聚合物基复合材料的导热性能研究

讨论了聚合物基高导热高绝缘纳米复合材料的导热机理与常用的导热理论模型。考虑到填充率、温度等的影响，用不同的理论模型计算了氧化铝纳米颗粒填充环氧树脂的热导率，并结合相关研究实验对不同的导热理论模型进行分析比较。     

聚合物基复合材料导热性的研究

讨论了聚合物基高导热高绝缘纳米复合材料的导热机理与常用的导热理论模型。考虑到填充率、温度等的影响，采用不同理论模型计算了用氧化铝纳米颗粒填充环氧树脂时材料的热导率，并结合相关研究实验对不同导热理论模型进行了分析比较。     

聚合物复合材料导热性能的研究

论述了填充聚合物复合材料的导热性及其变化规律;总结了复合材料导热的理论模型和导热系数预测方程,对比研究了各种导热模型的区别与联系;分析了影响复合材料导热特性的因素。     

聚合物纳米石墨烯复合材料导热性能研究进展

集成电路伴随着电子、航天和航空领域的发展而快速发展,但往往伴随着散热困难的问题,影响着使用效率和仪器寿命。从质量、耐蚀性、加工工艺和成本等方面考虑,聚合物复合材料是导热材料中最具发展前景的材料。然而聚合物固有的导热率非常低,因此,提高聚合物的导热率对于其在这些领域的应用显得非常重要,这在过去的20年中已经成为一个非常重要的研究课题。主要从以下两个方面进行介绍:(1)从分子链形态、链结构和链间耦合3个方面分析总结了聚合物的微观导热机理;(2)重点介绍近年来石墨烯填充聚合物纳米复合材料导热性能的主要研究进展以及未来的研究挑战。     

聚合物基导电复合材料研究进展

本文介绍了聚合物基导电复合材料的种类、用途及导电机理。并对碳系填料填充聚合物基导电复合材料及金属系填料填充聚合物基导电复合材料的研究进展进行了综述 ,最后展望了聚合物基导电复合材料的发展趋势。     

填充型聚合物基气敏导电复合材料

作为一种功能性复合材料,填充型聚合物基气敏导电复合材料在生物医学、化学化工以及环境科学等领域具有广阔的应用前景,综述了填充型聚合物基气敏导电复合材料的导电机制,影响因素及其近斯的研究进展。     

石墨烯填充对不同聚合物导热性能和热稳定性的影响

为研究同一制备方法下石墨烯质量分数对不同聚合物导热性能和热稳定性的影响,通过熔融共混法制备了石墨烯/聚酰胺(GE/PA6)、石墨烯/聚丙烯(GE/PP)、石墨烯/高密度聚乙烯(GE/HDPE)3种聚合物复合材料。结果表明,石墨烯能有效提高3种聚合物导热性能,当填充石墨烯质量分数达到10%时,PA6导热系数从0.32 W/(m·K)提升至1.30 W/(m·K);GE/PP导热系数从0.37 W/(m·K)提升至1.15 W/(m·K)、GE/HDPE导热系数从0.62 W/(m·K)提升至1.13 W/(m·K)。对制备的石墨烯聚合物复合材料进行热重分析。将纯聚合物与石墨烯质量分数1%,5%,10%的石墨烯聚合物复合材料对比,PA6的热稳定性逐渐提升,PP、HDPE的热稳定性先降低后升高。     

粒子填充聚合物基复合材料导热性能的数值模拟

根据电镜照片中观察的微观结构信息,基于两套新设计的算法建立了代表体积元(RVE)模型,基于此模型研究了粒子填充聚合物基复合材料的导热性能与微观结构的关系。通过对电镜照片的处理得到两个参数即稀疏区比重和稀疏区半径,建立了与实际体系相符的具有非均匀粒子分布结构的 RVE模型。制备了氧化铝/高温硫化硅橡胶导热复合材料,并测试了不同填充量下体系的热导率,用以验证模型的有效性。采用有限元方法求解RVE模型得到的热导率预测值与实验值进行对比,结果表明：填料用量在宽范围内预测结果与实验值均吻合很好; 与均匀分布或随机分布相比,存在稀疏区和富集区的非均匀分布的体系具有更高的热导率,这种差异在高填充量下当颗粒间形成导热网链时更为显著;在相同填充量下,不同的粒子空间分布结构可使体系热导率差别很大,是影响体系热导率的关键因素。     

Sn-Pb合金填充聚合物导电复合材料的PTC效应

通过球磨、热压制备了Sn-Pb/PS,Sn-Pb/HDPE复合材料。研究了复合材料的导电性能。结果证明:Sn-Pb／PS复合材料具有PTC效应,有PTC强度大、转变陡的突出优点;其 PTC性能是由填料相变的发生引起的。Sn-Pb／HDPE复合材料具有双PTC效应,两次PTC转变分别由基体和填料在其熔点处发生相变引起的,其 PTC强度也有独特之处。     

聚合物基导电复合材料的电阻机械效应(RME)

综述了聚合物基导电复合材料的电阻机械效应(resistancce-mechanical effect,RME),列举了砌RME的各种表现及其可能的内在机制,介绍了改善RME循环稳定性的方法。RME取决于导电填料和基体性质两方面因素,包括填料种类和形态分布、填料体积分数、基体粘弹性、基体与填料的相五作用。其次,应力或应变大小、加栽方式和加栽速率、加工方法以及环境温度和湿度等也是影响RME的重要因素。对于纤维填充复合体系,影响因素还包括纤维取向与长径比、外力方向等。     

不同形态填料填充导热复合材料的研究进展

概述了不同形态填料填充聚合物基导热复合材料的导热机理和国内外研究进展,阐述了几种重要的复合材料的性能,指出了该领域尚需解决的突出问题并对未来的发展方向进行了展望。     

Measurements of Thermal Conductivity and Electrical Conductivity of a Single Carbon Fiber

In this paper, the thermal conductivity of a single carbon fiber under different manufacturing conditions is measured using the steady-state short-hot-wire method. This method is based on the heat transfer phenomena of a pin fin attached to a short hot wire. The short hot wire is supplied with a constant direct current to generate a uniform heat flux, and both its ends are connected to lead wires and maintained at the initial temperature. The test fiber is attached as a pin fin to the center position of the hot wire at one end and the other end is connected to a heat sink. One-dimensional steady-state heat conduction along the hot wire and test fiber is assumed, and the basic equations are analytically solved. From the solutions, the relations among the average temperature rise of the hot wire, the heat generation rate, the temperature at the attached end of the fiber, and the heat flux from the hot wire to the fiber are accurately obtained. Based on the relations, the thermal conductivity of the single carbon fiber can be easily estimated when the average temperature rise and the heat generation rate of the hot wire are measured for the same system. Further, the electrical conductivity of the single carbon fiber is measured under the same conditions as for the thermal conductivity using a four-point contact method. The relation between the thermal conductivity and electrical conductivity is further discussed, based on the crystal microstructure.     

特殊形态结构导电高分子复合材料的电学性能

先使聚丙烯接枝马来酸酐(PP-g-MAH)与炭黑(CB)反应,再与聚丙烯/尼龙6(PP/PA6)共混制备出CB位于两相界面处的PP/PA6/PP-g-MAH/CB导电高分子复合材料,研究了材料的特殊结构和电学性能。结果表明,在PP/PA6/CB体系中CB粒子分布在PA6相,体系的逾渗阈值为2%;而在PP/PA6/PP-g-MAH/CB体系中,CB被PP-g-MAH诱导分布在两相界面处。PP/PA6两相为海岛结构时,PP/PA6/PP-g-MAH/CB体系仍可导电。PP/PA6/PP-g-MAH/CB体系的逾渗阈值降至1.6%,低于PP/PA6/CB体系。体系的正温度效应(PTC)强度远高于PP/PA6/CB体系,在90-135℃范围内不出现负温度效应(NTC)。PP/PA6/PP-g-MAH/CB体系的电学性能归结于其特殊的界面形态结构:导电通道由位于共混物界面处的PP-g-MAH和CB构建而成。     

聚氨酯/二氧化硅包覆多壁碳纳米管复合材料的导热与电绝缘性能

通过溶胶-凝胶法制备了厚度为30nm-50nm的二氧化硅(SiO2)包覆多壁碳纳米管(SiO2-MWNTs),并与聚氨酯(PU)复合制备了PU/SiO2-MWNT复合材料。研究了SiO2-MWNTs对PU导热电绝缘性能的影响。结果表明,SiO2包覆层增强了MWNTs与PU之间的界面相互作用,促进了MWNTs在PU中的分散。由于SiO2包覆层的电绝缘作用,PU/SiO2-MWNT复合材料保持了PU的电绝缘性能。同时SiO2包覆层作为过渡层,降低了PU与MWNTs间的模量失配,减少了声子的界面散射,提高了PU/SiO2-MWNT复合材料的导热性能。当SiO2-MWNTs的质量分数为0.5%和1.0%时,PU/SiO2-MWNT复合材料的热导率分别提高了53.7%和63.8%。     

导热型碳纤维增强聚合物基复合材料的研究进展

综述了导热型连续碳纤维增强聚合物基复合材料(CFRP)的研究与应用现状和进展,阐述了CFRP的声子导热和光子导热机理,介绍了不同铺层角度和铺层比的CFRP面内和厚度方向热导率计算模型及测试方法,分析了环氧树脂、氰酸酯、双马来酰亚胺等3类树脂体系和聚丙烯腈基(PAN)碳纤维、中间相沥青基碳纤维、气相生长碳纤维、碳纳米管纤维等4类增强体以及工艺方法等因素对CFRP热导率的影响.     

Predicting, Measuring, and Tailoring the Transverse Thermal Conductivity of Composites from Polymer Matrix and Metal Filler

The addition of conductive filler in a polymer matrix is an effective way to increase the thermal conductivity of the plastic materials, as required by several industrial applications. All quantitative models for the thermal conductivity of heterogeneous media fail for heavily filled composites. The percolation theory allows good qualitative predictions, thus selecting a range for some qualitative effects on the thermal conductivity, and providing a way to choose a range for some experimental parameters. The design of such composite materials requires a study of its thermal features combined with different mechanical, ecological, safety, technical, and economical restrictions. A specific small guarded hot plate device with an active guard, conductive grease layer, and controlled variable pressure was used for measurement of the transverse thermal conductivity on 15 mm sided samples of composite parts. Extensive thermal and composition measurements on filled thermoplastics show that the conductivity of the filler, its size and shape, and its local amount are, with the degree of previous mixing, the main factors determining the effective conductivity of composites. For injection-molded polybutylene terephtalate plates, the best filler is the short aluminum fiber. With fibers of 0.10 mm diameter, it is possible to obtain conductivities larger by factors of 2, 6, and 10 than those of polymer for aluminum contents of 20, 42, and 43.5 vol%, respectively.     

Thermal Conductivity of Opacified Powder Filler Materials for Vacuum Insulations1

The thermal conductivity of powder fillings for load-bearing vacuum insulations is investigated. Different opacifiers have been tested in mixtures with perlite powder, precipitated silica, and fumed silica. Using temperature-dependent thermal conductivity measurements, the radiative thermal conductivity and the solid conductivity of the powder samples are separated. Additionally, the influence of the pressure load on the solid conductivity is studied. The thermal conductivities of silica powders with added opacifier powders (carbon black, magnetite, silicon carbide, titanium dioxide) can be as low as 0.003 W·m^–1·K^–1 if the powder boards are pressed with moderate loads. The use of microporous silica powders as filler materials allows internal gas pressures even beyond 10 hPa with only a moderate increase of the overall conductivity.     

锥形量热仪确定聚合物材料导热系数的方法

通过对聚甲基丙烯酸甲酯聚合物材料在锥形量热仪实验条件下加热过程的分析和研究,建立了材料加热过程的数学模型。利用该模型来计算材料的平均导热系数,需要测量的物理量仅仅是物体表面或内部的温度,通过一次测试就可以得到不同温度范围内材料的平均导热系数,方法简单,可靠。利用文中的计算方法,得到PMMA在不同温度范围内的平均导热系数,结果表明,随温度范围的增加,材料平均导热系数值有增大的趋势。计算出的导热系数值在低温度范围与文献值比较接近。研究表明在高的温度范围内不能将传统测量的导热系数值用作火灾条件下材料的参数值。     

Thermal Conductivity of Sm3S4 System with Mixed Valence Sm Ions

The thermal conductivity () and electrical resistivity () of mixed-valence compound Sm₃S₄ have been measured in the temperature range 5 to 300 K. The present results and those presented previously [1] for the thermal conductivity between 80 to 850 K are interpreted in terms of the temperature-dependent fluctuating valence of Sm ions. Sm₃S₄ crystallizes in the cubic Th₃P₄ structure, and the cations with different valences occupy equivalent lattice sites. Divalent and trivalent Sm ions are randomly distributed in the ratio of 1:2 over all possible crystallographic cation positions (Sm²⁺ ₂Sm³⁺ ₂S^2– ₄). The behavior of the Sm₃S₄ lattice thermal conductivity _ph is extraordinary since valences of Sm ions are fluctuating (Sm³⁺Sm²⁺) with a temperature dependent frequency. In the interval 20 to 50 K (low hopping frequencies), _ph of Sm₃S₄ varies as _ph T ^–1 (it is similar to materials with static distribution of cations with different valences): at 95 to 300 K (average hopping frequencies 10⁷ to 10¹¹ Hz), _ph changes as _ph T ^–0.3 (it is similar to materials with defects). Defects in Sm₃S₄ appear because of local strains in the lattice by the electrons hopping from Sm²⁺ ions (with big ionic radii) to Sm³⁺ ions (with small ionic radii) and back (Sm²⁺Sm³⁺), at T>300 K (high hopping frequencies), _ph becomes similar to materials with homogenous mixed valence states [1].     

利用稳态法测量聚合物薄膜纵向热导系数

在一维稳态热传导模型的基础上,设计了一套用于测量聚合物薄膜纵向热导系数的实验装置,并利用Comsol软件对该测量装置进行数值模拟并优化设计。同时利用本文设计的实验装置,测量得到了不同温度下聚酰亚胺(PI)膜、聚四氟乙烯(PTFE)膜以及混合纤维素酯(MCE)膜的热导系数。在35℃~60℃的温度范围内热导系数测量值分别维持在0.21 W/(m.K),0.26 W/(m.K),0.13 W/(m.K)左右,标准不确定度在9.5%以下。测量结果与参考值相符,验证了实验装置的测试精度。