摩擦材料原材料的介绍（DOC X页）

摩擦材料原材料的介绍 摩擦材料原材料的介绍 DOCDOC X X页 页 摩擦材料用原材料from ifriction 徐仁泉编译xx07101无水氧化铝Aluminum Oxide Anhydrous Specific gravity3 1and more Moh hardness9 Look atthe hardness This is abrasive Stable athigh temperatures If particle size is too bigexpect drumscoring Fine powders 10microns will polishthe drumor disc Crystalline instructure it is similarto themineral corundum Aluminum oxide like mostabrasives nowadays is manufacturedrather thannatural Because ofthis improvedcontrol can be exercisedover chemicalposition and crystalline structure Crystalline aluminahas aconchoidal fracture and thegrains whencrushed or broken possess sharppoints andedges 无水的氧化铝 比重大于3 1莫氏硬度9磨料 高的温度 稳定性 如果微粒大划伤刹车鼓 10微米的细粉将抛光鼓轮或圆盘 结晶体在结构方面它与矿物刚玉相似 如同大多数磨料一样 现今 铝氧化物人造的好于天然的 因为这改进了化学的组成和结晶的结构的控制 当压碎时 结晶的矾土有一个蚌线的断口和颗粒 或断开的 拥有 锐利的点和边 氢氧化铝Aluminum Oxide Hydrated Aluminum OxideSpecific gravity2 4Moh hardness3 More afiller thanan abrasive Tends tofade but has good wear resistance Will polishthe opposing surface 氢氧化铝比重2 4莫氏硬度3 比磨料加得更多的填充物 有衰退趋势 但耐磨性好 将抛光对偶 铝粉96 pure aluminumin agranular form Especially suitedto low medium duty applications Blend of properties forgood refinementand wearreduction of the materialand rotorsurface especially in lining rail applications 在一种粒状的形式方面的纯的铝96 特别适用于中低负荷 混合料有好的特性和降低摩擦材料的磨损和 对偶表面摩擦副的磨损硅酸铝Aluminum SilicateKyanite Cyanite an aluminum silicate AlSiO oftenused in the calcined form willelevate friction levels Kaolin orChina Clay AlSiO2HO are amongthe orthosilicatesused infriction materials蓝晶石 蓝晶石 一个铝硅酸盐经常用于煅烧形式硅酸 铝将升高摩擦水平 高岭土或中国陶土 AlSiO2HO 是其中正硅酸盐 用于摩擦材料 煅烧氧化铝Fused Alumina Alundum alumina andis harderand more abrasive Typically97 alpha alumina 3 beta It isless amorphous has sharperfracture lineswhich impartmoreabrasivecharacteristics Large particleswill scorethe opposing surface Quantities inexcess of1 wt in afriction formulawill wearthe opposingsurface and in turn the brakelining 纯净矾土更多做磨料材料的熔化的矾土 刚铝玉 供 给者 它是更少地非晶的 典型的97 氧化铝 3 氧化铝 它的很少的 无定型相 有给与更更锋利的断口线更具有磨料的特征 大颗粒将划伤刹车鼓 在摩擦材料配方中超过1 重量 将磨损刹车片和对偶 硫化锑Antimony TrisulphideAntimony TrisulphideAn orangepigment used in redvulcanized rubber Not stable Bees blackandcrystalline stibnite when heatedtoxx50C Considered a lubricant at higher摩擦材料用原材料from ifriction 徐仁泉编译xx07102temperatures 450C Popular inEurope but notencouraged in the UnitedStates because of itstoxic nature Better ifyou canmanage withoutit Used inpyrotechnology and the manufatureof matches 硫化锑用于橘红色颜料用于硫化橡胶 不稳定的 当对200 250C被加热时变为黑的和结晶的 辉锑矿 通常在欧洲作为更高的温度 450C 的润滑剂 在美国因为它的毒性格不鼓励使用 最好你能不用它 用于火工产品和火柴的制造 重晶石Barytes Specific gravity4 4 Moh hardness3 0 3 5 A popularlow cost filler although itshigh specificgravity meansa lotof barytesis requiredto filla littlespace Increases densitysome customersstill thinka heavierblock issuperior toa lightweight block Relatively inerthigh heatstability Improves wear lowers friction level alittle Many of the bestformulas onthe marketare heavilyloaded withbarytes Yet somemanufacturers havedifficulty makingproducts withmore than5 The secretis in the process Barytes isnormally a fine powder 2 200mesh 98 325mesh and large quantities producea denseproduct imperviousto thediffusion ofgases duringbaking Those manufacturersusing copiousamounts ofbarytes rarelyopen bakeabove345F otherwiseblistering wouldour To bakeathighertemperatures requiresthe extraexpense ofconfined bakingon bakingforms Beware barytes can be contaminatedwith metaloxides likesilicon andiron oxides The moresilica in the barytesthe higherthe frictionlevel of the finishedproduct Barytes withsilica contentat say 10 is notnecessarily bad Just recognizeit isthere andit is affecting frictionlevel Make sureyour suppliersells aconsistent product In someplaces what is soldas barytesis in fact a mixtureof bariumand strontiumsulphates This doesno haveto bebad either Just don t switchback andforth fromone barytes to another PHYSICAL PROPERTIESOF BARYTESHighest Densityof anyExtender Contributes to particlepacking density1 Improves holdout2 Noise absorption3 Contributestoimproved adhesion4 Extremely LowSolubility Chemicallyinert1 Not affectedby acidsor alkalis2 Insoluble inwater3 Low reactivitywith binders extremely lowMgO andCaO content 4 Low OilAbsorption Lowresin demand reduction inneeded binderLow Moh s Hardness重晶石比重4 4 莫氏硬度3 0 3 5 流行的低的成本填充物 虽然它的高比重意味着很多重晶石去填充 增加密度 一些顾客仍认为重的块胜过轻的块相对地惰性的高的热 稳定性改善磨损 轻度降低摩擦 许多市场上最好的重负荷配方用重晶石 可是一些制造者5 或更多困难 秘密是在制造过程里 如果重晶石正常地是一个好的粉 2 200目筛 98 325个筛 当热处理时大量产产生的气体的扩散不 能透过的产品使用大量的重晶石制造的产品热处理很少超过345F5F 除非需要产生高温 以更高的温度烘需要额外的费用 当心 重晶石能如同硅和铁氧化物同金属氧化物被污染 在重晶石里的更多硅石成品的摩擦力更高 重晶石同硅石内容在 说 10 不算差恰好使正常的摩擦水平 确信你的供给者卖一个一致的产品 在一些地方什么购买的重晶石 事实上 还有一种钡和锶Sr硫酸盐 的混合物 这也不算是坏的 刚才不把其转回去上面重晶石的另一个问题 重晶石的物质属性高密度 对产品存储密度有好处 1 改进持久性2 噪声吸收3改进附着性能4 极端低的可溶性 化学上惰 性1 不被酸或碱影响2 在水里的不溶3 有关粘合剂于 MgO和CaO 比 有极端的低的反应惰性4 低的油吸收低的树脂要求 减少在需要粘合 剂用量 低的莫氏硬度玄武岩纤维Basalt FibersBasalt FibersProduced frommolten basaltrock whichis fiberizedby pouringonto adisc spinning摩擦材料用原材料from ifriction 徐仁泉编译xx07103at ahigh speed Air orsteam jetsattenuate thefiber Variations indisc speed air steam pressuresproduce differentfibers Similar torockwool butthe higheriron content lower calciumcontent Higher temperatureresistance thanslag fiber 玄武岩纤维从熔的玄武岩通过圆盘以高速离心的纺织纤维化 的方法生产 空气或蒸汽射流截断的纤维 圆盘速率的变化空气蒸汽的压力生产不同的纤维类似于岩石棉而铁 的含量更高更低的钙的含量 比矿渣纤维更高的耐温性 铁黑Iron Oxide Magite Black IronOxide Magite Black IronOxide isfound useful especially insemi metallic formulas as anagent forelevating coldfriction A popularingredient insemi metallic formulas A mild abrasive used asafinepowder below325mesh黑的铁氧化物 磁铁矿 黑的铁氧化物发现有用的 特别在半金属的配方作为提高冷的摩擦力 在半金属的配方的通用的成分 温和的磨料在325目下的细粉 黄铜末brass chipSpecific gravity8 5 Moh hardness3 5 Normal Admiralty brass62 copper38 zinc Often producedfrom machineshop swarf Degreased byheating orchemically Below4 cosmetic only Above4 by weightin a formula controlsfade dueto formationof copper oxide whichkeeps the frictionlevelup Tendency topolish Many paniesalso usebrass chippingsto helpdifferentiate betweenfriction materialgrades Products withhigher brasscontent usuallydesignates premiummaterial 8 5比重 3 5莫氏硬度 正常的状态 黄铜成分62 铜38 锌 经常用修配间屑生产 靠加热或化学方法脱脂 仅仅用4 以下 在配方中按上面重量4 的控制衰退是由于生成氧化铜它保持摩擦平 稳 磨光倾向 许多公司也使用黄铜末帮助区分摩擦材料的等级之间区别 有更高的黄铜含量的产品通常使特定的材料 青铜粉Bronze PowderBronze Powder An inertalloy ofcopper andtin providinga blendof propertiesthat assistswith thedemands of the industryfor wear and noisereduction Especially suitedfor premiumand heavyduty asbestos free applications 青铜粉一铜和锡的惰性的合金提供混合物减少工业的 磨损和降低噪声 特别适用于优质的重负荷无石棉摩擦材料 碳酸钙Calcium Carbonate Whiting Calcium Carbonate Whiting Specific gravity2 2 Moh hardness3 3 Tending to be used as analternative tobarytes to reduce cost Lower specificgravity meansless can be used Not asheat resistanceas barytes Usually goes in utilitygrade products Still it can be a veryaeptable fillerfor normalapplications 钙碳酸盐 白垩 2 2比重3 3莫氏硬度 趋向用作是减少成本的重晶石的替换物 更低的比重意味着更少的使用量 不象重晶石那样耐热通常多种用途的等级产品 正常的应用中仍然是很可接受的填充物 氢氧化钙Calcium Hydroxide Lime Calcium Hydroxide Lime Specific gravity2 0 Moh hardness2 5Imparts hardness Can beused摩擦材料用原材料from ifriction 徐仁泉编译xx07104in formulascontaining steelwool andiron particlesto inhibitrusting Sometimes usedasascavenger toabsorb gasesduring curing and reducede laminations Improves thermalstability ofpf resinsdelays fadeuntil highertemperatures A usefuladditive toreduce swelland growth 钙氢氧化物 石灰 2 0比重 2 5莫氏硬度 能用于配方包括钢纤维和铁微粒阻止生锈 有时用作一个在处理期间吸收气体并减少分离层的清道工 改进酚醛树脂的热稳定性和高温度的热力的衰退 有益的添加减少膨胀 Calferox CalferoxA fused inert materialin powderform consisting of a range of inorganic oxides Calcium Iron Silica Magnesium Manganese Aluminum and others Its processingand blendofpropertiesresults inpositive effectsand contributionstowards frictionperformance Can positivelyinfluence fade frictional stabilityand materialwear andalso pounds blends readilywith resinsand mostother ingredients Anti stiction of the frictionmaterial to the matingsurface may be positivelyinfluenced makingit particularlyuseful inrear hand brake applications Calferox一种在粉形式方面的熔化的 惰性的物质由 无机的氧化物 钙铁 硅石 镁 锰 铝和其他的人 组成 混合料使摩擦材料具有正面的效能结果 能确定地改进衰退 摩擦的稳定性和材料的耐磨性和同树脂和大多 数别的成分的复合物容易地的混合 防止摩擦材料黏结到对偶表面影响使用 特别是用于后轮手刹车的 使用 氧化铬Chromium OxideChromium OxideSpecific gravity5 2 Moh hardness2 5Enhances friction but notpopular because of highprice inmost parts of the world 氧化铬5 2比重2 5莫氏硬度 增强摩擦力 因为高价格因而 在世界的大多数地方不流行的 铜纤维Copper FiberSpecific gravity8 96 Moh hardness2 0 2 75 Improves frictionstability product integrity appearance andthermal distribution Decreases theuse ofother materialsin thematrix suchas variousexpensive lubricants steel fiber more expensivecopper fibers various metalliomponents etc resulting invaluable costsavings simplified formulae improved dispersionin mixingand excellentproduct appearance consistency ifriction Product Search铜纤维8 96比重2 0 2 75莫氏硬度硬度 改进摩擦稳定性 产品外观和热的分布 减少别的物质的使用例如昂贵的润滑剂和母体像钢纤维 不同的金 属的成分 等等 引起节约成本 简化配方 改进在混合方面的分散性 优秀的产品外 观和坚固性 铜粉Copper PowderSpecific gravity8 9 Moh hardness2 5 Increases effectiveness Good thermalconductor whichcan conductheat awayfrom frictionsurface into thefrictionmaterial itself This canhave bothdesirable andundesirable effects Beware oo muchcopper ina formulacauses wearopposingsurfacewear Probably because ofthecopperoxideformed In Europeand Japanit ismon to use largequantities ofcopper or brasspowders andparticles indisc brakepads wherehigh temperaturesare generated Such formulascan bealmost semi metallic High metalliontents raisethermal conductivityand this affects notonly performancecharacteristics butprocessing conditionslike presscuringandbaking 摩擦材料用原材料from ifriction 徐仁泉编译xx07105铜粉8 9比重 2 5号莫氏硬度 提高制动效能 好的热力的导体 提高摩擦材料自己的表面散热性 这些都是所希望的和防止不合需 要的缺点 在一个配方中铜太多导致对对偶表面的磨损 多半因为铜形成的氧 化物 在欧洲和日本在盘式制动器里它是普通的使用大量铜 或黄铜制的 粉和微粒因为哪里产生了高的温度 这样的配方几乎半金属的 高金属的含量不仅提高热力的传导率和不影响特性和工艺的压制和 热处理 丁氰橡胶Acrylonitrile Butadiene Rubber AcrylonitrileButadiene Rubber Nitrile NBR More difficult to processthan SBR Can beused alone or in bination with phenolic resinsin flexiblebrake linings Much betterheat resistancethan SBR and oilresistant too The possibilitiesof varyingthe NBRto resinratio areenormous For heavyduty applicationsthe resinpercentages willbe high producing arigid fade resistantproduct Acrylonitrile powderis beingfound inan increasingnumber of friction formulas Can reducewear rateand improvestability inresin basedformulations Partially cros linked and willflow Reacts withphenol andimproves bondingwith theformula 5 by weightis anormal amountto include 10 maybetoo much The adhesioncharacteristic makesit aparticularly attractiveingredient informulas withasbestos substitutes Contains nooils so it canimprove fade and low medium temperatureeffectiveness Wear tendsto bebetter Included inmany recentlydeveloped formulasfor rolling Can beused inPlough andEirich mixersrather thanthe slowersigma mixersusually associatedwith rubbercontaining formulas Improves toughnessof rolledproducts in the greenstate and resistscracking Contains about5 talc Allowance forthis shouldbe madewhen formulating Helps effectiveness presses more better conformabilitywith theopposingsurface One manufacturerclaims ithelps withpreforming 把丁氰橡胶对树脂比的配比变化可能性是巨大的丙 烯腈丁二烯橡胶加工比丁苯橡胶更加困难 能单独被使用 或与酚的树脂联合在一起制造软质的制动衫片比丁 苯橡胶更耐热和耐油例如重负荷应用树脂百分率比率将是高 产品 是影质的 耐衰退的产品 丙烯腈粉在一个摩擦材料配方中有增加的趋势 能减少磨损率和在树脂基的配方里改进的摩擦稳定性 部分地交联连接 他容易流动 对酚起反应并改进有配方的黏结性能 在5 按重量是一个正常的数 量包括 10 可能太多 用石棉替代品的配方中提高黏结特性 不含油 因此它能改进衰退和只低温的制动效能 耐磨性更好 在许多里包括近来发展的配方例如滚压法能用梨耙式混料机和比它 慢的 混合器的好 改进滚压产品在原始状态的韧性 和防止龟裂 改进在绿的状态方面的碾压过的产品的韧性 抵抗破裂 含有5 滑石粉 当配方在使用的表面压缩特性的一致性 一个制造商的这里帮助予 成型 天然橡胶Natural RubberNatural RubberNot usedmuch today In mostoftheworld costistoohigh andalthough ithasgoodprocessing characteristicsits performanceleaves a lot tobe desiredunder today s conditions Tends tosoften fadeandsmell whenhot 天然橡胶现在不大用在世界大多数地方 成本高虽然它有 好的工艺特性 它的特性水平有许多要考虑的问题比较软 当受热时衰退和嗅到 气味 丁苯橡胶Styrene ButadieneRubber StyreneButadieneRubber SBR Still beingfound inmany utilityfriction materials Often used inbinationwithphenolicresins whichimpart somerigidity andadd strengthand faderesistance Used inflexible coilmaterials Results inless fadethan formulationscontaining naturalrubber or摩擦材料用原材料from ifriction 徐仁泉编译xx07106linseed oilifriction 苯乙烯丁二烯橡胶 SBR 仍在许多有多种用途的摩 擦材料里发现 经常用于与酚醛树脂的使材料有一定的刚性 提高强度和耐磨性用 于弹性的刹车带材料 抗衰退方面比天然橡胶或亚麻子油的配方小 Enviroblend EnviroblendThere aretwo gradesof Enviroblend Standard andFibrous Standard gradeis aMu Powder iron silicia oxidepowder Bronze Powderblend Fibrous gradeis aMu Powder iron silicia oxidepowder Copper Fiberblend Quality controlledin termsof chemicalposition purity particle sizedistribution consistency andenvironmental factors Friction performance material rotor wearand processing improvements can be achieved at lower total formulation and process costs Decreases theuseofother materialsinthematrix steel fiber abrasives petroleum coke sponge iron black ironoxide and othervarious mineralfillers resulting insignificant costsavings throughsimplified formulaeand furthercost reductionson aprice pervolume basis Enviroblend标准的和纤维的 标准等级是微粉 铁 硅氧化物粉 青铜粉混合 纤维的等级是微粉 铁 硅氧化物粉 铜纤维混合 质量依据化学的组成 纯净 微粒大小分布 一致性和环境的因素 控制 摩擦性能 材料 对偶的磨损和 改进工艺和降低配方成本 减少在母体的材料 钢纤维 磨料 石油焦炭 海绵铁 黑的铁氧 化物和别的不同的矿物填充物 的使用量 通过一个简单的配方引起有特殊意义的节约成本减少单位体积的成 本 短切玻璃纤维Chopped Glass Fiber ChoppedGlass FiberGlassFiberhas beenused verysuessfully asa replacementfor asbestos Not likedby somebecauseof its low melting point For mostapplications thisis nota problem Some finddifficulties inprocessing asbestos free formulations Those witha modestamount ofglass fibercanbedifficulttopre form There areseveral pre forming techniqueswhich satisfactorilyhandle fiberglassmixes These processestend tobe proprietary Some importantpoints 1 Choose afiber withthe righttype ofsizing toanchor fibersinto theresin bond This assuresa goodlife 2 A mixingprocess whichpreserves fiberlength andintegrity This ensuresgood strengthand flexibility 3 A processwhich allowssufficient glassfiber inthe mixto impartthe goodcharacteristics associatedwith glass 短切玻璃纤维玻璃纤维很成功地作为一次为石棉的代用品不 喜欢的原因因为它的 熔化点低 为大多数应用中这不是一个问题发 现一些困难是在物石棉自配方中 那些有一定数量的玻璃纤维那些能难以予成型 有几种令人满意地控制玻璃纤维的混合的予成型技术这些方法是专 利一些重要的点1 选择一个正确的型号和规格的纤维在树脂黏合剂 只锚定纤维 这保证一个好的使用寿命 2 一个好的混合方法保证纤维长度和完整性 这确保好的力量和柔性 3 一个允许玻璃纤维在混料机里充分混合尤其是好的特性的玻璃纤 维混合料的工艺方法 云母Mica MicaLamella silicatewith molecularstructure linkedup insheets extendingin twodirections So itis inplatelet form and assuch contributesto physicalstrength ifthere isa goodbond betweenthe micaandtheresin orrubber bond An aluminumsilicate chemically closeto vermiculite Can bea useful ingredient insmall quantitiesup to5 especiallyincountries where摩擦材料用原材料from ifriction 徐仁泉编译xx07107mica isa lowcost indigenousraw material 云母分子结构的铝硅酸盐薄片 向两个方向延伸 由于片 状结构 有利于提高物理强度和对树脂和橡胶的黏结 化学成分接 近于蛭石 用量可以到5 在有些国家是低成本的原料丙稀氰Polya crlonitrile PAN iPolyacrlonitrile PAN Several producersin variouspartsoftheworld Was originallydeveloped asa replacementfor asbestosin asbestoscement sheetand slates One partof PANwill replacesix partsof asbestos It possessesgood reinforcingcharacteristics andisauseful ingredientin heavyduty frictionmaterials wheregood physicalstrength isrequired 丙稀氰 PAN 在世界各地都生产 原来作为为在石棉水泥板和石板瓦里的石棉的替换品一分丙稀氰将 替换六部分石棉 它具有好的加强的特征在重负荷摩擦材料具有好的增强作用 岩石棉Rockwool RockwoolSupplier NoneRemended ifriction ments This variesfrom manufacturerto manufacturerdepending uponwhich rawmaterials areused Blast furnaceslag wasthe originalingredient Basalt isused Sometimes ablend Limestone providescalcium andmagnesium oxides silica rockprovides silicates 岩石棉多种制造方法取决于原材料的用途鼓风炉渣是原 始的成分 玄武岩被使用 有时混合在一起 石灰石提供钙和镁氧化物 硅石岩提供硅酸盐 蛭石Vermiculite VermiculiteA micaceousmineral hydrated magnesiumaluminumsilicate Usually usedin itsexpanded state Heat resistant absorbent low densityfiller Not fibroussoitdoes notadd tothe physicalstrength ofthe product Used asa lowcostfiller with claimsit improveswear characteristics reduces swelland growth The juryis stillout onthe bestparticlesizetouse Up to10 by weighthas beenusedinaformula 蛭石云母的矿物 使镁铝硅酸盐的氢氧化物 通常用于膨胀蛭石耐热 吸收 低比重的填料 不含纤维 因此它增加产品的强度 用作一个低的成本填充物 同时有改进磨损特征 减少膨胀和生长 需要认定用合适规格的颗粒 配方中用量可以高达10 按重量 硅灰石Wollastonite WollastoniteCaSiO This materialvaries infiber lengthsdepending uponwhere itis mined Wollastonite found in partsof SouthAmerica isrelatively short and hasminimal reinforcingproperties But itcanbelow inprice and judiciouslyusedinextruded orrolled formulationswhere fiberorientation oursitcanbeausefulingredient Indian wollastonitefibers arelonger andcanbeseen indry mixformulas wherethey probablyreplace morecostly glassfibers Moh hardnessis5硅灰石供给者这种物质的纤维长度由矿物CaSiO 决定南美洲硅灰石发现是相对地短的 有最小的加强属性 而它价格低 有见识地用于滚压法配方 那里纤维定向是一个有用 的成分 印度的硅灰石纤维长 能在干法混合配方方面被看出他们多半替换更 加昂贵的玻璃纤维的地方 莫氏硬度是5鳞片石墨Flake Graphite摩擦材料用原材料from ifriction 徐仁泉编译xx07108Flake GraphiteFlake graphiteour naturally they arehighly graphitizedand mayapproach totalgraphitic carbon 鳞片石墨鳞片石墨自然地发生 他们是高度地石墨化并可能 接近全部的石墨的碳 石墨Graphite SuperiorGraphite Specific gravity2 3 Moh hardness1 5Ours naturallyin placeslike Ceylonand Mexico Also producedsynthetically The Achesonprocess heatsa mixtureof anthraciteor cokedust withsand toa whiteheat for24hours The binationof silicainthesand withthe carboncan formabrasive siliconcarbide Beware ofsynthetic graphitecontaminated thisway Beware of high ashcontents insome naturalgraphites Get intothe habitof checkinggraphite ashfor abrasiveness Chemically graphite isvery un reactive It issoft crystalline dark greyin color and greasytothefeel In burnsin airat700C 1300F A medium 200 250C temperature lubricant Graphite possesseslower muwhen wet as inhumid conditions Reduces frictionlevel but mayincrease fade Has beensuggested asan effectivecure forEMS Early morningsharpness With graphitesitisimportant toknow exactlywhatisbeing bought Carbon blockand coke amorphous carbons have thesame atomicarrangement asgraphite but aregenerally regardedas impureforms These arematerials beingmarketed asgraphite whichare oftennot muchdifferent fromcalcined petroleum coke Calcined petroleumcoke is98 99 fixed carbon Many areblends ofgraphite andcoke They maylook likegraphite They mayhave thecorrect ashcontent but theywill notbehave likegraphite A quickcheck forgraphite isto rubit betweenf