Overview of high-temperatureVulcanizedsilicone rubber:

High-temperatureVulcanizedsilicone rubberis a high molecularweight(40~80 by weight)polyorganicsiloxane(raw rubber)add a reinforcingfillerandotheradditives,organicperoxide is usedascuringagents,bycompressionmolding(molding,extrusion,calendering)orinjectionmolded,crosslinkedrubberandhigh temperature.Therubber is usuallyreferred to assilicone rubber.

High temperature sulfide silicone rubber of sulfide General is divided into two a stage for, first stage is will Silicon rubber, and fill strong agent, and additives, and sulfide agent and structure control agent for mixed refining, then will mixed refining material in metal mold in the pressure heating forming and sulfide, its pressure for 50 kg/cm2 around, temperature for 120~130℃, time for 10-30 minutes, second stage is will Silicon rubber from mold in the out Hou, put people oven within, Yu 200~250℃ Xia baking number hours to 24 hours, makes rubber further sulfide, Whilevolatileorganicperoxidedecomposition.

Silicone rubberreinforcingfillersofvarioustypesofsilica,itmakescuringadhesivestrengthincreases10times. Joinall kinds ofadditivesis to reducecosts,improveperformanceandgivingspecialpropertiessuch asflame retardant,conductive, and so on.Cross-linkingagentsare a variety oforganicperoxideslikebenzoylperoxide,dichlorobenzoylperoxideanddicumylperoxide,n-dimethyloxygen-2,5-ertedingji2,5-and so on.Structurecontrollingagentisplacedin order toavoidmixinghourslong,"structured" and therubbercompoundhardens,curedis difficult tojoinin,usemethylhydroxysiliconeoilorstructure of dihydroxydiphenylsilaneascontrolagents.

Silicone rubberchaincanbemethyl,ethyl,vinyl,phenyl,trifluoro-propyl, etc.Mostcommonly usedaremethyl,mayalsocauseothergroupstoimprove the processingpropertiesandotherproperties. So, according to side Kiki mission and rubber material formula of different, can get various different uses of silicone rubber, General can is divided into following several type: General type (containing methyl and vinyl base), and high temperature and low temperature type (containing phenyl, and methyl and vinyl base), and low compression permanent deformation (containing methyl and vinyl base), and low contraction (to volatile copies) and resistance solvent (fluoride silicone rubber),. Hereare severalimportanttypesofsilicone rubber.

1.Methyldimethylsiliconesiliconesilicone rubberareput intocommercialproductionof the firstcan-60~200℃range to maintaingoodflexibility,goodageingresistance,excellentelectricalinsulatingpropertiesandcharacteristicssuch as moisture,shockandphysicalinertia.

Dimethylsilicone rubber is mainlyused forcoatedfabrics,alsocan bemade of extrudedandrolledproductsforelectrical,aerospace,automotiveandmedicalindustries.Butdue to dimethylsilicone rubberVulcanizedlowactivity,used in the manufacture of thickproducts,curingdifficult,innerlayer of foamandpermanentdeformationat high temperature,ithasnowbeenreplacedbymethylvinylsilicone rubber.

2.Methylvinylsilicone rubberwithintroducingsmall amounts of vinylsilicone rubbermolecularstructurecangreatlyimprove the performance of silicone rubbervulcanizationprocess,insilicone rubberat present, therefore,containvinyl.Methylvinylsilicone rubberis the mostcommontype of silicone rubber,currentlyoccupy the leadingpositionintheproduction of siliconeat home and abroad.Becauseitintroducedsomeon the side-chainunsaturatedvinyl,so that itsprocessingperformanceandmechanicalpropertiesaresuperior to the twobasesilicone rubber. It except has II methyl silicone rubber General characteristics outside, also has more wide of using temperature range, can in a 60~260℃ range within keep good elastic, it than II methyl silicone rubber easy sulfide, has smaller of compression permanent deformation, better of resistance solvent of expansion sex and resistance high pressure steam of stability and excellent of Hardy sex,, and and because used activity lower of peroxide for sulfide, to reduced has sulfide Shi produced bubble and the rubber stability poor of weaknesses. Usuallymethylvinylsilicone rubberproducts that can bemadethicker.

Methylvinylsilicone rubberis the mostwidely usedvarietyinsilicone rubber,hasemergedin recent years a variety ofhigh performanceandspecial-purposesilicone rubber,mostlybased on the vinylsilicone rubberadhesive,such ashigh strength,lowcompression set of silicone rubbersilicone rubber,withoutsilicone,heat-resistantandconductivesilicone rubberaftermedicalsilicone rubber. Methyl vinyl base silicone rubber in aviation industrial Shang, widely as washer, and sealed material and the easy broken, and earthquake parts of cover; in electrical industrial in the can for electronic components, senior insulation material, resistance high temperature potential device of dynamic sealed circle, underground long-distance communications equipment of sealed circle; in medical Shang, due to methyl vinyl base silicone rubber on human of physiological reaction small, and nontoxic, so as surgical plastic, and artificial heart valve, and vascular,.

3.Methylphenylvinylsilicone rubbermethylphenylvinylsilicone rubberisinthemolecularchainofmethylvinylsilicone rubberintomethylphenylsiliconechainsordiphenylsiliconeproducts by chain link.

Sideintroducedphenylpolysiloxane,due to destruction of dimethylsiloxaneregularityofstructure,greatlyreducedthecrystallizationtemperature of thepolymer, and expand the scope of thelow temperatureapplications of polymermaterials. So, methyl phenyl vinyl base silicone rubber except has methyl vinyl base silicone rubber all of compression permanent deformation small, and using temperature range wide, and anti-oxidation, and resistance waiting, and earthquake, and moisture and good of electrical insulation performance outside, also has excellence of resistance low temperature, and resistance burn corrosion and resistance irradiation, performance. these performance with molecular chain in the phenyl content of different and has changes, generally, phenyl content (phenyl and Silicon Atomic of than) in 5~10% Shi said low phenyl silicone rubber, it has unique of Hardy performance, -70~-100¡æstillmaintain the elasticityofrubber,arealllow temperatureperformanceoneof the bestinrubber,combined with the advantagesofbothmethylvinylsilicone rubberand the cost is nothigh,soreplacemethylvinylsilicone rubbertrend.Phenyl-phenylsilicone rubberin the content20~40%says,ithasexcellentfireresistanceproperties,once the fireself-extinguished.Phenylcontentin relation to reheatershighphenylsilicone rubber,ithasexcellentradiationresistance,resistance to gamma-ray1xI08 rays.In General,withincreaseofphenylcontent,silicone rubbermoleculeschainsrigidityincreases,decreasinglow temperatureresistancesilicone rubber,butwith the phenylcontentincreases,improvedflameresistanceandradiationresistanceofVulcanizedrubber.

Methylphenylvinylsilicone rubberis the aerospaceindustry,cutting-edgetechnology, andothersectors of the national economy is one oftheimportantmaterialavailableformakingall kinds ofmoldingandcold-resistant rubberextrusionproductsforaviationindustryandforablative,parts of the heatorradiation-resistantseals,mat,tubesandrods, etc.

4.Fluorosiliconefluorosiliconerefers to gamma-trifluoro-propylpolysiloxane. Fluoride silicone rubber has excellent of resistance chemical material, and resistance solvent and resistance lubricants performance, this species silicone rubber in non-polar solvent in the of expansion rate small, Hardy sex and the hot stability good, anti-fire sex or, so in aircraft, and rocket, and missile, and spaceflight, and oil chemical in the as and fuel oil and lubricants contact rubber tube, and gasket, and sealed circle, and fuel box village,, also can for manufacturing resistance corrosion of clothes, and gloves and paint, and adhesive,.

5.Nitrilerubberpolymermolecularsidechainscontainingβ-acrylonitrilediethylornitrilepropylgamma-strongpolargroups,greatlyincreasingthemolecularinteractions,improvedoilresistance,solventresistanceperformance.Also,due to the introduction of a certainamountofalkylnitrile,underminedtheregularity of polymerstructureandgreatlyimproves the cold.Thetypeandcontent of alkylnitriles,agreatimpactonperformance, which contain7.5molar%nitrilepropylgamma-silicone rubber,similar to the low temperatureproperties of silicone rubberwithlowphenyl(theglasstransitiontemperatureof-114.5),goodoilresistanceRTV silicone rubber.R-nitrilesccontentincreasedto33~50Mole%,lesshardy,improvedoilresistance.Replacedbynitrileethylβ-γ-nitrileacrylicbaseimprovesheat resistanceofnitrilerubber,resistant to 250° chotairaging.

Mainadvantagesareofnitrilerubberresistant to oilsandbathagentperformance,range to maintainelasticityofat-180℃,therefore,can bemade of oilresistantrubberproductsused in aviationindustry,automobileindustryandpetroleumindustry;environment for high performanceaircraft can alsobeused assealantsandfuel tanksealant,-54cto200cor morecouldremainsealed.Nitrilerubbercommonequipmentavailableforprocessing.

6.PHENYLENEsilicone rubberphenylenesilicone rubberwithexcellentradiationresistancearethemainfeatures,itsradiationresistanceis10~15times the commonmethylvinylsilicone rubberforhigh5~10times that of RTV silicone rubber and,therefore,can beused in the aerospaceindustry,atomic energyindustryandnuclear reactorsashigh energyradiationresistanceofcable,sheath,gasketsandheatshrinkingtubes.

7.Ethylsiliconeon the side-chainpolysiloxaneintroductionofethylethylsilicone rubber,cold toleranceofitsperformanceisparticularlygood,dimethylsilicone rubberandthecoldbetter thanmethylvinylsilicone rubber.Ethylcontent the higherthecoldbetter.Butthereactivethanmethylethyl,therefore,since thegreater the content of ethyl,decline in the heat.Ethylusedaslow temperaturesilicone rubber,tocontaindiethyl-silicain the polymerchainis8Mole%respectively.Temperature is generallyethylsilicone rubber-70~200℃.

． NitrogenSiliconrubbersiliconerubberarethemainadvantages of nitrogenhasexcellentthermalstability,notexplodedin430~480℃, and some are evenresistant to high temperaturesofover500c.ProminentweaknessishydrolysisstabilityofSI: nrubber,wasonceconsidered a dead-end.Foundlaterintroducedinmainchainpolymersofcyclicsilazanewithgoodthermalstability.Siliconcontainingtwomodified by Arlenesilazaneelastomerheatto425degreesin the airwithout losingweight,570℃when weight loss is only 10%,andhasgoodhydrolyticstability.