聚合物基泡体复合材料的传热性能及机理

讨论了聚合物基泡体复合材料的隔热原理和性能。分析了一些估算填充聚合物复合材料热导率的公式。由于泡沫材料的固有特点，可以明显地改善复合材料的保温隔热性能。     

Thermal conductivity of polymer-based composites: Fundamentals and applications

Thermal management is critical to the performance, lifetime, and reliability of electronic devices. With the miniaturization, integration and functionalization of electronics and the emergence of new applications such as light emitting diodes, thermal dissipation becomes a challenging problem. Addressing this challenge requires the development of novel polymer-based composite materials with enhanced thermal conductivity. In this review, the fundamental design principles of highly thermally conductive composites were discussed. The key factors influencing the thermal conductivity of polymers, such as chain structure, crystallinity, crystal form, orientation of polymer chains, and orientation of ordered domains in both thermoplastics and thermosets were addressed. The properties of thermally conductive fillers (carbon nanotubes, metal particles, and ceramic particles such as boron nitride or aluminum oxide) are summarized at length. The dependence of thermal conductivity of composites on the filler loading, filler aggregate morphology and overall composite structure is also discussed. Special attention is paid to recent advances in controlling the microstructure of polymer composites to achieve high thermal conductivity (novel approaches to control filler orientation, special design of filler agglomerates, formation of continuous filler network by self-assembly process, double percolation approach, etc.). The review also summarizes some emerging applications of thermally conductive polymer composites. Finally, we outline the challenges and outlook for thermally conductive polymer composites.     

Influence of filler type and content on thermal conductivity and mechanical properties of thermoplastic compounds

Combining thermal conductivity with electrical isolation is a very interesting topic for electronic applications in order to transfer the generated heat. Typical approaches combine thermally conductive fillers with a thermoplastic matrix. The aim of this work was to investigate the influence of different fillers and matrices on the thermal conductivity of the polymer matrix composites. In this study, various inorganic fillers, including aluminum oxide (Al₂O₃), zinc oxide (ZnO), and boron nitride (BN) with different shapes and sizes, were used in matrix polymers, such as polyamide 6 (PA6), polypropylene (PP), polycarbonate (PC), thermoplastic polyurethane (TPU), and polysulfone (PSU), to produce thermally conductive polymer matrix composites by compounding and injection molding. Using simple mathematical models (e.g., Agari model, Lewis–Nielson model), a first attempt was made to predict thermal conductivity from constituent properties. The materials were characterized by tensile testing, density measurement, and thermal conductivity measurement. Contact angle measurements and the calculated surface energy can be used to evaluate the wetting behavior, which correlates directly with the elastic modulus. Based on the aforementioned evaluations, we found that besides the volume fraction, the particle shape in combination with the intrinsic thermal conductivity of the filler has the greatest influence on the thermal conductivity of the composite.     

Thermal conductivity of carbon nanotubes and their polymer nanocomposites: A review

Thermally conductive polymer composites offer new possibilities for replacing metal parts in several applications, including power electronics, electric motors and generators, heat exchangers, etc., thanks to the polymer advantages such as light weight, corrosion resistance and ease of processing. Current interest to improve the thermal conductivity of polymers is focused on the selective addition of nanofillers with high thermal conductivity. Unusually high thermal conductivity makes carbon nanotube (CNT) the best promising candidate material for thermally conductive composites. However, the thermal conductivities of polymer/CNT nanocomposites are relatively low compared with expectations from the intrinsic thermal conductivity of CNTs. The challenge primarily comes from the large interfacial thermal resistance between the CNT and the surrounding polymer matrix, which hinders the transfer of phonon dominating heat conduction in polymer and CNT.This article reviews the status of worldwide research in the thermal conductivity of CNTs and their polymer nanocomposites. The dependence of thermal conductivity of nanotubes on the atomic structure, the tube size, the morphology, the defect and the purification is reviewed. The roles of particle/polymer and particle/particle interfaces on the thermal conductivity of polymer/CNT nanocomposites are discussed in detail, as well as the relationship between the thermal conductivity and the micro- and nano-structure of the composites.     

Thermally conductive nylon 6,6 and polycarbonate based resins. I. Synergistic effects of carbon fillers

Increasing the thermal conductivity of typically insulating polymers, such as nylon 6,6, opens new markets. A thermally conductive resin can be used for heat‐sink applications. This research focused on performing compounding runs followed by injection molding and thermal conductivity testing of carbon filled nylon 6,6 and polycarbonate based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a milled pitch‐based carbon fiber. For each polymer, conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 2³ factorial design and a complete replicate in each polymer. The objective of this article was to determine the effects and interactions of each filler on the thermal conductivity properties of the conductive resins. From the through‐plane thermal conductivity results, it was determined that for both nylon 6,6 and polycarbonate based resins, synthetic graphite particles caused the largest increase in composite thermal conductivity, followed by carbon fibers. The combination of synthetic graphite particles and carbon fiber had the third most important effect on composite thermal conductivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 112–122, 2003     

Thermal Conductivity of Platelet-Filled Polymer Composites

Platelet-shaped particles of similar size and shape were investigated as fillers for improving the thermal conductivity of polymer–ceramic composite materials. The conductivities of composites filled with hard, stiff ceramic particles exceeded 3.5 W·(m·K)⁻¹, or >20 times the conductivity of the polymer matrix, and were shown to be almost independent of the intrinsic filler conductivity range of 33–300 W·(m·K)⁻¹. In contrast, the thermal conductivity of composites filled with soft, platelet-shaped BN fillers reached over 13 W·(m·K)⁻¹. A mechanism is proposed whereby deformation of the soft filler particles provides improved particle-to-particle connectivity and allows greater packing density, resulting in the ability to achieve much higher conductivity than is possible for hard and stiff particles of similar initial morphology. Experimental results are discussed in light of various thermal conductivity prediction models in the literature.     

充填时间及材料性质对注射压力的影响

本文介绍用数值模拟方法模拟注塑成型过程充填时间及材料性质对注射压力的影响，并以实实详细讨论了各因素对注射压力影响的原因，给出出充填时间的估算公式。     

聚合物/新型导热填料复合电介质的研究进展

综述了非常规新型导热粒子如纳米金刚石、碳化物、铁电陶瓷及其他无机功能粒子及其填充聚合物电介质的最新研究进展,重点探讨了新型导热粒子的含量、表面改性、加工方式等对聚合物复合材料的导热及介电性能的影响。介绍和分析了基于有机分子晶体为连续声子传递通路改性聚合物导热性能的研究及机理;在基体树脂内利用无机导热粒子及有机分子晶体可构筑连续的声子导热通路,从而达到降低界面热阻、提高体系热导率的目的。相比传统导热粒子,新型导热粒子在提高绝缘聚合物热导率的同时,还赋予体系其他物理性能如磁性、优良介电性能及储能等性能。     

Mechanical,thermal, and electrical conducting properties of CNTs/bio‐degradable polymer thin films

The objective of this study is to increase mechanical, thermal, and electrical properties of plasticizer free thermoplastic bio polymer, BIOPLAST GS 2189 (BP), a blend of poly lactic acid (PLA) and potato starch. This polymer is highly suitable for sheet molding, film processing; blown film extrusion and injection molding and fully biodegradable. Structural, mechanical, thermal, and electrical properties of these films were manipulated by reinforcement of multiwalled carbon nanotubes (CNTs) in BP. Thin films of various (1–5 wt %) percentages of CNTs/BP were prepared by using a high‐speed spin coating technique. These as‐prepared films are ～60–100 µm in thickness. The thickness measurements of these films were carried out using micrometry and optical microscopy. The maximum tensile strength (200%) and modulus (150%) was observed for 4 wt % loading of CNTs in BP as compared with the neat BP thin film. The X‐ray diffraction results show that the addition of CNTs in BP increases the crystallinity of BP. Electrical conductivity of this film also increased by 48% as compared with the neat BP polymer films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal transport properties of diamond-based nanofluids and nanocomposites

The focus of this work is to examine the effects nanoparticles, in particular nanodiamond, have on the heat transfer of fluids and polymer solids. Sample preparation techniques that provide suitable nanoparticle dispersion in both liquid and solid samples are discussed. Liquid suspensions are characterized by measuring particle size distributions and liquid viscosities; heat transfer properties are qualitatively compared via an ad-hoc thermal transport test setup. Polymer samples are visually characterized to ensure nanoparticle dispersion and thermal conductivity is measured using a flash lamp technique.     

耐高温高导热环氧树脂／玻纤／BN复合材料的制备

以4,4-二氨基二苯砜（DDS）和内亚甲基四氢邻苯二甲酸酐（NA）为复配固化剂,采用高温模压成型法制备耐高温高导热环氧树脂／玻纤／氮化硼（BN）复合材料。探讨了BN用量和偶联剂处理对复合材料冲击强度、导热性能和电阻率的影响。结果表明：当nDDS：nNA=3：1时,复合材料的耐热性能最佳。当BN质量分数为8％时,复合材料的冲击强度最高;导热性能随BN用量的增加而增加,当BN用量为15％时,热导率为0．7560W／（mk）,此时复合材料仍保持较高的体积、表面电阻率;当BN填充量为一定值时,偶联剂处理使冲击强度和导热性能得到进一步提高。     

钴基自修复聚酰胺导电高分子材料的制备与性能

以二聚脂肪酸、二乙烯三胺、尿素等为原料制备室温自修复型聚酰胺。通过溶液水热法制备导电单质钴颗粒,并采用纳米复合工艺将导电单质钴颗粒掺杂入自修复聚酰胺体系中,经高温模压制得一种新型钴基自修复聚酰胺导电高分子材料。采用傅里叶变换红外光谱仪、X射线衍射仪、扫描电子显微镜等仪器对单质钴和自修复聚酰胺进行结构表征。系统研究了自修复聚酰胺的自修复能力及抗溶胀性能,以及自修复导电高分子材料的导电和自修复性能。结果表明,所制备的单质钴平均粒径为3.43μm,且表面粗糙易于与聚酰胺基体复合;自修复聚酰胺基体在室温下的自修复次数可达20余次;当交联剂尿素用量为6.6 g/20 g二聚脂肪酸或交联温度为145℃时,自修复聚酰胺对水、碱溶液和油具有较好的综合抗溶胀性能。当单质钴质量分数达到50%后,自修复导电高分子材料的导电率发生突变,导电能力大幅提升;单质钴的加入降低了材料的自修复能力,但单质钴质量分数为50%的材料在室温下的自修复次数仍可达10余次。由于这种材料同时具有较好的导电性能和自修复性能,有望应用于可穿戴装备、电子器件等领域。     

LDPE/PEG插层剥离改性氮化硼导热复合材料的制备及其性能

以聚乙二醇(PEG)为插层剂,通过机械球磨法制备了PEG插层剥离改性氮化硼.以低密度聚乙烯(LDPE)为基体,PEG插层剥离改性氮化硼为导热填料,采用双辊开炼、压片成型制备LDPE/PEG插层剥离改性氮化硼导热复合材料,研究了改性氮化硼用量及粒径对复合材料导热性能、力学性能和电绝缘性能的影响.结果表明:随着PEG插层剥...     

EFFECTIVE THERMAL CONDUCTIVITY OF BINARY MIXTURES AT HIGH SOLID TO GAS CONDUCTIVITY RATIOS

The effective thermal conductivity of single size and binary mixtures of packed particle beds with stagnant gas at high solid/gas conductivity ratios is determined by a deterministic, unit cell approach. The model results are shown to be in good agreement with experimental data for various gas pressures and solid to gas thermal conductivity ratios up to 1300. A set of correlations for effective conductivity of binary mixtures as a function of gas pressure and particle size is derived. The effect of particle swelling on the effective conductivity of binary mixtures is studied by performing a parametric study of the contact area between the particles     

PB-1/BN导热复合材料的制备及性能研究

以聚丁烯-1(PB-1)为基体,二维片状氮化硼(BN)为导热填料,采用模压成型的方法制备了PB-1/BN导热复合材料。研究了BN用量对PB-1/BN导热复合材料导热性能、力学性能、流变性能以及结晶性能的影响。结果表明:BN的加入使复合材料的导热性能明显提高,当BN用量为50%时,复合材料的导热系数达到1.28 W/(m·K),与纯PB-1相比提高了266%;随着BN用量的增加,复合材料的力学性能明显下降;同时,其结晶温度和结晶度也有不同程度降低。     

Shear-controlled electrical conductivity of carbon nanotubes networks suspended in low and high molecular weight liquids

Controlling the electrical conductivity is a critical issue when processing material systems consisting of an insulating matrix filled with conductive particles. We provide experimental evidence that given shear rates result in specific conductivity levels in such different systems as high-viscosity carbon nanotube/polymer melt or low-viscosity carbon nanotube/epoxy fiber suspensions. The steady-state conductivities are independent of the initial state of the dispersion. The observed behavior is modeled phenomenologically by the competition between build-up and destruction of conductive filler network. A particle-level simulation of flowing fiber suspension also reflects the observed behavior. Our results show that properties of particulate suspensions can be controlled by steady shear. They should be considered to obtain reproducible properties in shear-based processing technologies as injection molding or resin transfer molding.     

多孔陶瓷热导率的影响因素及其有效热导率的数值计算方法

多孔陶瓷因具有孔隙率高、体积密度小、比表面积大等独特的表面物理特性而被广泛应用于保温材料、炉膛材料、热障涂层材料、高温烟气过滤材料等,研究多孔陶瓷导热机制并给出其有效热导率的计算方法既是重点又是难点。本文总结了国内外研究的多孔陶瓷热导率的影响因素,概述了多孔陶瓷有效热导率的计算方法,并重点分析了不同显微结构的不同计算方法。针对不同的应用领域对材料热导率的不同要求,提出通过控制显微结构控制热导率是今后多孔陶瓷热导率研究得发展趋势。     

Advances in Epoxy/Graphene Nanoplatelet Composite with Enhanced Physical Properties: A Review

In this review, development from graphene nanoplatelet, that is, comprised of short bulk of single layer graphene, into modified-polymer/graphene nanoplatelet composite is presented. Preparation methods of graphite, graphene, and graphene nanoplatelets have also been discussed. Graphene nanoplatelet and modified graphene nanoplatelet commend unique properties to composites such as excellent thermal and electrical conductivity as well as mechanical and barrier properties. Graphene nanoplatelet fabrication techniques by solution mixing, melt blending, and in situ polymerization are also discussed. Excellent dispersion of nanoplatelets in polymer/graphene nanoplatelet depends upon the selection of suitable fabrication technique. Moreover, the corresponding significance, exploitation, challenges, and future aspect of polymer/graphene nanoplatelet-based material is overviewed.     

Properties,environmental stability,and molding characteristics of polyphenylene sulfide

Polyphenylene sulfide is a new engineering plastic characterized by a unique combination of useful environmental, mechanical, and flame resistant properties. This paper presents a variety of new developments in molding methods and long term properties of polyphenylene sulfide. Optimum conditions for fabrication by injection molding, compression molding, and free sintering techniques are described along with a comprehensive tabulation of mechanical, factional, and electrical properties of various filled and unfilled compositions. The effect of injection molding conditions and post-treatments, such as annealing, on mechanical behavior is discussed. Long term stability of molded specimens of the polymer to a variety of chemical environments as well as oven aging studies are reported. The significance of these properties is illustrated by a discussion emphasizing new applications for various compositions based on polyphenylene sulfide.     

聚丙烯/鳞片石墨导热复合材料的制备及性能

以聚丙烯(PP)为基体,鳞片石墨(FG)为填料,通过添加偶联剂、开炼机混炼、模压成型的方法,制备了具有较高热导率和优良力学性能的PP/FG导热复合材料。考察了硅烷偶联剂的品种及用量、FG的粒径及含量对复合材料热导率和力学性能的影响。结果显示,使用偶联剂处理的FG对复合材料的力学性能具有一定的增强作用,但是材料的热导率降低;当KH 550添加量为FG含量的1%时,材料的力学性能最好;随着FG粒径的增大,材料的热导率明显提高,力学性能相应下降,粒径为17μm的FG与148μm的FG制备的复合材料相比,热导率提高了52.3%,拉伸强度和弯曲强度分别由34.4 MPa和51.5 MPa下降到25.1 MPa和43.0 MPa;随着FG含量的增加,材料的热导率增大,当17μm的FG含量为70%时,材料的热导率是纯PP的22.1倍,拉伸弹性模量和弯曲弹性模量也随之增大,断裂拉伸应变和断裂弯曲应变减小,拉伸强度和弯曲强度先减小后增大,并且在FG含量为20%时降到最低。