發(fā)布時(shí)間：2018-04-13 17:25

  本文選題：玻璃化轉(zhuǎn)變 + 等自由體積　； 參考：《西南石油大學(xué)》2017年碩士論文

【摘要】：玻璃化轉(zhuǎn)變問題是一個(gè)廣泛而深刻的物理難題。幾乎所有的物質(zhì)都有玻璃化轉(zhuǎn)變行為,卻并未有任意一種的材料的玻璃化轉(zhuǎn)變理論被認(rèn)為是完全成功的。玻璃化轉(zhuǎn)變對(duì)材料性能有著十分顯著的影響,例如光散射性、力學(xué)強(qiáng)度和模量、介電常數(shù)、松弛時(shí)間等等。并且其過程受熱歷史的影響很大,特別的,玻璃化轉(zhuǎn)變溫度與結(jié)晶轉(zhuǎn)變溫度不同,會(huì)隨著溫度變化速率的高低而改變。實(shí)驗(yàn)上,玻璃化轉(zhuǎn)變的研究越來越深入。實(shí)驗(yàn)參量包括分子量、主鏈結(jié)構(gòu)、支鏈結(jié)構(gòu)、支化度等化學(xué)參量,以及變溫速率、外壓等物理參量。實(shí)驗(yàn)手段從過去的體積膨脹法、差示掃描量熱儀(DSC,Differential Scanning Calorimeter)、動(dòng)態(tài)機(jī)械熱分析(DMA,Dynamic Thermomechanical analysis)等發(fā)展到正電子湮滅技術(shù)(PAT,Positron annihilation technique)。不同的實(shí)驗(yàn)數(shù)據(jù)往往支持不同的理論,除了一個(gè)經(jīng)驗(yàn)方程—WLF方程。這使得WLF方程理論化顯得尤為重要。理論上,層出不窮的舊理論和新理論被相繼提出。舊理論包括Adam-Gibbs理論、Cohen-Grest自由體積理論和Random First-order Transition理論等。新理論則包含動(dòng)力學(xué)理論和LCL模型等。在比較理論和實(shí)驗(yàn)結(jié)果的匹配度后,這些理論都比不上WLF方程。WLF方程是基于Flory等自由體積理論推導(dǎo)構(gòu)建的,可以說,證明了 Flory的等自由體積猜想,就等于證明了 WLF方程的基礎(chǔ)理論。基于上述考慮,本文從嚴(yán)格的準(zhǔn)靜態(tài)熱力學(xué)模型出發(fā),首先從Doolittle的自由體積與粘度方程中定義了玻璃化轉(zhuǎn)變,然后證明了玻璃化轉(zhuǎn)變區(qū)域中,理想單鏈體系在常壓下的自由體積比例是一個(gè)定值,與其他物理參數(shù)、化學(xué)參數(shù)無關(guān)。在比較實(shí)驗(yàn)結(jié)果和理論結(jié)果的過程中,許多模型被我們不斷的推演和重構(gòu),其中大多數(shù)并未對(duì)我們理解玻璃化轉(zhuǎn)變帶來多少幫助。本文最后采用的玻璃化轉(zhuǎn)變理論建立在松弛格子模型—RLM之上。除了 RLM以外,本文還推導(dǎo)了一個(gè)在理論證明過程中有啟示作用的模型—溶液析出模型。RLM模型的推演思路是:首先引入?yún)?shù)描述松弛過程和自由體積,然后求解熵函數(shù)。在對(duì)熵函數(shù)的極值和極點(diǎn)進(jìn)行分析時(shí),使用了小剪刀思想實(shí)驗(yàn)的方法,通過在小剪刀思想實(shí)驗(yàn)中設(shè)計(jì)熱力學(xué)路徑消去了中間參量,得到了 Flory早已預(yù)言卻從未在理論上證明的等自由體積比例β,該值為(?)。同時(shí)證明了在玻璃化轉(zhuǎn)變中,熵函數(shù)對(duì)溫度的一階導(dǎo)數(shù)不連續(xù)但函數(shù)值連續(xù)。此外,對(duì)高交聯(lián)度和高溫高壓條件下的系統(tǒng)進(jìn)行了理論解析。研究表明,其玻璃化轉(zhuǎn)變行為可以通過RLM進(jìn)行預(yù)測,其結(jié)果表達(dá)為一個(gè)三維相圖。
[Abstract]:The glass transition is an extensive and profound physical problem.Almost all materials have glass transition behavior, but no glass transition theory of any material is considered to be completely successful.The glass transition has a significant effect on the properties of the materials, such as light scattering, mechanical strength and modulus, dielectric constant, relaxation time and so on.In particular, the glass transition temperature is different from the crystallization transition temperature, and will change with the change rate of temperature.In the experiment, the glass transition is studied more and more deeply.The experimental parameters include molecular weight, main chain structure, branched chain structure, branching degree, and physical parameters such as temperature change rate, external pressure and so on.The experimental methods have been developed from volume expansion method, differential Scanning calorimeter and dynamic Thermomechanical analysis to positron positron annihilation technique.Different experimental data tend to support different theories, except for one empirical equation--WLF equation.This makes it particularly important to theorize the WLF equation.In theory, the old theory and the new theory have been put forward one after another.The old theories include Adam-Gibbs theory, Cohen-Grest free volume theory and Random First-order Transition theory.The new theory includes kinetic theory and LCL model.After comparing the matching degree of the theoretical and experimental results, none of these theories can be compared with that of WLF equation. WLF equation is derived from Flory's equal free volume theory. It can be said that Flory's conjecture of equal free volume is proved.The basic theory of WLF equation is proved.Based on the above considerations, this paper starts from the strict quasi-static thermodynamic model, defines the glass transition from the free volume and viscosity equations of Doolittle, and then proves that the glass transition region is in the glass transition region.The free volume ratio of the ideal single-chain system under atmospheric pressure is a constant value independent of other physical and chemical parameters.In the process of comparing the experimental results with the theoretical results, many models have been continuously deduced and reconstructed, most of which have not done much to help us understand the vitrification transition.The glass transition theory is based on the relaxation lattice model-RLM.In addition to RLM, this paper also deduces a model, solution precipitation model, in the process of theoretical proof. The deductive idea of RLM model is as follows: firstly, parameters are introduced to describe relaxation process and free volume, then entropy function is solved.In the analysis of extremum and extremum of entropy function, the method of small scissors thought experiment is used, and the intermediate parameter is eliminated by designing thermodynamic path in the thought experiment of small scissors.The iso-free volume ratio 尾, which has been predicted by Flory but never proved in theory, is obtained.It is also proved that the first derivative of entropy function to temperature is discontinuous but the value of function is continuous in the vitrification transition.In addition, the system with high crosslinking degree and high temperature and high pressure was analyzed theoretically.The results show that the glass transition behavior can be predicted by RLM and the results are expressed as a three dimensional phase diagram.
【學(xué)位授予單位】：西南石油大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB30
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本文編號(hào)：1745486