本文選題：分子模擬 + 聚乙烯　； 參考：《安徽大學(xué)》2017年碩士論文

【摘要】：高分子材料在電子、工程、機(jī)械等領(lǐng)域具有廣泛的應(yīng)用價(jià)值。然而,高分子材料較差的導(dǎo)熱性能,限制了其在熱管理材料領(lǐng)域的應(yīng)用。高分子本體的導(dǎo)熱率只有0.1-1 W/mK,遠(yuǎn)遠(yuǎn)低于陶瓷和金屬材料。通過加入導(dǎo)熱填料可以有效提高復(fù)合體系的導(dǎo)熱性能,然而填充型高分子復(fù)合材料的有機(jī)-無機(jī)界面嚴(yán)重影響材料的機(jī)械力學(xué)性能。隨著電子信息和新材料產(chǎn)業(yè)的發(fā)展,如何綜合提高高分子材料的導(dǎo)熱和機(jī)械力學(xué)性能成為高分子研究領(lǐng)域的重點(diǎn)。高分子的物理性能與其微觀形態(tài)結(jié)構(gòu)關(guān)系密切。高分子體系中晶體的尺寸和取向、導(dǎo)熱填料與基體的復(fù)合狀態(tài)、填料顆粒之間的物理/化學(xué)鍵合等因素對(duì)材料的性能有重要的影響。本文采用計(jì)算機(jī)模擬方法研究了聚合物結(jié)晶、導(dǎo)熱性能和聚合物交聯(lián)納米顆粒的影響因素和體系微觀結(jié)構(gòu)和狀態(tài)的演變規(guī)律。首先,采用分子動(dòng)力學(xué)的方法模擬了聚乙烯體系和聚乙烯/氮化硼復(fù)合體系導(dǎo)熱率隨拉伸作用的變化。采用非平衡分子動(dòng)力學(xué)(nonequilibrium molecular dynamics,NEMD)方法測(cè)定了聚合物體系導(dǎo)熱率與拉伸形變、拉伸速率、溫度、分子摩爾質(zhì)量的關(guān)系。結(jié)果表明:對(duì)于純聚乙烯體系,拉伸作用通過改變分子的取向結(jié)構(gòu)來達(dá)到提升導(dǎo)熱率的效果。隨著拉伸作用的進(jìn)行,分子由無序混亂的狀態(tài)達(dá)到沿拉伸方向高度有序的晶體結(jié)構(gòu),使得熱量在傳遞過程中沿分子鏈傳遞大于分子間傳遞,大大提高了導(dǎo)熱效率。拉伸速率、溫度、聚乙烯分子的分子質(zhì)量都會(huì)影響取向結(jié)構(gòu),達(dá)到相同的形變條件時(shí)拉伸速率越小分子的取向率越高;溫度也影響著拉伸取向的速率,對(duì)應(yīng)不同的拉伸速率,溫度的效果不一樣;分子的大小同樣影響聚合物的導(dǎo)熱速率,在相同的取向條件下,分子摩爾質(zhì)量越大聚合物的導(dǎo)熱系數(shù)越高。對(duì)于聚乙烯氮化硼復(fù)合體系,氮化硼片層由于自身的性質(zhì)使其誘導(dǎo)聚乙烯分子形成了有序結(jié)構(gòu)同樣提升了聚合物的導(dǎo)熱率。納米添加劑的作用不僅僅是利用自身高導(dǎo)熱的性質(zhì)在聚合物體系中形成導(dǎo)熱通路來提高材料導(dǎo)熱率,其與聚合物材料間的相互作用改變聚合物的結(jié)構(gòu)也是提升材料導(dǎo)熱性能的一個(gè)重要影響因素。然后研究了兩種不同構(gòu)型氮化硼納米材料對(duì)于聚合物結(jié)晶的影響。熔體條件下,通過對(duì)聚乙烯分子結(jié)晶過程中晶體構(gòu)象的演變、空間內(nèi)分子分布的變化以及分子擴(kuò)散特性的研究,結(jié)果表明氮化硼納米管誘導(dǎo)PE烷烴分子結(jié)晶的速率明顯要比氮化硼片層的快。納米材料由于自身維度的不同,誘導(dǎo)結(jié)晶的能力也不同,氮化硼納米結(jié)構(gòu)的曲率半徑會(huì)影響聚合物在其表面結(jié)晶的速率。構(gòu)象演變過程和鍵取向參數(shù)的變化表明,使氮化硼片層誘導(dǎo)結(jié)晶能力低于氮化硼納米管的原因是PE分子在氮化硼表面的多重的取向,而PE分子在氮化硼納米管表面的取向均是沿著納米管軸向方向,說明納米材料維度是影響聚合物結(jié)晶的重要影響因素。最后采用DPD方法討論一種納米填料納米鏈合成的影響因素,通過對(duì)表面接枝納米顆粒在溶液中的成鍵反應(yīng),系統(tǒng)地研究了反應(yīng)的影響因素。考慮了接枝鏈的長(zhǎng)度(從30到90)和接枝密度從低到高(0.04至0.16)和接枝鏈的剛性。確定了納米顆粒間成鍵率與接枝鏈長(zhǎng)度、接枝密度、接枝鏈剛度、濃度的關(guān)系。結(jié)果證明,控制納米粒子的接枝鏈的長(zhǎng)度是最有效的方法,接枝鏈的長(zhǎng)度存在一個(gè)最優(yōu)值,在不同的接枝密度下,當(dāng)接枝鏈長(zhǎng)度低于最優(yōu)質(zhì)時(shí)提高接枝鏈鏈長(zhǎng)度有利于納米顆粒間成鍵鏈接,當(dāng)接枝鏈長(zhǎng)度高于最優(yōu)值時(shí)提升接枝鏈長(zhǎng)度有相反作用。此外,改變接枝鏈的密度,接枝鏈的剛度也被認(rèn)為是一個(gè)重要因素。對(duì)于不同接枝密度的納米粒子,隨著接枝密度的增加,顆粒的結(jié)合速率變高。濃度對(duì)鍵形成的作用與接枝密度相近,當(dāng)增加納米粒子的濃度時(shí),納米粒子鏈更容易得到。
[Abstract]:Polymer materials have wide application value in the fields of electronics, engineering and machinery. However, the poor thermal conductivity of polymer materials restricts its application in the field of thermal management materials. The thermal conductivity of the polymer is only 0.1-1 W/mK, far below the ceramic and metal materials. The composite system can be effectively improved by adding heat conductive filler. The organic inorganic interface of filled polymer composites seriously affects the mechanical and mechanical properties of the materials. With the development of electronic information and new materials industry, how to improve the thermal conductivity and mechanical properties of polymer materials has become the key point in the field of polymer research. The crystal size and orientation of the polymer system, the composite state of the thermal conductive filler and the matrix, the physical / chemical bonding between the packed particles have an important influence on the properties of the materials. In this paper, the effects of polymer crystallization, heat conductivity and polymer crosslinked nanoparticles are studied by computer simulation. Firstly, the thermal conductivity of polyethylene system and polyethylene / boron nitride composite system was simulated with the change of tensile effect by molecular dynamics. The thermal conductivity and tension of the polymer system were measured by nonequilibrium molecular dynamics (NEMD) method. The relationship between deformation, tensile rate, temperature and molecular mole quality. The results show that for pure polyethylene system, the tensile effect is achieved by changing the molecular orientation structure to improve the thermal conductivity. As the tensile force is carried out, the molecules are in a disorder and chaotic state to achieve a highly ordered crystal structure along the extension direction, making the heat transfer. The transfer of the molecular chain along the molecular chain is greater than the intermolecular transmission, which greatly improves the thermal conductivity. The tensile rate, the temperature, the molecular mass of the polyethylene molecule all affect the orientation structure. When the same deformation condition is reached, the smaller the tensile rate is, the higher the orientation rate of the molecule; the temperature also affects the rate of tensile orientation, corresponding to the different tensile rate and temperature. The effect of the degree is different, the size of the molecule also affects the heat conduction rate of the polymer. Under the same orientation, the higher the molecular mole mass is, the higher the thermal conductivity of the polymer. For the polyethylene nitride composite system, the boron nitride lamellar formed the ordered structure of the polyethylene molecule by its own properties and promoted the polymerization. The thermal conductivity of the material. The effect of nano additive is not only to improve the thermal conductivity of the material in the polymer system, but also to improve the thermal conductivity of the material in the polymer system. The interaction between the polymer and the polymer material changes the structure of the polymer as well as a key factor to improve the thermal conductivity of the material. Then two kinds of isomorphism are studied. The effect of boron nitride nanomaterials on the crystallization of polymer. Under the melt condition, the evolution of the crystal conformation in the crystallization of polyethylene, the change in the molecular distribution in the space and the molecular diffusion characteristics are studied. The results show that the rate of PE alkanes induced by boron nitride nanotubes is faster than that of the boron nitride layer. The ability of rice materials to induce crystallization is different because of their own dimensions. The radius of curvature of boron nitride nanostructures will affect the rate of polymer crystallization on its surface. The change of conformation evolution and bond orientation parameters indicates that the reason for the crystallization ability of boron nitride layer to induce the crystallization ability is lower than that of boron nitride nanotube, which is the PE molecule in the boron nitride sheet. The orientation of the surface of PE molecules on the surface of BN nanotubes is along the axial direction of the nanotube, indicating that the dimension of nanomaterial is an important factor affecting the crystallization of the polymer. Finally, the influence factors of the nanoscale synthesis of a nano filler are discussed by the DPD method, and the surface grafting of nano particles in the solution is discussed. The influence factors of the bond reaction are systematically studied. The length of the graft chain (from 30 to 90) and the grafting density from low to high (0.04 to 0.16) and the rigidity of the graft chain are taken into account. The relationship between the bond rate of the nanoparticles and the length of the graft chain, the grafting density, the graft chain stiffness and concentration is determined. The results show that the grafting chain of the nanoparticles is controlled. Length is the most effective method. The length of graft chain has an optimal value. Under the different grafting density, the length of the chain chain chain is beneficial to the bond linkage between the nanoparticles when the length of the grafting chain is lower than the best quality. The stiffness of the grafted chain is also considered as an important factor. With the increase of the grafting density, the binding rate of particles becomes higher with the increase of the grafting density. The effect of concentration on the bond formation is similar to that of the grafting density. When the concentration of nanoparticles is increased, the nanoparticle chain is easier to get.

【學(xué)位授予單位】：安徽大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O631

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