PDMS在NMRI顯影劑上之應用(I)流變性質之探討

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Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/3596

Title:	PDMS在NMRI顯影劑上之應用(I)流變性質之探討
Authors:	陳怡真;Yi-Jian Chen
Contributors:	化學工程與材料工程研究所
Keywords:	流變學;矽氧高分子;粒子;顯影劑;乳液;核磁共振顯影;emulsions;rheology;PDMS;colloids;contrast agent;NMR
Date:	2000-06-09
Issue Date:	2009-09-21 12:18:35 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本文主要針對直鏈型及交聯型乳液之流變性質做探討。此直鏈型PDMS乳液可用來作為NMRI腸胃道系統之顯影劑，但為了避免被小腸吸收及基於毒性之考量，故研究中採用交聯型乳液來克服上述問題。並可藉由FT-IR及黏度之改變來證明交聯反應的產生，同時利用NMRI中明顯的對比效果可知，PDMS的確可作為腸胃道系統顯影之用。另外，研究中發現，乳液之體積分率採略大於或略小於φc時，可達到兼顧口服方便性及NMRI之訊號強度之目的。實驗中發現，在Steady-shear條件下，所有數據均能符合τ=τ0+Agm之經驗式，且乳液是一介於牛頓流體與高擠壓乳液(highly compressed emulsion)流體間之過渡區域。進一步發現其特性常數m與分散相之粒徑有成正比之關係，並可藉由一假設的有效應力(τeff=τ-τ0)以得知欲使流動中之粒子產生變形時所需的應力。此外，不論直鏈型或交聯型乳液於ψ>ψc的情況下，其τ0∼ψ1/3/2R。而在Oscillatory-shear狀態下，當ψ>ψc時，不論是直鏈型或交聯型皆有一降伏應力(τy)，且同樣有τy∼ψ1/3/2R之關係式；此關係雖為二種不同狀態下得到，但皆有相同之結果，此結果代表降伏應力之產生是由於粒子間之吸引力所造成。在ψ>ψc為compressed狀態下，其流變行為之結果可以τy作為分界分成彈性區及黏彈性二區；但在ψ<ψc為uncompressed狀態下時，其儲存模數(storage modulus；G?)和損耗模數(loss modules；G??)則有明顯的改變，且可分為三個區域。 The rheology properties of the linear PDMS emulsions and the crosslinked PDMS colloidal solutions were investigated. The linear PDMS emulsions have been proposed as a new contrast agent for the gastro-intestinal NMR image. To avoid possibly being absorbed by intestine, this work suggested the crosslinked PDMS colloidal solutions as an alternative to overcome this problem. Moreover, the variations of FT-IR spectra and viscosity were used to proof the hydrosilation reaction really occurred, as well as results of the NMR image revealed that PDMS colloids have potential application to improving contrast of water-selective image. We additionally found that volume fractions near ψc are better for coordinating comfortable oral administration and the desired intensity of NMR signal prepared emulsions or colloidal solution. Under the steady-shear circumstance, these colloids' experimental data could be modeled byτ=τ0+Agm. According to this model, we defined the rheology properties of our samples to be in a transition from a Newtonian fluid to a fluid of the highly concentrated emulsions. For these samples, the characteristic constant m could be related to the diameter (2R) of the disperse phase by the relationship ln (2R)~m. Hypothetically the effective stress (τeff=τ-τ0) was proposed to realize how much the stress was required to initiate a deformation while these colloids were in a flowing field. We found additionally that at compressed condition(ψ>ψc) both linear PDMS emulsions and crosslinked PDMS colloidal solutions had an empirical relationshipτ0∼ψ1/3/2R. As the steady-shear experiment, the samples under the oscillatory-shear conditions both the two kinds of samples (linear PDMS and crosslinked PDMS)also have the similar relationship τy∼ψ1/3/2R in whichτy was the yield stress of the oscillatory-shear experiment. We believed that yield stress(τ0 orτy) were dominated by the attraction force rather than the rigidity of the dispersion phases where the attraction force was affected by the hydrogen bonding and van der wall force in the samples. Under the compressed circumstances(ψ>ψc), their oscillatory-shear responses could be categorized into the elastic region and the viscolastic region, which were distinguished by the yield stress. For the uncompressed colloids(ψ<ψc), the apparent variations of the storage and loss modulus exhibited three distinguishable regions.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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