本文選題：聚合物　切入點(diǎn)：X射線散射　出處：《中國(guó)科學(xué)技術(shù)大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：結(jié)晶型聚合物在成型過(guò)程中往往都要經(jīng)歷復(fù)雜流場(chǎng)的作用,這會(huì)對(duì)聚合物熔體中分子鏈的伸展和取向情況產(chǎn)生影響,從而影響其結(jié)晶動(dòng)力學(xué)、晶體結(jié)構(gòu)和晶體形態(tài)等結(jié)晶行為。因此,有必要對(duì)流動(dòng)場(chǎng)下聚合物的結(jié)晶行為進(jìn)行充分系統(tǒng)的研究。盡管目前有許多理論能夠定量或半定量地描述流動(dòng)誘導(dǎo)結(jié)晶的過(guò)程并預(yù)測(cè)流動(dòng)誘導(dǎo)結(jié)晶的結(jié)果,但這些結(jié)論大多都是基于均勻流場(chǎng)的假設(shè)。在通常的加工條件下,處于非線性區(qū)高分子熔體的非線性流動(dòng)行為會(huì)使得分子鏈對(duì)流場(chǎng)的響應(yīng)變得非均勻。而即便是均勻流場(chǎng),分子鏈對(duì)流場(chǎng)的響應(yīng)也不會(huì)宏觀外場(chǎng)完全一致。因此為了更為準(zhǔn)確地理解流動(dòng)誘導(dǎo)結(jié)晶的本質(zhì),有必要對(duì)流動(dòng)誘導(dǎo)結(jié)晶實(shí)驗(yàn)中分子鏈對(duì)流場(chǎng)的響應(yīng)進(jìn)行關(guān)注。本論文主要著眼于非均勻流場(chǎng)和均勻流場(chǎng)下分子鏈對(duì)流場(chǎng)的響應(yīng)及其對(duì)結(jié)晶的影響。通過(guò)自主研發(fā)的與X射線聯(lián)用剪切裝置,同時(shí)采集聚合物流變信息和結(jié)晶過(guò)程中結(jié)構(gòu)演化信息,將不同均勻性流場(chǎng)下分子鏈響應(yīng)與結(jié)晶行為相關(guān)聯(lián),得到不同流動(dòng)模式熔體與結(jié)晶之間的關(guān)系。同時(shí),針對(duì)均勻流場(chǎng)(拉伸流場(chǎng)),結(jié)合小角中子散射技術(shù)定量描述了鏈變形程度和串晶生成之間的關(guān)系。主要結(jié)果和結(jié)論總結(jié)如下:(1)采用交聯(lián)氘/氫聚乙烯共混體系,研究了拉伸場(chǎng)下串晶生成前后分子鏈真實(shí)變形情況,結(jié)果顯示串晶的形成不需要很大的分子鏈形變,這說(shuō)明鏈內(nèi)構(gòu)象并不是影響串晶生成的唯一要素,而鏈內(nèi)構(gòu)象和鏈間密度耦合才更為關(guān)鍵。此外,在拉伸之后的結(jié)晶過(guò)程中,分子鏈運(yùn)動(dòng)行為與樣品所處的拉伸狀態(tài)密切相關(guān)。對(duì)于拉伸至硬化區(qū)的樣品,體系內(nèi)會(huì)有周期性高濃度氘代聚乙烯區(qū)域的產(chǎn)生。相反的,拉伸程度較弱的樣晶體系內(nèi)不會(huì)形成周期性高濃度氘代聚乙烯區(qū)域。(2)設(shè)計(jì)并制造了一臺(tái)與X射線聯(lián)用具有快速降溫功能的剪切裝置,該裝置的快速降溫的功能使得我們能夠在高溫對(duì)樣品進(jìn)行剪切并快速降溫至較低溫度進(jìn)行等溫結(jié)晶,將樣品流變性能和結(jié)晶行為進(jìn)行對(duì)應(yīng),研究不同鏈響應(yīng)導(dǎo)致的不同流動(dòng)行為與結(jié)晶的關(guān)系。(3)使用自主研發(fā)的快速降溫裝置,研究了瞬時(shí)和緩慢兩種電機(jī)加速方式對(duì)樣品流變和結(jié)晶行為的影響。實(shí)驗(yàn)結(jié)果顯示緩慢加速能夠消除剪切過(guò)程中流場(chǎng)的非均勻性,提高分子鏈對(duì)流場(chǎng)的響應(yīng),使樣品取向度增加,提高流場(chǎng)對(duì)聚合物熔體的作用效果。同時(shí),比對(duì)不同剪切速率和加速時(shí)間樣品的結(jié)晶行為發(fā)現(xiàn),對(duì)于不同剪切速率,流動(dòng)誘導(dǎo)結(jié)晶對(duì)于加速時(shí)間有依賴性。(4)使用快速降溫剪切裝置并結(jié)合廣角X射線散射,采用不同剪切速率和加速時(shí)間對(duì)不同流動(dòng)模式下聚合物流變和結(jié)晶行為進(jìn)行了研究。結(jié)果顯示不同加速模式下分子鏈初始對(duì)流場(chǎng)的響應(yīng)不同會(huì)引起熔體解纏結(jié)行為出現(xiàn)差異,從而對(duì)熔體流變行為和結(jié)晶動(dòng)力學(xué)以及晶體取向造成影響。
[Abstract]:The crystallization kinetics of crystalline polymer is affected by the effect of complex flow field during the molding process, which will affect the stretching and orientation of molecular chain in polymer melt. Crystalline behavior such as crystal structure and crystal morphology. It is necessary to study fully and systematically the crystallization behavior of polymers in flow field, although there are many theories that can describe the process of fluid-induced crystallization quantitatively or semi-quantitatively and predict the results of fluid-induced crystallization. However, most of these conclusions are based on the assumption of uniform flow field. Under the normal processing conditions, the nonlinear flow behavior of polymer melt in the nonlinear region will make the response of the flow field of the molecular chain non-uniform, and even the homogeneous flow field. The response of the flow field of the molecular chain is not completely consistent with that of the external field. Therefore, in order to understand more accurately the essence of fluid-induced crystallization, It is necessary to pay attention to the response of the molecular chain flow field in the flow induced crystallization experiment. This paper focuses on the response of the molecular chain flow field and its effect on the crystallization under the inhomogeneous flow field and the uniform flow field. In conjunction with an X-ray shearing device, At the same time, the rheological information of polymer and the information of structure evolution during crystallization were collected, and the molecular chain response and crystallization behavior under different homogeneity flow fields were correlated, and the relationship between melt and crystallization in different flow modes was obtained. For the uniform flow field (tensile flow field), the relationship between chain deformation and crystal formation is quantitatively described in combination with small angle neutron scattering technique. The main results and conclusions are summarized as follows: 1) the cross-linked deuterium / hydrogen-polyethylene blend system is used. The real deformation of molecular chains before and after the formation of string crystals under tensile field is studied. The results show that the formation of string crystals does not require a large amount of molecular chain deformation, which indicates that the conformation of chains is not the only factor affecting the formation of string crystals. Moreover, in the crystallization process after stretching, the molecular chain movement behavior is closely related to the tensile state of the sample. There will be periodic high concentration deuteriated polyethylene regions in the system. A shearing device with rapid cooling function in conjunction with X-ray was designed and manufactured in a sample system with weak tensile degree, which does not form periodic high concentration deuterium polyethylene region. The rapid cooling function of the device enables us to shear the samples at high temperatures and rapidly drop them to lower temperatures for isothermal crystallization, which corresponds to the rheological properties and crystallization behavior of the samples. To study the relationship between different flow behavior and crystallization caused by different chain responses. The effects of instantaneous and slow motor acceleration modes on the rheology and crystallization behavior of the samples are studied. The experimental results show that the slow acceleration can eliminate the inhomogeneity of the flow field in the shear process and improve the response of the molecular chain flow field. At the same time, comparing the crystallization behavior of samples with different shear rates and accelerating time, it is found that, for different shear rates, the effect of flow field on polymer melts is improved. Fluid-induced crystallization is dependent on acceleration time. 4) using a rapid cooling shear device combined with wide-angle X-ray scattering, The rheology and crystallization behavior of polymer in different flow modes were studied by using different shear rates and acceleration time. The results show that the different responses of initial flow field of molecular chain in different accelerated modes will lead to the difference of melt unentanglement behavior. Thus, the melt rheological behavior, crystallization kinetics and crystal orientation are affected.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：O631.1

【參考文獻(xiàn)】

相關(guān)期刊論文 前2條

1 Dong Liu;Kunpeng Cui;Ningdong Huang;Zhen Wang;Liangbin Li;;The thermodynamic properties of flow-induced precursor of polyethylene[J];Science China(Chemistry);2015年10期

2 Fang-zhen An;高雪芹;雷軍;Cong Deng;Zhong-ming Li;Kai-zhi Shen;;Vibration Assisted Extrusion of Polypropylene[J];Chinese Journal of Polymer Science;2015年05期

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本文編號(hào)：1607119