Rheology W20 PDF

ω 20. Rheology[ 유변학」 flow studying) : the sclence of deformatonand flow. Viscometry Testng= Measurement ofa flud' resistanceto flow...

ω 20. Rheology[ 유변학」 flow studying) : the sclence of deformatonand flow. Viscometry Testng= Measurement ofa flud' resistanceto flow s ' of #2. Importance theology Characterisation &classficatcon of materials - Rhelogicalmeasurementsdescribetheflowbehaviour Eerids & semssolids of. - Insigats into viscosity elasticity viscoelastieity , , , understandstractare to - Raw maaterial - Finished Products Quality Control - physical staablity consistency , In ratcty ,patieat compatibiliy ,dg bioawaslababaty Difference contaminatcon poormixg - can indicate , , variabslaty Adhesive of transdermal patches - performance Process optsomisation. - by understanding how matercals behave ander stress &strains. select suitable erpmeut -. ANewton 's experiment shear stress ① FfA (Nmror Pal Forcelarea = = velocity of top layer = Displaceventftime V = xIt [ms> shearstrain[ strain) Bisplacementfheight = γ = × /it Canstless) shearstrasntate= Veloatyof toplayerfHeight γ " = (시 (s") -Defnition of Tarms #3. Viscometry shearstress( O]forsonalforoefarea [N/m iN 6 m= Poa I ) - straasn[r ) :resuttant bythesample neight displacementdausded shear (strarn )ratelry shear : D strain In certaEn tㆍme $ , sthear. a time rate viscosityI n 3: shearstressdiwided byshear Ls units : Pascal second Pas[SI) bisplacanntap.. #4 shear strafn (r) =.. Poise P (CGs) ARemember. u [NntorPas) I Pas #5 Dynamic viscosity lop =. I mPas I /n. EPS = 0 M = β Kinefic √ Cm > Viscosity s √ = /9 - Mormalised valne of viscosity. of flow veloity -  =5 v = =0 - 001 ms- #6. Newtonian flow Ostwald U - fube viscometer Laminarflow of IEusdhenderthenfluenceofgrauty. Record fmeto flowfromL toD. k - et Dynamic viscosity : n = = Fnstrumentonstant density x × frme  nake. t = X어 × 800 × 100. = ω. 008 Pas Ostwald U tube viscometer -.  viscometer ( Nentonian flow) #n ) Falling sphere Dewiceusedtocalcalate theynamicviscostyof afluid bymeasurg the tne rerired for ball to fall a spherical a centatondistancewonder grauity throgh aa tube , filled the fluid whose determined viscosity is to be use stokes'law 'g(o e) -. 」 = s measure time that between tho pass poouts o] Rotational Rheometer(non -efonian flon) o upper mobile plate. s paralkelplate(stanlessstee ,fitancum efo) Cone → plaate. o Lower stat conary plate Expersmertal platesoum settays sizetsysizeomuetuer. , 4 plate , - Femperature of plates  #T Factors that affect. viscosity ↑. Temperature (T) → viscosstyd. pressure [ P) P s viscostyp Tameltl P Viscosty ↓ Thixotropc syst. s. > 시간이지남에따라 점도가 감소하는 현상 - shear stress (O ) Nentoniaon - newtonian - systen Newtonian system ? of Viscossty regardless applied constant shear s fluids that have a , stress rasu rate viscossty (n ) = xchange with rate of shean - - Flow behavion = IEnear( shear stressa shear rate) shear stress nr I 임 ! viscosthear σ = δ rate. = ~ constant example of Newtonian flow - wwater - Petrol. - glycero이 - Aydrogen gas Non Nentonian - system ⇒ Fluids whose chagdependg wiscosity onappliedshearstress or strasm rate. shear stress dependent uiscossty I s shean - thunin flowCeag. cream) - s shear-thickeng flow [e g Couc suspensiou) -.. flo) s BnghamflowLe..trothpaste, needs applied pressure g to en dependent viscosity 1 Thsxotrop' flow ( g - c e.. bentonte , ketchup) 1 ) shear thenningflow[ 전단음력받을때 점도가감소하는유동특성 ) - L xtinear exs ketchup 병 압릴 가하면 잘 흐른다 , flowbeginsassoonasshearstress xiineaar isapplked Viscosity ' highat s lowshear raates and vice versa Power law where " eratiou : ① = nr' nst shear solutions [eg gels formation) thennng polymer - of -.  shear 2) - thickening flow = psendoplastic flow. The opposite behautour to shear thiuning flow high at high shear rate and Viscoscty. ss oice varsa where usl 'm faw eration : 8 np power = > 감자 전문에게 치면 단달 산살 , → 흐물 ! 3. Binghan flow [ yield stress 넘으면 흐르기 시작하며, Nentonian flow 처럼 흐른다 ) Newtonian flow begaus. when sress reached yceld Oy is - yieldstress behaviour 4 Thixotro. Loixotropy= fIme- dependent shear - thinning behaviour then mixed becomes uiscosity ↓ st Kpacd. a ap , but sets after re application -  shear stress ^ AA YTeld stress - No flow untll a cerfain shear stress is applied > shean Raate * Visco elasticity aproducts Many s Materiabs exhibit elastlaty Visco - , and Iike elastic solids theybehavelikeviscousIerids sme process Ia i - e. - an cothers ex ) coucentrated saspensiou s Buring storage st needs , to behave like a solld to prevent sedimentation s Dugapplication t , needsto behave tikea flucd eg. so that it flows a the and bristles of the brush an be eventypanted. Phase angle (8) For Perey elastic Material. -. stress(O] cand strasoaCr )are exacty n phase s ∴ phase anghe = 0. Viscous Matertal For purey 0 s σ and r are 144of a ayce out of phase s Therefore pthase angle = 900 phase angle(8) Measureof. = elastiaty The higher the phase angle the viscous [액체) s , more s The tower the phase caghe,the more eloastla [고체 ) - Parameters En Oscillatiou * Comples Modulus [G * ) - Comples Modulus (Pal e stracutress * LossCviscous Modlus) fndicate likenature Con of uid sample + ,. a " G (Pa) * sin8 * storage (Elastic) Modulus + Indecate solid lce nature of - sample G'(Pa ) λ Coss , phase angle obeys A ynamicViscosty→ , relatedto shear viscossty if sample Cox Merzrule - " ' G n (Pas) = Fredrency At Test modes - rotational nheometershave or rangeof testmodes : - VisEometry (shear) - OsEillaTiou Creep andrecovery - rwet sponge model ' elastic solid [storage modulus) bry = ifadd water (Enelastio, Viscous] Closs oddlus] - Comples viscoelastia behawjour (Complex modolas Soakwithhony- hagher modelas rector suoonof modeli ) Gompler -. * Viscoelastic behavsor = wiscous t elastic - Visousbehawgour = materials that flow - Eoulds lasticbehaviour structemed materials that deform - = reversably - Solid - visco elastia behaviour = structured Kaids which exhibit both viscous & elastec polymer poly gels properties melts, - creams eg. mer ,. * Oscillation lleasurement types - Amplitude sweep , - Frevengsureep. Temperature sreep - - TKme expencent [thixotropic)