氟改性和硅改性丙烯酸聚氨酯涂层的制备及环境行为

目的研究氟改性和硅改性丙烯酸聚氨酯涂层在不同环境中的失效行为。方法通过溶液聚合法制备具有一定羟基含量的丙烯酸酯树脂,再将丙烯酸树脂与多异腈酸酯固化剂配合,获得丙烯酸聚氨酯涂层。通过在丙烯酸酯合成中引入含氟丙烯酸酯单体,制得氟改性丙烯酸聚氨酯涂层;通过在固化过程中引入氨基硅油,制得硅改性丙烯酸聚氨酯涂层。利用傅里叶变换红外光谱(FT-IR)分析涂层的化学组成。对涂层试样进行温度环境实验(室温和100,150℃)、湿热环境实验和氙灯老化实验,分析涂层疏水性、光泽度等表面特性的变化。结果氟、硅改性有效提高了涂层的疏水性。未改性、氟改性和硅改性三种涂层在100℃以下的环境中服役时,疏水性和光泽度比较稳定。硅改性涂层在150℃的高温环境中较未改性和氟改性涂层失效慢。湿热环境对三种涂层的接触角和光泽度等性能影响不大。氟改性涂层在氙灯老化环境中的失效程度较另外两种涂层轻。结论氟改性涂层耐光老化性能较好,硅改性涂层耐温性较好。     

Preparation of refractive-index-controlled silicone microspheres and their application in polycarbonate light diffusing materials

ABSTRACT

Light-diffusing materials (LDMs) are essential for diffusing indoor light-emitting diode (LED) illumination to soft light. The size and refractive index of the light-diffusing agent are the two main parameters that influence the light-diffusing properties of LDMs. Modulation of silicone microspheres’ refractive index and their influence on the light-diffusing properties of LDMs were systematically explored. An environmentally friendly, dispersant-free polymerization method carried out in an aqueous solution was developed for the preparation of silicone microspheres with different refractive indices. The prepared microspheres and LDMs were characterized by scanning electron microcopy (SEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). Results showed that the refractive index of the prepared microspheres can be regulated by adjusting the copolymerization composition. Prepared silicone microspheres could be uniformly dispersed in a polycarbonate (PC) matrix, and the refractive index had a marked influence on the light-diffusing properties of the resulting LDMs. The silicone microspheres and LDMs both exhibited excellent thermal stabilities.     

Determination of siloxanes in silicone products and potential migration to milk,formula and liquid simulants

A pressurised solvent extraction procedure coupled with a gas chromatography–mass spectrometry–selective ion monitoring (GC–MS–SIM) method was developed to determine three cyclic siloxanes, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6) and three linear siloxanes, octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), dodecamethylpentasiloxane (L5), in silicone products. Additionally, two different extraction methods were developed to measure these siloxanes migrating into milk, infant formula and liquid simulants (50 and 95% ethanol in water). The limits of quantification (LOQs) of the six siloxanes ranged from 6?ng/g (L3) to 15?ng/g (D6). Silicone nipples and silicone bakewares were extracted using pressurised solvent extraction (PSE) and analysed using the GC–MS–SIM method. No linear siloxanes were detected in the silicone nipple samples analysed. The three cyclic siloxanes (D4, D5 and D6) were detected in all silicone nipple samples with concentrations ranging from 0.5 to 269?µg/g. In the bakeware samples, except for L3, the other five siloxanes were detected with concentrations ranging from 0.2?µg/g (L4) to 7030?µg/g (D6). To investigate the potential migration of the six siloxanes from silicone nipples to milk and infant formula, a liquid extraction and dispersive clean-up procedure was developed for the two matrices. The procedure used a mix of hexane and ethyl acetate (1?:?1, v/v) as extraction solvent and C₁₈ powder as the dispersive clean-up sorbent. For the liquid simulants, extraction of the siloxanes was achieved using hexane without any salting out or clean-up procedures. The recoveries of the six siloxanes from the milk, infant formula and simulants fortified at 50, 100, 200, 500 and 1000?µg/l ranged from 70 to 120% with a relative standard derivation (RSD) of less than 15% (n?=?4). Migration tests were performed by exposing milk, infant formula and the liquid simulants to silicone baking sheets with known concentrations of the six siloxanes at 40°C. No siloxanes were detected in milk or infant formula after 6?h of direct contact with the silicone baking sheet plaques, indicating insignificant migration of the siloxanes to milk or infant formula. Migration tests in the two simulants lasted up to 72?h and the three cyclic siloxanes were detected in 50% ethanol after an 8-h exposure and after 2?h in 95% ethanol. The highest detected concentrations of D4, D5 and D6 were 42, 36 and 155?ng/ml, respectively, indicating very limited migration of D4, D5 or D6 into the two simulants.     

The role of vehicle interactions on permeation of an active through model membranes and human skin

Previous work from this group has focused on the molecular mechanism of alcohol interaction with model membranes, by conducting thermodynamic and kinetic analyses of alcohol uptake, membrane partitioning and transport studies of a model compound (i.e. methyl paraben) in silicone membranes. In this article, similar membrane transport and partitioning studies were conducted in silicone membranes to further extend the proposed model of alcohol interactions with silicone membranes to include other vehicles more commonly used in dermal formulations, that is, isopropyl myristate (IPM), dimethyl isosorbide (DMI), polyethylene glycol (PEG) 200, PEG 400 and Transcutol P^® (TC). More importantly, membrane partitioning studies were conducted using human SC to evaluate the application of the proposed model of solvent‐enhanced permeation in simple model membranes for the more complex biological tissue. The findings support a model of vehicle interactions with model membranes and skin where high solvent uptake promotes drug partitioning (i.e. K) by enabling the solute to exist within the solvent fraction/solvent‐rich areas inside the membrane or skin in a concentration equivalent to that in the bulk solvent/vehicle. High solvent sorption may also ultimately impact on the membrane diffusional characteristics, and thus the diffusion coefficient of the solute across the membrane. The implications for skin transport are that increased partitioning of a drug into the SC may be achieved by (i) selecting vehicles that are highly taken up by the skin and also (ii) by having a relatively high concentration (i.e. molar fraction) of the drug in the vehicle. It follows that, in cases where significant co‐transport of the solvent into and across the skin may occur, its depletion from the formulation and ultimately from the skin may lead to drug crystallization, thus affecting dermal absorption.     

Thermal stability and mechanical properties of room temperature vulcanized silicone rubbers

Based on much of the importance of RTV on the field of self-cleaning application for its nontoxic, tasteless, and thermal stability, the effects of D₄-SiO₂ on mechanical properties, Al(OH)₃ and decabromodiphenyl oxide ethyl(DBDPE) on flame retardant property of RTV matrix were investigated firstly. Then, a new kind of complex fire retardants was compounded. The morphology of additives and fracture appearance of composites were demonstrated by SEM. The hot property of RTV-based composites was outlined by TG. It is found that D₄-SiO₂/Al(OH)₃/DBDPE/Sb₂O₃/RTV composites were of better comprehensive performances in mechanical property, hot property, fire resistance property, and insulating property, which presented tear 26.73 kN/m of strength, 279.8% of elongation at break, 2.81 MPa of tensile strength, FV-0 at the level of flame retardant property, 46 of Oxygen index (OI) 3.03 × 10¹⁵ Ωm of Volume electric resistivity, the range of decomposition temperature was 370°C to 650°C, and the percentage of remain weight was 26.4%. Those properties was acquired on the condition of 11 wt % D₄-SiO₂ + 20 wt % Al(OH)₃ + 15 wt % DBDPE+ Sb₂O₃ at the amount of 3.0 wt % to 3.7 wt %. This investigation leads the authors to a conclusion that D₄-SiO₂/Al(OH)₃/DBDPE/Sb₂O₃ is a kind of better combination modifier than anyone kind of which in comprehensive properties for RTV. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal,hydrolytic, anticorrosive,and tribological properties of alkyd‐silicone hyperbranched resins with high solid content

Novel alkyd hyperbranched resins (AHBRs) modified with a Z‐6018 silicone (a polysiloxane intermediate) and with high solid content were synthesized by etherification reaction using an acid catalyst. Different molar ratios of AHBR to silicone were used. Structural, thermal, hydrolytic, anticorrosive, and tribological properties were studied using infrared (IR) analysis, nuclear magnetic resonance (NMR), vapor pressure osmometry (VPO), thermogravimetric analysis (TGA), acid value, electrochemical impedance spectroscopy (EIS), and pin‐on‐disk friction. IR and NMR provide evidence of grafting of the silicone on AHBR; the efficiency of grafting was quantified by TGA. Thermal stability was studied also by acid value analysis. Grafting increases the number average molecular mass, enhances thermal stability, and improves significantly hydrolytic stability. Corrosion resistance on steel is improved by two orders of magnitude, hence our modified materials can be used as highly effective anticorrosion coatings. Grafting lowers dynamic friction dramatically, more so at higher concentrations of silicone. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of MQ silicone resins

MQ silicone resins, which represent a broad range of hydrolytic condensation products of monofunctional silane (M) and tetrafunctional silane (Q), were synthesized by reaction of water glass with hexamethyldisiloxane. The optimum reaction time and the optimal reaction temperature is 30 min and 30–40°C, respectively. Concentrated hydrochloric acid is the best one among those catalysts tested. In large-scale experiments (420–1680 mL), the favorable feeding order is catalyst first, and then water glass, the mixture of hexamethyldisiloxane and ethanol last and most MQ silicone resin was observed. The structure of MQ silicone resin was characterized by FT-IR and GPC spectra. The MQ silicone resin shows narrow molecular weight distribution and the number average molecular weight of MQ silicone resin is 2917. The silicone pressure sensitive adhesive prepared from as-synthesized MQ resin has good tack (29#) and 180° peel adhesion (5.630N/20 mm). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Use of low‐level plasma for enhancing the shrink resistance of wool fabric treated with a silicone polymer

This study examines the effects of an atmospheric pressure plasma (APP) pre‐treatment on the shrink resistance of wool fabric treated subsequently, by the pad/dry method, with an aqueous emulsion of the amino‐functional polydimethylsiloxane, SM 8709. Optimal shrink resistance (with no impairment of fabric handle) was obtained after a low‐level plasma treatment (1–3 s exposure time), using 5% of the polymer emulsion. Higher levels of silicone polymer could be used to achieve shrink resistance in the absence of a plasma pre‐treatment, but the fabric handle would be adversely affected. X‐ray photoelectron spectroscopy (XPS) studies showed that the bulk of the covalently bound surface lipid layer was removed after a plasma exposure time of 30 s. For treatment times of 3 s or less, however, the removal was incomplete, suggesting that optimum shrink resistance (after treatment with the silicone polymer) was associated with the modification of the surface layer rather than its complete destruction. Scanning electron micrographs (SEMs) revealed that the plasma pre‐treatment did not lead to any physical modifications (such as smoothening of the scale edges), even for long exposure times, and had no significant impact on the extent or nature of the inter‐fibre bonding of the polymer. Confocal microscopy showed uniform spread of polymer on single fibres. It is concluded that the main impact of the plasma pre‐treatment was to enhance the distribution of polymer both on and between fibres and to improve adhesion of polymer to the fibre.     

Kinetic and characterization of UV-curable silicone urethane methacrylate in semi-IPN-structured acrylic PSAs

To improve the thermal stability of general acrylic pressure-sensitive adhesives (PSAs), polydimethylsiloxane (PDMS) was used and UV curing was employed. Silicone urethane methacrylate (SiUMA) was synthesized and introduced into acrylic PSAs for a semi-interpenetrating polymer network structure. The structure of the SiUMA was investigated through C NMR, H NMR, and FT-IR. The kinetics and behaviors of SiUMA (S1) were found by adding photoinitiators (PI) of 0.5, 1.0, 5.0, and 10?phr in a binder, which were examined using the photo-DSC (pDSC). After setting PI as 5.0?phr in a binder and UV intensity as 1000?mJ/cm², the SiUMA, which was prepared by a radical polymerization, was added to acrylic PSA to 20, 40, 60, and 80% composition, and its kinetics and behaviors were analyzed by pDSC. Finally, the peel strength was checked to evaluate adhesion performance of the acrylic PSAs. The reaction rate was increased with increasing amounts of S1 and PI. Peel strength was dropped sharply with increasing crosslinking density.     

Hydrophobic recovery of repeatedly plasma-treated silicone rubber. Part 1. Storage in air

Silicone rubber is used for a wide variety of biomedical and industrial applications due to its good mechanical properties, combined with a hydrophobic surface. Frequently, however, it is desirable to alter the surface hydrophobicity of silicone rubber. Often this is done by plasma treatments but the effects are usually transient. In this study, surfaces of medical grade silicone rubber have been repeatedly modified by means of oxygen, argon, carbon dioxide, and ammonia RF plasma treatments with a 24 h time interval in between treatments. Treated samples were stored in air prior to surface characterization by water contact angle measurements, X-ray photoelectron spectroscopy (XPS), streaming potential measurements, and profilometry for surface roughness. The carbon percentage of the surfaces decreased after plasma treatment, while the silicon and oxygen percentages increased irrespective of the plasma used. The formation of Si-O-Si bridges between siloxane chains after plasma treatment was demonstrated by the appearance of a new component in the Si_2p peak but the degree to which this occurred differed per gas. Streaming potential measurements in a 10 mM potassium phosphate buffer indicated a more negatively charged surface for treated samples compared to untreated samples (-23.3 mV at pH 7.0). Surface roughness increased slightly for repeatedly plasma-treated samples from R_A = 0.35 μm to R_A = 0.46 μm, while scanning electron microscopy showed the presence of several 'cracks' spanning the surface after repeated treatment. Argon, carbon dioxide, and ammonia plasmas significantly reduced the advancing water contact angle from 115° to 58°, 72°, and 85°, respectively, on a more permanent basis (especially when the treatments were repeated after recovery). Oxygen plasma effects on water contact angles generally disappeared within 5 h, also after repeated treatment.