Corrosion resistance properties of spray- and dip-coated 3-glycidoxypropyltrimethoxysilane (GLYMO)–tetraethoxysilane (TEOS) Ormosil films have been investigated using salt spray analysis. 1H–13C and 1H–29Si CP/MAS NMR analyses indicate that organic content and hydrolysis water ratio affect the Ormosil structure, and in turn, the corrosion resistance properties of the Ormosil film. For spray-coated samples, films derived from the 11 mol% GLYMO Ormosil prepared using hydrolysis water content (W=2 and 4) provided good corrosion protection, as this combination of organic content, water ratio, and deposition method produced films of the appropriate thickness, hydrophobicity, and density for good corrosion protection. Films prepared from high organic contents (25 and 67 mol% GLYMO) and low hydrolysis water content values (W=1 and 2) exhibited the best corrosion resistance for films prepared by dip coating. Presumably, these films comprise a dense network structure with organic groups dispersed throughout the film, providing a hydrophobic barrier coating capable of repelling water and corrosion initiators. 相似文献
Summary: Two different types of biodegradable polyester composites, PLLA fiber‐reinforced PCL and PCL/PLLA blend films were prepared at PCL/PLLA ratio of 88/12 (w/w), together with pure PCL and PLLA films. Their enzymatic degradation was investigated by the use of Rhizopus arrhizus lipase and proteinase K as degradation enzymes for PCL and PLLA chains, respectively. In the FRP film, the presence of PLLA fibers accelerated the lipase‐catalyzed enzymatic degradation of PCL matrix compared with that in the pure PCL film, whereas in the blend film, the presence of PLLA chains dissolved in the continuous PCL‐rich domain retarded the lipase‐catalyzed enzymatic degradation of PCL chains. In contrast, in the FRP film, the proteinase K‐catalyzed enzymatic degradation of PLLA fibers was disturbed compared with that of the pure PLLA film, whereas in the blend film, the proteinase K‐catalyzed enzymatic degradation rate of particulate PLLA‐rich domains was higher than that of pure PLLA film. The reasons for aforementioned enhanced and disturbed enzymatic degradation are discussed.
Normalized PCL weight loss of pure PCL, FRP, and blend films as a function of Rhizopus arrhizus lipase‐catalyzed enzymatic degradation time. 相似文献
In this paper, DLC multilayer films consisting of alternating layers of soft and hard carbon films were deposited on Si wafer by a plasma CVD deposition system. Different DLC multilayer films were prepared by varying the sub-layer thickness (from 1000 to 25 nm) and the ratio of hard to soft sub-layer (H/S) thickness (from 1:1 to 4:1). By using a ball-on-disk tribo-tester, the friction and wear properties of the DLC multilayer films were measured in vacuum, O2 and dry-air environments respectively. By comparing with single-layer DLC film, the change of the multilayer structure has little influence on friction coefficient of the multilayer films. However, the wear rate of the DLC multilayer films is restricted effectively by constructed the multilayer structure in the film. The wear rate of the multilayer films is lower than that of the single film in reactive (O2 and dry-air) environments. An DLC multilayer film with excellent wear resistance, approximately in the level of 10−8 mm3/Nm in different environments (dry-air, O2 and vacuum), is obtained as the DLC multilayer film at a certain sub-layer thickness and ratio. 相似文献
Summary: Dielectric cyclosiloxane bearing polysilsesquioxanes (CS‐PSSQs) were prepared by acid catalyzed polymerization using 2,4,6,8‐tetramethyl‐2,4,6,8‐tetra(trimethoxysilylethyl)cyclotetrasiloxane. The molecular weight, and content of the functional end‐groups of the CS‐PSSQs were found to be dependent on the process parameters, such as the molar ratio of water and catalyst to the ? OCH3 group of the silane monomer, the amount of solvent, and the poly(ε‐caprolactone) (PCL) content, etc. Based on these CS‐PSSQ prepolymers, nanoporous organic/inorganic hybrid thin films were fabricated by spin‐coating mixtures of these prepolymers with star‐shaped PCL on the silicon substrate, and subsequently heating them at 150 and 250 °C for 1 minute each and then at 420 °C for 1 hour. A dielectric constant as low as 2.28 was achieved for the nanoporous PCL/CS‐PSSQ (3:7 v/v) film, along with low moisture absorption in ambient and water conditions, primarily due to the presence of hydrophobic moieties such as ethylene and methyl groups of the polymer and nano‐sized hydrophobic pores inside the matrix, resulting in the film having stable dielectric properties. Moreover, the PCL/CS‐PSSQ (3:7 v/v) nanohybrid film revealed a nanoporous structure containing ca. 1.52 nm of average‐sized mesopores, as measured by the N2 adsorption method. The CS‐PSSQ‐only film showed high mechanical strengths having an elastic modulus and hardness of 6.64 and 0.88 GPa, respectively, for the 7 500 Å thick film and 2.41 and 0.38 GPa, respectively, for the PCL/CS‐PSSQ (3:7 v/v) film. In addition, the crack velocity of the CS‐PSSQ‐only film was found to be ca. 10?11 m · s?1 in ambient conditions and an aqueous environment, probably due to the enhanced hydrophobicity and mechanical toughness of the incorporated methyl group, siloxane unit and ethylene moieties in the polymer matrix.
In this paper, a multilayer barrier thin film, based on polyvinylidene difluoride (PVDF)–silicon dioxide (SiO2), has been fabricated on a PET substrate through a novel method of joint fabrication techniques. The inorganic SiO2 thin film was deposited using a roll-to-roll atmospheric atomic layer deposition system (R2R-AALD), while the organic PVDF layer was deposited on the surface of SiO2 through the electrohydrodynamic atomization (EHDA) technique. The multilayer barrier thin films exhibited very good surface morphology, chemical composition, and optical properties. The obtained values for arithmetic surface roughness and water contact angle of the as-developed multilayer barrier thin film were 3.88 nm and 125°, respectively. The total thickness of the multilayer barrier thin film was 520 nm with a high optical transmittance value (85–90%). The water vapor transmission rate (WVTR) of the barrier thin film was ~?0.9?×?10?2 g m?2 day?1. This combination of dual fabrication techniques (R2R-AALD and EHDA) for the development of multilayer barrier thin films is promising for gas barrier applications. 相似文献
Flexible polymeric films are not only widely used in conventional packaging as substitute for glass and aluminum foil packaging but are also proposed as encapsulation for novel products, like flexible solar cells or organic light‐emitting devices. The two essential properties of the polymeric packaging are flexibility and good permeation barrier properties against gases and vapors. This article deals with vacuum web coating as a common way of increasing barrier properties of polymeric films and the problems related to this procedure. Defects caused by particles and surface imperfections are found to dominate the permeation rate for such coated polymeric films. Atomic force microscopy, electron and also optical microscopy was used for analysis of the coating layer. Three‐dimensional numerical simulations were performed for modeling of the influence of defect size, spacing and film thickness. Results of numerical modeling and of many practical experiments show that the permeability is almost independent of the substrate film thickness when a critical thickness is exceeded. In most cases the defects can be treated as independent of each other. The gas permeability of vacuum web‐coated polymeric films can be quantitatively predicted by a simple formula. For gases, like oxygen, it is shown that a statistic analysis of the defect sizes by optical microscopy is sufficient. For water vapor transmission, however, the structure of the coating layer itself has also to be taken into account. 相似文献