by d. Particularly high linear correlations were found on a semi-logarithmic scale for the DC and d with a _n. a _n increased as the DC increased, whereas d decreased.     

Search of high-capacity cathode materials based on lithium–iron silicate compounds

The crystal structures of 197 lithium–silicate compounds have been analyzed using the method of crystal chemistry analysis (TOPOS software package). The compounds whose structures are characterized with a combination of high values of such parameters as the channel radius, stability, gravimetric capacity, and capacity per volume unit have been revealed: LiFeSiO₄ (R3?), Li₄Fe₂Si₃O₁₀ (C2/c), Li₂FeSiO₄ (Pc2₁ n), and Li₂FeSiO₄ (C222₁). It has been demonstrated that lithium–iron silicates of the monoclinic syngony have high values of the capacity per volume unit, as compared to those of the rhombic syngony. The structural stability of the Li₂FeSiO₄ (Pc2₁ n) framework has been corroborated using the method of computer simulation within the scopes of the electron density functional theory. The obtained information could facilitate creation of novel cathode materials of high capacity and specific accumulated energy.     

Effect of the 3<Subscript>d</Subscript>-Transition Metal Oxides on the Surface Tension of the Sodium Silicate Melt

The effect of 3d-transition metal oxides on the surface tension of the 17.5Na₂O · 82.5SiO₂ · nRO (R = Mn, Fe, Co, Ni, Cu; n = 0.1–10) melt is revealed in the temperature range 1250–1450°C. It is found that cobalt oxide in the range of low concentrations (0.1–1.0 mol %) is characterized by anomalously low values of the surface tension. In the case of CoO oxide, the surface tension increases as the temperature increases and the melts containing MnO, FeO, NiO, and CuO oxides have negative temperature coefficients. In the range of high concentrations of the studied oxides (n = 10 mol %), the surface tension of melts decreases with an increase in the atomic number of cation in the sequence Mn → Fe → Co → Ni → Cu.     

Another new family of “extended” glucidoamphiphiles. Synthesis and surfactant properties for different sugar head groups and spacer arm lengths

Following a new four-step route, we prepared a family of “extended” glucidoamphiphiles from D-glucose, D-galactose, and xylitol in which the n-dodecyl chain is attached to the glucidic moiety by the linkage Z=O-Et-O-Et-O-(α-PP-O-) _n′ where-O-(α-PP-O-) _n is a poly-(α-propyloxy) commercial oligomeric mixture (with average length n=6, 10, and 14). This amphiphilic behavior study showed that (i) the glucose derivative exhibits water solubility and hydrophilic-lipophilic balance values that are close to those found for the glucose compound with Z=-O-(α-PP-O-) _n (without the Et-O-Et group), (ii) all these compounds are more strongly hydrophilic than the corresponding glucidic derivatives with Z=O, (iii) the increase of the poly-(α-propyloxy) chain length from ñ=6 to ñ=14 tends to reduce the hydrophilicity slightly.     

Dielectric properties of silver-doped nanoporous silicate glasses in the temperature range between –50 and +250°C

The results of measuring dielectric parameters of nanoporous silicate glasses with a nanopore size of 3.5 and 25.7 nm, either doped with silver or not, in the temperature range between–50 and +250°C and the frequency range of 0.1–10⁶ Hz are reported. It is demonstrated that when silver nanoparticles are formed in glass pores, some silver remains in the form of subnanosized molecular clusters Ag _n and molecular complexes Ag _n –(OH) _m . The key dielectric properties of the relaxation centers are determined for different temperature ranges.     

β-SiAlON–BN composites by infiltration-mediated SHS under high pressure of nitrogen gas

Infiltration-mediated SHS of β-S_i6–z Al _z O _z N_8–z –BN composites was explored upon variation in applied nitrogen pressure, amount of combustible and low-melting components in green mixture, sample size, and BN content of resultant composites. Synthesized ceramic composites of different density and BN content were characterized by their strength parameters, tribological behavior, and thermal shock resistance.