Transport and related properties of paint films. II. Dynamic mechanical properties and humidity effects

A systematic four-stage investigation of eight unpigmented coating formulations, including three vinyl, two polyurethanes, and three epoxy systems was done to provide baseline structural information upon which an improved understanding and an optimization of protective coatings can be founded. First, the results from dynamic mechanical measurements are provided and discussed for the base polymer component in each coating system. Second, the effects of humidity on the dynamic mechanical properties of these base polymers were determined at room temperature. The extent of property degradation was monitored by calculating the T_g depression with increased humidity, assuming a temperature–humidity superposition. The extent of degradation, as monitored by the T_g, was found to correlate directly with the level of hydrogen bonding in these coatings. Third, the influence of typical coating additives (a TCP plasticizer and a rosin hardener) on the properties of two of the vinyl coating systems was investigated. In the final stage, the synergistic effects of absorbed moisture and these additives on the coatings properties were investigated at room temperature. Increases in the concentration of these additives was found to magnify the degradation effect of increased humidity. This magnified degradation has been assigned to increased water absorption with increases in the concentration of either of these additives.     

Transport properties of dichloromethane in glassy polymers. I. Atactic polystyrene films

Sorption and diffusion of dichloromethane vapor were measured in atactic polystyrene films, obtained with different cooling conditions and after controlled aging times at different temperatures. The diffusional behavior is characterized by three zones, depending on temperature and penetrant activity. In Zone I, at low activity, the diffusion coefficient is independent of vapor concentration; Zone II is characterized by concentration-dependent diffusion, whereas in Zone III structural transformations are possible. The study of diffusion at three temperatures allowed building of a temperature-penetrant concentration diagram, which is very useful to visualize the different zones of behavior. The aging at room temperature has no effect on the curve of sorption as a function of vapor activity, whereas it determines two effects on the diffusion: a decrease of the zero concentration diffusion coefficient and a more and more anomalous behavior with the aging time. The aging at 70°C produces the same effects on the diffusion behavior as the aging at room temperature; in addition, a decrease sorption is observed at low penetrant activity. The possible presence of ordered domains, impermeable to the vapor, in the samples stored at 70°C, was suggested on the basis of sorption results.     

The mechanical properties of films and their relation to paint chipping

A correlation has been made between dynamic mechanical properties and impact resistance of a multicoat paint system. It has been determined that the shear or rigidity modulus and damping of free primer films are some of the parameters that control the impact characteristics of the system. Those films of low modulus and high damping show the best chip resistance. A series of physical and chemical modifications were made on the primer and chipping results were compared with dynamic mechanical properties of free paint films. It was found that increasing cure temperature, addition of catalysts, decreasing the oil length of the resin, increasing the amount of pigmentation and increasing the tension and strain rate all led to increased paint chipping and increases in the modulus of rigidity. Two new primers were synthesized which incorporated the above results and were found to give increased gravel impact resistance.     

Composition and structure of sol-gel platinum-doped silicate films

X-ray electron spectroscopy and atomic force microscopy are used to investigate silicate films obtained by the sol-gel method and doped with 1, 10, and 20% platinum. The changes in the structure of a silicate film, which are due to doping with platinum, and the effect of the platinum concentration and heat-treatment temperature and atmosphere on the composition and surface morphology of the doped films are determined. __________ Translated from Steklo i Keramika, No. 6, pp. 28–31, June, 2007.     

Transport properties of molten tetra-alkylammonium picrates—I. Viscosity

Viscosities and densities of some molten tetra-alkylammonium picrates have been measured near the glass temperature. The temperature dependence of viscosity shows systematic departures from Arrhenius behaviour and is better expressed by the free volume theory. The calculated T_O values allow the assumption that the existence of short range forces due to polarization of the CC bonds, originating on the far CH₃ groups by the inductive effect, have an important effect on transport phenomena in these melts.Comparison of our results with those of the Adam-Gibbs theory suggests that a corresponding temperature scale based on isoentropic states is probably the most useful basis for correlating liquid structural properties.     

Transport properties of dichloromethane in glassy polymers. II. Amorphous syndiotactic polystyrene films

Sorption and diffusion of dichloromethane vapor were measured in amorphous syndiotactic polystyrene films, obtained with different cooling conditions and after controlled aging times at different temperatures. The diffusional behavior, at the temperature of 25°C, was characterized by three stages, depending on penetrant activity. In the first stage, at low activity, the diffusion coefficient was independent of vapor concentration; the second stage was characterized by concentration-dependent diffusion, whereas in the third stage, at high activity, the strong interaction solvent–polymer increased the mobility, allowing the polymer crystallization. The different cooling conditions neither have an effect on the diffusional behavior nor on the sorption curve. The aging, both at room temperature and at 70°C, did not change the diffusion parameters, but led to the appearance of more and more anomalous sorption behavior. The sorption curve, as a function of vapor activity, did not show any difference for the fresh and the aged-at-room temperature samples, whereas the samples aged at 70°C presented a lower sorption at low activity. The presence of ordered domains, impermeable to the penetrant at low activity, was suggested on the basis of sorption results. The solvent-induced crystallization was investigated for all the samples. Crystallization was induced at an activity of 0.45 for the fresh and the aged-at-room temperature samples; at variance, the samples aged at 70°C crystallize at a slightly higher activity, reaching, nevertheless, a higher level of crystallinity. © 1993 John Wiley & Sons, Inc.     

Natural weathering of polypropylene films. I. Exposure time and yield properties

The yield properties of about 500 h of outdoor weathering (in the rainy season) of polypropylene (PP) films have been studied. The yield strain, plastic strain, and initial modulus, work of yield attained local maxima at 48- and 240-h exposure time; elastic strain attained near double maxima at these times. The yield stress reached a local minimum for the 144-h exposed film before increasing with further exposure hours. The increase in yield strain, plastic strain, and initial modulus were explained in terms of crosslinking chemocrystallization; decreases were due to chain scission and leaching. Critical dissolution time data, interpreted in proportion to density, crystallite thickness, and percent crystallinity, increased with PP exposure time, reaching a maximum at 48 h before decreasing to values even lower than that of unexposed film from the 120-h exposure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 667–673, 1998     

分散剂结构和用量对调色乳胶漆性能的影响

设计了乳胶漆基础配方,研究了分散剂结构和用量对调色乳胶漆性能的影响。实验结果表明,乳胶漆的稳定性、耐水性、展色性、遮盖力等性能与分散剂结构与用量密切相关。当分散剂选用S110时,且用量为乳胶漆的5‰~7‰时,制备得到的乳胶漆在稳定性、耐水性、展色性较其它分散剂有明显优势。     

Structure and properties of impact copolymer polypropylene. I. Chain structure

In this work, impact copolymer polypropylene (ICPP) was fractionated into 4 fractions. ICPP and the 4 fractions were studied using Fourier transform infrared and ¹³C nuclear magnetic resonance analysis. The results demonstrate that fraction A is ethylene–propylene rubber, fraction B is ethylene–propylene (EP) segmented copolymer, fraction C is ethylene–propylene block copolymer, and fraction D is polypropylene with a few ethylene monomers in the chain. The differences in properties between different impact copolymer polypropylenes should be due to their fractions' differences in composition and chain sequence structure. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 93–101, 1999     

Transport properties of photogenerated charge carriers in black diamond films

Surface nanostructured diamond films by ultrashort pulse laser treatment, named black diamond, demonstrated a huge increase in the photogeneration capability for photons with sub-bandgap energy (<5.47?eV). Here we analyze in detail the transport properties of photogenerated charge carriers in several black diamond samples, in order to better understand the electronic behavior of defect levels introduced by the laser treatment. If compared with the pristine diamond films, the mean charge carriers’ mobility-lifetime product, evaluated from the over bandgap photocurrent characteristics, remarkably increases in every black diamond set up to a defined absorbed accumulated laser fluence before decreasing at the highest fluence values. We attribute this effect to the laser-induced introduction of fast traps for one charge carrier type, that increases with fluence. At the same time, an increasing density of recombination centers, capturing permanently the charge carriers, is formed. A trade-off treatment condition can be found in order to maximize the sensitivity to sub-bandgap photons and the mean mobility-lifetime product as well as to limit the effect of recombination centers.     

Permeability of paint films towards chloride ion

An apparatus for determining the permeability of paint films towards chloride ion is described. This set-up implements the time-lag, method and consists of a permeation cell made up of two chambers divided by a supported paint film. The upper chamber contains an aqueous sodium chloride solution and the lower one, water. The permeability is obtained from the conductivity history read at the lower chamber. Osmotic pressure issue is addressed and the reproducibility of the results reported. The time-lag, method is not described in any standard. The requirement concerning “surface protection systems for concrete” for chloride ion permeability is not quantified in prEN 1504-2. The standard establishes that this requirement is “subject to national standards and national regulations” but when the capillary adsorption of water is lower than 0.01 kg/(m²h^0.5) the diffusion of chloride ion is not to be expected. Some experimental results prove this is not correct and, in Portugal, the National Laboratory of Civil Engineering (LNEC) has proposed a threshold permeability value of 10⁻¹⁴ m²/sec for coatings claiming to be corrosion protective.     

Viscoelastic properties of latex paint films in tension: Influence of the inorganic phase and surfactants

The tensile properties of latex coatings were investigated with a set of custom formulated artist-type paints at an age of 1 year. All films in the study contained a poly(methyl methacrylate-cobutyl acrylate) binder exhibiting a glass-transition at approximately 10 °C. The viscoelastic behaviour of the latex matrix is first highlighted through a series of experiments involving different strain histories and temperatures. Influence of the inorganic particle concentration and geometry is then illustrated using TiO₂ and calcined kaolin for the secondary phase. Experimental data from a wide range of conditions are summarised through master curves of secant modulus and failure strains using time–temperature superposition. The results indicate that the latex films behave in a rheologically simple manner and it is possible to predict the response outside of the experimental time-scale. An analysis by similar methods is also given for TiO₂ pigmented films with/without surfactant removed by immersion in water. Differential scanning calorimetry and atomic force microscopy were also used in conjunction with mechanical tests. The combined findings suggest that a fraction of surfactant migrates to the TiO₂ interface during film formation, where it interferes with adhesion of the acrylic matrix.     

Structure and electronic properties of bismuth anodic oxide films—I. Photoeffects

Estimates of the conduction electron mobility, lifetime and trap density of anodic bismuth oxide films, obtained by measuring the transient response of a polarized bismuth anode to an intense flash of white light, showed that the films had a highly defective structure. for thicker films (～240 nm) the photo-response arose from the production of electron-hole pairs in the bulk of the film, but for very thin films (～5 nm) the response arose from photo-emission of electrons from the metal into the film, and effects attributed to the decay of space charges of both electrons and mobile ions were observed.The photo-response was used to investigate the possible formation of films of bismuth oxo-halides under conditions in which these compounds were thermodynamically stable. Incorporation of iodide and bromide into the very thin films at pH 5 was detected. No effect of chloride was observed. Comparison with cyclic voltammetric results indicated that an anodic layer of bismuth oxoiodide might be formed by direct nucleation on to the metal surface.     

Polyamine-modified urea-formaldehyde resins. I. Synthesis,structure, and properties

The objective of this study was to improve the durability and stability of urea–formaldehyde-bonded wood products by decreasing the internal stress developed during resin cure and by improving the ability of the cured resin to withstand cyclic stresses. This paper presents initial results from modifying a urea–formaldehyde resin by incorporating di- and trifunctional amines. The amines were incorporated by adding them as amines during resin synthesis, by adding urea-capped amines during resin synthesis, and by using amine hydrochlorides as acidic curing agents. Addition of amines during resin synthesis produced uncurable resins. However, modification with urea-capped amines or curing with amine hydrochlorides provided cure rates comparable to that of unmodified resin cured with ammonium chloride. These modifications also reduced the tendency of the resin to crack and fracture and substantially improved the resistance of bonded joints to cyclic stress imposed by cyclic wet–dry exposures. Resins cured with amine hydrochlorides had lower formaldehyde liberation than those cured with ammonium chloride. Thus, incorporation of flexible di- and triamines offers promise for improving the durability and stability of urea–formaldehyde-bonded wood products.     

Composition and structure of the anodic films on titanium in aqueous solutions

Surface-enhanced Raman spectra of the amorphous film on titanium have been obtained for the first time. The anodic corrosion film at low potentials is identified to be highly disordered TiO₂ with some Ti₂O₃ also present. The presence of the anatase and rutile modifications of TiO₂ at high voltages ( 80V) is confirmed.     

Composition and structure of the cation permselective membranes I. Evaluation of the electrochemical models

The swollen permselective membrane is a multiphase system composed of polyelectrolyte gel, inert polymer acting as a reinforcing agent and of low molecular weight electrolyte filling the pores and nonselective domains. Endeavour has been undertaken to apply the electrochemical models of membranes for the computations of their phase composition. The computations have been performed for some cation selective membranes equilibrated with sulphuric acid solutions, which are called NAFION, PE-PSSA, and IONAC. The results prove that only the Guillou model fulfills some of the chosen criteria of adequacy. It has been also stated that the fraction of the nonselective domains found by any of the models exceed the one established from electrolyte sorption data.