Silicone Epoxy Research Articles

Extraction of dielectric and magnetic properties of carbonyl iron powder composites at high frequencies

In this paper, we examine carbonyl iron composites in silicone rubber and epoxy matrices. Transmission measurements were performed at W (70 to 110 GHz) and Ka (26 to 40 GHz) bands and effective permittivity and permeability of composites with 10% volume fraction of carbonyl iron powder (CIP) were extracted at these frequencies. To extract permittivity and permeability of carbonyl iron powder in W and Ka bands, we use Looyenga formula. We extract permittivity and permeability of CIP from both silicone rubber and epoxy based composites and good agreement is achieved.

Study on high‐solid content Si/PU polyurethane dispersion with PES/PPG composite soft segment

AbstractA polyol consists of silicone chains and epoxy acrylate structures, referred to as silicon polyether (PES), was used to prepare crosslinked Si/PU dispersions. Both PES and propylene oxide glycol (PPG) were mixed as soft segments. The effects weight ratios of PES to PPG on properties of the resultant polyurethane dispersions were studied. Morphology and properties of the Si/PU dispersions were characterized by particle size, transmission electron microscopy (TEM), and viscometer. It is shown that the Si/PU dispersions possessed wider particle size distribution and higher average particles diameter because of the use of PES, which contains crosslinked silicone side chains. The Si/PU dispersions have higher solid content as compared to the conventional water‐based polyurethane, because of the volume fraction ratio of bigger particle to small particle from the Si/PU dispersions. As increasing weight ratio of PES to PPG, the solid content of the Si/PU dispersions increased firstly, and then decreased. When the ratio ranges from 4 : 10 to 5 : 10, solid content of the Si/PU dispersions is up to 55%. It was also noticed that apparent viscosity of the Si/PU dispersions decreased with increasing PES to PPG ratio. In the Si/PU dispersions, solid content was increased and viscosity was decreased by the use of PES. Therefore, PES is a potential compound for the application of PU dispersions. In addition, stability of the crosslinked Si/PU dispersions decreases slightly at high‐ and low‐temperature; however, which can meet the basical requirements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

A New Statistical Approach for Analysis of Tree Inception Voltage of Silicone Rubber and Epoxy Resin under AC Ramp Voltage

Weibull distribution has been used widely by many researches around the world especially in the analysis of high voltage experimental data. Unfortunately, the statistical techniques used to analyse the high voltage experimental data are not highly accurate. In view of the foregoing, this paper presents a new statistical approach to analyze the tree inception voltage of silicone rubber and epoxy resin. The tree inception voltage of silicone rubber and epoxy resin was measured via camera-equipped online monitoring system. The leaf-like specimen was used as test sample. AC ramp voltage was applied to obtain the tree inception voltage of silicone rubber and epoxy resin. It was observed that, the electroluminescence emission and ultraviolet (UV) radiation occurred indicating the early stage of tree occurrence. The obtained results were analysed statistically by using fitting method. Anderson-Darling goodness-of-fit test was performed in order to obtain the best fitting distribution. Comparison was made between the best-fitted distribution and Weibull distribution. Based on Anderson-Darling tests, the tree inception voltage of silicone rubber and epoxy resin was best fitted with Johnson SB distribution. Based on this fitted distribution, the value of tree inception voltage for silicone rubber and epoxy resin was calculated and equalled to 11.80 kV and 20.11 kV respectively. From this study, it was found out that the best-fitted distribution for the value of tree inception voltage for silicone rubber and epoxy resin is the Johnson SB distribution by means of Anderson-Darling goodness-of-fit test.

Galvanic corrosion of Ni–Cu–Al composite coating and its anti-fouling property for metal pipeline in simulated geothermal water

A novel anti-fouling epoxy-silicone composite coating containing Ni–Cu–Al alloy powder for metal pipeline in geothermal water was fabricated based on the basic principles of galvanic corrosion. Fouling behaviors of the surface of composite coating in the simulated geothermal water were studied in comparison with stainless steel and epoxy-silicone resin coating. The results indicated that composite coating possessed a good anti-fouling performance. In the geothermal water, Ni2+, Cu2+ and Al3+ ions, originated from interface electrochemical corrosion, were released into bulk solution. These metal ions intensively inhibited nucleation and crystal growth rate of CaCO3 fouling on the surface of composite coating, and promoted precipitation of CaCO3 fouling in the bulk-solution, which could be easily washed away by flowing water. But for 304 stainless-steel and epoxy-silicone resin coating, CaCO3 fouling grew easily and adhered firmly to their surfaces, and influenced the transport efficiency of geothermal water for pipelines.

Synthesis and Characterization of Modified Epoxy-Silicone Resin

Chosed silicone resin with better waterproof and weatherability as raw material, epoxy resin and polyester as modifiers, developed a modified adhesive resin. By researching of the relation between content and property, the matching curing agent with polyfunctional groups was prepared, the modified resin was completely solidified. Properties test and analysis demonstated that the cured modified resin provided super resistance of salt fog and better surface abrasion resistance and perfectible high-temperature resistance

A molecular method to assess bioburden embedded within silicon-based resins used on modern spacecraft materials

AbstractCurrent assessments of bioburden embedded in spacecraft materials are based on work performed in the Viking era (1970s), and the ability to culture organisms extracted from such materials. To circumvent the limitations of such approaches, DNA-based techniques were evaluated alongside established culturing techniques to determine the recovery and survival of bacterial spores encapsulated in spacecraft-qualified polymer materials. Varying concentrations ofBacillus pumilusSAFR-032 spores were completely embedded in silicone epoxy. An organic dimethylacetamide-based solvent was used to digest the epoxy and spore recovery was evaluated viagyrB-targeted qPCR, direct agar plating, most probably number analysis, and microscopy. Although full-strength solvent was shown to inhibit the germination and/or outgrowth of spores, dilution in excess of 100-fold allowed recovery with no significant decrease in cultivability. Similarly, qPCR (quantitative PCR) detection sensitivities as low as ∼103CFU ml−1were achieved upon removal of inhibitory substances associated with the epoxy and/or solvent. These detection and enumeration methods show promise for use in assessing the embedded bioburden of spacecraft hardware.

Thermally resistant UV-curable epoxy–siloxane hybrid materials for light emitting diode (LED) encapsulation

A UV-curable epoxy–siloxane hybrid material (epoxy hybrimer) was fabricated by photo-cationic polymerization of a sol–gel derived cyclo-aliphatic epoxy oligosiloxane (CAEO) blended with oxetane cross-linker in the presence of an onium salt. Antioxidants for fabrication of the UV-curable epoxy hybrimer with high thermal resistance against yellowing were incorporated in the UV-curable epoxy hybrimer. The UV-curable epoxy hybrimer with the antioxidants showed high thermal resistance without yellowing during 120 °C thermal aging. High thermal resistance of the UV-curable epoxy hybrimer was similar and higher compared to those of commercial thermally curable silicone and UV-curable epoxy LED encapsulants, respectively. The thermally resistant UV-curable epoxy hybrimer was successfully encapsulated on a LED without any cracking or delamination, and maintained a flat surface on the LED without distortion of the designed flat shape. Before/after thermal and blue light aging, the performance of the LED encapsulated by the UV-curable epoxy hybrimer was not changed. On the basis of its excellent properties as a LED encapsulant, the UV-curable epoxy hybrimer can be utilized as a UV-curable LED encapsulant for white LEDs.

Preparation and Characterization of the Transparent Hybrids of Silicone Epoxy Resin and Titanium Dioxide Nanoparticles via Sol–Gel Reactions

In order to prepare transparent hybrid films of high refractive index, nanoparticles of TiO2 were prepared and dispersed in a silicone epoxy (SE) resin synthesized from diphenyl silane diol and [2-(3,4-epoxycyclohexyl)ethyl] trimethoxysilane by sol-gel reactions. It was found that amorphous TiO2 nanoparticles of about 5 nm modified with hexahydro-4-methyl phthalic anhydride [HMPA] were dispersed in the SE resin without agglomerations. The refractive index of the hybrids increased linearly with increasing the TiO2 contents. The hybrid containing 30 wt% of the TiO2 particles showed light transmittance of 94% at 450 nm and refractive index of 1.63. The fine dispersion of the TiO2 nanoparticles was attributable to the sol-gel reactions between the SE resin and TiO2 nanoparticles and the modification of the TiO2 particles with HMPA.

Experiment of Beam Crack Repair Using Shape Memory Alloy

In this paper, the repair capacity of SMA wire by using internal and external installation was studied. The SMA wires were embedded in epoxy resin and silicon cement mortar beams made of polymer clay, and then three-point bending test was conducted on the composite beam. The ability of beams which embedded SMA wires was also studied. On the other hand, the SMA wires were installed in the external of the epoxy polymer clay cement mortar, then three point bending test was also used and its self-repair ability was also studied. The results show that the crack can be repaired very well under these two methods. If there are cracks in existing buildings, we can use an external installation method to repair them. In order to ensure the new buildings crack free, both methods are feasible.

Zinc-graphite composite coating for anti-fouling application

In this paper, an anti-fouling composite coating was fabricated by blending zinc-graphite alloy powders with epoxy-silicone resin and characterized by EDS, SEM, XRD and ion titration. Compared with stainless steel and epoxy-silicone resin coating, the composite coating significantly inhibited the deposition of CaCO 3 fouling. Only a small amount of fouling was observed on the surface of composite coating after it was immersed in CaCl 2/NaHCO 3 solution. The galvanic corrosion of zinc-graphite powders could release Zn 2+ ions, which can reduce partially the nucleation and crystal growth rate of CaCO 3 on the surface of composite coating. It was found that the morphologies of CaCO 3 fouling changed from calcite to aragonite as the existence of composite coating. Meanwhile, CaCO 3 fouling was prone to precipitate in bulk solution rather than on the surface of composite coating.

Epoxy silicone based matrix materials for two-photon patterning of optical waveguides

3D polymeric optical waveguides play an intrinsic role in a rapidly developing area of broadband communications. Advances in the field of electronics means there is a greater demand for higher speeds, larger data storage, smaller components and the improvement in the design of integrated optical circuits. Two-photon photopolymerisation (2PP) is a promising three-dimensional microfabrication technique, which can be used to produce structures in the sub-micron region. With the use of near-infrared (NIR) lasers, 3D optical waveguides can be fabricated in polymer-based matrix materials, based on the increase of the refractive index in the vicinity of the laser focus.The development of a new polysiloxane material, used in the study of the integration of optical interconnects on printed circuit boards is presented. The desirable properties of epoxy functional silicones crosslinked with diamines deem them suitable for such applications. An epoxy terminated polysiloxane; crosslinked with an aminopropyl disiloxane has been developed as a suitable material for the fabrication of optical waveguides by two-photon absorption (TPA). The material fulfils a number of requirements including a good refractive index contrast between the matrix material and inscribed waveguide, full flexibility and high thermal stability.The matrix material was characterised by Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA) The optical waveguides were characterised by phase contrast microscopy, and were directly integrated onto specially designed PCB’s by correctly positioning waveguide bundles between optoelectronic components using TPA, making it possible to detect transmitted photocurrents.

The preparation and performance of a novel room-temperature-cured heat-resistant adhesive for ceramic bonding

A novel adhesive for joining ceramic materials was made using silicon–epoxy interpenetrating polymer networks (IPNs) as matrix (based on silicon resin (SR) and diglycidyl ether of bisphenol A (DGEBA) epoxy resin (EP)), γ-glycidoxypropyltrimethoxysilane (γ-GPS) as cross-linking agent, dibutyltin dilaurate (DBTDL) as catalyst, Al, low melting point glass (GP) and B4C powders as inorganic fillers, low molecular polyamide (LMPA 650) as curing agent. The character and heat-resistance property of the IPNs and adhesive were tested by FT-IR, DSC and TG. The compressive shear strength of ceramic joints was investigated at different temperatures in atmosphere surroundings. The modification mechanism of inorganic fillers was studied using XRD. Results showed that the IPNs were a homogeneous morphology of inter-crosslinked network structure with single Tg. The adhesive could be cured at room temperature with good heat-resistance property due to the chemical bond of epoxy group and Si–O–Si. The optimum compressive shear strength (9.44MPa at 1000°C) occurred at SR/EP ratio: 9/1, content of KH560: 2%, Al/GP/B4C ratio: 3.2/4/3, fillers/IPNs ratio: 6/4. The adhesive had good heat-resistance property with 10% weight loss at 435°C. Failure mode of joint was mixing failure due to the high chemical bonding force.

Development of High-Performance Optical Silicone for the Packaging of High-Power LEDs

Silicone materials with a relatively high-refractive index have been introduced for the encapsulation of high-power light-emitting diodes (LEDs), and LEDs with relatively short wavelengths. However, most of those existing silicone encapsulants still suffer from thermal and radiation induced degradations and thus lead to reliability issues and a shorten lifetime. A new high-performance silicone has been developed and its performance is compared with other commercial silicone and optical grade epoxy in high-power white LEDs. The new materials had been found to suffer less loss in the lumen output during the aging test and high-temperature/high-humidity test, as well as the Joint Electron Devices Engineering Council (JEDEC) reliability test. It is concluded that this material is excellent for the packaging of high-power white LEDs and high-power colored LEDs, because of its ability in maintaining high-transparency and great radiation/thermal resistance.

Synthesis, characterization, and properties of silicone–epoxy resins

AbstractSilicone–epoxy (SiE) resins were synthesized through the hydrolytic condensation of 2‐(3,4‐epoxycyclohexylethyl) methyldiethoxysilane (EMDS) and the cohydrolytic condensation of EMDS with dimethyldiethoxysilane. Structural characterization was carried out by 1H‐NMR, 29Si‐NMR, and mass spectrometry analysis; the resins were linear oligomers bearing different numbers of pendant epoxy groups, and the average number of repeat SiO units ranged from 6 to 11. Methyhexahydrophthalic anhydride was used to cure the SiE resins to give glassy materials with high optical clarity. The cured SiE resins showed better thermal stability and higher thermal and UV resistances than a commercial light‐emitting diode package material (an epoxy resin named CEL‐2021P). The effect of the epoxy value on the thermal and mechanical properties and the thermal and UV aging performances of the cured SiE resins were investigated. The SiE resins became more flexible with decreasing epoxy value, and the resin with the moderate epoxy value had the highest thermal and UV resistances. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

UV Curable Heat Resistant Epoxy Acrylate Coatings

Polymeric materials are exposed to high temperatures that results in lowering of the film integrity. A blend of an epoxy resin with the silicone acrylate resin was developed to provide high heat resistance UV cured coatings. Earlier siliconized epoxy coatings had been developed by conventional curing. But due to environmental awareness, high productivity rate, low process costs and energy saving UV curable coatings are enjoying considerable growth. Thermally stable UV cured coatings used in the present study were developed from silicone acrylate and epoxy acrylate resin with different diluents and photoinitiator. Such coatings provide higher thermal stability (693 K) along with physical and chemical resistance. In addition, such coatings can also be obtained by using functional amino silanes. The resin developed provides a simple and practical solution to improve heat resistance along with physical and chemical resistance of the UV cured coatings. The purpose of this research paper is to develop UV curable heat resistant coatings by the combination of inorganic and organic polymer, taking epoxy acrylate as a base resin.

Development of a high performance hybrid epoxy silicone resin for coatings

Purpose – The purpose of this paper is to develop a novel organic‐inorganic (epoxy‐silicone) hybrid resin for application in heat resistant surface coatings.Design/methodology/approach – Thermally stable aminosilicone resin was prepared by using diethoxydimethyl silane and γ‐aminopropyldiethoxy methyl silane.Findings – The hybrid epoxy silicone resin shows significant properties such as toughness, chemical resistance and thermal stability.Research limitations/implications – The prepared amino siloxane was cured by commercially available epoxy resin PG 100 and toluene diisocyanate in different ratios at high as well as at room temperature to develop high‐temperature vulcanisation and room temperature vulcanisation resin systems.Practical implications – The hybrid epoxy silicone resin may be used as heat resistant coatings due to their low shrinkage and lesser internal stress.Originality/value – The developed hybrid epoxy silicone resin was novel for application in thermally stable coatings.

Dielectric properties of carbon black and carbonyl iron filled epoxy–silicone resin coating

The dielectric properties of epoxy–silicone resin coatings containing carbon black (CB) and carbonyl iron (CI) particles as a function of frequency (2–18 GHz) and the CB volume content (0.2–1%) have been investigated. The complex permittivity of the coatings increased with increasing CB content, which mainly attributed to the interfacial polarization at the CB/resin/CI particles interfaces. The complex permittivity also decreased rapidly with increasing frequency in the low frequency range while decreased slowly in the high frequency range. The changes of dielectric properties with frequency and the CB volume content were discussed using the power-law decay and the concept of interfacial polarization.

Effect of Heat Treatment on the Microwave Electromagnetic Properties of Carbonyl Iron/Epoxy-Silicone Resin Coatings

Microwave absorbing properties of the carbonyl iron particles filled epoxy-silicone resin coatings showed visible degression when the coatings were heat treated at 300°C with different time. The complex permittivity and permeability of the coatings before and after heat treatment were measured. After heat treatment at 300°C, the real part of permittivity of the coatings increased with increasing treatment time and showed frequency dependence dielectric response. The complex permeability showed remarkable variation while the resonance frequency of the coatings heat treated at 300°C shifted from 7 to 12 GHz. The electromagnetic results indicated that microwave absorbing properties of the coatings showed more dependent on the complex permeability. The results showed that the difference of the electromagnetic and microwave absorbing properties before and after heat treatment was mainly attributed to the crystalline state transition of carbonyl iron particles.

Preparation and characterization of thermally stable epoxy-titanate coatings

Epoxy-polyamide coatings are used to protect metallic substrates in corrosive atmosphere. Thermal stability of the coating can be improved by the addition of inorganic cross-linking agent. Epoxy resin is incorporated with small percentage of silicone resin and cured with two types of hardeners such as polyamide and butyl titanate. The physical properties, heat resistance properties and electrochemical impedance behaviour of these coatings on steel in 0.5 M NaCl solution have been studied. The result implies that the heat resistant character of the titanate-cured coating is increased from 260 to 370 °C. The impedance study has shown that the coating resistance exerted by both the systems is in the range of 10 5 Ω cm 2 after 6 days of immersion in 0.5 M NaCl. FTIR and Raman spectroscopy analysis confirm the presence of titanate linkage in the cured polymer coating. Thermal stability data indicate that the epoxy silicone resin cured with titanate hardener possesses higher thermal stability than that cured by polyamide hardener.

Synergistic effects of β‐cyclodextrin containing silicone oligomer on intumescent flame retardant polypropylene system

AbstractThe effects of β‐cyclodextrin containing silicone oligomer(CDS), as a synergistic agent, on the flame retardancy and mechanical properties of intumescent flame retardant polypropylene composites were studied by adding different amounts of CDS in intumescent flame retardants. The limiting oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were utilized to evaluate the synergistic effects of CDS in the composites. It was found that after a little amount of CDS partially replaced a charring‐foaming agent (CFA) in IFR, LOI values of the composites were enhanced and they obtained a UL‐94 V‐0 rating. IFR system containing 6.25wt% CDS presented the best flame retardancy in PP. The experimental results obtained from LOI and UL‐94, TGA, SEM, and mechanical properties indicated that the combination of CDS and CFA presents synergistic effects in flame retardancy, char formation, and mechanical properties of the composites. This is probably due to different structures of polyhydroxyl macromolecules (CDS and CFA), the existence of dimethyl silicone group in CDS, and the toughness of epoxy silicon chain in CDS. SEM results proved that the interfacial compatibility between IFR and PP was improved by CDS. Copyright © 2009 John Wiley & Sons, Ltd.