usp32-616-BULK-DENSITY-AND-TAPPED-DENSITY-堆密度和振实密度

616BULKDENSITYANDTAPPEDDENSITY松密度和紧密度Thebulkdensityofasolidisoftenverydifficulttomeasuresincetheslightestdisturbanceofthebedmayresultinanewbulkdensity.Moreover,itisclearthatthebulkingpropertiesofapowderaredependentonthe“history”ofthepowder(e.g.,howitwashandled),andthatitcanbepackedtohavearangeofbulkdensities.Thus,itisessentialinreportingbulkdensitytospecifyhowthedeterminationwasmade.固体的松密度的测量很困难，测量时，轻微的震动就会导致松密度的不同。因此，可以知道粉末的松散性取决于粉末的来历。而且压紧之后，会有一个密度范围。因此，报告松密度时，必须说明结果是如何得到的。Becausetheinterparticulateinteractionsthatinfluencethebulkingpropertiesofapowderarealsotheinteractionsthatinterferewithpowderflow,acomparisonofthebulkandtappeddensitiescangiveameasureoftherelativeimportanceoftheseinteractionsinagivenpowder.Suchacomparisonisoftenusedasanindexoftheabilityofthepowdertoflow.Thebulkdensityoftenisthebulkdensityofthepowder“aspoured”oraspassivelyfilledintoameasuringvessel.Thetappeddensityisalimitingdensityattainedafter“tappingdown,”usuallyinadevicethatliftsanddropsavolumetricmeasuringcylindercontainingthepowderafixeddistance.微粒的相互作用不仅影响粉末的松散性，而且影响粉末的流速。粉末的松密度和紧密度的比较，可以看出微粒的相互作用的相对重要性的量度标准。这样一个比较常被用于粉末流动能力的一个指标。粉末的松密度的测量就是直接将粉末倾入一个量器。紧密度是被叩后的极限密度，通常使用一个设备，将一个装有固定高度粉末的量筒举起，落下。BULKDENSITYBulkdensityisdeterminedbymeasuringthevolumeofaknownmassofpowdersamplethathasbeenpassedthroughascreenintoagraduatedcylinder(MethodI)orthroughavolume-measuringapparatusintoacup(MethodII).松密度的测量是将已知质量的样品的粉末过筛进入一个量筒（方法Ⅰ）或通过一个体积测量器进入一个容器（方法Ⅱ）。MethodI—MeasurementinaGraduatedCylinder方法Ⅰ:用量筒测量Procedure—Unlessotherwisespecified,passaquantityofmaterialsufficienttocompletethetestthrougha1.00-mm(No.18)screentobreakupagglomeratesthatmayhaveformedduringstorage.Intoadry250-mLcylinderintroduce,withoutcompacting,approximately100goftestsample,M,weighedwith0.1%accuracy.Ifitisnotpossibletouse100g,theamountofthetestsampleandthevolumeofthecylindermaybemodifiedandthetestconditionsspecifiedwiththeresults.Selectasamplemasshavinganuntappedapparentvolumeof150to250mL.A100-mLcylinderisusedforapparentvolumesbetween50mLand100mL.Carefullylevelthepowderwithoutcompacting,ifnecessary,andreadtheunsettledapparentvolume,Vo,tothenearestgraduatedunit.Calculatethebulkdensity,ingpermL1,bytheformula:步骤：除非有特殊说明，先将足够量的样品过筛（1.00-mm编号18）去除存储时可能形成的大块。称取约100g（精确至0.1%）的样品置250-mL的量筒，不要压实。如果不可能用100g样品，样品量和量筒大小可以改变。报告结果时说明测试条件。样品的质量的选择为不叩实外观体积为150至250mL.一个100-mL的量筒可用于的外观体积为50mL和100mL之间。小心地夷平样品粉末不要压实，如果需要，读取未处理的外观上的体积，V0至最接近的刻度。计算松密度，g/mL,用下列公式：(M)/(Vo).Generallyreplicatedeterminationsaredesirableforthedeterminationofthisproperty.一般需重复测量。MethodII—MeasurementinaVolumeter方法Ⅱ：用体积计测量Theapparatus(Fig.1),装置如图一：Fig.1.ScottVolumeter.conformingtothedimensionsinASTMB329-90(ScottVolumeter)2,consistsofatopfunnelfittedwitha1.00-mm(No.18)screenorthescreenopeningspecifiedintheindividualmonograph.Thefunnelismountedoverabaffleboxcontainingfourglassbaffleplatesoverwhichthepowderslidesandbouncesasitpasses.Atthebottomofthebaffleboxisafunnelthatcollectsthepowderandallowsittopourintoacupofspecifiedcapacitymounteddirectlybelowit.Thecupmaybecylindrical(25.00±0.05mLvolumewithaninsidediameterof30.00±2.00mm)orasquare(16.39±0.05mLvolumewithinsidedimensionsof25.4±0.076mm).符合美国材料实验协会B329-90的尺寸（斯科特体积计），顶部有一个漏斗，上面放一个合适的1.00mm的筛子（除非有特殊说明，编号18）,漏斗装在一个由4个玻璃挡板组成的导料槽上，粉末顺着玻璃挡板滑行和反跳。在导料槽的底部是一个用来聚拢粉末的漏斗，在漏斗的正下方放置一个指定容量的样品收集容器。此容器可以是圆柱的（体积25.00±0.05mL，内径30.00±2.00mm）或正方的（体积16.39±0.05mL，内径25.4±0.076mm）.Procedure—Allowanexcessofpowdertoflowthroughtheapparatusintothesamplereceivingcupuntilitoverflows,usingaminimumof25cm3ofpowderwiththesquarecupand35cm3ofpowderwiththecylindricalcup.Carefullyscrapeexcesspowderfromthetopofthecupbysmoothlymovingtheedgeofthebladeofaspatulaperpendiculartoandincontactwiththetopsurfaceofthecup,takingcaretokeepthespatulaperpendiculartopreventpackingorremovalofpowderfromthecup.Removeanymaterialfromthesidesofthecup,anddeterminetheweight,M,ofthepowdertothenearest0.1%.Calculatethebulkdensity,ingpermL,bytheformula:步骤：将样品粉末倒入设备，直至样品收集容器的粉末溢出。用至少25m3的粉末洒在正方形状的样品收集容器上或用至少35m3的粉末洒在圆柱状的样品收集容器上，垂直方向地用一个抹刀在容器的顶部平稳的移动，仔细地刮掉多余的粉末。注意抹刀要在垂直方向运动，防止从容器压紧或切除粉末。移除容器边缘的任何物质，称粉末的质量，M,精确到0.1%，用下列公式计算粉末的密度，g/mL(M)/(Vo)inwhichVoisthevolume,inmL,ofthecup.Generallyreplicatedeterminationsaredesirableforthedeterminationofthisproperty.V0样品收集容器的体积，mL一般需重复测量。TAPPEDDENSITY振实密度Tappeddensityisachievedbymechanicallytappingameasuringcylindercontainingapowdersample.Afterobservingtheinitialvolume,thecylinderismechanicallytapped,andvolumereadingsaretakenuntillittlefurthervolumechangeisobserved.Themechanicaltappingisachievedbyraisingthecylinderandallowingittodropunderitsownweightaspecifieddistancebyeitheroftwomethodsasdescribedbelow.Devicesthatrotatethecylinderduringtappingmaybepreferredtominimizeanypossibleseparationofthemassduringtappingdown.振实密度是用机械振动装有粉末的量筒。观察量筒的初始的体积之后，用机械轻叩量筒，直到体积不再变化为止，记录体积。用机械轻叩量筒，就是将量筒举起至下述2个方法规定的高度，然后让量筒自由落下。当轻叩时，设备使量筒不停的旋转是首选的，这样，当量筒自由落下时，可以将任何可能的粉块的分离减到最少。MethodI方法ⅠProcedure—Unlessotherwisespecified,passaquantityofmaterialsufficienttocompletethetestthrougha1.00-mm(No.18)screentobreakupagglomeratesthatmayhaveforme