CaCO_3颗粒模板法制备聚合物超亲水/超疏水表面

以碳酸钙(CaCO3)颗粒层为模板,运用简单的热压和酸蚀刻相结合的方法制备聚合物超亲水/超疏水表面.首先在玻璃基底上均匀铺撒一层CaCO3颗粒,以此作为模板,通过热压线性低密度聚乙烯(LLDPE)使CaCO3颗粒均匀镶嵌在聚合物表面,获得了超亲水性质;进一步经酸蚀得到了具有微米和亚微米多孔结构的表面,其水滴静态接触角(WCA)可达(152.7±0.8)°,滚动角小于3°,具备超疏水性质.表面浸润性能和耐水压冲击性能研究表明该超疏水表面具有良好的稳定性和持久性.用同样工艺微模塑/酸蚀刻其它疏水性聚合物,得到类似结果.     

Influence of microstructure on space charges of polypropylene

The correlation of chemical structure, crystalline morphology, and space charge distribution under a dc electrical field was investigated with three kinds of poly(propylene) (PP) with a different chemical structure, that is, homogeneous PP and block copolymer and random copolymer of PP. The space charge distribution of the samples was prominently affected by their chemical sequence structure and crystalline microstructure. Among samples of different PPs, all isothermally crystallized at 140 °C, the sample of random coPP represents the most well proportional space charge distribution and the smallest number of space charges. The effect of thermal history on the space charge distribution was also investigated by the samples of block coPP. The sample thermally treated at 50 °C clearly represents a better proportional distribution than that at higher temperature of 140 and 100 °C. Subsequent experiments indicate that the better proportional distribution attributes to imperfect and fine sperulites with the fine distribution of the “amorphous” region. The imperfect and fine sperulites originate from the random incorporation of ethylene segments or units into PP chains or from the low annealing temperature, and play an important role in the formation of shallow traps and transportation of space charges. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 365–374, 2002; DOI 10.1002/polb.10100     

Influence of O2 Plasma on Surface Properties of PC-TiO2 Nanocomposite Film

In this work, polycarbonate-TiO₂ nanocomposite films were prepared with different percentages. The aim was to consider the effect of O₂ LF plasma (50 Hz) on the hydrophilicity, surface energy, and surface morphology of polycarbonate and polycarbonate-TiO₂ nanocomposite. Structure of samples was determined by using X-ray diffraction analysis. In comparison with the reference sample, the samples’ structure did not change after plasma treatment. Surface properties of polycarbonate and polycarbonate-TiO₂ nanocomposite films were studied by X-ray photoelectron spectroscopy (XPS), contact angle measurement, atomic force microscopy (AFM), and Vickers microhardness tester. XPS analysis showed that the surface of samples became more oxidized due to plasma treatment. The water contact angle significantly decreased from 88° to 15° after plasma treatment. It was observed that the hardness of the nanocomposite films was not modified after plasma treatment.     

Local surface charge dissipation studied using force spectroscopy method of atomic force microscopy

We propose herein a method to study local surface charge dissipation in dielectric films using force spectroscopy technique of atomic force microscopy. By using a normalization procedure and considering an analytical expression of the tip‐sample interaction force, we could estimate the characteristic time decay of the dissipation process. This approach is completely independent of the atomic force microscopy tip geometry and considerably reduces the amount of experimental data needed for the calculation compared with other techniques. The feasibility of the method was demonstrated in a freshly cleaved mica surface, in which the local charge dissipation after cleavage followed approximately a first‐order exponential law with the characteristic time decay of approximately 7–8 min at 30% relative humidity (RH) and 2–3.5 min at 48% RH. Copyright © 2015 John Wiley & Sons, Ltd.     

Surface properties of hydrosilylated polyolefins annealed in supercritical carbon dioxide

Two hydrosilylated polyolefin compounds are obtained by reacting polypropylene (PP) and polyethylene (PE) with di‐ and multi‐functional hydride‐terminated poly(dimethylsiloxane) (dH‐PDMS and mH‐PDMS), respectively. The PDMS‐rich surface layers on these two samples show different Si concentrations but similar thicknesses. Samples of these materials are annealed in supercritical carbon dioxide (scCO₂) at various temperatures and pressures for different periods of time. On the PP/dH‐PDMS sample, an increase in the annealing temperature does not affect the Si concentration up to 120°C. However, the Si concentration is sharply reduced at T = 150°C at which point the surface appears to be covered by SiO₂ particles. Annealing the PP/dH‐PDMS sample for short times leads to submicron scale SiO₂ particle formation on the surface. The particles form aggregated clusters that spread all over the surface uniformly when the annealing time is extended. However, Si concentration on the PE/mH‐PDMS sample surface is enhanced as the annealing temperature increases, reaching a maximum at an annealing temperature of 100°C. No particle formation is observed on the PE/mH‐PDMS sample surface. The contact angle of both samples is found to increase with annealing temperature. Increasing the scCO₂ pressure leads to a higher Si concentration on the surfaces of both samples. On the other hand, increasing the CO₂ pressure leads to opposite trends in contact angle with the PP/dH‐PDMS sample exhibiting an increasing contact angle and the PE/mH‐PDMS sample exhibiting a decreasing one. Copyright © 2007 John Wiley & Sons, Ltd.     

Optically transparent superhydrophobic TEOS-derived silica films by surface silylation method

Optically transparent silica films were prepared at room temperature (~27°C) by keeping the molar ratio of TEOS:MeOH:H₂O (0.001 M NH₄F) constant at 1:19.29:6.20, respectively. A surface chemical modification of the films was done with alkylchlorosilanes at different concentrations from 0 to 1 vol. % and aging times varied from half to 2 h. The DMCS and TMCS surface modified silica films showed the static water contact angle of 146° and 162°, respectively. When the DMCS and TMCS modified films were cured at temperatures higher than 240 and 275°C, respectively, the films became superhydrophilic. Further, the humidity study was carried out at a relative humidity of 90% at 30°C temperature over 60 days. We characterized the water repellent silica films by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, % of optical transmission, humidity tests and contact angle measurements.     

Preparation and Properties of Polyether Pentaerythritol Mono‐maleate grafted Linear Low Density Polyethylene by Reactive Extrusion

A reactive type nonionic surfactant, polyether pentaerythritol mono‐maleate (PPMM) was synthesized in our laboratory. PPMM was adopted as a functionalizing monomer and grafted onto linear low density polyethylene (LLDPE) with a melt reactive extrusion procedure. FT‐IR was used to characterize the formation of grafting copolymer and evaluate their degree of grafting. The effects of monomer concentration, reaction temperature and screw run speed on the degree of grafting were studied systematically. Isothermal crystallization kinetics of LLDPE and LLDPE‐g‐PPMM samples was carried out using DSC. Crystallization rates of grafted LLDPE were faster than that of plain LLDPE at the same crystallization temperature. The tensile properties and light transmission of blown films were determined. Comparing with neat LLDPE film, no obvious changes could be found for the tensile strength, elongation at break and right angle tearing strength of LLDPE‐g‐PPMM film. The wettability is expressed by the water contact angle. With an increasing percentage of PPMM, the contact angles of water on film surface of LLDPE‐g‐PPMM decrease monotonically. The acceleration dripping property of film samples was investigated. The dripping duration of LLDPE‐g‐PPMM film and commercial anti‐fog dripping film at 60°C were 76 days and 17 days, respectively.     

Radiation chemistry of linear low-density polyethylene. II. Kinetics of alkyl and allyl free-radical decay reactions

Quenched and annealed samples of linear low-density polyethylene (LLDPE) were γ irradiated in vacuo at 77 K; the kinetics of the alkyl free-radical decay reactions were studied at room temperature, and of the allyl free-radical reactions at 60, 70, and 80°C. The ESR signals saturate at a slightly higher microwave power in the LLDPE than in high-density polyethylene (HDPE), and the alkyl radicals start decaying at a lower temperature in the LLDPE than in the HDPE. As in the HDPE the decay of the alkyl free radicals at room temperature in the LLDPE follows the kinetic equation for two simultaneous first-order reactions with the fraction of the faster-decaying component being slightly greater in the quenched than in the annealed samples. In the case of the allyl free radicals the decay at 60°C follows the equation based on one fraction of the radicals decaying according to second-order kinetics in the presence of other nondecaying radicals. At higher temperatures the data are best understood in terms of a second-order rate equation with a continuously variable time-dependent rate constant as suggested by Hamill and Funabashi.     

Charge decay properties of poly(propylene) samples (PP) with various stereochemical compositions

Charge decay properties at 90°C have been studied for four poly(propylene) (PP) samples of different content of isotactic (mm), syndiotactic (rr) and heterotactic (mr, rm) triads. Comparing the charge decay properties with the previously measured space charge distribution and taking into account the specific stereochemical sequences which characterize each of the samples, it is apparent that mmrm and rrrm sequences furnish better storage properties. In contrast, mmrr and short heterotactic sequences would both exhibit worse retention power of negative and positive charge. Correlations – although still tentative – justify those specific stereochemical sequences as being well defined factors for determining the electrical properties of PP.     

Wettability characterization of transparent MgF<Subscript>2</Subscript> nanoparticle coatings with SiO<Subscript>2</Subscript> binder covered with fluoroalkylsilane self-assembled monolayers

SiO₂-added MgF₂ nanoparticle coatings with various surface roughness properties were formed on silica-glass substrates from autoclaved sols prepared at 100–180 °C. The samples were exposed to fluoro-alkyl silane (FAS) vapor to give hydrophobicity. All nanoparticle samples before FAS treatment had transmittances higher than 93% and such values were preserved even after FAS treatment. We examined root mean square roughnesses of the nanoparticle coatings with a Scanning Probe Microscope. We also examined their static and dynamic wettabilities with a contact angle meter and calculated their adhesive energies and surface free energies (SFEs). The surface roughness of the nanoparticle coating increased with the increase of the autoclave temperature. In addition, higher autoclave temperature caused increases in the sliding angle and decreases in the SFE. Interestingly, the higher the contact angle was, the larger the sliding angle was, although smaller sliding angle was expected with a larger contact angle.     

Controlled migration of antifog additives from LLDPE compatibilized with LLDPE grafted maleic anhydride

This paper summarizes a study of controlled migration of an antifog (AF) additive; sorbitan monooleate (SMO), from linear low density polyethylene (LLDPE) films containing a compatibilizer, LLDPE grafted maleic anhydride (LLDPE‐g‐MA). LLDPE/LLDPE‐g‐MA/SMO blends were prepared by melt compounding. Bulk and surface properties of compression molded LLDPE films containing SMO and LLDPE‐g‐MA were characterized using Fourier transform infrared spectroscopy and contact angle measurements. Thermal properties were investigated using a thermal gravimetric analyzer. Diffusion coefficient (D) was calculated, and AF properties were characterized using a “hot fog” test. Compression molded films were characterized for their morphology using high‐resolution scanning electron microscopy, and rheological properties were measured using a parallel‐plate rotational rheometer. It was found that the LLDPE/LLDPE‐g‐MA/SMO systems are characterized by a slower SMO migration rate, a lower diffusion coefficient, and lower contact angle values compared with LLDPE/SMO blends. These results are well correlated with results of a hot fog test. Morphological studies revealed a very fine dispersion of SMO in the LLDPE films, when 3 phr LLDPE‐g‐MA was combined with 1 phr SMO. Thermal analysis results show that the incorporation of 3 phr LLDPE‐g‐MA and 1 phr SMO significantly increases the decomposition temperature of the blend at T > 400°C. At high shear rates, the LLDPE blends show that the AF and the compatibilizer have a lubrication effect on LLDPE. Copyright © 2014 John Wiley & Sons, Ltd.     

Sliding Wear Behavior of Nanoclay Filled Polypropylene/Ultra High Molecular Weight Polyethylene/Carbon Short Fiber Nanocomposites

In the present investigation, authors made an attempt to study the sliding wear behavior of polypropylene/ultrahigh molecular weight polyethylene (PP/UHMWPE, 90/10) blends loaded with 30% carbon short fibers (CSF) as reinforcement and nanoclay as filler material. The nanocomposites have been prepared with varying amounts viz., 0, 1, 2 and 3 wt% of nanoclay. The composites were prepared by melt mixing at 60 rpm extruder speed and compression moulding at 180°C. From all the composites, 6 mm diameter and 25 mm length sliding wear specimens were prepared. Sliding wear loss, specific wear rate and coefficient of friction were investigated by using computerized pin-on–disc machine at normal applied loads of 20, 30 and 40 N; at a sliding velocity of 1.5 m/s and at two abrading distances viz., 200 and 300 m. The wear behavior data reveals that 3 wt% nanoclay filled composite exhibits higher wear resistance and lowest specific wear rate as compared to other nanocomposites. Also morphological study was carried out for wear out surfaces of all the composites using scanning electron microscopy (SEM).     

A new charging mode of Li-ion batteries with LiFePO<Subscript>4</Subscript>/C composites under low temperature

Li-ion batteries with LiFePO₄/C composites are difficult to be charged at low temperatures. In order to improve the low temperature performance of LiFePO₄/C power batteries, the charge–discharge characteristics were studied at different temperatures, and a new charging mode under low temperature was proposed. In the new charging mode, the batteries were excited by current pulses with the charge rates between 0.75 C and 2 C, while the discharge rates between 3 and 4 C before the conventional charging (CC–CV). Results showed that the surface temperature of Li-ion battery ascended to 3 °C at the end of pulse cycling when the environment temperature was −10 °C. Comparing with the conventional charging, the whole charge time was cut by 36 min (23.4%) and the capacity was 7.1% more at the same discharge rate, respectively.     

Pre-irradiation grafting of span 60-IAH onto polyethylene to improve dripping properties of water on polyethylene films

A reactive type dripping anti-condensation agent, Span 60-IAH, was grafted onto linear low density polyethylene (LLDPE) by β-ray pre-irradiation and reactive extrusion. Effects of total dose, monomer concentration and extrusion temperature and rate on the degree of grafting were studied in detail. It was shown that the optimum conditions for grafting were the extrusion temperature of 130–220°C, screw run speed of 90 rpm and total β-ray dose of 12.5 kGy. The structure of the LLDPE-g-(Span 60-IAH) (LS) was characterized by Fourier-transform infrared spectroscopy (FT-IR). The tensile properties and light transmission properties of extruded films were determined. The thermal behavior of the LS was investigated by using differential scanning calorimetry (DSC). Compared with pure LLDPE, the crystallization temperature (T_c) of LS increased about 3°C. Accelerated dripping properties of film samples were investigated. The dripping duration of the LS film and a commercial anti-fog dripping film at 60°C were 45 days and 17 days, respectively, indicating a significant improvement.     

Superhydrophobic surface by immobilization of polystyrene on vinyl-modified titania nanoparticles

Abstract  

The organic–inorganic nanocomposite films were fabricated by grafting polystyrene (PS) onto the vinyltriethoxysilane (VTEOS) modified titanium dioxide nanopowders using free radical polymerization. The composition of the surfaces and the structure for the PS grafted titania (PS-g-TiO₂) were examined by infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis, and the rough surface was confirmed by the evaluation of the morphological characteristics of the coating using hybrid particles. The wetting properties of the VTEOS modified titania and PS-g-TiO₂ films were investigated, which show the maximum static water contact angles of 160° and 154°, and minimum sliding angles of 3° and 4°, respectively.     

Surface mechanical properties of low‐molecular‐weight polystyrene below its glass‐transition temperatures

Lap shear and friction force measurements were carried out on a series of monodisperse polystyrene (PS) films below the corresponding glass‐transition temperatures. It showed that adhesion between the PS/PS interface was possible at the temperature below the bulk T_g, and the lower the molecular weight of PS, the lower the temperature at which the interfacial strength was detectable. The examination of a series of molecular weights indicated both the surface molecular motion and the magnitude of the interfacial strength were dependent on molecular weight and its distribution. And a steep increase of the friction force with increasing the test temperature was observed around 0 ∼ 30 °C. The contact angle of water versus molecular weight measurements also showed a transition at room temperature. The behavior observed in this study was supposed to be due to the increased molecular mobility, and was in good agreement with the measured surface transition temperatures by DSC. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 654–658, 2000     

Structure and properties of polypropylene crystallized from the glassy state

Glassy isotactic propylene (PP) films of thickness up to 0.3 mm were obtained by an ultraquenching technique. The structure and properties of the as-quenched and subsequently crystallized samples were characterized by various techniques. Electron microscopy indicates the glass has no structure larger than 25 Å. X-ray diffraction shows PP crystallizes from the glass into a smectic structure at ca. ?20°C and then transforms to monoclinic microcrystals at ca. 40°C; a nodular structure (80 to 100 Å in diameter) was observed on the surface. The transformation temperature increases with the film thickness. Annealing above the α-relaxation temperature results in an increase in the nodule size. A correspondence was found between the diameter of the nodules observed on the surface and long spacings obtained by small-angle X-ray scattering from the bulk. Dynamic mechanical spectra show the presence of two relaxation-like peaks at ca. ?10°C and 10°C for the as-ultraquenched samples. X-ray scattering, differential scanning calorimetry (DSC), and torsion pendulum measurements show PP crystallizes from the glass at a temperature, depending on the rate of heating, that corresponds to the lower relaxation peak temperature.     

Plasma pretreatment of polycarbonate substrates for indium zinc oxide film deposition

The influence of plasma treatment of polycarbonate (PC) substrates on the morphological, electrical, and adhesion properties of deposited amorphous transparent indium zinc oxide (IZO) by direct current magnetron sputtering was investigated by analyzing atomic force microscopy, contact angles, Hall, and nano‐scratch measurements. The surfaces of PC substrates were performed by plasma treatment at various processing times in Ar/O₂ mix atmosphere. The atomic force microscopy images indicated that the microstructure of the substrates considerably influenced the surface morphology of deposited IZO films, and the least surface roughness of IZO was obtained after 5‐s plasma treatment. The IZO film deposited on PC with 5‐s plasma treatment presented an improved electrical conductivity and thermal stability after annealing at 120 °C in air, whereas the significant decrease in carrier concentration and increase in resistivity with extending plasma treatment time were observed, which was attributed to the elevated oxygen adsorption during annealing for a loosely packed structure. Moreover, the adhesion properties of IZO films with PC substrates decreased after 30‐s plasma treatment because of the significant difference on the surface polarity between the PC and thin films and the increased roughness caused by plasma etching. Copyright © 2016 John Wiley & Sons, Ltd.     

Switchable Adhesion of Superhydrophobic ZnO Nanorod Film

We have fabricated superhydrophobic zinc surface with reversible transformation between sliding state and adhesion by a simple hydrothermal method. Uniformly ZnO₂ nanorod was obtained at 120°C. After self-assembling of a film of n-octadecanethiol, the surface with a water contact angle (CA) of 153 ± 2°, exhibited a nonwetting property. The surface showed switchable adhesion just upon introducing UV illumination and heating treatment in turn.     

Study of the morphology,thermal and mechanical properties of irradiated isotactic polypropylene films

Thin films of isotactic polypropylene (iPP) are of great economical importance and their production is quite challenging due to the need of very fast uniaxial or biaxial expansion. During the expansion, critical problems usually arise, like structure disruption, shear thinning, causing material, energy and time losses. This work aims to study the surface morphology and compare the thermal, mechanical properties of PP films irradiated by gamma ray in an acetylene atmosphere after uniaxial expansion. PP films were made by compression molding at 190 °C with cooling in water at room temperature and irradiated by gamma ray, at (5, 12.5 and 20 kGy) under acetylene atmosphere. After irradiation the samples were submitted to thermal treatment at 90 °C for 1 h and then stretched out at 170 °C using an Instron machine. The surface of PP films, pristine and modified, (i.e., irradiated), was studied using optical microscopy (OM) and scanning electron microscopy (SEM). The changes in morphology, crystallinity and tensile parameters, like yield stress, rupture stress and elongation strain of the PP with irradiation dose were investigated. The results showed some evidences of gel formation due to crosslinking and/or long chain branching induced by radiation.