Silicone elastomers for electronic applications. II. Effects of noncrosslinked materials

We performed applied functional tests to examine how the noncrosslinked fraction of a cured silicone elastomer affected the performance of electrical devices and the solderability and adhesion on gold‐plated printed circuit boards. To obtain information about the spreading tendencies of commercial silicone elastomers, and to complement the function tests, we conducted so‐called creep tests to examine the migration and spreading of the noncrosslinked fraction. The electrical tests, performed with both reference oligomers and cured commercial poly(dimethyl siloxane)s, showed that failure occurred even at very low silicone contamination levels. The solderability and adhesion, however, were not affected by the presence of poly(dimethyl siloxane)s, especially not the reference solutions, which consisted mainly of volatile siloxanes. The creep tests, performed on commercial silicone elastomers, indicated that the noncrosslinked, nonvolatile part had to be taken into account in a discussion of silicone contamination. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3780–3789, 2003     

Interpenetrating polymer networks based on poly(styrene‐co‐butylacrylate‐co‐hydroxyethyl methacrylate) and SiO2

Copolymer such as poly(styrene‐co‐butylacrylate‐co‐hydroxyethyl methacrylate) p (St‐BA‐HEMA) was prepared via free radical emulsion polymerization method. The resulting copolymer was converted to silicone secondary crosslinked interpenetrating polymer network (IPN) by condensation reaction with tetraethyl orthosilicate (TEOS). The obtained copolymers were characterized by using Fourier transform infrared spectroscopy (FTIR). Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Optical microscopy (OM) is used for studying the morphology, and then the effects of silicone concentrations, the reflux time, and composition on the phase morphology of P (St‐BA‐HEMA)‐SiO₂ IPNs were discussed. The broadening of the transition region was observed with the prolongation of the reflux time, and the tendency for aggregation of silicone on the surface was observed with Teflon as substrate plate. However, an optically transparent film was easily achieved at higher temperature due to the chemical crosslink and physical entanglement between the two phases of P (St‐BA‐HEMA)‐SiO₂. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Functionalization of polymethylhydrosiloxane gels with an allyl ureido benzocrown ether derivative: Complexation properties

Crosslinked polymethylhydrosiloxane (PMHS) thin films prepared by sol–gel polycondensation have been functionalized by Pt‐catalyzed hydrosilylation of SiH groups with an allyl ureido crown ether precursor. To this purpose, both 4′‐allylurea‐benzo‐15‐crown‐5 ( 1 ) and 1‐allyl‐3‐propyl‐urea ( 2 ) were synthesized and characterized. We have shown that competitive side‐reactions occurred following hydrosilylation due to the hydrolysis of part of the SiH groups resulting in the formation of new crosslinks Si(CH₃)O_3/2 as shown by solid‐state ²⁹Si‐NMR. This is explained by the deactivation of the Pt catalyst toward hydrosilylation by amide groups. For thin films (～ 1 μm) prepared on silicon wafers, a quantitative method based on FT‐IR transmission spectroscopy was used to measure the crosslinking density of the network, and the percentage of functionalization (SiC %) following hydrosilylation. The results are discussed in relation to the mesh size of the network, and the diffusion of alkenes and water molecules within lightly crosslinked PMHS gels obtained by varying the amount of triethoxysilane crosslinker (mol %) from 15 to 1%. The self‐organization properties of ureido groups by H‐bonding were studied by FT‐IR for the functionalized thin films. The complexation properties of the crown ether 1 ‐functionalized thin films were evidenced by using FT‐IR following diffusion‐reactions of NaSCN and KSCN salts in CHCl₃ : MeOH solvent mixtures within thin films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation,structural evolution,and performance of heat-resistant organosilicon polymer adhesives for joining SiC ceramics

There is an urgent need for heat-resistant adhesives with high bonding strength in order to able to fabricate large and complex SiC components for aeronautical and astronautical applications. In this study, heat-resistant organic adhesives prepared using an organosilicon polymer and inorganic additives (B₄C and SiO₂) were used successfully to bond SiC ceramics. The prepared adhesives were characterised through shear strength tests as well as using thermogravimetry-differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-diffraction analysis, and scanning electron microscopy. The adhesives exhibited high room-temperature shear strengths (greater than 15 MPa) after being subjected to heat treatments at 200–1200°C. Further, the high-temperature shear strengths of the adhesives at 200, 400, 600, 800, and 1000°C were 10.5, 10.1, 7.7, 8.6, and 8.4 MPa, respectively. The high performance of the adhesives indicated that they should be suitable for joining SiC-based materials for use in high-temperature applications.     

Diffraction Gratings in Hybrid Sol‐Gel Films: On the Understanding of the Relief Generation Process

Hybrid organic‐inorganic materials based on the sol‐gel synthesis of an organically modified silicon alkoxide have demonstrated their great potential for optical applications. They offer a high versatility in terms of chemical, physical properties and macroscopic shape molding of the final component. Recently, a photolithographic process allowed the generation of relief optical elements without requiring a wet treatment to reveal the latent image. It enabled a low cost, simple and quick method for the fabrication of integrated optical components. The aim of the present paper is to give new insights into the mechanisms of surface self‐corrugation leading to gratings generation in hybrid sol‐gel films. A study of the relief formation was led by giving particular attention to the kinetic aspects of the polymerization of the organic component. The control of the C?C double bonds conversion of methacrylate functionalized alkoxides in case of photopolymerization is therefore an essential issue to tailor material properties. The study also focuses on the influence of physico‐chemical parameters that govern the relief generation and underlines the particular role of temperature. Kinetics of surface corrugation point out the importance of strain relaxation, mass‐transfer by flowing and organic network formation during the photolithographic process. Some illustrations of the generated diffraction gratings are given.

Interferogram of the diffraction grating obtained after 120 s exposure through a chromium mask.     

硅／磷协同阻燃剂的制备及应用

以甲基三甲氧基硅烷（MS）为前驱体，高聚合度聚磷酸铵（APPⅡ）为载体，采用溶胶一凝胶工艺，制备硅／磷协同阻燃剂。通过电镜表征（SEM，TEM）发现该阻燃剂为硅／磷包覆结构，在详细讨论硅氧烷溶胶制备工艺的影响因素的基础上，将该阻燃剂与水性聚氨酯复合制成阻燃涂层剂，用于织物的阻燃涂层整理。结果表明，该阻燃剂相对APP而言，能赋予织物优异的阻燃、高强力及防“霜化”等效果。且随着硅／磷比增加，阻燃效果及织物强力和静水压均提高，并最终稳定；随着阻／胶比增加，阻燃效果提高，织物强力及静水压反而下降。     

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     

Conductive effect of an electronic/ionic complex conductivity modifier for silicone elastomers

This study examined silicone, which demonstrated an ionic/electronic compounding conductivity effect through the complexation of polypyrrole (Ppy), carbon black (CB), and a poly(propylene oxide)–poly(ethylene oxide) copolymer with 20 wt % LiClO₄ (PEL). Rigid‐body pendulum rheometry was used to observe the processing conditions for the polymer blends, and energy‐dispersive X‐ray spectrometry was used to analyze the distribution depth of the polymer blend surfaces for Ppy. In addition, a digital electrometer was used to test the surface resistance of the composites, and an impedance meter was used to test the dielectric constant and loss factor. The results showed that PEL‐obstructed silicone molecular chain crosslinking, transformed from liquid to solid films, required a higher temperature for curing than silicone because the linear molecular structure of the polymer electrolyte was wound around the silicone polymer network structure, forming a semi‐interpenetrating network. This showed that the Ppy molecule could permeate SP10 blends more deeply. After the silicone was treated with the PEL modifier, the conductivity of Ppy was obstructed. On the other hand, the conductivity of CB showed no significant difference in the SP10 blends. Therefore, after the silicone matrix treatment of the electronic/ionic complex conduction process, there was no incremental effect on the conductivity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 711–720, 2005     

Hemin-Doped,Ionically Crosslinked Silicone Elastomers with Peroxidase-Like Reactivity

The encapsulation of hemin in polymer systems represents a powerful tool for the preparation of synthetic enzymes. Reported systems largely focus on the creation of hydrogels or microreactors that require a degree of modification to the hemin molecule itself. The straightforward synthesis of hydrophobic hemin-aminosilicone crosslinked silicone elastomers is described with peroxidase like reactivity. Elastomers are formed from purely ionic interactions between commercial aminoalkylsilicones and native hemin, which acts as a crosslinker. Elastomers prepared from ethylene diamine-based silicones are robust elastomers in which hemin is retained, while hemin can leach monoamine analogues into the adjacent aqueous environment. The system is easily tunable, allowing for precise control of the hemin concentration and the physical properties of the elastomer. Upon exposure to peroxide-containing solutions, elastomers readily oxidize the substrate 3′,3′,5′,5′-tetramethylbenzidine at the interface. Elastomers containing excess amine show greater catalytic efficiency due to the coordination of the amines to the iron center of hemin, which is known to be activating. The reaction can be followed using UV-visible spectroscopy; rates of reaction and Michaelis–Menten parameters are derived.     

毛型整理剂2F1T的应用

介绍了毛型整理剂2F1T的组成和对中长毛型华达呢的整理工艺,并同其它后整理剂进行对比。实验表明:此产品优于其它后整理剂,整理后的中长织物各项指标达到部颁标准,成本也合算,经济效益可观。