本文選題：石墨烯氣凝膠 + 聚合物復合材料��； 參考：《北京化工大學》2017年博士論文

【摘要】：聚合物因其具有耐腐蝕、質輕、優(yōu)良力學以及易加工等特性,在人們的生產與生活中的應用愈發(fā)廣泛。近年來隨著能源、電子等領域的迅猛發(fā)展,人們對具有導電和導熱等功能特性的聚合物材料需求越來越大。然而除少數聚合物本身具有導電性外,多數聚合物是電與熱的絕緣體,聚合物本身已經不能滿足多功能性的需求,開發(fā)具有導電導熱和電磁屏蔽等功能性的聚合物復合材料是擺在科研工作者面前的重要課題。通過填充功能性納米填料制備聚合物功能復合材料具有成本低、開發(fā)周期短、易于推廣等優(yōu)點,在國內外受到廣泛關注。功能納米填料不僅能夠為聚合物提供多功能特性,還對聚合物具有一定的增強作用,然而單純加入這些納米填料通常需要很高的填充量,不利于復合材料的加工成型,同時多數納米填料具有剛性,會大大降低復合材料的韌性。因此,如何在獲得高導電導熱性能的同時,通過特定內部結構形成填料網絡、減小填料用量,同時改善復合材料的力學性能,是我們亟待解決的難題�；谝陨戏治�,本論文分別以熱固性環(huán)氧樹脂(epoxy)和熱塑性聚丙烯(PP)為基體,以各向異性三維石墨烯氣凝膠(AGAs)、碳納米管(CNTs)、碳酸鈣(CaC03)、氮化硼(BN)、石墨烯納米片(GNPs)和石墨化碳纖維(GCFs)為填料,制備了一些具有特定內部結構的復合材料,在表征材料力學性能的同時,系統(tǒng)研究了不同填料及填料結構狀態(tài)對聚合物復合材料導電、電磁屏蔽或者導熱性能的影響。本論文的主要內容包括以下四個部分:1.環(huán)氧樹脂/各向異性三維石墨烯氣凝膠復合材料電磁屏蔽性能的研究。在聚合物/石墨烯復合材料體系的研究中,石墨烯片的分散和空間分布狀況是決定其性能至關重要的因素。本研究中采用定向冷凍和冷凍干燥的方法制備了具有高度取向網絡結構的取向結構石墨烯氣凝膠(AGA),AGA在軸向(冷凍方向)和徑向(垂直于軸向)兩個方向上具有不同的微觀結構和性能特征。1300 ℃高溫熱處理能夠提高石墨烯的品質,基于熱處理取向石墨烯氣凝膠(TAGA)和熱處理各向同性石墨烯氣凝膠(TGA)制備的環(huán)氧樹脂復合材料,其導電和電磁屏蔽性能顯著提高。epoxy/TAGA復合材料具有各向異性的力學和電學性能,且在極低的TAGA含量下就具有優(yōu)異的電磁屏蔽效能。其中,TGA含量0.8wt%的環(huán)氧樹脂復合材料電磁屏蔽效能為27 dB,而TAGA含量0.8 wt%的環(huán)氧樹脂復合材料在徑向方向上測得電磁屏蔽效能高達32 dB,軸向方向上為25 dB。在TAGA含量僅為0.2 wt%時,環(huán)氧樹脂復合材料的徑向方向屏蔽效能就達到25 dB,能夠滿足高于20 dB的實際應用需求。2.環(huán)氧樹脂/熱處理各向異性三維石墨烯氣凝膠復合材料的導電及導熱性能研究。利用三維網絡結構作為骨架,制備導熱復合材料近年來受到學者們的廣泛關注。本研究采用定向冷凍干燥的方法制備了 AGAs,通過熱處理獲得TAGAs并以此為導熱網絡結合真空浸漬的方法構筑環(huán)氧樹脂復合材料,研究了材料在石墨烯片取向方向(軸向方向)和垂直于軸向方向(徑向方向)上的導電導熱及力學性能。AGA與TAGA具有高度取向的結構,因此制得的環(huán)氧樹脂復合材料具有各向異性的結構和性能。通過對不同質量分數(0.5、0.8、1.2、1.5 wt%)在不同熱處理溫度(1000、1600、2200、2800 ℃)下的電導率和熱導率進行分析探討,發(fā)現(xiàn)提高填料的填充量以及石墨烯的熱處理溫度均對材料的導電導熱性能有促進作用。在2800 ℃熱處理溫度下,含量1.5 wt%的各向異性復合材料在軸向方向上分別具有1054 S·-1和6.57 W·m-1·K-1的超高電導率及熱導率。此外,定向冷凍速率越高,TAGA具有越小的泡孔孔徑,小孔徑有利于復合材料的導熱和力學性能,但對電導率影響不大。本研究中所制得的epoxy/TAGA復合材料具有杰出的導電導熱性能,具有巨大的實際應用價值。3.聚丙烯/碳納米管/碳酸鈣復合材料的導電與韌性性能研究。本研究采用熔融共混的方法制備了 PP/CNT/CaC03復合材料,研究了其電學和力學性能。CNTs的引入賦予PP導電性,但它對材料的韌性破壞很大,因此向復合材料中加入第三組分CaC03納米顆粒來制備三相復合材料。CaCO3納米顆粒的加入在提高PP/CNT復合材料沖擊強度和楊氏模量的同時,還起到了體積排除的作用,提高了導電率、降低了逾滲閾值。加入30 wt%的CaCO3后,材料電導率提高,導電逾滲閾值由導電填料含量6.2 wt%降低到5.6 wt%,PP/9 wt% CNT復合材料的沖擊強度由16.0 KJ·m-2提高到24.4 KJ·m-2。為了增強無機填料和聚合物間的界面性能,本文還使用了一種特殊的鋁酸酯偶聯(lián)劑對納米CaC03顆粒進行表面處理,它對于材料的導電及沖擊性能有積極影響。加入相對CaC03含量5 wt%的偶聯(lián)劑后,三相復合材料導電逾滲閾值進一步降為3.6 wt%,沖擊強度提高到33.1 KJ·m-2。以上結果表明CaC03納米顆粒具有提高PP/CNT兩相復合材料韌性和導電性的雙重作用,具有導電性與韌性的PP納米復合材料有希望應用于更廣泛的領域中。4.聚丙烯/氮化硼/石墨烯納米片(石墨化碳纖維)復合材料的導熱性能研究。三相導熱復合材料是以PP為基體,采用熔融復合的方法與BN和其他兩種碳系填料加工制備而成。通過比較BN與氮化鋁(AlN)、碳化硅(SiC)填充PP復合材料在導熱和力學性能的差異后,選擇BN作為一種導熱填料,GNPs或GCFs作為第二種導熱填料。在填料總含量保持60wt%不變情況下,改變GNPs或GCFs的含量(1-5wt%),發(fā)現(xiàn)增加碳系填料含量能有效提高復合材料導熱性能,其中GNPs表現(xiàn)更突出。此外,鈦酸酯偶聯(lián)劑起到了促進填料分散、降低界面熱阻和提高熱穩(wěn)定性等作用,有利于復合材料的導熱性能�？偺盍狭繛�60 wt%,偶聯(lián)劑處理的GNPs或GCFs含量為5 wt%時,三相復合材料熱導率分別為1.55 W·m-1·K-1和1.36 W·m-1·K-1,分別比不含碳系填料的PP/60 wt%BN熱導率(0.73 W·m-1·K-1)高 86 %和 112 %,并高于 PP/80 wt%BN 熱導率(1.35 W·m-1·K-1)。碳系填料的加入,在不影響復合材料彎曲模量的同時,對彎曲強度有一定改善。以上結果表明,碳系填料的引入可減少了導熱填料用量、降低了材料加工難度,并在一定程度上改善了復合材料力學性能。
[Abstract]:Polymers have become more and more widely used in the production and life of people because of their corrosion resistance, light quality, good mechanics and easy processing. In recent years, with the rapid development of energy and electronics, the demand for polymer materials with electrical and thermal conductivity is becoming more and more important. In addition, most polymers are electrical and thermal insulators. Polymer itself can not meet the needs of multifunction. It is an important task for researchers to develop polymer composites with conductive and conductive heat and electromagnetic shielding. The polymer functional composites are prepared by filling functional nano fillers. It has the advantages of low cost, short development cycle, easy to spread and so on. It is widely concerned at home and abroad. Functional nano fillers can not only provide multi-functional properties for polymers, but also have a certain enhancement to polymers. However, the addition of these nanoscale filler is usually very high, which is not conducive to the processing of composite materials. Most nanometers are rigid and will greatly reduce the toughness of composite materials. Therefore, it is a difficult problem to solve the problem that how to form a packing network through a specific internal structure, reduce the amount of filler and improve the mechanical properties of the composite at the same time, while obtaining high conductivity and thermal conductivity, it is a difficult problem to resolve. A number of composite materials with specific internal structures were prepared by using epoxy and PP as the matrix, with anisotropic three-dimensional graphene aerogels (AGAs), carbon nanotubes (CNTs), calcium carbonate (CaC03), boron nitride (BN), graphene nanoscale (GNPs) and graphene carbon fiber (GCFs) as fillers. At the same time, the effects of different packing and packing structure on the conductive, electromagnetic shielding or thermal conductivity of polymer composites are systematically studied. The main contents of this paper include the following four parts: Study on the electromagnetic shielding properties of 1. epoxy resin / anisotropic three-dimensional graphene aerogel composite. In the study of the material system, the dispersive and spatial distribution of graphene sheets is a crucial factor determining its performance. In this study, oriented structure graphene aerogels (AGA) with highly oriented network structure were prepared by directional freezing and freeze drying, and two sides of AGA in axial direction (freezing direction) and radial (perpendicular to axial). The high temperature heat treatment at.1300 C can improve the quality of graphene, based on the thermal treatment oriented graphene aerogels (TAGA) and the thermally treated isotropic graphene aerogels (TGA), the conductive and electromagnetically shielding properties of the composites are significantly improved for the.Epoxy/TAGA composite. With anisotropic mechanical and electrical properties and excellent electromagnetic shielding effectiveness under extremely low TAGA content, the electromagnetic shielding effectiveness of the epoxy resin composite with TGA content 0.8wt% is 27 dB, while the epoxy resin composite with TAGA content of 0.8 wt% can measure the electromagnetic shielding effectiveness of up to 32 dB in the radial direction, in the axial direction. When the content of TAGA is only 0.2 wt%, the shielding effectiveness of the epoxy resin composite material in the radial direction is 25 dB, which can meet the practical application requirements of the epoxy resin / heat treatment anisotropic three-dimensional graphene aerogel composite material higher than 20 dB. The conductive and thermal properties of the anisotropic three-dimensional graphene aerogel composite material are studied. The three-dimensional network structure is used as the skeleton to prepare the guide. Thermal composites have been widely concerned by scholars in recent years. In this study, AGAs was prepared by the method of directional freeze drying. TAGAs was obtained by heat treatment and used as a heat conduction network to construct epoxy resin composite with vacuum impregnation. The orientation direction (axial direction) and perpendicular to axial square of the material were studied. The conductivities and mechanical properties of.AGA and TAGA in the direction of (radial direction) have a highly oriented structure, so the prepared epoxy resin composite has anisotropic structure and properties. The conductivity and thermal conductivity of different mass fraction (0.5,0.8,1.2,1.5 wt%) at different heat treatment temperatures (1000160022002800 degrees C) are divided. It is found that the filling amount of the filler and the heat treatment temperature of graphene can promote the conductive and thermal conductivity of the material. Under the heat treatment temperature of 2800 C, the anisotropic composites with 1.5 wt% content have the ultra high conductivity and thermal conductivity of 1054 S. -1 and 6.57 W. M-1. K-1 respectively in the axial direction. The higher the freezing rate, the smaller the pore size of the TAGA, the small aperture is beneficial to the thermal conductivity and mechanical properties of the composite, but it has little effect on the conductivity. The epoxy/TAGA composites obtained in this study have excellent conductive and conductive properties, and have great practical application value of.3. polypropylene / carbon nanotubes / calcium carbonate composites. The study of electrical and toughness properties. PP/CNT/CaC03 composites were prepared by melt blending. The electrical and mechanical properties of.CNTs were introduced to PP electrical conductivity, but the toughness of the materials was greatly destroyed. Therefore, third components of CaC03 nanometers were added to the composite materials to prepare the three phase composite.CaCO3 nanoscale. When adding the impact strength and Young's modulus of the PP/CNT composites, the particles also play the role of volume exclusion, increase the conductivity and reduce the percolation threshold. After adding CaCO3 of 30 wt%, the conductivity of the material is increased and the percolation threshold of the conductive filler is reduced from 6.2 wt% to 5.6 wt%, and the impact strength of the PP/9 wt% CNT composite material. From 16 KJ. M-2 to 24.4 KJ. M-2. to enhance the interfacial properties between inorganic fillers and polymers, a special aluminate coupling agent is used to surface treatment of nano CaC03 particles. It has a positive effect on the conductive and impact properties of the materials. After adding a coupling agent with a relative CaC03 content of 5 wt%, a three-phase composite material is added. The conductive percolation threshold is further reduced to 3.6 wt%, and the impact strength is increased to 33.1 KJ. M-2.. The results show that CaC03 nanoparticles have double effects on improving the toughness and conductivity of PP/CNT two phase composites. The PP nanocomposites with conductivity and toughness are expected to be applied to.4. polypropylene / boron nitride / graphene in a wider field. Study on the thermal conductivity of nanocomposite (graphene carbon fiber) composite material. The three-phase thermal conductive composite is made of PP as the matrix and fused with BN and other two kinds of carbon fillers. By comparing the thermal and mechanical properties of BN with aluminum nitride (AlN) and silicon carbide (SiC) filled PP composites, the choice of BN is chosen. For a kind of thermal conductive filler, GNPs or GCFs as second kinds of thermal conductive filler. The content of GNPs or GCFs is changed when the total content of the filler remains unchanged (1-5wt%). It is found that increasing the content of the carbon system filler can effectively improve the thermal conductivity of the composite, and the GNPs performance is more prominent. In addition, the titanate coupling agent plays a role in promoting the dispersing of the filler and reducing the boundary. The thermal conductivity of the composites is beneficial to the thermal conductivity of the composite. The total filler amount is 60 wt% and the GNPs or GCFs content of the coupling agent is 5 wt%, the thermal conductivity of the three-phase composite is 1.55 W. M-1 K-1 and 1.36 W. M-1. K-1 respectively, which is 86% and 1 higher than the PP/60 wt%BN thermal conductivity (0.73). 12%, and higher than the PP/80 wt%BN thermal conductivity (1.35 W. M-1. K-1). The addition of carbon fillers, without affecting the flexural modulus of the composite, has a certain improvement in bending strength. The above results show that the introduction of carbon fillers can reduce the amount of thermal conductive filler, reduce the difficulty of the material addition, and improve the composite force to a certain extent. Learning performance.
【學位授予單位】：北京化工大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB332

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本文編號：1941491