Ethyl Silicone Resins

This compounded cured elastomer or rubber99 shares with all the other methyl silicone products the common characteristic of exceptional thermal stability. The material does not melt when heated in air at 300° C., which is far above the decomposition temperature of natural rubber or of any of the synthetic organic elastomers. Service over long periods of time at 150° C. does not destroy its elasticity. 

As with silicone oil, the properties of silicone rubber change slowly with temperature the elasticity persists down to —55° C. Although the mechanical properties require improvement before the material can be recommended for usage under severe stress or abrasion, it is well suited to other applications where thermal stability and resistance to chemical reagents are more important than tensile strength or tear resistance. 

Methyl silicone rubber also shares the excellent electrical properties of the resins and oil. A molded sample with silica filler had a dielectric constant of 3.0 at room temperature over a range of 60 to 1010 cycles. The loss factor remains at 0.004 from 60 to 107 cycles and then rises rapidly to 0.037 at 109 cycles and 0.055 at 1010 cycles. At 102° C. the values remain the same except for a small decrease in dielectric constant (caused by a decrease in density) and a slight indication of enhanced d-c conductivity. The rubber does not seem to be affected by ozone. 

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Ethyl Silicone Resins. Polymeric ethyl silicon ox-... 

The preferred CjHs to Si ratio for ethyl silicone resins is 0.5 to l.S. Below 0.5, the products are brittle masses which shrink and crack as they condense above 1.5 they are difficult to condense to tbe solid state at a C2HS to Si ratio of 2, the polymers remain liquid. Very stable to heat and most chemical reagents. 

Ethyl silicate (tetraethoxysilane) is often used without modification as a water-repellent material for concrete and masonry in general. All, or nearly all. the ethoxyl groups are hydrolyzed by the moisture of the air to form cross-linked watcr-rcpcllcnt polymers. The material is applied in desirable thickness, dissolved in some volatile solvent which soon evaporates. Silicone resins which arc partially condensed before application, or even fully condensed, can also be used here. In the latter case, hardness is achieved on evaporation of the solvent. Certain silicone resins arc useful as hydrophobic agents for the impregnation of paper and fabrics. 

Ethyl phenyl silicone is another alkyl-aryl silicone which may be made either from ethylphenyldichlorosilane41 or by cocondensation of mixed ethyl and phenyl chlorosilanes. The cross-linked ethyl phenyl silicone resins have good dielectric and mechanical properties, but their maximum service temperatures in air are somewhat lower than those for methyl phenyl silicone, being limited to about 250° C. for... 

It is necessary that the discussion be confined to those organosilicon products which, on the basis of available information, show the greatest promise of widespread use. This would seem to mean the methyl, ethyl, and various alkyl-aryl silicone resins, methyl silicone oils and elastomers, and the methylchlorosilanes for water-repellent films. 

The elastomers investigated were prepared by curing a silicone resin (supplied by Rhodia Silicones) containing a blend of ingredients polysiloxane-diols, small amounts of hydrogen-methyl polysiloxane, tetraalkoxy silane and fumed silica filler. An organotin ingredient, stannous 2-ethylhexanoate, supplied as a 77% w/w solution in 2-ethyl hexanoic acid, was used as a cure initiator. Typically, 5 wt. of initiator is mixed into the polysiloxane resin. After the initial cure, the material is post-cured at 70°C for 16 h in an air oven. 

On the other hand, the chlorosilanes react with methyl alcohol or ethyl alcohol to give the mixture of alkoxides (R2Si(OR )2 and RSi(OR )3), and the silicone resins are also prepared by condensation of the mixture. The temperature range of the condensation is 200-250 "C. The condensation becomes fast with catalysts such as organic acid metal salts (e.g., Pb, Zn, Fe and Sn) or amines. 

HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HNS NTO NTO/HMX NTO/HMX NTO/HMX PETN PETN PETN PETN PETN PETN PETN PETN PETN PETN RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX TATB/HMX Cariflex (thermoplastic elastomer) Hydroxy-terminated polybutadiene (polyurethane) Hydroxy-terminated polyester Kraton (block copolymer of styrene and ethylene-butylene) Nylon (polyamide) Polyester resin-styrene Polyethylene Polyurethane Poly(vinyl) alcohol Poly(vinyl) butyral resin Teflon (polytetrafluoroethylene) Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Cariflex (block copolymer of butadiene-styrene) Cariflex (block copolymer of butadiene-styrene) Estane (polyester polyurethane copolymer) Hytemp (thermoplastic elastomer) Butyl rubber with acetyl tributylcitrate Epoxy resin-diethylenetriamine Kraton (block copolymer of styrene and ethylene-butylene) Latex with bis-(2-ethylhexyl adipate) Nylon (polyamide) Polyester and styrene copolymer Poly(ethyl acrylate) with dibutyl phthalate Silicone rubber Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Epoxy ether Exon (polychlorotrifluoroethylene/vinylidine chloride) Hydroxy-terminated polybutadiene (polyurethane) Kel-F (polychlorotrifluoroethylene) Nylon (polyamide) Nylon and aluminium Nitro-fluoroalkyl epoxides Polyacrylate and paraffin Polyamide resin Polyisobutylene/Teflon (polytetrafluoroethylene) Polyester Polystyrene Teflon (polytetrafluoroethylene) Kraton (block copolymer of styrene and ethylene-butylene)... 

As outlined in the previous chapters, the preparation of silicone polymers involves first the preparation of organosilicon halides or esters, secondly the hydrolysis of an appropriate mixture of these intermediates, and finally the condensation or rearrangement of the polymers to achieve the desired molecular arrangement. Only in the first step is there a choice of preparative methods the second and third steps are carried out in much the same way, regardless of how the intermediates were made. From the standpoint of synthesis, the problem therefore comes down to the preparation of the methyl-, ethyl-, and phenylchlorosilanes or ethoxysilanes. Of these the methyl compounds are the most important, because they are used directly for the water-repellent treatment and are the only intermediates required for the oils, elastomers, and some types of resin. 

Polyaddition adhesives include epoxy and polyurethane polymers which can either be 100% solids, water-based, reactive or non-reactive hot melts or contain solvents mostly to regulate viscosity. Typical solvents include methyl ethyl ketone, acetone, mineral spirits, toluene, and xylene. Polycondensation adhesives include phenol-formaldehyde resin, polyamides, polyesters, silicones and polyimides. With the exception of polyesters (which require ethanol and N-methylpyrrolidone as solvents) and polyimides (which require... 

Unidirectional carbon fiber reinforced SiC/C composites were fabricated by Tani et al [213] using reaction bonding. The prepreg for the composites was prepared by the filament winding method, with a mixed slurry of phenolic resin, sihcon powder and ethyl alcohol, then die pressed at 130°C and sintered in Ar. The formation of SiC took place through a reaction between the carbon from the pyrolyzed phenolic resin and the silicon powder above a temperature of about 1320°C and was completed by 1420°C. The bulk density of the composites was about 1.7 gcm. The average flexural strength of the composites with a Si/C ratio of 0.2, 0.4 and 1 was about 310, 250 and 150 MPa respectively. 

The composites were fabricated by passing the carbon yam through a slurry containing silicon powder, phenol resin and ethyl alcohol. SiC was formed by the reaction between the Si and the carbon from the phenol above 1320°C and completed at 1420°C. The carbon fiber was not damaged and fiber pullout was observed on the fracture surface. A bulk density of 1.7 to 1.8 gcm and a flexural strength of about 130 MPa were achieved. Impregnation with molten Si at 1600°C increased the bulk density, but decreased the flexural strength, due to the reaction of the carbon fiber with the Si. 

Some specific recent applications of the chromatography-mass spectrometry technique to various types of polymers include the following PE [130, 131], poly(l-octene), poly(l-decene), poly(l-dodecene) and 1-octene-l-decene-l-dodecene terpolymer [132], chlorinated polyethylene [133], polyolefins [134,135], acrylic acid, methacrylic acid copolymers [136, 137], polyacrylate [138], styrene-butadiene and other rubbers [139-141], nitrile rubber [142], natural rubbers [143,144], chlorinated natural rubber [145,146], polychloroprene [147], PVC [148-150], silicones [151,152], polycarbonates (PC) [153], styrene-isoprene copolymers [154], substituted PS [155], polypropylene carbonate [156], ethylene-vinyl acetate copolymer [157], Nylon 6,6 [158], polyisopropenyl cyclohexane-a-methylstyrene copolymers [195], cresol-novolac epoxy resins [160], polymeric flame retardants [161], poly(4-N-alkylstyrenes) [162], pol)winyl pyrrolidone [31,163], vinyl pyrrolidone-methacryloxysilicone copolymers [164], polybutylcyanoacrylate [165], polysulfide copolymers [1669], poly(diethyl-2-methacryloxy) ethyl phosphate [167, 168], ethane-carbon monoxide copolymers [169], polyetherimide [170], and bisphenol-A [171]. 

Figure 6-61. Heat-resistance properties of resins retaining 50 percent of properties obtainable at room temperature with resin exposure and testing at elevated temperature. Zone 1 Acrylics, cellulose esters, LDPE, PS, PVC, SAN, SBR, UF, etc. Zone 2 Acetals, ABS, chlorinated polyether, ethyl cellulose, EVA, ionomer, PA, PC, HDPE, PET, PP, PVC, PUR, etc. Zone 3 PCTFE, PVDF, etc. Zone 4 Alkyds, fluorinated ethylene-propylene, MF, polysulfone, etc. Zone 5 TS acrylic, DAP, epoxy, PF, TS polyester, PTFE, etc. Zone 6 Parylene, polybenzimidazole, silicone, etc. Zone 7 PAI, PI, etc. Zone 8 Plastics in R D etc. Since plastics compounding is rather extensive, certain basic resins can be modified to meet different heat-resistance properties.

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