서론및기계적물성측정현황.( 원리와응용 ) f{ Å \Ç V{âÄ To Start this Seminar 1. Organic Materials(Polymers) 에대한관점 2. Vision 은깊게, Touch 는넓게. 유기물질은보이는현상과는다른화학적물리적조성에의한변수가매우다양하고, 환경 ( 온 / 습도 ) 에의한변화가시간에따라동적으로결정됩니다. 3. 측정기구와측정변수의한계는분명히다르므로측정기구의선택은신중해야합니다. 4. ( 사용효율 / 장비가격 ) X 100 = 100%????? 1
MEMS(Micro Electro Mechanic System) & NEMS(Nano Electro Mechanic System) - MEMS : Micrometer, g(mg) 수준의길이, 하중을조절, 측정, 구성할수있는전자기계체계. - NEMS : Nanometer, ug(ng) 수준의길이, 하중을조절, 측정, 구성할수있는전자기계체계. 사용및요구현황 ( 계측및가공장치분포 ) 투자및연구현황 후가공 / 표면가공 ( 코팅, 증착, 점착 ) 소재사용분포 NEMS (nm, ug, ng) MEMS (um, g, mg) MKS/CGS (cm, mm, kg, g) NEMS (nm, ug, ng) MEMS (um, g, mg) MKS/CGS (Ton, m, cm, mm, kg, g) 2012 -> 2013 NEEDS : Machine with mks/cgs unit-> MEMS -> NEMS 길이와하중의정밀도조절및측정 제품의규격평가관점 : 성능 > 정밀도 > 정확도 학술적평가관점 : 성능 > 정밀도 > 정확도 Nano Micro Milli Micro Kilo & Milli Milli 정밀도 < 기능성 기능성 ~ 정밀도 정밀도 반도체 치공구 의료 자동차, 기계 우주항공 비접촉표면측정 Laser CCD SEM 접촉식표면측정 3 차원형상표면조도 AFM 소재구성수준에따른재료및표면측정장치 전기전자 제약, 의료 반도체 / 디스플레이 microtxa Nano UTM Miniature UTM Hysitron(USA) TOPTAC2000 CSM(SWISS) TXi(UK) Micro Materials(UK) Rheometer Asylum Res.(USA) DMA Nanovea(USA) 나노소재 의료, 바이오 2
측정요구규격에따른장비의정밀도 / 대상장비 측정요구 Control 신뢰성 대상장비 ( 응력조절측정가능장비에한함 ) 표면특성 kg, m g, cm, mm mg, um kg, cm g, mm, um mg, nm Micrometer 표면조도측정, 3 차원형상측정 microtxa ug, ng, nm ug, ng, nm, pm AFM 측정요구 Control 신뢰성 대상장비 ( 응력조절측정가능장비에한함 ) kg, m kg, cm UTM 재질특성 g, cm, mm mg, um ug, ng, nm g, mm, um mg, nm ug, ng, nm, pm TOPTAC2000, Texture Analyzer Rheometer TMA, DMA, Dilatometer Nano UTM microtxa 기타비접촉측정장비 : SEM, TEM, Laser Vision, CCD Vision, Ultra Sonic etc. 표면재질분석방법접촉식비접촉식광학적분석전기 / 전자특성분석실측영상분석관능분석표면조도계 3 차원형상측정점착력측정 microtxa 점탄성측정방법 Rheometer DMA Texture analyzer (Toptac Series) UTM 표면조성분석방법 AFM SEM EPMA/ESCA FTIR/ATR/Image scan 3
표면분석장치 SPM(Scanning Probe Microscope ) 의종류 - AFM ( Atomic Force Microscope ) : 부도체시료의측정가능 - STM ( Scanning Tunneling microscope ) : 최초의원자현미경 - MFM ( Magnetic Force Microscope ) : 시료의자기력측정가능 - LFM ( Lateral Force Microscope ) : 시료표면의마찰력측정가능 - FMM ( Force Modulation Microscope ) : 시료의경도측정가능 - EFM ( Electrostatic Force Microscope ) : 시료의전기적특성측정가능 - SCM ( Scanning Capacitance Microscope ) : 시료의 capacitance 측정가능 ROUGHNESS MEASURING EQUIPMENT Y L Measure Length Rmax Ra ROUGHNESS ( 거칠기 ) 측정은기재의거친정도를측정함으로써기재거칠기를측정하는하나의지수로써사용된다. 기재가심한거칠기를가질경우그로인한 CRACK/BROKEN 이예상된다. ROUGHNESS SPEC LIMIT : MAX 0.3 um PRINCIPLE OF MEASUREMENT : STYLUS METHOD (CONTACT) LASER METHOD (NON-CONTACT) MEASURING RANGES : 0.25 mm f(x) Ra = 1/L 0 f(x) dx L X 용어정리 Rmax ( 최대높이 ) : 한기준길이안에서단면곡선의최저점으로부터최고점까지의높이 Ra ( 중심선평균거칠기 ) : 한기준길이내의산과골의높이를기준선을중심으로평균하여얻어지는값 4
3 차원형상측정기개발현황 ( 출처 덕인 /KRISS 측정클럽발표자료 ) PDP 격벽 3D 레이저 (CCD) 구조분석사례 KRISS 측정클럽발표자료 5
I wonder if some stress applied As a view point of Material Viscoelasticity And very small stress have applied Principles of Rheology (cont d.) Introduction to Viscoelasticity Ideal Solid Most Materials Ideal Liquid Hooke Newton Most materials behave such that they have a combination of viscous and elastic responses under stress or deformation. Materials behave in the linear manner, as described by Hooke and Newton, only on a small scale in stress or deformation. 6
점탄성의측정 Dynamic Mechanical Analyser의개념 DMA Curves for Epoxy resin 7
Schematic Concept Deformation Molecular Motion Unstrained State Strained State 11 10 9 8 7 6 5 4 3 F F Secondary Dispersion Localized Motion E Glassy D C Temperature Rubbery B Cross-linked E D C B A Hookean Second Primary Highly Visco Elastic Behavior Transition Transition Flow (gamma) (beta) (alpha) (rubbery) (melt) Bend & Stretch Bonds Side Groups Increasing Main Chain Gradual Crystalline Polymer Crystal-crystal slip Main Chain Large Scale Mobility A Chain Slipping R. Seymour, 1971 Common changes show as: MW MWD Crosslink Density Crystallinity E tan δ 8
Oscillation Experiments of Rheometer Stimulus Response phase lag, δ Stress or Strain is varied sinusoidally Separates Elastic and Viscous effects The modulus and Viscosity of Oscillation experiments are called Complex Modulus and Complex Viscosity. Linear and Non-Linear Stress-Strain Behavior of Solids 1000 Linear Region G is constant Non-Linear Region G = f(γ) 100.0 100.0 10.00 G osc. stress (Pa) σ Critical Strain γ c 1.000 0.010000 0.10000 1.0000 10.000 100.00 % strain 0.01000 1000.0 9
1.000E5 Newtonian and Non-Newtonian Behavior of Fluids Newtonian Region η Independent of γ Non-Newtonian Region η = f(γ) 1.000E5 10000 η (Pa.s) η 1000 σ (Pa) 100.0 σ 10.00 10000 1.000E-5 1.000E-4 1.000E-3 0.01000 0.1000 shear rate (1/s) γ 1.000 1.000 분자량 vs. Thermal behavior 분자량이커지면 Tg, Tm 상승 일정분자량이상에서는 Tg, Tm 감소가능성 분자량분포가좁을수록 Tg, Tm 상승 분자량분포가넓은이유는저분자량영향 점도는분자량에직접영향 Molecular functional groups vs. Thermal behavior 관능기의가지가크면 Tg, Tm 감소 alpha, beta, gamma, delta transition 관능기의입체규칙성증가 - 결정도증가 -Tg, Tm 증가 관능기의 2 차결합 ( 수소결합, Van der waals, chelation, etc.)- 구조적치밀도증가 -Tg, Tm 증가 Dipole mement 존재 (-Cl, -F)- 치밀도증가 Benzene ring 포함 -Tg, Tm 급상승 Impurity vs. Thermal behavior 수분, 이온, low molecules, oligomer 상호작용이없이단순히 mix 되어있는경우 -Tg, Tm 감소 - 구조적혼란 상호작용존재 - 치밀도상승 -seed 역할 Critical point 존재 - 임계함량이상은 Tg, Tm 감소및구조파괴 10
간단하고대칭성구조이면, 입체규칙성이크면, 분자간인력또는결합이강하면, 곁가지가없고분자량이크면, 높은 Tm 및결정화도 사슬의유동성이작을수록 ( 방향족사슬등 ) 치환기의크기와극성이클수록분자량이클수록 ( 어느한계까지 ) 가교도가증가할수록 높은 Tg 공중합체의 Tm, Tg 불규칙공중합체는결정성파괴로 Tm 및결정화도감소 하나의 Tg Block 및 Graft 공중합체는미세상분리 성분중합체각각의 Tm, Tg 가능 고분자혼합물 (blend) 의 Tg 상용성이없으면각각의 Tg 상용성이있으면중간에하나의 Tg 용매, 가소제가혼합되면 Tg 강하 일반적으로 Tg ; 1/2 ~ 2/3 Tm 표면에의응력적용 Stress Values as a results: Length, Load Creep Elastic Recovery Viscous 95%~ 50%~ 30%~ 60%~ 50%~ 80%~ 90%~ 80%~ Applied force of Total stress 60%~ 50%~ [Temperature/Time & Humidity] 11
Basic Parameters and Units 2 Stress = Force /Area [Pa, or dyn/cm ] σ = tensile stress, τ = shear stress Strain = Geometric Shape Change [no units] ε = tensile strain, γ = shear strain Strain. or Shear Rate =. Velocity Gradient or d(strain)/dt [1/s] ε = tensile strain rate, γ = shear strain rate 2 Modulus = Stress / Strain [Pa or dyn/cm ] E = Youngs or Tensile, G = Shear Modulus 2 Compliance = Strain / Stress [1/Pa or cm /dyn] Typically denoted by J Viscosity = Stress /Strain Rate [Pa.s or Poise] Denoted by η S.I. units = c.g.s. X 10 Viscoelasticity Defined Range of Material Behavior Solid Like ---------- Liquid Like Ideal Solid ----- Most Materials ----- Ideal Fluid Purely Elastic ----- Viscoelastic ----- Purely Viscous Viscoelasticity: Having both viscous and elastic properties 12
Response for Classical Extremes Spring Purely Elastic Response Dashpot Purely Viscous Response Hookean Solid σ = Eε or τ = Gγ Newtonian Liquid σ = ηγ In the case of the classical extremes, all that matters is the values of stress, strain, strain rate. The response is independent of the loading. Response for a Viscoelastic Material At short times (high frequencies) the response is solid-like At long times (low frequencies) the response is liquid-like THE HISTORY OF LOADING IS CRUCIAL 13
Time-Dependent Viscoelastic Behavior: Solid and Liquid Properties of "Silly Putty" T is short [< 1s] T is long [24 hours] Deborah Number [De] = τ / Τ Time-dependent Viscoelastic Behavior: The Deborah Number Old Testament Prophetess who said : "The Mountains Flowed before the Lord" Everything Flows if you wait long enough! Deborah Number, De - The ratio of a characteristic relaxation time of a material (τ) to a characteristic time of the relevant deformation process ( Τ ). De = τ/τ 14
The Deborah Number Hookean elastic solid - τ is infinite Newtonian Viscous Liquid - τ is zero Polymer melts processing - τ may be a few seconds High De Low De Solid-like behavior Liquid-like behavior IMPLICATION: Material can appear solid-like because 1) it has a very long characteristic relaxation time or 2) the relevant deformation process is very fast Stress Relaxation Experiment 0 tim e Response of Classical Extremes Hookean Solid Newtonian Fluid 0 stress for t>0 is constant tim e tim e 0 stress for t>0 is 0 15
Stress Relaxation Experiment Response of Material Stress decreases with time starting at some high value and decreasing to zero. tim e For small deformations (strains within the linear region) the ratio of stress to strain is a function of time only. This function is a material property known as the STRESS RELAXATION MODULUS, G(t) G(t) = σ(t)/γ 0 Creep Recovery Experiment Stress is applied to sample instantaneously, t1, and held constant for a specific period of time. The strain is monitored as a function of time (γ(t) or ε(t)). The stress is reduced to zero, t2, and the strain is monitored as a function of time (γ(t) or ε(t)). Stress t 1 t time 2 16
Creep Recovery Experiment t 1 tim Response of Classical e Extremes t 2 Stain for t>t1 is constant Strain for t >t2 is 0 Stain rate for t>t1 is constant Strain for t>t1 increase with time Strain rate for t >t2 is 0 t 1 tim t tim t 2 2 e e t 1 Creep Recovery Experiment: Response of Viscoelastic Material Creep σ> 0 σ/η Recovery σ = 0 (after steady state) Recoverable Strain t 1 t 2 time Strain rate decreases with time in the creep zone, until finally reaching a steady state. In the recovery zone, the viscoelastic fluid recoils, eventually reaching a equilibrium at some small total strain relative to the strain at unloading. Reference: Mark, J., et.al., Analysis Physical, Development Properties of Polymers and,american Enhancement Chemical Society, 1984, p. 102. 17
Creep Recovery Experiment Creep σ > 0 Recovery σ = 0 (after steady state) σ/η Less Elastic Creep Zone Recovery Zone More Elastic t 1 t 2 time Definition of Rheology Rheology is the science of flow and deformation of matter. 18
Geometry of Shear for Rheometers Concentric Cylinders Cone & Plate Plate & Plate Torsion Motor applies Torque, Strain read from Optical Encoder. Motion Flow (Flow, Creep, Stress Relaxation) Oscillation Squeeze Flow/ Pull Off 19
List of Symbols γ = Strain γ = Strain Rate σ = Stress Kγ = Strain Constant θ = Angular Motor Deflection in Radians Kσ = Stress Constant M = Torque Gc = Gravity constant = 98.07 Pascals (SI) = 980.7 dyn/cm 2 (cgs) Ω = Motor angular velocity in radians/sec. β = Cone angle in radians H = Gap for parallel plate in mm R = Radius of plate or cone in mm R1 = Radius of concentric cylinder bob in mm R2 = Radius of concentric cylinder cup in mm Typical Viscosity Values (Pa-s) Asphalt Binder ------------------ 100,000 Polymer Melt -------------------- 1,000 Molasses --------------------------100 Liquid Honey --------------------10 Glycerol -------------------------- 1 Olive Oil ------------------------- 0.01 Water ----------------------------- 0.001 Air --------------------------------- 0.00001 Need for Log scale 20
More on Viscosity According to Isaac Newton, viscosity is constant for all times and shear-rates Newtonian Fluids Viscosity is dependent on Temperature and Pressure Viscosity may not be constant Non-Newtonian Fluids Viscosity of Non-Newtonian fluids can depend on Time : Thixotropy, Rheopexy Shear-rate : Shear-thinning, Pseudoplasticity, Dilatency Time-Dependence At constant shear-rate, if viscosity Decreases with time - Thixotropy Increases with time - Rheopexy Non-Newtonian, Time Independent Fluids Shear-Thinning A decrease in viscosity with increasing shear rate. Also referred to as Pseudoplasticity. Shear-Thickening An increase in viscosity with increasing shear rate. Also referred to as Dilatancy (a special case of shear-thickening). 21
Non-Newtonian, Time Dependent Fluids Thixotropy A decrease in apparent viscosity with time under constant shear rate or shear stress, followed by a gradual recovery, when the stress or shear rate is removed. Rheopexy An increase in apparent viscosity with time under constant shear rate or shear stress, followed by a gradual recovery when the stress or shear rate is removed. Also called Anti-thixotropy or negative thixotropy. Reference:Barnes, H.A., Hutton, J.F., and Walters, K., An Introduction to Rheology, Elsevier Science B.V., 1989. ISBN 0-444-87469-0 Non-Newtonian, Time Dependent Fluids Rheopectic Viscosity Shear Rate = Constant Thixotropic time 22
Time-Temperature Temperature Superposition Principle TTS is an EMPERICAL relationship TTS is based on the observation that, for a single material, the curves of the viscoelastic properties, generated at different temperatures, are similar in shape when plotted against log time or log frequency. The Curves generated at different temperatures can be exactly superimposed by shifting along these axes. TTS applies to stress relaxation, creep and dynamic mechanical measurements Time and Temperature: Two Sides of the Same Coin log Frequency (E' or G') (E" or G") (E' or G') (E" or G") Temperature log Time log Time 23
감사합니다. 24