氮化硼/石墨烯共混对环氧树脂复合材料导热性和形状记忆效应的影响

采用不同摩尔比的熔融氢氧化钠和氢氧化钾剥离六方氮化硼。分别利用原子力显微镜、扫描电子显微镜和透射电子显微镜观察剥离效果发现,氢氧化钠和氢氧化钾摩尔比为2∶1时,氮化硼被剥离成4个原子层的氮化硼纳米片,剥离效果较好。为了提高环氧树脂的导热性,研究了不同质量比的氮化硼纳米片(BNNS)和石墨烯(Gr)混合物对其导热性能的影响。实验结果表明,BNNS和Gr混合物对环氧树脂导热性的影响优于单一的BNNS和Gr。当m(BNNS)∶m(Gr)=1∶4时,环氧树脂的导热系数最高,从纯环氧树脂的0.22 W/(m·K)增加到0.42 W/(m·K)。同时,该混合物还改善了环氧树脂的形状记忆效果,当m(BNNS)∶m(Gr)=1∶4时,复合材料的形状回复率可达到100%;70℃时,纯环氧树脂的形状回复时间为30 s,复合材料的形状回复时间缩短为4 s。     

非共价改性石墨烯的制备及环氧树脂复合材料导热性能

采用非共价键表面修饰制备了聚乙烯吡咯烷酮（PVP）改性的石墨烯（GR@PVP）,通过共混方式将其作为填料与环氧树脂（EP）复合得到了不同填充量的EP/GR复合材料。红外光谱和热重分析结果表明,聚乙烯吡咯烷酮成功接枝到石墨烯表面。动态力学热分析和热性能测试结果表明,EP/GR@PVP复合材料的储能模量、玻璃化转变温度和损耗因子峰高度均比EP/GR复合材料有所降低,表明聚乙烯吡咯烷酮增强了环氧树脂复合材料的柔韧性。采用扫描电子显微镜观察复合材料断面形貌,GR@PVP在环氧树脂中分散均匀,且与基体相容性好。当填料质量分数为2.0%时,EP/GR@PVP复合材料的热导率比纯EP和EP/GR复合材料分别提高了205.3%和52.6%,25℃EP复合材料的表观黏度为13.29 Pa·s,符合电子封装材料对复合材料加工黏度的需求(<20 Pa·s)。其研究为进一步制备高导热、低黏度的电子封装材料提供了一种简便的方法。     

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。     

石墨烯纳米片/环氧树脂复合材料的制备与介电性能研究

以天然鳞片石墨为原料,通过Hummers法制备氧化石墨,微波热解剥离制备出少层数的石墨烯纳米片。以硅烷偶联剂KH-560为改性剂,超声共混制备石墨烯纳米片/环氧树脂复合材料。采用FT-IR和SEM分析样品的微观结构和形貌,测试其介电性能。结果表明,随着石墨烯纳米片添加量的增加,复合材料介电常数呈现先增大后减小的趋势,当石墨烯纳米片含量为0.3%(质量分数)时,介电常数达到最大;石墨烯纳米片对复合材料介电损耗的影响与之相反;偶联改性使复合材料的介电常数增大,介电损耗减小。     

阻燃杂化纳米粒子改性环氧树脂

以甲基丙烯酸DOPO乙酯(HEPO)和甲基丙烯酸缩水甘油酯(GMA)共聚合成了PHEPO-b-PGMA(PHDG)嵌段共聚物,将其接枝于氨基改性的SiO_2纳米粒子表面,获得新型阻燃SiO_2-PHDG核壳结构杂化纳米粒子。将SiO_2-PHDG引入到双酚A型环氧树脂E51中,制备了一系列P,Si含量可调的阻燃改性环氧树脂。采用扫描电镜和透射电镜对SiO_2-PHDG、改性环氧树脂断面及烧蚀后炭层进行形貌分析;动态力学分析、热重分析、差示扫描量热法及极限氧指数(LOI)研究表明,SiO_2-PHDG可使阻燃元素P,Si以"捆绑式"较好地分散在环氧树脂基体中,在较低P,Si含量下表现出优良的协同阻燃效果,当SiO2-PHDG的添加量为8%时,改性环氧树脂的LOI由26.0上升到32.8。此外,添加适量的SiO_2-PHDG可一定程度上提高环氧树脂的热稳定性及力学性能。     

石墨烯/黑磷纳米复合粒子对环氧树脂阻燃与热稳定性能的影响

近年来,具有蜂窝状褶皱片层结构的黑磷(BP)在阻燃高分子复合材料领域展现出潜在的应用前景.本工作采用高能球磨方法制备出石墨烯/黑磷纳米复合粒子(G-BP),以拉曼光谱与X射线衍射表征其结构,并利用极限氧指数(LOI)、UL 94垂直燃烧测试和热重分析探究G-BP含量对环氧树脂基体热稳定性与阻燃性能的影响.结果表明:在环氧树脂中添加2％G-BP,其高温残炭量从14.8％提高至25.3％,LOI提高至25.5％,且UL 94垂直燃烧等级达到V1级;G-BP添加量为5％时,环氧树脂的LOI达27.5％,且UL 94垂直燃烧等级通过V0级.G-BP通过气固双相阻燃协同机理,明显改善了环氧树脂的成炭性与阻燃性.     

氧化石墨烯纳米片/环氧树脂复合材料的制备与性能

氧化石墨烯(GO)是石墨烯重要的衍生物之一,通过氧化和超声波分散制备了GO纳米片/环氧树脂复合材料。采用XRD、拉曼光谱、FTIR和TEM表征了GO纳米片的结构与形貌,研究了GO纳米片用量对GO纳米片/环氧树脂复合材料热稳定性、力学性能及介电性能的影响。结果表明:GO纳米片的加入提高了GO纳米片/环氧树脂复合材料失热稳定性;随着GO纳米片填充量的增加,GO纳米片/环氧树脂复合材料的冲击强度和抗弯性能先提高后降低,其介电常数和介电损耗则先减小后增加。GO纳米片填充量为0.3wt%的GO纳米片/环氧树脂复合材料的失重5%时的热分解温度由纯环氧树脂的400.2℃提高到424.5℃,而冲击强度和弯曲强度分别在GO纳米片填充量为0.2wt%和0.3wt%时达到最大,冲击强度由纯环氧树脂的10.5kJ/m2提高到19.7kJ/m2,弯曲强度由80.5 MPa提高到104.0 MPa。     

氮化硼纳米片的制备及其增强环氧树脂复合材料导热性能的研究进展

随着对新型高导热、高绝缘热界面材料需求的显著增加,具有多种优异性能的环氧树脂(EP)已被广泛用作导热复合材料的基体,然而其固有的低热导率限制了其实际应用.通过向EP中引入具有高导热系数及高绝缘性的氮化硼纳米片(BNNS)可有效弥补EP的缺陷,从而显著提高复合材料的综合性能.基于国内外研究,介绍了BNNS的不同制备方法,...     

三聚氰胺磷酸盐和季戊四醇在EVA中的阻燃研究

研究了三聚氰胺磷酸盐(M P)和季戊四醇(PER)作为膨胀型阻燃剂(IFR)在乙烯-醋酸乙烯酯共聚物(EVA)中的阻燃作用。采用氧指数法和垂直燃烧法研究了M P和PER不同配比对EVA阻燃效果的影响。实验结果表明,M P和PER的配比不同对体系的阻燃有很大影响。在M P和PER总添加量为50%时,M P/PER质量比为2∶1时显示出最好的阻燃效果,阻燃EVA体系氧指数最高,垂直燃烧达到V-0级。采用热分析研究了膨胀型阻燃EVA体系的热分解特性,以及采用激光拉曼光谱等手段对材料燃烧后形成的膨胀炭层进行了表征。     

石墨烯及其复合材料导热性能的研究现状

阐述了单层石墨烯、石墨烯带及石墨烯复合材料的导热性能。介绍了各种测试模型,综述了石墨烯的层数、纵横比、几何结构、边缘粗糙度、衬底耦合作用、温度等因素对其导热性能的影响。提出了石墨烯及其复合材料导热性能可深入研究的方面。     

BN纤维对石墨烯微片/聚丙烯复合材料导热绝缘性能的影响

采用熔融共混法制备BN纤维-石墨烯微片/聚丙烯（BN纤维-GNP/PP）高导热绝缘复合材料,结合有限元模拟、SEM、XRD、导热导电测试结果,探究了BN纤维含量和长度对BN纤维-GNP/PP复合材料导热绝缘性能的影响。结果表明:BN纤维-GNP/PP复合材料中BN纤维含量和长度的增加可增大GNP分布范围,增大BN纤维与GNP的接触概率;在GNP含量为7wt%、100 μm BN纤维含量为20wt%时BN纤维-GNP/PP复合材料的热导率较PP提高了4.2倍,同时电绝缘性略有提高。模拟结果表明,高含量100 μm BN纤维的加入使BN纤维-GNP/PP复合材料导热网络的构建趋于完整,局部热通量较低的区域减少。片状GNP与纤维状BN二相填料的"协同效应",使GNP和BN纤维分别作为"岛"和"桥"形成了一种特殊的"双网络"结构,BN纤维作为高导热"桥"阻隔了相邻GNP间导电通路的形成,从而提高了BN纤维-GNP/PP复合材料的导热绝缘性能。      

纸泥/环氧酚醛树脂复合物与环氧酚醛树脂的阻燃性研究

将含各类阻燃剂加入到环氧酚醛树脂和纸泥/环氧酚醛聚合物中,用UL-94等级燃烧测试法测定体系的燃烧等级,结果表明:TCEP和无机阻燃剂对环氧酚醛树脂有阻燃作用,但卤化和磷酸化的阻燃剂能增强纸浆/环氧酚醛复合材料的阻燃性.用热重分析仪和差示扫描量热仪对复合材料进行热分析研究阻燃机理,结果显示环氧酚醛树脂材料和纸泥/环氧酚醛复合材料的阻燃性取决于本身的热容和热分解行为.     

石墨烯微片/聚丙烯导热复合材料的制备与性能

通过熔融共混法制备了两种不同型号石墨烯微片（GNPs）填加的GNPs/聚丙烯（PP）导热复合材料,研究了GNPs型号（KNG180,KNG150）和含量对其导热性能、密度、结晶性能和热稳定性能的影响。结果表明,KNG180 GNPs/PP复合材料密度高于KNG150 GNPs/PP,同时KNG180对提高聚丙烯结晶度的效果优于KNG150。随着石墨烯微片含量的增加,两种复合材料导热系数均明显增大,而且KNG180填充的复合材料导热性能明显优于KNG150;当KNG180的添加量为60%（质量分数）时,GNPs/PP复合材料的导热系数从纯聚丙烯的0.087 W/（m·K）提高到1.32 W/（m·K）,提高了14倍多。石墨烯微片的加入显著提高了聚丙烯的热稳定性,当KNG180或KNG150的质量分数为10%时,聚丙烯达到最大热失重速率时的温度从345.1 ℃分别提高到374.6 ℃和397.9 ℃,但是当石墨烯微片超过一定含量时,热稳定性会下降。     

无机填料对环氧模塑料导热和阻燃性能的影响

采用两种无机填料Si₃N₄和Al(OH)₃ 复合填充环氧树脂制备了环氧模塑料(EMCs), 研究了两种填料用量及单独添加和复合添加对环氧模塑料导热性能和阻燃性能的影响。研究结果表明, 单独添加Si₃N₄或Al(OH)₃对环氧模塑料导热性能和阻燃性能的影响规律基本一致, 即随着填料含量的增加, 环氧模塑料的导热性能和阻燃性能均有不同程度的提高; 复合添加Si₃N₄和Al(OH)₃对环氧模塑料的导热性能和阻燃性能均起到积极作用, 但是随着填料中Si₃N₄与Al(OH)₃体积比的变化, 材料导热性能与阻燃性能会产生交叉耦合作用。当 填料中Si₃N₄与Al(OH)₃体积比为3∶2, 总体积分数为60%时, 环氧模塑料的导热率可以达到2.15 W/(m·K), 氧指数为53.5%, 垂直燃烧达到UL-94 V-0级。      

Synergistic flame retardancy effect of graphene nanosheets and traditional retardants on epoxy resin

Novel non-toxic halogen-free flame retardants are replacing traditional flame retardants in polymer and polymer matrix composite structures. In this study, graphene nanosheet (GNS) is investigated in combination with traditional layered double hydroxide (LDH), layered rare-earth hydroxide (LRH), and phosphorus-based flame retardant (DOPO) to enhance the flame retardancy of epoxy resin. A synergistic flame retardancy effect is achieved in GNS/LDH and GNS/DOPO systems where combined GNS and LDH increased the viscosity of the epoxy melt, and limited the flame propagation through inhibition of dripping. The limiting oxygen index of epoxy increased from 15.9 to 23.6 with addition of 0.5 wt.% each of GNS and LDH. With the addition of 2.5 wt.% of both GNS and LDH, the total heat release of epoxy resin also reduced from 33.4 MJ/m² to 24.6 MJ/m². The synergistic effect of GNS and DOPO adopted a different mechanism. The addition of 2.5 wt.% of GNS and DOPO reduced the peak heat release rate from 1194 kW/m² to 396 kW/m², and the total heat release rate from 72.5 MJ/m² to 48.1 MJ/m². The synergistic mechanisms of the flame retardants were closely analyzed and correlated with the flame retardant properties.     

Effect of imidazolium phosphate and multiwalled carbon nanotubes on thermal stability and flame retardancy of polylactide

A series of composites based on polylactide (PLA), have been prepared by melt-blending with multiwalled carbon nanotubes (MWNT) and Tri(1-hydroxyethyl-3-methylimidazolium chloride) phosphate (IP) functionalized MWNT (MIP). The morphology, thermal stability and burning behavior of the composites were investigated by Field Emission Scanning Electron Microscopy (FESEM), Thermogravimetric Analysis (TGA) and Cone Calorimeter Test (CCT), respectively. Significant improvement in fire retardant performance was observed for the PLA/MIP composite from CCT (reducing both the heat release rate and the total heat release) and TGA (increasing the char residue) compared to PLA/MWNT. SEM and Raman spectroscopy were utilized to explore the surface morphology and chemical structure of the char residues. It revealed that the catalytic charring effect of IP, the physical crosslinking effect of MWNT, and the combined effect of both IP and MWNT (forming continuous and compact char layers) were very efficient in improving the flame retarding properties of PLA/MIP composite.     

Experiments and modeling for thermal conductivity of graphite nanoplatelets/carbon composites

In this work, the graphite nanoplatelets/carbon composites were fabricated from graphite nanoplatelets and pitch powders by a hot-pressing technology followed by carbonization and graphitization. The XRD and pole figure results show that the incorporation of pitch induces the decrease of size (L_a) and orientation degree of graphitic crystallites, while the in-plane thermal conductivity of graphitized sample is increased with the increasing pitch content up to 6 wt.%, achieving a maximum value of 405 W/m K. The pitch binders are filled into the voids to bridge two or more graphite nanoplatelets particles together to form extra thermal paths, which makes a great contribution to the enhancement of thermal conductivity. A thermal conductivity model for the graphitized composites is constructed based on a bridging mechanism, and the predicted results fit well with the experimental results.     

Enhanced thermal conductivity of nanofluids containing graphene nanoplatelets prepared by ultrasound irradiation

Stable ethylene glycol (EG)-based nanofluids containing graphene nanoplatelets (GnPs) were prepared by intensive ultrasonication without any surfactant. The structural properties of the commercially produced GnPs were confirmed using the nitrogen gas adsorption method, Fourier transform infrared spectroscopy, X-ray diffraction method, Raman spectroscopy, and high-resolution transmission electron microscopy. After ultrasound irradiation, the GnP aggregates were broken into thinner and smaller-sized nanosheets, which is beneficial for a stable dispersion. The ultrasonic-treated GnPs showed a constant value of thermal conductivity enhancement, k/k _o (= 1.127 ± 0.002) at 2 vol% in the temperature range of 10–90 °C. From the analyses of the thermal conductivities of the GnP nanofluids as functions of GnP concentration and temperature, it was concluded that the thermal conductivity increased as the GnP concentration and the temperature increased. Furthermore, the experimentally measured thermal conductivities of the EG-based GnP nanofluids were much higher than the theoretically calculated values based on the Hamilton–Crosser correlation, which is due to higher specific surface area and two-dimensional structures of the GnPs.     

Flame retardancy and thermal properties of epoxy acrylate resin/alpha-zirconium phosphate nanocomposites used for UV-curing flame retardant films

This paper reported the UV-curing flame retardant film, which consisted of epoxy acrylate resin (EA) used as an oligomer, tri(acryloyloxyethyl) phosphate (TAEP) and triglycidyl isocyanurate acrylate (TGICA) used as flame retardant (FR). The flame retardancy and thermal properties of films were reinforced by using alpha-zirconium phosphate (α-Zr (HPO₄)₂H₂O, α-ZrP). The morphology of nanocomposite film was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the organophilic α-ZrP (OZrP) layers were dispersed well in epoxy acrylate resin. Microscale Combustion Calorimeter (MCC), thermogravimetric analysis (TGA) and thermogravimetric analysis/infrared spectrometry (TGA-IR) were used to characterize the flame retardant property and thermal stability. It was found that the incorporation of TAEP and TGICA can reduce the flammability of EA. Moreover, further reductions were observed due to the addition of OZrP. The char residue for systems with or without OZrP was also explored by scanning electron microscopy (SEM).     

Enhanced thermal conductivity in polymer composites with aligned graphene nanosheets

We developed highly aligned graphene nanosheets (GNSs) in epoxy composites with incorporating magnetic GNS–Fe₃O₄ hybrids under a magnetic field with the aim to take full advantage of the high inplane thermal conductivity of graphene. GNS–Fe₃O₄ hybrids were fabricated by a simple coprecipitation method, and their morphology, chemistry, and structure were characterized. GNS–Fe₃O₄ hybrids were found to be homogenously dispersed and well aligned through the direction of the magnetic field in the epoxy matrix, as confirmed by SEM observation and Raman spectra analysis. The resulting epoxy/GNS–Fe₃O₄ composites possessed high thermal conductivity in a parallel magnetic-alignment direction at low GNS–Fe₃O₄ loadings, which greatly outperformed the composites with randomly dispersed bare GNSs. The obtained results indicated that the magnetic alignment of magnetic-functionalized GNSs is an effective way for greatly improving the thermal conductivity of the graphene-based composites.