Silicone Gum Research Articles

Reactivity of Si‐H and Si‐vinyl end functionalized siloxanes toward PBT: A model system study

AbstractBased on a previous model compound study, we investigated the melt reactivity of Si‐H and Si‐vinyl end‐functionalized siloxane oligomers towards polybutylene terephthalate (PBT) in the presence of platinum(0)‐catalyst. We clearly observed grafting of the Si‐H functional oligomer onto PBT and have also indications for grafting of the Si‐vinyl oligomer. The grafting efficiencies and kinetics of both siloxane model compounds are compared and roughly quantified by infrared spectroscopy. This result indicates that the same reactive groups that are used to vulcanize silicone gums at high temperature can also be used to favor compatibility with a polyester matrix, opening perspectives toward polyester‐siloxane thermoplastic elastomers. POLYM. ENG. SCI. 45:1067–1072, 2005. © 2005 Society of Plastics Engineers

807 マイクロカプセルPCM(MECPM)と樹脂材の複合材料の熱特性(G06-2 熱物性・加工,G06 熱工学)

In this paper, the results of heating and cooling examination conducted in order to investigate the thermal characteristics of Composite Materials of Microencapsulated PCM (MEPCM) and Resin, Gum, were reported. In this study, the composite materials were made by being MEPCM mixed into polyurethane resin or silicon gum. The maximum rate of MEPCM in polyurethane resin was 30wt%, on the other hand, the one of MEPCM in silicone gum of which is low coefficient of viscosity was 50wt%.

914 硬さ測定用カテーテルに関する基礎的研究

This paper describes the development of a catheter sensor for measurement of stiffness of the blood vessel wall. The basic sensor is constructed with a piezoelectric transducer (PZT), which acts as the tactile sensor and employs the phase shift principle. Two type of catheter sensor were developed. One type was built with a contact tip angle at 45 degrees in order to emit ultrasonic waves directly to the inside wall. The objective of the construction of the other type was to miniaturize its outside diameter as much as possible. Different concentrations of silicone gum and rubber models of blood vessels were used for measurements. Result show that the sensors could distinguish between silicone gum samples of different levels of hardness and determine the hardness/softness of neoplasm in blood vessel model. Thus, the catheter sensor developed here may prove very useful for inner measurements of blood vessels and may also be useful in detecting intraluminal obstruction due to tumor presence.

911 エンドスコーピックサージェリー用触覚センサの基礎的研究

Nowadays, endoscopic surgery is performed regularly in the clinical domain. Using this technique, the surgeon performs operations remotely with various tools and without internal manual contact. Thus, typical palpation cannot be performed and therefore tactile information is unavailable. In order to measure stiffness internally, we developed a new tactile sensor using the phase shift method with ultrasonic waves and demonstrated its feasibility with stiffness measurements of silicone gum. The tactile sensor could clearly distinguish different degrees of silicone gum stiffness at different levels of pressure and is thus useful for relative internal stiffness measurements.

Measurement of spatially nonuniform phase changes of a light beam utilizing the reflectivity characteristic of a self-pumped phase-conjugate mirror

We describe a new method for measuring spatially nonuniform phase changes of a light beam from the spatial nonuniformity of the phase changes, which is obtained by detecting the relative reflectivity change of a self-pumped phase-conjugate mirror. The method is designed to decrease the accumulation of calculating errors. The usefulness of these methods is verified through computer simulations and measurements of the phase changes caused by spatially nonuniform deformation of a semitransparent sheet of silicone gum.

Monitoring of S- and R-tocainide in human plasma after heptafluorobutyrylation, separation on Chirasil-Val and electron-capture detection.

The conditions for the heptafluorobutyrylation of tocainide have been studied. An almost instantaneous reaction was obtained with 0.01% of heptafluorobutyric anhydride in toluene at 40 degrees C. Higher anhydride concentration caused degradation of the initially formed derivative, mainly by the loss of water, as shown by mass spectral analysis. Tocainide was isolated from plasma by extraction into dichloromethane at alkaline pH. Gas chromatographic separation was performed with a fused-silica capillary column coated with a methyl silicone gum. The enantiomers were separated on a glass capillary column coated with Chirasil-Val. Upon analysing 0.1 ml of plasma eight times the precision was 4.7% at the 10 mumol/1 level for the S-form of tocainide.

Application of solid-phase extraction in the method development for determination of SEPA, an acronym for soft enhancement of percutaneous absorption, in human, rat, and rabbit serum using GC–FID method

A new nonaqueous topical minoxidil formulation containing SEPA (2- n-nonyl-1,3-dioxolane) for enhancement of percutaneous absorption was under evaluation. SEPA does not have chromophore for either ultraviolet or fluorescence detection using liquid chromatography and has no functional groups for derivatization. Therefore, a direct gas-chromatographic method with flame-ionization detection (GC–FID) was developed. Owing to the limited detection response of the FID detection, it needs a selective and concentrated extract for GC–FID analysis to improve the assay sensitivity to meet the requirement for pharmacokinetic evaluation after topical application. In addition, SEPA is a very volatile compound. Any extraction procedures involving evaporation will result in a poor recovery. The application of solid-phase extraction (SPE) makes it possible to achieve a selective and a 10-fold concentrated extract with an absolute extraction recovery of approximately 90%, which greatly improved the assay sensitivity. This method involved the extraction of SEPA and the internal standard (2- n-heptyl-1,3-dioxolane) from serum (0.1–1 ml) with 100 μl of hexane-chloroform (1:1, v:v) using a 50 mg 1.0 ml −1 phenyl SPE column (Varian, Harbor City, CA, USA), followed by direct GC–FID analysis on a fused-silica column chemically bonded with cross-linked methyl silicone gum phase (Hewlett Packard Ultra-1, 12 m×0.2 mm×0.33 μm, Avondale, PA, USA). The assay demonstrated a lower limit of quantitation of 2.5 ng ml −1 and a linear range of 2.5 to 250 ng ml −1 with intra- and inter-assay precision and accuracy of ≤10%.

A tactile sensor for detection of physical properties of human skin in vivo

A spring loaded tactile sensor with displacement sensing has been evaluated for non-invasive assessment of physical properties, stiffness and elasticity, of human skin in vivo. The tactile sensor consists of a piezoelectric vibrator (61 kHz) with a vibration pickup, electronics and PC with software for measurement of the change in frequency when the sensor is attached to an object. Integrated with the tactile sensor is a displacement sensor that shows the compression of the spring that loads the sensor element against the object during measurement. Under certain conditions (e.g. fixed contact pressure) this change in frequency monitors the acoustic impedance of the object and is related to the stiffness of soft tissue. The experimental results on silicone gum and on healthy Japanese and Swedish women indicated that the instrument was able to detect changes in stiffness and elastic related properties of human skin, related to age, day-to-day variations and application of cosmetics. The instrument was concluded to be easy to handle and suitable for field work.

Strain-hardening Property and Internal Deformation of Polymer Composite Melts under Uniaxial Elongation.

Uniaxial elongational viscosity of low density polyethylene (LDPE) gave the strain-hardening property. However, talc-filled LDPE showed almost no strain-hardening property and glass-fiber-filled LDPE exhibited the strain-softening property. The cause of almost no strain-hardening property or strain-softening property was discussed from flow observation of internal deformation using visual model experiments. Silicone gums including a glass bead or a glass fiber with a black silicone gum marker were elongated. The internal strain in a glass-bead-filled system was larger than the external strain along the elongational axis, and the received internal strain was larger around a particle than far way from a particle. The internal strain in a glass-fiber-filled system did not depend on the location when the initial orientation of the fiber was perpendicular to the elongational direction. While, the received internal strain next to the fiber without the both edges was almost none when the initial fiber was parallel to the elongational direction. Nonuniformities of internal flow by the addition of fillers seem to be associated with no strain-hardening property or strain-softening property.

Quantitation of cocaine and cocaethylene in small volumes of rat whole blood using gas chromatography-mass spectrometry

A simple solid phase extraction (SPE) technique combined with gas chromatography-mass spectrometry (GC/MS) operated in selected ion monitoring (SIM) mode is described for quantitation of cocaine and cocaethylene in small samples (250 μl) of rat whole blood. Use of ( N-[ 2H 3C])-cocaine and (N- [ 2H 3C])-cocaethylene internal standards resulted in high sensitivity and selectivity for this analytical method. Analysis was performed using a Hewlett-Packard 5890 GC equipped with a 7673A Automatic Liquid Sampler linked to a Hewlett-Packard 5972 Mass Selective Detector. Separation of analytes was accomplished on a cross-linked methyl silicone gum capillary column (Ultra 1: 12m × 0.2mm (i.d.) × 0.33 μm). Linearity was established over a wide range of concentrations (5.0–2000.0 ng ml −1) with good precision. Limits of detection (LOD) were 1.0 and 2.0 ng ml −1 for cocaine and cocaethylene, respectively. This analytical method was designed for use in pharmacokinetic experiments studying the formation of cocaethylene following ethanol pretreatment in rats administered cocaine.

Determination of salicylate- and benzophenone-type sunscreen agents in cosmetic products by gas chromatography-mass spectrometry

A novel simple method to detect salicylate- and benzophenone-type sunscreen agents in cosmetic products by gas chromatography-mass spectrometry (GC-MS) has been developed. Seven sunscreen agents (two salicylate-type and five benzophenone-type) were used for this study. Sunscreen agents and cosmetic product solutions were prepared by dissolving in dimethylformamide, and silylated with bis-trimethylsilyltrifluoroacetamide-trichloro-methylsilane (BSTFA). Silylated sunscreen agents were separated on a cross-linked methyl silicone gum column. The identification of each sunscreen agent was accomplished by retention time and mass spectrum library search with a computer, and the quantitation was made in the selected-ion monitoring (SIM) mode of GC-MS. Silylation increased the detection limits of all sunscreen agents about 20–170-fold. Linearity was maintained over the range 1–300 μg ml for each sunscreen agent. Each cosmetic product (i.e. sun lotion, sun cream and sun cream foundation) was found to contain amounts of the sunscreen agents. This method was sensitive and gave 95.2–104.1% recovery of each sunscreen agent from these cosmetic products. From these results, we concluded that silylation with BSTFA followed by GC-MS analysis allows the simple, convenient and exact determination of sunscreen agents from cosmetic products.

Blood and urinary benzene determined by headspace gas chromatography with photoionization detection: application in biological monitoring of low-level nonoccupational exposure.

A simple and sensitive gas chromatography (GC) headspace method was developed for the determination of benzene in blood and urine. 1.0 ml of venous blood or urine sample in a headspace vial containing chlorobenzene as an internal standard was incubated at 60 degrees C for 30 min and 0.5 ml headspace gas was used for GC analysis. Unmetabolized benzene in blood or urine was detected at 2.5 min using a silicone gum capillary column and a photoionization detector. The proposed method appears to be more sensitive and reliable than other existing methods, with recovery and reproducibility generally over 90% and a detection limit of 0.64 and 0.51 nmol/l for blood and urinary benzene, respectively. The proposed method was validated with blood and urine samples collected from 25 nonsmokers and 50 smokers. The blood and urine concentrations of benzene in nonsmokers were significantly lower (P < 0.001) than those in smokers: the mean concentrations for blood and urinary benzene, respectively, were 1.42 and 4.21 nmol/l for nonsmokers and 1.49 and 5.19 nmol/l for smokers. A significant correlation (r = 0.61, P < 0.001) was also found between benzene in blood and benzene in urine. These findings suggest that benzene in urine as well as benzene in blood can be used for the biological monitoring of low levels of benzene exposure. Although there was a close correlation between benzene in blood and benzene in urine, no correlation was found between benzene in blood or benzene in urine and the number of cigarettes smoked.

Silicone gum of OV-225 type for open-tubular gas chromatography

A silanol-terminated silicone having 25% cyanopropyl, 50% methyl and 25% phenyl substitution was prepared and a method for its immobilization in open-tubular columns was developed. This stationary phase showed good thermal stability at temperatures up to 300°C, and it was immobilized to 80% by means of thermal treatment. Its selectivity was excellent for the separation of azaarenes.

Determination of furan-based amines in reaction mixtures by gas chromatography

A protocol which employs a methyl silicone gum capillary column for gas chromatographic analysis of the products of the acid- catalyzed reaction of furfurylamine with aldehydes is presented, and its efficacy is demonstrated.

Preparation and characterization of silicone membranes for supported liquid membrane applications

Poly organo-silicone menbranes were prepared from dimethyldichlorosilane (DMDCS) as the starting material. The preparation roughly involved three steps: hydrolysis of DMDCS, preparation of silicone gum from the hydrolysed product and crosslinking of the silicone gum with tetraethoxysilane (TEOS), using a tin-salt catalyst. It is shown that swelling of silicone membranes in non-polar solvents can be greatly reduced by incorporating a large amount of TEOS in the membrane matrix. The water and non-polar solvent uptake, chemical and thermal stability, nitrogen gas permeability and tensile strength of the membranes were studied. The porosity and pore size of membranes moderately swollen in non-polar solvent indicate that these membranes are suitable for application as supported liquid membrane (SLM). The transport of rare earth samarium ions through these membranes using di(2-ethyl hexyl) phosphoric acid (D2EHPA) as extractant are reported.

ヒツジ用シリコーンゴム製第一胃カニューレの作製と装着方法の検討

[in Japanese]

Effects of phenylethynylsilicon compounds on heat-curable silicone rubber. Part 2.–Phenylethynylvinyldiethoxysilane

The effects of (phenylethynyl)vinyldiethoxysilane (PVDES) as a crosslinker on heat-curable silicone rubber (HCSR) have been investigated. PVDES, which can, in certain specific amounts, improve the mechanical properties of vulcanizates, is a good crosslinker of silicone rubber. The tensile strength and the tear strength of some vulcanizates can reach 12.80 MPa and 56.4 kN m–1respectively, and the modulus of elasticity at 100% extension 4.10MPa. PVDES can also be used as a good hydrosilation curing retarder of silicone rubber. By adding 0.05 parts or more of PVDES to 100 parts of silicone gum the stocks could be stored at room temperature (20 ± 1 °C) for more than 50 days. The sol fractions and crosslinking density of the vulcanizates have been also measured.

Possible methylation of inorganic mercury by silicones in the environment

Organosiloxanes (silicones) are being released to the environment in increasing quantities, and there are questions concerning the reactivity of silicones as methylating agents under environmental conditions. Specifically, the interaction of inorganic mercury and polydimethylsiloxanes, and other silicones, to give methylmercury is important in this context. To this end a series of laboratory experiments, in which inorganic mercury, short and long chain silicones, cyclic siloxanes, oxidized silicone gums, and industrial formulations containing silicones, were conducted. In all cases, there was evidence of the production of methylmercury, a finding of potential significance. Analyses for methylmercury and related silicon-containing degradation products were conducted using a combination of gas chromatography, mass spectrometry, and head-space gas analysis.

Amidines : XXVI. Retention indices of N 1,N 1-dimethylpropionamidines, isobutyramidines, pivalamidines and phenylacetamidines on a non-polar column

The retention indices of 92 compounds, comprising four series of N 2-substituted N 1,N 1-dimethylamidines, R xN = C(R z)N(CH 3) 2, each containing the same set of 23 variable substituents at the imino nitrogen atom, have been measured on a non-polar GE SE-30 silicone gum rubber column. The values obtained for each series were correlated with those of corresponding model compounds, such as primary amines, R xNH 2, substituted hydrocarbons, R xH, ethyl esters of corresponding carboxylic acids, R zCOOC 2H 5, and dimethylamides, R zCON(CH 3) 2. Support is provided for an earlier conclusion that for the prediction of retention indices the correlation method should be used instead of additivity rules. It has been found that the regression parameter characterizing the influence of substitution at the imino nitrogen atom on the retention index depends on the type of substituent at the amidino carbon atom. On the basis of the retention indices of 115 compounds the parameters of an equation for the prediction of the retention indices ofN 1,N 1-dimethylamidines containing an alkyl or aralkyl substituent at the amidino carbon atom were found.

Simultaneous determination of germanium, arsenic, tin and antimony by molecular emission cavity analysis after hydride generation and gas chromatographic separation

Arsenic (0.1–5 μg), antimony (1–40 μg), tin (0.5–10 μg) and germanium (0.2–10 μg) are determined simultaneously by reduction to their hydrides with sodium tetrahydroborate(III), followed by gas chromatographic separation on a column of 10% E-301 silicone gum rubber on Porapak Q, and measurement of the emissions at 490 nm in an oxygen/hydrogen flame within a cavity. Detection limits for 1-ml samples are 35 ng As, 400 ng Sb, 85 ng Sn and 100 ng Ge. A more sensitive determination of arsenic (0.05–3 μg) and antimony (0.1–5 μg) in binary mixtures is also described; the detection limits are 15 ng As and 40 ng Sb.