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Rheology

Rheology. Complex Fluids & Molecular Rheology Lab., Department of Chemical Engineering. 中央大學化材系講稿 10/28/2011. ●. Deformable. Small molecule. Macromolecule. 什 麼 是 流 變 ( Rheology) ?. Rheology is the science of fluids . More specifically, the study of Non-Newtonian Fluids 流體.

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Rheology

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  1. Rheology Complex Fluids & Molecular Rheology Lab., Department of Chemical Engineering 中央大學化材系講稿 10/28/2011

  2. Deformable Small molecule Macromolecule 什 麼 是 流 變(Rheology)? • Rheology is the science of fluids. More specifically, the study of Non-Newtonian Fluids • 流體 Newton’s law of viscosity 牛頓流體 - 水、有機小分子溶劑等 非牛頓流體 - 高分子溶液、膠體等 黏度η為定值 黏度不為定值 (尤其在快速流場下)

  3. 非牛頓流體的三大特徵 • 特徵時間與無因次群分析

  4. 非 牛 頓 流 體 的 特 徵 • 非牛頓黏度(Non-Newtonian Viscosity) - Shear Thinning Flow curve for non-Newtonian Fluids 牛頓流體 (甘油加水) 非牛頓流體 (高分子溶液)

  5. 正向應力差值的效應(Normal Stress Differences) - Rod-Climbing 牛頓流體 (水) 非牛頓流體 (稀薄高分子溶液)

  6. 記憶效應(Memory effects) -Elastic Recoil - Open Syphon Flow

  7. Time-dependent effects (搖變性) Thixotropy behavior Anti-thixotropy behavior A decrease (thixotropy) and increase (anti-thixotropy) of the apparent viscosity with time at a constant rate of shear, followed by a gradual recovery when the motion is stopped • The distinction between a thixotropic fluid and a shear thinning fluid: • A thixotropic fluid displays a decrease in viscosity over time at a constant • shear rate. • A shear thinning fluid displays decreasing viscosity with increasing shear • rate.

  8. 非 牛 頓 流 體 的 不 穏 定 性: 黏 彈 性 效 應 “The mountains flowed before the Lord” [From Deborah’s Song, Biblical Book of Judges, verse 5:5], quoted by Markus Reiner at the Fourth International Congress on Rheology in 1963 • 收縮流道 - 描述非牛頓流體行為之程度 流體的特徵或 “鬆弛”時間 流動系統的特徵時間 剪切速率 非牛頓流體 (0.057%聚丙烯醯胺/葡萄糖 溶液) 牛頓流體 (葡萄糖漿)

  9. Lubrication High-speed coating Rolling Spraying • 典型製程之流場強度範圍 Injection molding Pipe flow Chewing Extrusion Sedimentation Typical viscosity curve of a polyolefin- PP homopolymer, melt flow rate (230 C/2.16 Kg) of 8 g/10 min- at 230 C with indication of the shear rate regions of different conversion techniques. [Reproduced from M. Gahleitner, “Melt rheology of polyolefins”, Prog. Polym. Sci., 26, 895 (2001).]

  10. 小振幅反覆式剪切流: 黏性與彈性檢定 Exp b: Small-Amplitude Oscillatory Shear Flow Oscillatory shear strain, shear rate, shear stress, and first normal stress difference in small-amplitude oscillatory shear flow

  11. It is customary to rewrite the above equations to display the in-phase and out-of-phase parts of the shear stress Storage modulus Loss modulus Storage and loss moduli, G’ and G”, as functions of frequency ω at a reference temperature of T0=423 K for the low-density polyethylene melt shown in Fig. 3.3-1. The solid curves are calculated from the generalized Maxwell model, Eqs. 5.2-13 through 15

  12. 解決流變問題的途徑為何? 傳統 vs. 現代(未來)

  13. 流體加工性質 基本流變性質 macrorheology microrheology microscopy/spectroscopy birefringence/dichroism light/ neutron scatterings particle tracking the De, Wi numbers 機械量測 光學量測 molecular orientation / alignment particle size distribution/ diffusivity micro/mesoscopic structures 本質方程式 closure approximations 分子動力理論 flow pattern monomer mobility, elastic modulus etc. flow pattern 模流分析 量子、原子、多尺度計算 物質特性(化學合成) Traditional route Modern (predictive) route

  14. Polarizer Analyzer PMT VV and VH polarizations; θ = 30° to 150° Multi-angle dynamic/static light scattering

  15. Morphologies of MEH-PPV Solutions translational internal 1 mg/mL MEH-PPV/toluene 1 mg/mL MEH-PPV/chloroform MEH-PPV/toluene MEH-PPV/chloroform

  16. Flow Birefringence Measuring System 高分子溶液於流場下,會因流場大小的不同,造成高分子鏈被拉伸、旋轉與變形的程度不同,因此我們可以藉由流變儀搭配光學雙折射系統,量測高分子鏈於不同流場下的變化情形。 何謂雙折射: 當光經過非均向介質,會分解為兩道不同路徑的折射光,其一恆遵守折射率定律的正常光 (ordinary ray,o-ray ) ,其光的偏振方向,即電場振動方向是垂直於光軸,另一道即是違反折射率定律的光為異常光 (extraordinary ray,e-ray ) ,其光的偏振方向是平行於光軸。當光於雙折射材料中傳播時,因其具有兩個不同方向的主軸,光在兩軸中前進時的速度分別為C1、C2,且C1>C2,因此我們將軸向1稱為快軸 (fast axis),軸向2稱為慢軸 (slow axis)。所以光在兩分量間會有相位延遲現象產生,稱為光波相位差,我們即可從相位差中推得折射率差。 雙折射現象 為樣品厚度, 為光的波長。 流變雙折射: 高分子溶液的流動光學雙折射 (flow birefringnece) 有兩個來源:本質的雙折射 (intrinsic birefringence) 和形狀的雙折射 (form birefringence)。前者與高分子片段的非均向性極化有關,當鏈的構形發生改變時,鏈局部的非均向性會變成巨觀的非均向性,因而造成本質的雙折射。後者與高分子片段密度的非均向性相關,在稀薄溶液系統中較為重要。 光波之相位延遲

  17. Phase modulated flow birefringence(PMFB) 分析與量測: 本實驗的光學雙折射主要基於Frattini和Fuller的相位調變系統來作量測 [Frattini and Fuller J.Rheol. 28,61(1984);Fuller et al (1985)]。假設δ和χ分別代表樣品的相位延遲量和方位角,I為接收器量測到的光強,Io為光彈調變器上的入射光強;δm代表光彈調變器的相位延遲量,δm = A sin ωt,其中A為相對相位振福,ω為光彈調變器的共振頻率。 我們即可從探測器上得到光強 推算出: 進而利用應力-光學定律進行檢測 應力-光學定律目的主要為了將光學特性轉換成流變特性。高分子流體於流場下,因流場產生的應力場使其具光學的非均向性,其主應力差值的張量與折射率差值的張量成一比例關係,其比例即為應力-光學常數C。因此,我們可利用此比例關係來進行檢驗。

  18. 實驗裝置: 實際實驗裝置 示意圖 聚苯乙烯溶液的雙折射量測結果: 以分子量200萬之聚苯乙烯溶於 DOP下,配置10wt% 的溶液進行量測,利用應力-光學定律進行檢測。 實驗結果: 固態材料 (四分之一波片) 量測結果: 相位延遲量之理論與實驗值比較 方位角之理論與實驗值比較

  19. 原理: 利用同調入射光於撞擊粒子後產生之散射光,其光程差於接收器產生的干涉原理,經由適當的分析可推知溶質在溶液中的結構與動態情形。 Small-Angle Light Scattering (SALS)

  20. 裝置實體與示意圖:

  21. 實驗校正: Fig.1Comparison of the predicted scattering pattern Fig. 2. Comparison of the form factor (the airy function) of a 50 μm pinhole with the predicted by the Mie theory with experimentally measured one. the experimentally measured one. 應用: SALS之量測角度範圍一般為1°≦θ≦10°,多半作為較大尺度結構解析之用途。其應用範圍可為高分子材料之混合(mixing)、分層(demixing)、相變化(phase changes)、結構破壞(structure break-up)、與結構整合(structure build-up)等相關研究。

  22. Flow Wide-Angle Light Scattering 高分子在靜止狀態為捲曲體,可視為球狀體,在施加流場後高分子鏈開始變形,由球狀轉為橢圓狀,並隨流動方向排向與拉伸;藉由此系統可即時量測高分子的排向情形與拉伸變形的程度。左圖中 G為梯度方向(gradient direction),V為流體方(flow direction),χ 為方向角(orientation angle)。 簡介 流動光散射與一般光散射最大不同,在於流場下可同時觀測流體的機械性質及微觀結構變化,以更直接掌握高分子於加工過程中其微結構與分子型態的變化。此外本系統亦可搭配光纖,利用其體積小、可彎曲的特點而有效增加量測系統的靈活度。 原理 當所施加的剪切速率(shear rate)足夠壓制高分子鏈本身的轉動擴散(rotational diffusion)運動,此時高分子鏈的構形將偏離其於靜止狀態下的特性,並逐漸朝流動方向伸展與排向,同時造成高分子鏈大小與形狀(orientation)不同程度的改變(deformation)。藉由測量方向角(orientation angle,χ)以及使用Zimm-plot分析其迴旋半徑Rg,可得知流場下高分子鏈的拉伸與排向的程度。

  23. 原理與實驗分析 如圖示:方向角χ為長軸與速度梯度的夾角;θ為入射光與偵測器的夾角;ψ’為速度梯度與散射向量的夾角。 [Ellen C. Lee, Macromolecules 1997, 30, 7313-7321] 如圖:最高點為 ,利用 可得知 χ [Leeet al., Macromolecules 1997, 30, 7313-7321]

  24. 實驗裝置 本系統需依照流變儀之立體條件所設計,包含光學夾具、折射率匹配槽,雙圓心旋轉桌板等皆需自行設計。 實驗校正 本系統需確定散射光強與散射體積之比例關係,因此選用甲苯做靜態光散射校正。此外與一般光散射校正不同處為,需對自製桌板做校正及注意光纖光強之接收。 實驗裝置簡圖 雙圓心旋轉台之操作原理為,選定入射光及偵測器夾角θ後,即固定散射向量 q 的大小。此時轉動桌板後散射向量 q 與梯度方向 G 的夾角ψ’即可任意改變。

  25. 即時光學—流變系統 示意圖與功能 I. Particle Interactions II. Microstructures III. Molecular Anisotropy

  26. Quartz couette cell (Rheology) 2-D detection (θ andφdirs.) (Flow Light Scattering) Phase-modulated light (Flow Birefringence/Dichroism) CCD camera (Flow SALS) in situ rheo-optical measuring system實體圖

  27. 多尺度分子計算 (Multiscale Computations) 無可調參數 AND 絕對預測能力?

  28. Parameter-Free Multiscale Simulations (5) Dumbbell model & BD simulation Coarse- graining (4) Bead-chain model & BD simulation Coarse- graining (3) Ellipsoid-chain model & MC simulation (2) Monomer model & CGMD/LD simulation Coarse- graining Shie, S. C.; Hua, C. C.; Chen, S. A., Macromol. Theor. Simul.2007, 16, 111. Shie, S. C.; Lee, C. K.; Hua, C. C.; Chen, S. A., Macromol. Theor. Simul.2010, 19, 179. Lee, C. K.; Hua, C. C.; Chen, S. A., J. Chem. Phys.2010, 133, 064902. Lee, C. K.; Hua, C. C., J. Chem. Phys. 2010, 132, 224904. Lee, C. K.; Hua, C. C.; Chen, S. A., J. Phys. Chem. B2009, 113, 15937. Lee, C. K.; Hua, C. C.; Chen, S. A., J. Phys. Chem. B2008, 112, 11479. Hua, C. C.; Chen, C. L.; Chang, C. W.; Lee, C. K.; Chen, S. A., J. Rheol.2005, 49, 641. Lee, C. K.; Hua, C. C.; Chen, S. A., Macromolecules, 2011, 44, 320–324 Lee, C. K.; Hua, C. C, Optoelectronics / Book 1,( InTech, ISBN 978-953-307-276-0) Lee, C. K.; Hua, C. C.; Chen, S. A., (to be submitted). (1) Atomistic model & MD simulation Linking Quantum chemistry calculation

  29. A Software Package under Development for Multiscale simulations Analysis tools Main program Dumbbell model & BD simulation RDF Bead-chain model & BD simulation Structure factor Ellipsoid-chain model & MC simulation Intensity Monomer model & CGMD/LD simulation Atomistic model & MD simulation Back-Mapping techniques The mutiscale simulation package developed at Complex Fluids & Molecular Rheology Laboratory by C. K. Lee, S. C. Shie, and C. C. Hua, in the Department of Chemical Engineering, National Chung Cheng University, Taiwan, R.O.C

  30. Single-Chain Conformations of Conducting Conjugated Polymers from Solution to the Quenching State: A Multiscale Simulation PANI-EB MEH-PPV Toluene (T) Vacuum (V) Chloroform (CF) Chlorobenzene (CB) Mixed CF and T Mixed CF and CB Mixed CF and T vdw + HB + π-π vdw only Mixed CF and CB

  31. Morphologies and Pair Interactions in Fullerene-Conjugated Oligomer Hybrids Investigated by Atomistic Molecular Dynamics

  32. Links between Molecular dynamics and Quantum chemical calculations Force-field validation: PPV backbone, dihedral angle Energy level diagram for a donor–acceptor heterojunction: Structures refined by semi-empirical (SE) and density functional theory (DFT) Excitation energies of a single chain MEH-PPV, calculated by ZINDO/S method Chlorobenzene (CB) Mixed Nonane and CB (1:1) Quantum calculations were carried out using Gaussian 09 software package as provided by the NCHC

  33. 誰把流變做大了?

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