Effect of DC glow discharge treatment on the surface energy and surface resistivity of thin film of polypropylene

A change in the surface energy and surface resistivity of a thin film of polypropylene (PP) of thickness 100 μm was investigated, using direct current (DC) glow discharge. The thin film of the PP was treated for various discharge powers and treatment time and the modification in the surface energy and the surface resistivity was observed. To investigate the modification in the surface energy after DC glow discharge treatment, contact angle of two test liquids formamide and de‐ionized water over the surface of PP film was measured. By measuring the contact angle the change in surface energy and its two polar and dispersive components have been measured. It was observed that at a given power level of DC glow discharge surface energy and its polar component increases with increase of the treatment time, attains a maximum value, and then becomes almost constant. Correspondingly, with increase in surface energy, a decrease in surface resistivity was observed. Also, a change in surface morphology was observed by atomic force microscopy and by FT‐IR spectra generation of polar groups at the surface of PP film. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 767–772, 2007     

咪唑型Gemini表面活性剂的合成及性能

以咪唑、溴代烷烃为主要原料,将咪唑环的氮原子进行保护,经4步反应制得5个咪唑型Gemini表面活性剂(C10-2-C10、C12-2-C12、C14-2-C14、C14~(-4)-C14、C14-6-C14),用红外光谱和核磁共振氢谱对其结构进行了表征。它们的CMC依次为:2.7×10~(-4)、2.4×10~(-4)、2.0×10~(-4)、3.3×10~(-4)、3.9×10~(-4)mol/L;γCMC依次为:30.60、30.55、30.51、36.32、37.41 m N/m;在石英表面的最大接触角依次为:70°、73°、75°、72°、68°;最大泡沫高度依次为:87、99、125、186、231 mm;最大泡沫半衰期t0.5依次为:218、608、1 157、2 329、2 770 s。结果表明,C14-2-C14的表面活性最高,对石英表面润湿力最低;C14-6-C14的发泡能力和泡沫稳定性最强。当疏水链增长时,咪唑Gemini表面活性剂的表面活性、降低表面张力效率和接触角都增大;而当连接基团增长时,表面活性、降低表面张力效率和接触角都降低。     

Low-rate Dynamic Contact Angles on Poly(methyl methacrylate/n-butyl methacrylate) and the Determination of Solid Surface Tensions

Low-rate dynamic contact angles of 12 liquids on a poly(methyl methacrylate/n-butyl methacrylate) P(MMA/nBMA) copolymer are measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It is found that 6 liquids yield non-constant contact angles, and/or dissolve the polymer on contact. From the experimental contact angles of the remaining 6 liquids, it is found that the liquid- vapour surface tension times the cosine of the contact angle changes smoothly with the liquid-vapour surface tension, i.e., γ_iv cos θ depends only on γ_iv for a given solid surface (or solid surface tension). This contact angle pattern is in harmony with those from other inert and noninert (polar and non-polar) surfaces [34-42, 51 -53]. The solid-vapour surface tension calculated from the equation-of-state approach for solid -liquid interfacial tensions [14] is found to be 34.4 mJ/m², with a 95% confidence limit of \pm 0.8mJ/m², from the experimental contact angles of the 6 liquids.     

Preparation, characterization and wettability of porous superhydrophobic poly (vinyl chloride) surface

A porous superhydrophobic poly (vinyl chloride) surface was obtained by a simple approach. The water contact angle and the sliding angle of the superhydrophobic poly(vinyl chloride) surface were 154 ± 2.3o and 7o, respectively. The porous superhydrophobic PVC surface remained superhydrophobic property in the pH range from 1 to 13. When the superhydrophobic PVC surface was immersed in water with the temperatures ranging from 5 °C to 50 °C for 1 h to 30 days, the water contact angle remained higher than 150°. After outdoor exposure for 30 days, the contact angle still remained 150o.     

Experimental characterization of contact angle and surface energy on aramid fibers

In this paper, both contact angles and surface energy of aramid fibers are investigated using the liquid droplet method. First, the contact angles between matrix resin and aramid fibers are measured at different degrees of cure, which indicate that the contact angles increased initially and then decreased after the consolidation. Second, surface energy components of aramid fibers are determined from the contact angle using the geometric-mean equations. Finally, the influences of various surface treatments on the surface energy of aramid fibers are analyzed. These results play an important role for designing and evaluating the fiber/matrix interfacial strength of aramid fiber-reinforced composites.     

表面活性离子液体的表面性能及在水溶液中聚集行为的研究进展

综述了表面活性离子液体的表面活性及在水溶液中聚集行为的主要研究成果,重点介绍了影响表面活性离子液体表面活性的因素及表面活性离子液体在水溶液中形成的有序聚集体。在此基础上,分析了表面活性离子液体的表面活性及在水溶液中的聚集行为研究存在的问题和未来的发展方向。     

Combination of fumed silica with carbon black for simultaneously improving the thermal stability,flame retardancy and mechanical properties of polyethylene

The combination of fumed silica (SiO₂) with carbon black (CB) for improving thermal stability, flame retardancy and mechanical properties of linear low density polyethylene (LLDPE) was investigated. The temperature at the maximum weight loss rate of LLDPE was dramatically increased by 92 °C, and the peak value of heat release rate measured by cone calorimeter was significantly reduced by 80.7%. The improved thermal stability and flame retardancy of LLDPE were partially attributed to the formation of a percolated network structure in LLDPE matrix, and partially to the accelerated oxidation crosslinking reaction of LLDPE or other radicals by CB and SiO₂. More importantly, although both SiO₂ and CB were used without any pre-treatment, ternary LLDPE nanocomposites showed much higher mechanical properties compared to those of neat LLDPE. This was ascribed to good dispersions of two kinds of nanoparticles and strong matrix-nanoparticle interfacial interactions with LLDPE matrix.     

Aging effects of repeatedly glow-discharged polyethylene: influence on contact angle,infrared absorption,elemental surface composition,and surface topography

Aging effects of repeatedly oxygen glow-discharged polyethylene surfaces were determined by water contact angle measurements, infrared (IR) spectroscopy, X-ray photoelectron (XPS) spectroscopy, and surface topography determination. Glow-discharged surfaces were stored at room temperature and in liquid nitrogen for 8 days prior to the next glow-discharge (Gld) treatment. This cycle was repeated up to 13 times. Hydrophobic recovery of the polyethylene surface, as determined by contact angle measurements, became less when the number of glow-discharge treatments increased. Hydrophobic recovery was suppressed when the samples were stored in liquid nitrogen. After five glow-discharge treatments it was possible to detect the incorporation of hydroxy groups by IR spectroscopy, while XPS spectroscopy showed that repeated glow-discharge gives rise to a higher oxygen to carbon ratio and a broadening of the C_Is peak, suggesting the incorporation of C-O and C=O bonds in the surface layer of polyethylene. The surface roughness of repeatedly glow-discharge-treated polyethylene remained almost unaltered in the submicrometer range (0.30-0.35 μm), although scanning electron microscopy revealed fine-grained structures for samples after a large number of Gld treatments. It can be concluded from this study that repeated oxygen glow-discharge treatments of polyethylene create more stable, hydrophilic surfaces than can be obtained with only one treatment. However, even after repeated glow-discharge treatments, polymer surface dynamics cause a small hydrophobic recovery.     

Investigation on the effects of fabrication parameters on the structure and properties of surface‐modified membranes using response surface methodology

Surface Modifying Macromolecules (SMM) were used to alter the hydrophobicity of polyetherimide (PEI) hollow fiber membranes and the effects of three fabrication parameters, which are the mass fraction of PEI and SMM in the casting dope and air gap, on the properties of fabricated membranes were investigated by application of Response Surface Methodology (RSM). The fabricated membranes were characterized in terms of mean pore size (r_P,m), permeation rate of helium gas at 1 bar transmembrane pressure difference, membrane porosity, and contact angle of water with inner and outer surfaces of membrane. The regression models obtained for mean pore size and permeation rate have good statistical parameters and are accurate. The model for r_P,m predicts that plot of r_P,m versus air gap has a minimum point, whereas the plots of r_P,m versus PEI (wt %) and SMM (wt %) have maximum points. The regression model developed for membrane porosity predicts that membrane porosity decreases when air gap increases. Since water was used as bore fluid, the model developed for inner surface contact angle has low accuracy but the model developed for outer surface contact angle predicts that contact angle increases with SMM concentration in dope solution but there is a maximum point versus air gap. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Surface characterization of intermediate modulus graphite fibers via surface free energy measurement and esca

Electron spectroscopy for chemical analysis (ESCA), combined with surface derivatization and contact-angle measurements on single fibers, is used to characterize the surface of intermediate modulus (280 GPa tensile modulus) graphite fibers. Selective surface derivatization of the —COH, —COOH and —C = O functional groups with fluorine-enriched tag molecules is used to obtain a quantitative measure of their surface abundance. Quantitative information on the abundance of these functional groups is then correlated with the total and the acid-base free energy data obtained from contact-angle measurements. The three techniques provide complementary information, more completely characterizing the surface acidity of the fiber than any one of the techniques alone.     

水溶性高分子NCP和HPAM对钙质蒙脱土表面润湿性的影响

用JF99A粉体接触角测量仪测定了水溶性阳离子聚合物NCP溶液和部分水解聚丙烯酰胺HPAM溶液在粉体钙质蒙脱土上的润湿性. 实验结果表明NCP溶液在0~1 g/L浓度范围内蒙脱土表面的润湿接触角比水在蒙脱土表面的润湿接触角小，并且比浓度相当的HPAM溶液在蒙脱土表面的润湿接触角要小得多；相同浓度NCP和HPAM溶液中达到吸附平衡的蒙脱土干燥过筛处理后的样品对水的润湿接触角也是前者小于后者，其差别比各自溶液在蒙脱土上的润湿性的差别更大，即经NCP处理后的蒙脱土对水的润湿性明显变好，而经HPAM处理后的蒙脱土对水的润湿性变差.     

Direct fluorination of Twaron fiber and investigation of mechanical thermal and morphological properties of high density polyethylene and Twaron fiber composites

Composites consisting of high density polyethylene (HDPE) reinforced with randomly oriented chopped Twaron fibers (both fluorinated and nonfluorinated) show a significant increase in mechanical and thermal properties. To increase the better fiber matrix adhesion, the Twaron fiber is surface fluorinated using elemental fluorine. The surface of the Twaron fiber becomes very rough and the diameter of Twaron fiber increases from ～ 12 to 14 μm after fluorination. The composites were prepared using solution method to overcome the damage of the fiber. The tensile strength and the Young's modulus increases with increasing fiber content. The tensile strength and modulus of modified fiber (fluorinated Twaron fiber) composites is much higher than nonmodified fiber composites indicating that there is better mechanical interlocking between the modified fiber and the matrix. Thermal properties obtained from DSC and DTA‐TG analysis of the fluorinated fiber composites are also improved. Contact angle measurements, as well as the surface energy measurements, indicate that the composites are more wettable and is maximum for fluorinated fiber composites i.e., surface energy for fluorinated fiber composites is highest. Crystallinity is also higher for fluorinated fiber composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Multi-step derivatization and analysis of the surface of nonporous silicate glass

Multi-step heterogeneous phase chemical reaction schemes were used to develop different surface chemistries on nonporous glass substrates. Reliable analysis of the products of reaction was needed, because many of the functional groups introduced to the surface were intended to serve as reactive sites for further chemical tailoring to meet specific applications. Because the mass of the surface derivatization layer was only parts per million of the substrate mass, analysis of the reaction products was daunting. However, surface evaluation was accomplished by using several analysis methods in combination and by using the particular glass geometry most suitable to each analysis method.     

Synthesis, Characterization and Surface Properties of Cross-linked Polyurethane Dispersions Modified by Organosiloxane

A series of cross-linked polyether-polyester polyurethane dispersions modified with organosiloxane were prepared based on hydroxyl-terminated polydimethylsiloxane (HTPS) as hydrophobic component and 3-aminopropyl-triethoxysilane (APTS) as cross-linker as well as a bridge between polyurethane (PU) and polysiloxane (PSIL). It was discovered that polydimethylsiloxane segments were incorporated into PU chains chemically and organosiloxane was preferentially oriented toward the surface layer of the film by making a comparison of attenuated total reflection (ATR) spectra between the copolymer and the blend of PU and PSIL, which was further confirmed by investigation of electron spectroscopy for chemical analysis (ESCA). The relationships between surface properties of the film formed from polyurethane dispersion and organosiloxane content were also studied. The results showed that water contact angle of the film increased with the increase of organosiloxane content. Interestingly, it was also found that water contact angle of PUS film increased firstly and then decreased when film-forming temperature varied from 25℃ to 55℃.     

On the thermodynamic functions of gas-solid adsorption and liquid-solid immersion,and their relation to adhesion,contact angle and surface tension

The thermodynamic functions of gas-solid adsorption and liquid-solid immersion are summarized on a literature basis. For adsorption, the isosteric and calorimetric methods are compared; for immersion, the Gibbs free energy of adhesion as a function of relative pressure is introduced.The thermodynamic functions reported are enthalpy, Gibbs free energy and entropy of adsorption, immersion and adhesion. All the formulae given contain only those values that result from adsorption, immersion, contact angle or surface tension of the liquids measurements.Interrelations between the thermodynamic functions of adsorption, immersion and adhesion are also given. They permit cross checks and substitution of measurements, e.g., of immersion for adsorption measurement.Typical values are reported and plots of some thermodynamic functions versus coverage are discussed with respect to height and decrease of the powder-adsorptive interaction with layer thickness.     

Surface grafting of polymers onto glass plate: Polymerization of vinyl monomers initiated by initiating groups introduced onto the surface

The surface grafting of polymers onto a glass plate surface was achieved by the polymerization of vinyl monomers initiated by initiating groups introduced onto the surface. Azo groups were introduced onto the glass plate surface by the reaction of 4,4′-azobis(4-cyanopentanoic acid) with isocyanate groups, which were introduced by the treatment with tolylene-2,4-diisocyanate. The radical polymerization of various vinyl monomers was initiated by azo groups introduced onto the glass plate surface and the corresponding polymers were grafted from the surface: The surface grafting of polymers was confirmed by IR spectra, and the contact angle of surface, with water. The contact angle of the glass plate increased by the grafting of hydrophobic polymers, but decreased by the grafting of hydrophilic polymers. The radical postpolymerization was successfully initiated by the pendant peroxycarbonate groups of grafted polymer on the surface to give branched polymer-grafted glass plate. The cationic polymerization of vinyl monomers was also successfully initiated by benzylium perchlorate groups introduced onto the glass plate surface and the corresponding polymers were grafted onto the surface. The contact angle of the glass plate surface obtained from the cationic polymerization of styrene was larger than that obtained from the radical polymerization. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2165–2172, 1997     

离子液体催化碳酸二甲酯和乙醇酯交换合成碳酸甲乙酯

考察了碱性离子液体催化碳酸二甲酯和乙醇酯交换反应合成碳酸甲乙酯的过程, 筛选出催化性能较好的离子液体1-丁基-3-甲基咪唑溴盐（［Bmim］Br）作为催化剂, 并对酯交换反应条件进行优化。结果表明,［Bmim］Br对反应表现出优异的催化性能,在常压、反应温度90 ℃、反应时间12 h、n(碳酸二甲酯)∶n(乙醇)=1∶1和［Bmim］Br用量为碳酸二甲酯质量的2%条件下,碳酸二甲酯转化率为71.1%,碳酸甲乙酯选择性为81.8%。经回收和循环利用 3次,催化剂仍保持较好的催化活性。     

固液界面效应影响竖壁沟流波动研究

基于最小能量原理分析的竖壁沟流流动模型,认为当壁面为存在接触角滞后的非理想表面时,其控制方程的边界条件与滞后接触角有关,并分析了流量存在波动时沟流厚度的波动原因和范围.实验研究了一些液体在不同表面上的沟流流动,结果表明了沟流波动与界面效应有关的假设的合理性,沟流的实际厚度介于由滞后角限定的某一范围内,并且与沟流平均流量有关.若流率波动未超出由滞后接触角及沟流基础流量限定的范围时,沟流只在厚度方向发生波动;若流率波动超出这一范围,则沟流在宽度方向也开始伸缩.     

Plasma treatment effect on the surface energy of carbon and carbon fibers

The surface energy dispersive (γ^D_S) and polar (γ^P_S) components of carbon model surfaces (bal planes, prismatic surfaces, vitreous carbon) and of carbon fibers (high strength and high modulus, respectively) were determined systematically before and after plasma treatment. The method used is essentially based on the wetting contact angle measurements within two liquids. In all cases (γ^P_S) is markedly increased by the plasma treatment. For carbon fibers, with increasing plasma treatment duration (γ^P_S) is increasing toward a limiting value (-30 mJ/m²) while (γ^D_S) is depressed toward low values (-10 mJ/m²). The parallel evolution of surface topography is followed by SEM observations. The changes in surface energy of carbon model surfaces is also discussed.