Micromeritics《药剂学》第六章粉体学基础第六节粉体的吸附及粘附第七节粉体的压缩性质 英文PPTPPT.pptx

MicrometiticsClass 1 No.4 HeHuan§6 Adhesion cohesiondefinitionAdhesion: Attraction between two unlike surfaces. E.g. between a particle and a hopper wall.Cohesion: Attraction between like surfaces. E.g. component particles of a bulk solid.causesDry condition: Electrostatic forceWet condition: Moisture exists on the surface of the particles to form a liquid bridgeThe particle size Filled discontinuityFlow abilitySo we use Granulation methods to increase the particle size or adding a glident to prevent the adhesion and cohesion.§7 Compression properties of powdersCompressionConsolationCompactionChange of compressing force volumeA-b：particles rearrangement，not change the forms.B-c: Elastic deformation occurs in the contact point of the particles. Temporary bridge.C-d: plastic deformation or broken. porosity↓, contact area of particles↑, bridging action ↑. Particle breakage and the new interface increase bonding force.D-e: solid compaction process, volume change is not obvious. Mainly plastic deformation. Binding force is larger.Granular material performance obviously, Powder material performance is not obvious.Three types of deformationA:elastic deformation: Deformed when pressure is applied, restored when the pressure was released. no binding force.B:Plastic deformation: Deformed when pressure is applied, cannot restored when the pressure was released. Binding force emerge.C: Brittle deformation: particle crushed and deformed under pressure, cannot restored when the pressure was released.Force analysis during the compression processAxial forceRadial forcePoisson ration Usually be 0.4-0.5Relationship between andCoefficient of die-wall friction: Coefficient of lubricant efficiency:frictionLower impulsionThe lubrication efficiency indexUpper impulsionR↑, the better Lubrication efficiency Compression cycle diagramWhen the material is perfectly elastic material compression cycle graph becomes a straight line, the compression process and relieve pressure on the proce