Changes of solubility parameters during evaporation of solvents as a factor influencing the self-stratification of epoxy/acrylic systems

Behaviour of solutions of binary mixture of epoxy/acrylic resins during solvent evaporation was examined. Properties of various liquid compositions at different stages of solvent evaporation were characterised by their solubility parameters and surface tension. Both parameters were calculated from the weight fractions of particular components determined by gas chromatography (GC). Phase separation during solvent evaporation and self-stratification were observed and characterized using optical microscopy and FTIR methods. The results of investigations indicate the possibility of using these methods in order to foresee behaviour of binary compositions.     

水性丙烯酸酯/改性氯化聚丙烯复合涂层材料的制备及性能研究

将丙烯酸(AA)、丙烯酸丁酯(BA)、甲基丙烯酸甲酯(MMA)进行溶液自由基聚合得到水性丙烯酸酯共聚物(WPA);同时采用丙烯酸(AA)、丙烯酸丁酯(BA)改性得到接枝改性氯化聚丙烯(MCPP);将二者进行复合制备复合涂层材料。通过探索WPA中AA的用量（AA质量占WPA合成中单体总质量的百分数,下同）对WPA乳液及WPA/MCPP复合乳液的乳液性能的影响,确定AA用量为12%, WPA与MCPP复合后乳液性能最佳。研究了不同WPA与MCPP比例对乳液性能、涂层表面张力和附着力的影响。结果表明,随着WPA用量增多,乳液粒径减小,涂层表面张力提高,附着力稍有降低。m(WPA):m(MCPP)=3:7时,乳液粒径98nm,表面张力47mN/m,附着力0级。复合涂层材料乳液性能稳定,表面性能和附着力良好,具有广阔应用前景。     

Effect of the viscosity ratio on the morphology and properties of PET/HDPE blends with and without compatibilization

The influence of the molecular weight of polyethylene on the morphology and mechanical properties of blends of high‐density polyethylene (HDPE) dispersed as droplets in a poly(ethylene terephthalate) (PET) matrix at various compositions was investigated. The difference of morphologies can be easily explained by the influence of the molecular weight on the viscosity ratio and therefore, on the critical capillary number. The compatibilizing efficiency of copolymers containing glycidyl methacrylate groups was also addressed in relation to their nature, the protocol for their drying and the molecular weight of the HDPE phase. The increase of adhesion between PET and HDPE was found to have a larger influence on tensile properties than the reduction of interfacial tension. The amount of compatibilizer needed for adhesion improvement depends on the interfacial area that is defined by both the interfacial tension and viscosity ratio of the components. A qualitative relation between the optimum amount of compatibilizer and the critical capillary number can be written. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

自交联含氟乳液与水性环氧树脂共混乳液自分层的研究

为制备出高性能、低成本的含氟树脂,在优选出环氧固化剂的基础上,将含氟乳液与环氧乳液共混,研究了共混乳液间表面张力差、共混工艺、GMA(甲基丙烯酸缩水甘油酯)用量对共混树脂自分层的影响。控制好这些影响因素,利用光电子能谱(XPS)、差示量热扫描(DSC)对共混乳胶膜进行了表征、分析。结果表明,成膜时树脂会产生自分层,表层富集含氟树脂,底层则以环氧树脂为主,中间依靠两种树脂中的反应基团形成过渡层,这样得到的涂膜具有优异的表面性能和良好的附着性能,经一次涂装就能达到底表合一的效果,乳胶膜的附着力达到了1级。该研究成果已顺利通过中试。     

Influence of temperature,molecular weight,and molecular weight dispersity on the surface tension of PS,PP, and PE. I. Experimental

In this work, the influence of temperature, molecular weight (M?_n), and molecular weight dispersity (MWD) on the surface tension of polystyrene (PS) was evaluated using the pendant drop method. The influence of temperature on the surface tension of isotatic polypropylene (i‐PP) and of linear low‐density polyethylene (LLDPE) was also studied here. It was shown that surface tension decreases linearly with increasing temperature for all the polymers studied. The temperature coefficient ?dγ/dT (where γ is the surface tension, and T, the temperature) was shown to decrease with increasing molecular weight and to increase with increasing MWD. The surface tension of PS increased when the molecular weight was varied from 3400 to 41,200 g/mol. When the molecular weight of PS was further increased, the surface tension was shown to level off. The surface tension was shown to decrease with increasing molecular weight distribution. Contact angles formed by drops of diiomethane and water on films of PS with different molecular weights were measured at 20°C. The surface energies of those polymers were then evaluated using the values of the different pairs of contact angles obtained here using two different models: the harmonic mean equation and the geometric mean equation. It was shown that the values of the surface energy obtained are slightly less than are the ones extrapolated from surface‐tension measurements in the rubbery state. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1907–1920, 2001     

Wettability of polytetrafluoroethylene and polymethyl methacrylate by aqueous solutions of TX-100 and TX-165 mixture with propanol

The measurements of the contact angle of the aqueous solutions of TX-100 and TX-165 mixture with propanol on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA) were carried out. On the basis of the obtained results, the dependence between the cosine of contact angle and surface tension as well as between the adhesion and surface tension of the solutions in the light of the work of adhesion of the solutions to the PTFE and PMMA surface was discussed. The dependence between the adhesion and surface tension for PMMA was correlated to the surface concentration of propanol as well as TX-100 and TX-165 mixture concentration determined from the Frumkin equation at the PMMA-air, PMMA-solution and solution–air interfaces. For this purpose, the surface tension of PMMA covered by a surface active agent film was determined using the Neumann et al. equation and next the PMMA–solution interface tension was evaluated from the Young equation. The values of the surface tension of PMMA covered by propanol and surfactants mixture layer were applied to describe the changes of the adhesion work of solutions to PMMA surface as a function of propanol and surfactants mixture concentration. The adhesion work of the aqueous solutions of TX-100 and TX-165 mixture with propanol to the PTFE and PMMA surfaces was discussed in the light of the adhesion work of particular components of the solutions. On the basis of the results obtained from the contact angle measurements, the standard Gibbs free energy of adsorption of particular components of solution was also considered.     

Interfacial tension in polymer melts. Part II: Effects of temperature and molecular weight on interfacial tension

Interfacial tension is one of the most important parameters that govern the morphology of polymer blends and the quality of adhesion between polymers. However, few data are available on interfacial tension due to experimental difficulties. A pendant drop apparatus was used for the determination of the interfacial tension for the polymer pair polypropylene/polystyrene (PP/PS). The effects of temperature and molecular weight were evaluated. The range of temperatures used was from 178° to 250°C, and the range of molecular weights used was from 1590 to 400,000. The interfacial tension decreased linearly with increasing temperature. With only one exception, higher molecular weight systems showed weaker dependence of interfacial tension on temperature than lower molecular weight systems. Also, polydisperse systems showed a stronger dependency on temperature than the monodisperse systems. The value of the interfacial tension, which increases with molecular weight, appears to level off at molecular weights above the entanglement chain length. For the polymer pair PP/PS, the dependency of the interfacial tension on the number average molecular weight appears to follow the well-known semi-empirical (?2/3) power rule over most of the range of molecular weights. Comparable correlations were obtained with values of the power between ?1/2 and ?1.0.     

Adhesion Mechanisms of Polyurethanes to Glass Surfaces I. Structure-Property Relationships in Polyurethanes and Their Effects on Adhesion to Glass

Polyurethanes were prepared from toluene diisocyanate (TDI), 1-4-butane diol (BDO) and polycaprolactone-based triols with varying molecular weights. Among each molecular weight triol-based urethane, hard segment content was varied from 20% to 70%. Differential scanning calorimetry, tensile testing, and Iosipescu shear testing were done on all the various urethanes prepared. Thermal characterization data revealed the dependence of phase separation on hard segment content as well as on the triol molecular weight. Tensile data and Iosipescu shear data further confirmed the observations made from the DSC data. The data further indicated that phase separation can greatly improve the modulus of cross-linked segmented urethanes. Adhesion of these urethanes to glass surface was evaluated using soda-lime float glass plate. Urethane samples were cast on the air side of the glass plates and adhesion was measured in shear mode. Adhesion data indicated that in addition to hard segment content, modulus, cross-link density, and molecular weight of the triols, phase separation seems to be a major factor in controlling adhesion. Surfaces of the failed adhesion samples were also analyzed and the failure mode was found to be cohesive, in varying degree, with the different urethane systems.     

Adhesion properties of swollen hydrogels evaluated by a point‐contact method

The adhesion of swollen hydrogels was studied with the use of a simple tack‐evaluation technique using a point contact in the air at room temperature. The hydrogels used here were poly(sodium acrylate) gel physically crosslinked by aluminum ions. The adhesion properties were examined under different experimental parameters, i.e., separation velocities, normal loads, and waiting periods prior to separation. The effects of the material parameters resulting from the different degrees of the crosslinking on the adhesive properties were also examined. As a result, the adhesion force and the separation energy showed a power‐law behavior with different powers, which depended on the experimental and material parameters. The adhesion properties were determined by the bulk viscoelasticity as well as the surface physical and chemical properties. The results were discussed in terms of the surface molecular interaction and the bulk viscoelastic and viscous properties on the basis of the measurements of the apparent contact area, the ATR FTIR spectrum, and the dynamic viscoelasticity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of surface properties on the adhesion between PVC and wood veneer laminates

The interface between plastic and wood fibers strongly influences the mechanical properties of a plastic/wood-fiber composite. This paper presents a means for evaluating the effectiveness of surface treatment on the wood-fibers in the PVC/wood-fiber composites by investigating the adhesion between PVC and laminated wood veneers. Wood veneers were first treated with γ-aminopropyltriethoxysilane, dichlorodiethylsilane, phthalic anhydride, and maleated polypropylene for surface modification. The chemical modification made on the wood surfaces was then characterized using different complementary surface analytical techniques: X-ray photoelectron spectroscopy and surface tension measurements. The surface tension was determined from the equation of state for interfacial tensions and the measured contact angles of glycerol sessile drops on the wood veneers (both untreated and treated) and on PVC using the Axisymmetric Drop Shape Analysis–Contact Diameter (ADSA-CD) approach. The adhesion property was evaluated by measuring the tensile shear strength of single lap joints between two wood veneers bonded with a PVC film. The adhesion between PVC and wood veneer laminates was significantly improved when wood veneers were treated with amino-silane, while no improvement was observed for the other adhesion promoters. Our experimental results indicate that matching the surface tension is not sufficient to ensure good adhesion between PVC and wood veneers.     

Surface modification of drawn gel-cast ultra-high molecular weight polyethylene films

Gel-spun ultra-high molecular weight polyethylene (UHMWPE) fibers have superior properties but their use in composite material applications is limited by their poor adhesion to polymer matrices. Previous studies have shown that etching improves the adhesion of epoxy to the fibers, but leads to a reduction in mechanical properties. The purpose of this research was to use uniaxially drawn gel-cast UHMWPE films as a model system since both films and fibers have a highly oriented fibrillar structural hierarchy. Etching has detrimental effects on the mechanical properties and crystallinity of these very thin films. The small amount of carbonyl and carboxyl groups added to the surface through etching raises the film's surface tension and enhances wetting by epoxy. Even though the unmodified film cannot be bonded with epoxy, the interlaminar shear strength between epoxy and the etched films approaches the cohesive strength of the epoxy. A combination of interfacial and UHMWPE cohesive failures is observed. The increase in adhesion is attributed to the slight increase in surface oxygen.     

Stratification and phase separation in block copolymer coatings

Stratification, i.e. spontaneous formation of separate layers from a liquid coating containing inherently incompatible resinous components, provides a means of improving the adhesion of coatings. For mixtures of conventional homogeneous resins, surface and interface tensions are considered to be the driving forces for self-stratification, leading to films with separation patterns somewhere between purely spinodal decomposition textures and neatly separated A/B double layers.

Inherently domain-forming block copolymers mixed with partly compatible resins give various different separation patterns ranging from ABA-sandwich structures to physically interpenetrating networks of co-continuous phases with homogeneous layers — sometimes monomolecular ones — at film surfaces.

Besides tailoring adhesion to difficult substrates, block copolymer binders offer chances to achieve new interesting mechanical property profiles as required, e.g. for coatings for plastics or for stone chip-resistant surfacers useful in the automotive industry.

The temperature-dependence of mechanical properties is significantly reduced in comparison with conventional homogeneous coating binders.     

Poly(amidoamine) dendritic structures,bearing different end groups,as adhesion promoters for urea–formaldehyde wood adhesive system

A series of core‐shell poly(amidoamine) (PAMAM) dendritic compounds bearing different end groups such as  OH, NH₂, and NH₃⁺⁻Cl up to the third generation were prepared via successive Michael addition of a nucleophilic core (ethylenediamine) to methylacrylate followed by amination steps using ethylenediamine for the amine‐terminated while ethanolamine for the hydroxyl‐terminated compounds, also the protonated ammonium salt terminated form was obtained by cationization of the amine‐terminated form using hydrochloric acid solution. The Surface activity and aggregation behavior of the corresponding aqueous solutions of the prepared generations with their different end groups were studied and confirmed by surface tension measurements using ring method technique. The prepared dendrimers showed high surface activity and the measurements revealed their ability to self aggregate in water at very low concentrations, critical aggregation concentrations (CACs). The CACs were found to decrease with increasing the generation number, which implies that molecular weight and structure play important rules in controlling the surface activity and CAC. The dendritic compounds proved to be effective as adhesion promoters for urea formaldehyde (UF) resins when applied as wood adhesive systems, which was ascribed in partial to the improved wetting over the substrate, a role that is fundamentally related to the huge number of function groups present at the interface. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Surface Activity and Performance Properties of Gemini Salts of Linear Alkylbenzene Sulfonate in Aqueous Solution

Gemini salts of linear alkylbenzene sulfonate (LABS) were prepared by neutralization of sulfonic acid with a series of low-molecular-weight diamines in aqueous solution. The equilibrium surface activity of Gemini salts of LABS was determined by measuring the surface tension as a function of surfactant concentration to determine the critical micelle concentration (CMC), surface tension at the CMC (γ_CMC), and the area per molecule at the air-water interface (Ų). Electrical conductivity was measured as a function of surfactant concentration to determine the CMC and counterion binding. Dynamic surface tension was measured using a bubble pressure tensiometer to infer the rate at which the surfactant migrates to the air-water interface. Equilibrium interfacial tension against mineral oil was measured using a spinning drop tensiometer. Dynamic interfacial tension was measured using a drop volume tensiometer. The surface tension, CMC, and interfacial tension of Gemini salts of LABS decreased compared to monovalent organic and inorganic salts. The CMC decreases with increasing molecular weight of the diamine spacer group. Dynamic surface and interfacial tension of Gemini salts of LABS are lower than monovalent salts. The foam volume of Gemini salts of LABS was determined using a high shear blender test. The foam volume of Gemini salts of LABS is lower than monovalent salts and depends on the size of the spacer group. Hard-surface cleaning was measured using artificial soil applied to white Formica tiles. Soil removal was determined by optical reflectance as a function of abrasion cycles. Gemini salts of LABS show reduced hard-surface cleaning performance compared to monovalent salts. Detergency of different types of soils on cotton and polyester/cotton fabric was determined by optical reflectance measurements. Gemini salts of LABS show improved cleaning performance compared to monovalent salts. Cleaning performance increases with increasing molecular weight of the diamine spacer group. In situ neutralization of LABS with organic diamines is a simple and efficient way to prepare anionic Gemini surfactants for industrial scale applications.     

Interactions of Glycols with Dodecyl Isothiouronium Cationic Surfactant on the Surface Active Parameters

Surface properties of the dodecyl isothiouronium cationic surfactant in a mixed solvent of water and polyethylene glycol of different molecular weights varied from ethylene glycol to polyethylene glycol-600 were determined using surface tension and conductivity measurements. The results showed an increase in the surface properties including critical micelle concentration, effectiveness and efficiency, compared to the surfactant in pure water as the solvent. The interaction between the cationic surfactant and the glycols was described and the molecular weight of the different glycols was rationalized.     

Wear behavior of silicone rubber/carbon black coatings on 6061 aluminum alloy surfaces

In this paper, the effects of structural and process variables on wear resistance of silicone rubber/carbon black coatings on 6061 aluminum alloy surfaces are studied. Testing parameters have been optimized for maximum wear resistance based on taguchi orthogonal design with six important parameters, viz. polydimethylsiloxane (PDMS) molecular weight, oxime/OH ratio, catalyst weight percent, pigment weight percent, surface preparation method and adhesion promoter type. The analysis of variance showed that the wear resistance strongly depends on oxime/OH ratio and catalyst weight percent. PDMS molecular weight and pigment weight percent also have intermediate effects. Neither the surface preparation method nor adhesion promoter type had any effects on wear resistance in this study. The optimum sample was prepared according to the best levels of each factor and the wear resistance in optimum conditions was reasonably in agreement with the experimental data. Scanning electron microscopy analysis of wear surface and debris showed two mechanisms: cohesive wear with fatigue mechanism and interfacial wear with adhesion mechanism.     

Influence of block molecular weight on the adhesion properties of segmented polyamides

The effects of molecular weight variations in the hard and soft segments on the adhesion strength of segmented polyamides against aluminium, copper, and steel were investigated using 180° peel strength measurements. It was found that the adhesion strength of the segmented polyamides was largely influenced by block molecular weight variations. The nature of the substrate, the rate of peeling, cooling in different environments, and thermal ageing, etc. had significant effects on the adhesion strength of the joints, whereas variation in the moulding conditions used in these experiments did not have much impact on the strength of the joints. The joint strength increased with a decrease in hard block molecular weight at a constant soft block molecular weight of 1000, or with an increase in soft block molecular weight at a constant hard block molecular weight of 1100.     

高聚物结构对表面张力与相对分子质量关系的影响

以若干组分子结构不同的高聚物为研究体系,采用熔体悬滴测量装置系统地测量了不同相对分子质量的高聚物的表面张力。讨论了高聚物分子结构对其表面张力与相对分子质量关系的影响。通过对实验数据的分析推导出高聚物表面张力与相对分子质量的关系式,并对传统的关系式进行了改进,由于改进后的关系式考虑了高聚物分子结构的影响,因此具有更广泛的适用性,可以较好地解释一些传统关系式不能解释的实验现象。     

Effects of pigmentation on siloxane–polyurethane coatings and their performance as fouling-release marine coatings

Siloxane–polyurethane paints were formulated and characterized for coating properties and performance as fouling-release (FR) marine coatings. Paints were formulated at 20 and 30 pigment volume concentrations with titanium dioxide, and aminopropyl-terminated poly(dimethylsiloxane) (APT-PDMS) loadings were varied from 0 to 30% based on binder mass. The coatings were characterized for water contact angle, surface energy (SE), gloss, and pseudobarnacle (PB) adhesion. The assessment of the FR performance compared with polyurethane (PU) and silicone standards through the use of laboratory biological assays was also performed. Biofilm retention and adhesion were conducted with the marine bacterium Cellulophaga lytica, and the microalgae diatom Navicula incerta. Live adult barnacle reattachment using Amphibalanus amphitrite was also performed. The pigmented coatings were found to have properties and FR performance similar to those prepared without pigment. However, a higher loading of PDMS was required, in some cases, to obtain the same properties as coatings prepared without pigment. These coatings rely on a self-stratification mechanism to bring the PDMS to the coating surface. The slight reduction in water contact angle (WCA) and increase in pseudobarnacle release force with pigmentation suggests that pigmentation slowed or interfered with the self-stratification mechanism. However, increasing the PDMS loading is an apparent method for overcoming this issue, allowing for coatings having similar properties as those of clear coatings and FR performance similar to those of silicone standard coatings.     

The Formation of Chemically Modified γ-Alumina Microporous Membranes

Abstract

A technique for the chemical modification of 40Å γ-alumina membranes with Tridecafluoro-1,1,2,2,-tetrahydrooctyl-1-trichlorosilane is presented. The modification is carried out in order to reduce the membrane's pore size so that selective separation of low molecular weight liquid mixtures may be possible. Pure gas permeability measurements with He, H₂, Ar, and SF₆ are reported for an unmodified and two modified membranes which varied in their reaction times from one day to two weeks. The permeability measurements indicate that the short-term modification produced a membrane that still had an appreciable amount of surface flow, while the membrane modified for two weeks had a hindered surface transport. Also reported are data on the separation of toluene from a high molecular weight (M～660) lube oil. The data indicate an increase in selectivity due to the short-term modification; however, after the two-week modification, the selectivity drops to near unity.