有机硅/二氧化钛复合材料的制备及抗紫外线性能分析

在有机硅弹性体中添加二氧化钛,通过不同的混合比例,在150 ℃下采用压模工艺制备厚度为0.8 mm的有机硅/二氧化钛复合材料。性能测试结果表明,有机硅/二氧化钛复合材料具有很高的防紫外线效果,但弹性强力和模量降低。复合材料的防紫外线效果和弹性性能与有机硅弹性体在乳液中的含量有关。     

Transport properties and mechanical behavior of poly(methyl‐phenylsiloxane) membranes as a function of methyl to phenyl groups ratio

Membranes based on dimethyl and methyl‐phenylsiloxane were synthesized and then fully characterized. Transport properties and mechanical behavior were determined as a function of different methyl/phenyl group ratios and the effects of these groups on results were established. Membrane transport properties were evaluated from n‐hexane absorption studies. Static tensile stress–strain deformation measurements, stress–hysteresis determination, and stress–relaxation studies were performed to assess the mechanical behavior of these membranes. The results indicate that both physical–mechanical and transport properties are strongly affected by the methyl group content. The increase of the phenyl groups in the polymer chain impairs mechanical properties as a result of which decrease in crosslinking degree and gas permeability due to the diminution in free volume and penetrant solubility. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1624–1633, 2002     

The network structure of silicone release coatings

Silicone release coatings are used by the pressure-sensitive adhesive industry for labeling applications. A background discussion of silicone release coatings is presented. Methodology for determining the network structure of photolytically cured systems prepared by the cationic ring opening polymerization of an epoxy silicone fluid is described. Under typical polymerization conditions, these networks contain no unreached epoxides and have very low degrees of polymerization (D _p), indicating that termination is competitive with propagation. A method has also been developed to determine the network structure of thermally cured systems prepared by the platinum-catalyzed hydrosilylation of silicone vinyl compounds with silicone hydrides. The nature of the cross-links and the types of residual functionality have been determined and the systems have been shown to undergo a postcure.This paper was presented at the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.     

3D-Printed Silicone Substrates as Highly Deformable Electrodes for Stretchable Li-Ion Batteries

Stretchable energy storage devices receive a considerable attention at present due to their growing demand for powering wearable electronics. A vital component in stretchable energy storage devices is its electrode which should endure a large and repeated number of mechanical deformations during its prolonged use. It is crucial to develop a technology to fabricate highly deformable electrode in an easy and an economic manner. Here, the fabrication of stretchable electrode substrates using 3D-printing technology is reported. The ink for fabricating it contains a mixture of sacrificial sugar particles and polydimethylsiloxane resin which solidifies upon thermal curing. The printed stretchable substrate attains a porous structure after leaching the sugar particles in water. The resulting printed porous stretchable substrates are then utilized as electrodes for Li-ion batteries (LIBs) after loading them with electrode materials. The batteries with stretchable electrodes exhibit a decent electrochemical performance comparable to that of the conventional electrodes. The stretchable electrodes also exhibit a stable electrochemical performance under various mechanical deformations and even after several hundreds of stretch/release cycles. This work provides a feasible route for constructing LIBs with high stretchability and enhanced electrochemical performance thereby providing a platform for realizing stretchable batteries for next generation wearable electronics.     

Preparation and surface properties of silicone-modified polyester-based polyurethane coats

A series of novel silicone-modified polyesters (SPE) were prepared by substituting part of diol with low molecular weight hydroxyl-terminated poly(dimenthylsiloxane) (PDMS). Then, isophorone diisoclanate (IPDI) as hard segments and 1,4-butanediol as chain extender were added to SPE to prepare a silicone-modified polyurethane (SPU). The effects of the type of diol, diacid, and hydroxyl-terminated PDMS, and the amount of hydroxyl-terminated PDMS on the preparation and surface properties of SPU were investigated. It was found that the amount of PDMS incorporated into a polyester chain was relatively higher when 1,6-hexanediol (HDO) and 1,10-decandiol (DDO) were used as diol and the PDMS with lower molecular weight was used as organosilicone compound. Consequently, the SPU coats with HDO as diol, adipic acid (AA) as diacid, and short chain PDMS as silicone segment had the lowest surface-free energy since it had the highest and most homogeneous distribution of silicone segments at its top layer surfaces.     

3D‐Printed Silicone Materials with Hydrogen Getter Capability

Organic getters are used to reduce the amount of reactive hydrogen in applications such as nuclear plants and transuranic waste. The present study examines the performance of getter loaded silicone elastomers in reducing reactive hydrogen gas from the gas phase and their capability of being 3D printed using direct ink writing techniques. The samples are placed in closed vessels and exposed to hydrogen atmosphere at pressures of 580 torr and 750 mtorr and at a temperature of 25 °C. The hydrogen consumption is measured as a function of time and normalized to getter concentration in the polymer. The performance of the getter‐loaded silicone elastomer containing 1,4‐bis[phenylethynyl]benzene (DEB) as the organic getter and Pd/C catalyst (ratio of 3:1 DEB to catalyst) decreases with increasing the resin's curing temperature. Chemical analysis suggests that DEB reacts with the silicone resin at high temperatures. In addition, it is demonstrated that the increased surface area of 3D printed composites results in improved getter performance.     

Blends of high‐density polyethylene with solid silicone additive

Silicone masterbatch (SMB) is a pelletized formulation containing 50% of an ultrahigh molecular‐weight polydimethylsiloxane dispersed in polyethylene. This SMB is designed to be used as an additive in polyethylene‐compatible systems to impart benefits such as processing improvement and modification of surface characteristics. In this work, binary blends of high‐density polyethylene (HDPE) and SMB were prepared by melt‐mixing technique to study the influence of this masterbatch on the processing and mechanical properties of HDPE. Ternary blends were also prepared by the addition of silane‐grafted polyethylene (HDPE‐VTES) as compatibilizer. The blends were analyzed by melting flow rate (MFR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and tensile tests. Data of final torque and MFR showed that SMB improved the processability of pure HDPE. DSC results showed differences in crystalline behavior between binary and ternary blends. In the former, the degree of crystallinity increased up to 10 wt % of SMB content; beyond this concentration, it decreased. In ternary blends, a reverse behavior was observed. The morphologic study showed silicone particles uniformly distributed in HDPE matrix. With high SMB concentration, the addition of HDPE‐VTES significantly reduced the size of silicone particles. In the range of SMB composition studied, the mechanical properties of blends lower slightly compared to pure HDPE. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2347–2354, 2002     

Influence of methacryl polyhedral oligomeric silsesquioxane on the thermal and mechanical properties of methylsilicone resin

A methacryl polyhedral oligomeric silsesquioxane (POSS)‐reinforced methylsilicone resin was prepared in this work. The structures of the obtained products were confirmed with Fourier transform infrared and atomic force microscopy. The influence of methacryl‐POSS on the thermal behavior of the methylsilicone resin was studied by thermogravimetric analysis and isothermal thermogravimetric analysis. The results showed that the thermal stability of the methylsilicone resin was improved, and the degree of thermooxidative degradation was lowered; this was due to the retardation of polymer chain motion and the formation of a protective layer of SiO₂. The interlaminar shear strength and flexural strength of quartz fiber/methylsilicone resin composites were tested to determine the effects of methacryl‐POSS on the mechanical properties of methylsilicone resin. The results revealed that the mechanical properties of the methylsilicone composites also increased obviously after the incorporation of methacryl‐POSS because of the increase in the cure degree and rigidity of the resin. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigating the surface properties of polyurethane based anti‐graffiti coatings against UV exposure

A permanent anti‐graffiti coating based on a polyurethane resin was prepared by incorporating different levels of an OH‐functional silicone modified polyacrylate additive. Static contact angle measurements and dynamic mechanical thermal analysis (DMTA) were employed to evaluate surface free energy and mechanical properties of the coating specimens, respectively. Effect of ageing condition on the graffiti properties of the coating samples was evaluated utilizing an accelerated weathering test. Color changes, surface morphology, and variations in the mechanical properties were also examined prior to and after being exposed to UV irradiation for 864 h in a QUV chamber. Results showed that surface free energy of the samples decreased with replacement of polyol with additive up to 5 mol %. A Scanning electron microscope equipped with energy dispersive X‐ray detector revealed that for the samples containing more than 5 mol % additive, there was an enrichment of silicone at the interface of films and air. At long exposure times and higher concentrations of additive, depreciation of graffiti properties was seen. DMTA and attenuated total reflectance‐fourier transform infra‐red studies before and after ageing showed that the silicone additive tended to degrade while it could cause an increase in crosslinking density. Water contact angles and atomic force microscopy images after ageing revealed that the cause of the depletion in anti‐graffiti properties was attributed to the deterioration of the silicone additive. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

An investigation of scratch testing of silicone elastomer coatings with a thickness gradient

Silicone elastomer coatings are currently being investigated as foul release coatings on ships hulls. Previous tests on silicone duplex elastomer coatings used a progressive load scratch test. It has been shown that the durability of uniform silicone duplex elastomer coatings is a function of thickness, indentation modulus, and stylus and that the failure mechanism depended on coating thickness and stylus. When applying silicone coatings to a ship's hull, there are regions on the ship where the coating is not uniform. This article investigates the effect of a thickness gradient on the durability of a single layer silicone elastomer coating. In these tests, a constant normal load was used as the stylus moved transversely to the surface. It was found that when the scratch test started in the silicone coating and proceeded in the direction of decreasing coating thickness (“Elastomer to Metal”), there was first a scratch tract followed by the initiation of detachment of the coating, then by gross detachment of the coating. When the scratch started on the exposed aluminum surface and proceeded into the silicone in the direction of increasing coating thickness (“Metal to Elastomer”), there was first gross detachment of the coating, followed by recovery (i.e., silicone coating is intact) and a scratch tract into the silicone. It was also found that the coefficient of friction was much higher in the silicone when the scratch test was going in the direction of decreasing coating thickness as opposed to the scratch test going in the opposite direction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012