c-BN对绝缘高导热硅橡胶性能的影响

采用聚二甲基硅氧烷基础胶、含氢硅油交联剂、立方氮化硼(c-BN)导热填料,制备了绝缘高导热硅橡胶;研究了c-BN的不同含量对硅橡胶导热性能、绝缘性能、物理性能的影响。结果表明:填充改性c-BN粉体可以大幅度提高硅橡胶体系的导热性能,在c-BN用量为80%时导热系数为7.16 W/(m·k),热阻为3.39 cm~2K/W;c-BN粉体会降低硅橡胶体系的绝缘性能和力学弹性,但当用量不超过80%时,击穿强度大于6 k V/mm、体积电阻率大于1×1012Ω·cm、硬度小于55、压缩永久变形小于30%,符合实际使用中的绝缘需要,符合产品安装和使用的条件,不易被压碎、压裂而且具有一定弹性。     

改性芳纶/聚苯胺复合导电纤维的制备

以聚对苯二甲酰对苯二胺(简称芳纶,PPTA)纤维为基材,使用环氧氯丙烷(ECP)对PPTA表面进行有机修饰,得到了ECP改性的PPTA纤维(ECP-PPTA),然后使苯胺单体在ECPPPTA表面接枝聚合,制备了ECP-PPTA/PANI复合导电纤维。用傅里叶变换红外分光光度计(FT-IR)、扫描电子显微镜(SEM)、热重分析仪(TGA)及X射线衍射分析仪(XRD)等分析测试方法对ECP-PPTA及ECP-PPTA/PANI复合导电纤维进行了表征。结果表明:PPTA经ECP改性后,PANI成功接枝在PPTA表面,制备的ECP-PPTA/PANI复合导电纤维的电阻率低于PPTA/PANI纤维的,其室温电阻率最低为0.32MΩ·m。     

THIEC改性三聚氰胺甲醛树脂泡沫的制备及其性能表征

首先,采用三-(2-羟乙基)异氰酸脲酯(THIEC)作为增韧剂对三聚氰胺甲醛树脂(蜜胺树脂)进行化学改性,以提高树脂的韧性。然后,将改性蜜胺树脂与表面活性剂、发泡剂、固化剂、成核剂等充分混合搅拌,采用普通热发泡法制得三聚氰胺甲醛树脂泡沫(蜜胺泡沫)。用扫描电子显微镜(SEM)、氧指数仪、万能电子试验机、导热系数仪对蜜胺泡沫的形态结构、阻燃性能、力学性能及热绝缘性能进行了测试和分析。探究了发泡剂、固化剂用量对蜜胺泡沫表观密度及形态的影响。结果表明:当THIEC、发泡剂、固化剂、成核剂的用量依次为蜜胺树脂质量的15%、10%、6%、2%,发泡温度为80℃时,蜜胺泡沫的压缩强度达到150kPa、极限氧指数为34、导热系数为0.027W/(m·K),综合性能良好。     

聚酰亚胺基导热绝缘复合薄膜的研究进展

聚酰亚胺(PI)薄膜作为综合性能最优异的聚合物材料之一,已经被广泛应用于各类微电子器件。随着电子元器件的功率密度急剧增加,热积累问题已经成为制约其发展的瓶颈。具有高导热性能的PI绝缘薄膜材料被认为是解决上述热积累问题的有效方法之一。由于PI薄膜的本征导热性能较差,近年来,国内外研究学者在提高PI薄膜导热性能方面做了大量工作。本文从阐述热量在PI薄膜中的传输机理出发,概述了近年来导热PI绝缘薄膜的研究进展与发展现状,重点讨论了绝缘导热型填料、导电导热型填料以及三维导热骨架等增强PI绝缘复合薄膜导热性能的策略,最后对PI基导热绝缘复合薄膜研究进展和未来可能的发展趋势进行了总结和展望。     

勃姆石纤维增强二氧化硅气凝胶的制备及性能

以六水合氯化铝为铝源, 通过水热法制备勃姆石纤维; 以甲基三甲氧基硅烷和正硅酸乙酯为硅源共前驱体, 采用溶胶-凝胶法进而常压干燥制备了勃姆石纤维掺杂的二氧化硅复合气凝胶; 探究了勃姆石纤维的掺杂量对复合气凝胶性能的影响. 当勃姆石纤维的掺杂量(质量分数)为1%时, 气凝胶的机械性能最好, 能够承受17.1%的压缩应变, 最大压缩强度为1.12 MPa, 压缩模量高达2.57 MPa, 复合气凝胶在150 ℃仍然具有较低的导热系数(0.0670 W·m^?1·K^?1). 勃姆石纤维能够一定程度地抑制二氧化硅颗粒在高温下的烧结和相转变, 对二氧化硅气凝胶的耐高温性能有显著的提升作用, 复合气凝胶在1100 ℃高温热处理后, 仍能保持良好的隔热性能和较高的机械强度.     

六方氮化硼/聚合物导热复合材料研究进展

随着电子技术快速的发展,聚合物材料自身较低的热导率已不能满足现代电子器件的散热需求,因此提高聚合物热导率,实现高效率的传热具有重要意义。六方氮化硼(h-BN)具有良好的高电击穿强度,导热性能、介电性能、低吸湿率、高温耐氧化等诸多特性,是制备低介电常数、低介电损耗和高导热聚合物的理想填料。本文分别从目前制备BNNSs的主要方法及提高BN复合材料热导率的不同思路两个方面,综述了以六方氮化硼(h-BN)为填料的导热聚合物复合材料的研究现状。     

LaNiO3/Pd复合薄膜电极材料在碱性溶液中的电化学行为研究

用射频磁控溅射法在Si(111)衬底上沉积制备金属Pd膜、LaNiO3单层膜和Pd/LaNiO3复合薄膜,利用XRD,SEM,EDS能谱、四元探针和电化学方法系统研究了退火处理和表面覆Pd对Pd/LaNiO3复合薄膜电极的相组织结构、表面形貌、电学以及电化学储氢行为的影响。结果表明,700℃退火1 h后,LaNiO3薄膜具有结晶度较佳的钙钛矿型菱方结构组织和最小的电阻率(0.79 mΩ·cm),退火温度高于800℃后,LaNiO3菱方型结构组织开始分解,电阻率增加。LaNiO3薄膜在空气中退火后其表面化学吸附氧转变为晶格氧,导致LaNiO3薄膜氧元素含量明显增加。电化学测试结果表明,在碱液中金属Pd膜具有良好的析氢电催化活性和较好的电化学储氢性能,其最大放电容量为130 mAh·g-1。退火态LaNiO3单膜电极放电容量很小(27 mAh·g-1),当表面覆Pd后退火态LaNiO3/Pd复合薄膜电极放电容量增加至181 mAh·g-1,扣除其表面Pd膜吸氢容量后LaNiO3薄膜电极的实际放电容量最高达到400 mAh·g-1。LaNiO3表面镀Pd后能极大改善和提高LaNiO3薄膜电极的电催化活性和电化学储氢容量。     

静电纺丝复合反渗透膜的改性制备与脱盐性能

利用静电纺丝技术在无纺布上制备PET纳米纤维膜, 并用交联壳聚糖对其进行改性得到壳聚糖改性纳米纤维复合膜. 以间苯二胺(MPD)和均苯三甲酰氯(TMC)为单体, 采用界面聚合法在壳聚糖改性纳米纤维复合膜的表面制备聚酰胺分离层, 得到新型静电纺丝纳米纤维基复合反渗透膜. 新型复合反渗透膜具有典型的聚酰胺复合反渗透膜的表面脊-谷结构. 从膜的表面形貌、 亲水性、 分离性能等3个方面对水相MPD溶液中阴离子表面活性剂十二烷基苯磺酸钠(SDBS)的含量对膜结构和性能的影响进行了系统研究. 结果表明, SDBS的含量对膜形态结构的均匀性和亲水性有一定影响, 且随着SDBS含量的增加, 膜的脱盐率先增大后减小, 而通量小幅度上升后, 先减小后增大, 呈现规律性变化.     

形状记忆聚偏氟乙烯/丙烯酸酯/碳纳米管纳米复合材料的导电及导热性能

利用聚偏氟乙烯(PVDF)微小结晶的物理交联点作用,制备了形状记忆性能优异的聚偏氟乙烯/丙烯酸酯聚合物(PVDF/ACM)共混材料,为提高其导电及导热性能,于其中引入了碳纳米管(CNT),系统研究了PVDF/ACM/CNT三元体系纳米复合材料的导热及导电性能。结果表明,碳纳米管在PVDF/ACM体系中分散均匀;在基本保持其形状记忆性能的前提下,碳纳米管的加入使材料导热性能及导电性能有较大程度的提高:质量分数为4%的CNT使材料25℃的电阻值降低至5000Ω/square,导热系数提高至0.157 W/(m·K)。     

抗污染PVA/PVDF电纺纳米纤维复合超滤膜的制备及过滤性能

以聚对苯二甲酸二醇酯(PET)无纺布为基底,聚偏氟乙烯(PVDF)纳米纤维为支撑层,聚乙烯醇(PVA)纳米纤维膜为分离层,采用静电纺丝法制备超滤膜,并用水/丙酮混合溶液对复合纳米纤维膜表面进行溶液处理,再加入戊二醛交联改性得到致密分离层.采用扫描电子显微镜(SEM)和红外光谱(FTIR)表征了复合超滤膜的表面,用水接触角(WCA)表征复合超滤膜的亲水性.在0.02 MPa恒压下死端过滤油/水乳液,测试复合超滤膜的过滤性能.结果表明,最优条件下制备的复合超滤膜死端过滤油/水乳液的通量为(42.50±4.78)L/(m~2·h),截留率达到(95.72±0.33)%;循环使用5次后,依然具有较好的过滤性能,常压下死端过滤复合超滤膜的纯水通量为(3469±28)L/(m~2·h).     

Electric-Field-Induced Alignment of Functionalized Carbon Nanotubes Inside Thermally Conductive Liquid Crystalline Polyimide Composite Films

The positive liquid crystals, 4′-heptyl-4-biphenylcarbonitrile (7CB), are used to functionalize carbon nanotubes (LC-CNT), which can be aligned in the liquid crystalline polyimide (LC-PI) matrix under an alternating electric field to fabricate the thermally conductive LC-CNT/LC-PI composite films. The efficient establishment of thermal conduction pathways in thermally conductive LC-CNT/LC-PI composite films with a low amount of LC-CNT is achieved through the oriented alignment of LC-CNT within the LC-PI matrix. When the mass fraction of LC-CNT is 15 wt %, the in-plane thermal conductivity coefficient (λ_∥) and the through-plane thermal conductivity coefficient (λ_⊥) of the LC-CNT/LC-PI composite films reach 4.02 W/(m ⋅ K) and 0.55 W/(m⋅K), which are 90.5 % and 71.9 % higher than those of the intrinsically thermally conductive LC-PI films respectively, also 28.8 % and 5.8 % higher than those of the CNT/LC-PI composite films respectively. Meanwhile, the thermally conductive LC-CNT/LC-PI composite films also possess excellent mechanical and heat resistance properties. The Young's modulus and the heat resistance index are 2.3 GPa and 297.7 °C, respectively, which are higher than the intrinsically thermally conductive LC-PI films and the thermally conductive CNT/LC-PI composite films under the same amount of CNT.     

石蜡/膨胀石墨/石墨烯复合相变储热材料的制备及性能

以石蜡(PA)作为相变储热材料、 膨胀石墨(EG)作为主导热材料和支撑材料, 石墨烯气凝胶(GA)作为导热增强材料和辅支撑材料制备了PA/EG/GA复合相变材料, 研究了GA添加量对复合相变材料相变温度、 相变潜热、 导热性能以及循环稳定性的影响. 结果表明, 所制备的80%PA-17%EG-3%GA复合相变材料导热性能良好, 循环稳定性出色. 与80%PA-20%EG复合材料相比, 该材料的相变温度、 相变潜热以及循环稳定性无明显变化, 但导热系数由4.089 W/(m·K)提升到了5.336 W/(m·K), 显示出良好的应用前景.     

Multifunctional Thermally Conductive Composite Films Based on Fungal Tree-like Heterostructured Silver Nanowires@Boron Nitride Nanosheets and Aramid Nanofibers

Thermal conduction for electronic equipment has grown in importance in light of the burgeoning of 5G communication. It is imperatively desired to design highly thermally conductive fillers and polymer composite films with prominent Joule heating characteristics and extensive mechanical properties. In this work, “solvothermal & in situ growth” method is carried out to prepare “Fungal tree”-like hetero-structured silver nanowires@boron nitride nanosheet (AgNWs@BNNS) thermally conductive fillers. The thermally conductive AgNWs@BNNS/ANF composite films are obtained by the method of “suction filtration self-assembly and hot-pressing”. When the mass fraction of AgNWs@BNNS is 50 wt%, AgNWs@BNNS/ANF composite film presents the optimal thermal conductivity coefficient of 9.44 W/(m ⋅ K) and excellent tensile strength of 136.6 MPa, good temperature-voltage response characteristics, superior electrical stability and reliability, which promise a wide application potential in 5G electronic devices.     

Influence of graphene reinforcement in conductive polymer: Synthesis and characterization

Lightweight conductive polymers are considered for lightning strike mitigation in composites by synthesizing intrinsically conductive polymers (ICPs) and by the inclusion of conductive fillers in insulating matrices. Conductive films based on polyaniline (PANI) and graphene have been developed to improve through‐thickness conductivity of polymer composites. The result shows that the conductivity of PANI enhanced by blending polyvinylpyrrolidone (PVP) and PANI in 3:1 ratio. Conductive composite thin films are prepared by dispersing graphene in PANI. The conductivity of composite films was found to increase by 40× at 20 wt% of graphene inclusion compared with PVP and PANI blend. Fourier‐transform‐infrared (FTIR) spectra confirmed in situ polymerization of the polymer blend. The inclusion of graphene also exhibits an increase in Tg by 21°C. Graphene additions also showed an increase in thermal stability by approximately 148°C in the composite films. The mechanical result obtained from DMA shows that inclusion of graphene increases the tensile strength by 48% at 20 wt% of graphene reinforcement. A thin, highly conductive surface that is compatible with a composite resin system can enhance the surface conductivity of composites, improving its lightning strike mitigation capabilities.     

Electrically conductive nanocomposites with segregated structure based on poly(vinylidene fluoride-<Emphasis Type="Italic">co</Emphasis>-tetrafluoroethylene) and reduced graphene oxide

An approach was described to obtaining polymer composites with segregated structure that have high electrical conductivity at low concentrations of an electrically conductive filler. According to this approach, thin layers of electrically nonconductive nanodispersed graphene oxide are applied to the surface of polymer particles and conduction is produced by heat and chemical treatments. Hot pressing of the modified powder leads to combination of layers of the graphene-like filler to form a single electrically conductive network. For the first time, reduction of graphene oxide on the surface of polymer particles with hydrazine vapor at room temperature was performed. Comparison of the electrical conductivities of composites obtained by the thermal and chemical methods of graphene oxide reduction showed that the chemical reduction method gives composites with higher conductivities than the thermal method does. The maximum conductivity (0.5 S/m) was reached in a composite containing 0.6% chemically reduced graphene oxide.     

兼具导热和自修复功能的聚合物复合材料

针对聚合物复合材料存在的结构受损导致导热和力学强度降低的问题,提出利用导热填料增强自修复聚合物,实现导热性能和力学强度的快速修复.通过对双(3-氨丙基)封端的聚二甲基硅氧烷(H2N-PDMS-NH2)进行端基改性,得到脲基嘧啶酮(UPy)双封端的聚二甲基硅氧烷(UPy-PDMS-UPy),于60°C下20 h后拉伸强度修复效率可达86.6%.进一步填充羟基化氮化硼(mBN)制备兼具自修复功能的导热复合材料,研究发现mBN的填充导致复合材料强度提高但韧性降低,对导热性能和自修复功能分别起积极和不利影响.当mBN含量为30 wt%时,热导率高达2.579 W·m-1·K-1,于60°C下40 h后拉伸强度修复效率达82.0%.红外热像仪显示,损伤处接触10 h后,m BN-30/UPy-PDMS-UPy上表面温度接近初始温度,展现出导热通路的修复特征,实现导热与自修复功能的兼备.     

Study on insulating thermal conductive BN/HDPE composites

Thermal conductivity of boron nitride (BN) reinforced high density polyethylene (HDPE) composites was investigated under a special dispersion state of BN particles in HDPE, i.e., BN particles surrounding HDPE matrix particles. The results indicated that the special dispersion of BN in matrix gives the composites high thermal conductivity at low filler content; moreover, the smaller BN particles can more easily form conductive chains of filler compared to the larger filler particles. Examining the dependence of electrical insulation and mechanical properties of the composites on BN content demonstrated that the reinforced composites containing 30% by volume of filler has good electrical insulation and mechanical properties.     

原位化学氧化聚合制备聚苯胺/丝素复合导电膜

采用原位化学氧化聚合方法在蚕丝丝素蛋白膜表面生长聚苯胺,制备得到表面均匀覆盖导电聚合物的复合导电丝素膜,其电导率约为3×10^-2S/cm。纤维表面与导电聚合物的相互作用改善了原丝素膜的耐热性能,但并未降低其力学性能。     

Thermal conductive PS/graphite composites

Polystyrene (PS) was compounded with graphite that possesses high thermal conductivity and layer structures, and the PS/graphite thermal conductive nano‐composites were prepared. Thermal conductivity of PS improved remarkably in the presence of the graphite, and a much higher thermal conductivity of 1.95 W/m K can be achieved for the composite with 34 vol% of colloidal graphite. The Maxwell‐Eucken model and the Agari model were used to evaluate the thermal conductivity of the composites. For the purpose of improving the interfacial compatibility of PS/graphite, realizing the exfoliation and nano‐dispersion of graphite in the PS matrix, three intercalation methods, including rolling intercalation, solvent intercalation, and pan milling intercalation, were applied to prepare the composites, and the morphologies, thermal conductivities, and mechanical properties of the composites were investigated. It should be noted that the one prepared by pan milling intercalation not only had excellent thermal conductivity but also much higher mechanical properties, resulting from a high degree of layer exfoliation of the graphite, the formation of the chain structure agglomerates of the graphite, and the creation of more conductive paths under the strong shear stress of pan milling. Copyright © 2008 John Wiley & Sons, Ltd.     

Facile synthesis of microfibrillated cellulose/organosilicon/polydopamine composite sponges with flame retardant properties

Cellulose composite sponges with good mechanical, heat-insulating and flame retardant properties were constructed by a facile method. Simultaneous polymerization of dopamine and hydrolysis of organosilicon in the suspension of microfibrillated cellulose could provide the stiffness and flame ratardancy of the composite sponges. The hybrid sponges had low density (15.1–28.5 mg/cm³) and desirable compression strength (76.6–135.8 kPa). Scanning electron microscopy (SEM) and thermal conductivity tests revealed that the sponges are composed of a three-dimensional cellulosic network and the porous structure endowed them low thermal conductivity [~0.046 W/(m K)]. With the addition of organosilicon (45 wt%) and polydopamine (PDA) (10 wt%), a 456% improvement in BET surface area of the sponge could be achieved. The limiting oxygen index (LOI) of the composite sponge could be as high as 29.5 with 15 wt% PDA and could self-extinguish at once when it was removed from torch. That was owing to the promoted materials carbonization ability of silicon and radical scavenging activity of dopamine.