Research progress of thermally conductive polyimide and its composites
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摘要: 随着电子设备朝着小型化、集成化和多功能化的趋势不断发展,实现电子材料的高导热性能对电子设备的稳定运行和使用寿命至关重要。聚酰亚胺(PI)因其优异的耐热性能和力学性能被广泛应用于热管理领域,然而传统PI的本征导热系数较低,难以满足电子器件的快速散热需求,发展新型高导热PI及PI复合材料成为目前国内外的研究重点。本文从PI分子链结构、分子链取向及分子间相互作用等方面阐述了非晶型与液晶型两类本征型导热PI的制备与性能调控,系统探讨了填料表面修饰、杂化改性、取向设计、三维网络构筑等方法对PI复合材料结构与性能的影响规律,最后对高导热PI及PI复合材料研究中面临的挑战进行了总结与展望。Abstract: With the continuous development of electronic equipment towards miniaturization, integration and multifunction, the high thermal conductivity of electronic materials has become critically significant to ensure the stable operation and service life of electronic equipment. Polyimide (PI) is widely used in the thermal management field because of its excellent heat resistance and mechanical properties. However, the intrinsic thermal conductivity of traditional PI is low, which is difficult to meet the rapid heat dissipation requirements of electronic devices. The development of new highly thermally conductive PI and PI composites has become a research hotspot. This paper introduces the preparation and performance regulation of amorphous polyimides and liquid crystalline polyimides based on the molecular chain structure, molecular chain orientation and molecular interaction of intrinsic thermally conductive PI, and discusses the influence of surface modification, constructing hybrid fillers, orientation design, three-dimensional network structure on the structure and performance of PI composites. Finally, the challenges of highly thermally conductive PI and PI composites are summarized and prospected.
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Key words:
- polyimide /
- thermal conductivity /
- polymer composites /
- intrinsic thermal conduction /
- filler /
- structural design
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图 2 (a) 液晶聚酰亚胺(LC-PI)的合成化学反应;(b) 液晶PI薄膜的低(上)和高(下)固有热导率的机制示意图;(c) 室温下LC-PIIV薄膜的偏光显微镜(POM)图像;(d) LC-PI薄膜的面内导热率λ∥和面外导热率λ⊥值[14]
ODA—4, 4′-diaminodiphenyl ether; TPE-Q—1, 4-bis(4-aminophenoxy)benzene; PI—Polyimide
Figure 2. (a) Synthetic chemical reaction of liquid crystalline polyimide (LC-PI); (b) Schematic diagram of the mechanisms for low (up) and high (down) intrinsic thermal conductivities of liquid crystal PI; (c) Polarizing microscope (POM) images of LC-PIIV films at room temperature; (d) In-plane thermal conductivity λ∥ and out-plane thermal conductivity λ⊥ of LC-PI films[14]
图 3 (a) EPPOSS@Gh-BN和PI/EPPOSS@Gh-BN复合薄膜的制备示意图;纯PI (b)和PI/EPPOSS@Gh-BN复合材料(c)的扫描电镜图像; 含不同填料的PI复合薄膜的拉伸强度(d)、介电损耗(e)、导热系数和热扩散系数(f)[27]
Figure 3. (a) Schematic diagram of the synthesis of EPPOSS@Gh-BN and PI/EPPOSS@Gh-BN nanocomposite film; SEM micrographs of pure PI (b) and PI/EPPOSS@Gh-BN composites (c); Tensile strengths (d), dielectric losses (e), thermal conductivity and thermal diffusivity (f) of the PI nanocomposite films with different fillers[27]
图 4 (a) 银-聚多巴胺-六方氮化硼(h-BN@Ag)填料和PI复合膜的制备示意图;(b) PI复合薄膜的热传输模型;1wt%h-BN@Ag (c) 和10wt%h-BN@Ag (d)填充含量的h-BN@Ag/PI复合薄膜的扫描电镜图;(e) 纯PI和h-BN@Ag/PI复合薄膜的热重曲线[32]
Figure 4. (a) Schematic illustration of the preparation of silver-polydopamine-hexagonal boron nitride (h-BN@Ag) fillers and PI composite films; (b) Heat transport models of the PI composite films; SEM images of h-BN@Ag/PI composite films filled with 1wt%h-BN@Ag (c) and 10wt%h-BN@Ag (d) filler contents; (e) TGA curves of pure PI and h-BN@Ag/PI composite films[32]
DMAc—N, N-dimethylacetamide; T5—Temperatures at the mass loss of 5%; T30—Temperatures at the mass loss of 30%; R700—Residual rate at 700 oC
图 5 (a) 石墨烯(GF)和移动磁场感应下的石墨烯-氮化硼/聚酰亚胺(GF-BN/PI(MF))复合膜的制备示意图;(b) GF-BN/PI(MF)复合薄膜的运动磁场感应和导热机制示意图;(c) 纯PI和填充含量为30wt%的不同PI复合膜的导热性能;(d) 30wt%GF-BN/PI(MF)薄膜撕裂断裂表面的扫描电镜图像[43]
Figure 5. (a) Schematic illustration of preparation of the graphene (GF) and the graphene-boron nitride/polyimide under moving magnetic field induction (GF-BN/PI(MF)) composite film; (b) Schematic diagram of the moving magnetic field induction and heat conduction mechanism of the GF-BN/PI(MF) composite film; (c) Thermal conductivity of the pure PI and the different PI composite films with 30wt% filler content; (d) SEM images of the fracture surface of 30wt%GF-BN/PI(MF) film[43]
图 6 (a) PI/GF、PI/AlN和PI/GF/AlN复合材料的热流传递模型;填料含量对PI/GF/AlN复合材料的热扩散系数和导热系数的影响:(b) AlN;(c) GF[49];(d) PI-BN-B复合薄膜的力学化学辅助制备及其对BN的影响;(e) 力学化学辅助制备的PI复合膜(PI-BN-B)和原位聚合制备的PI复合膜(PI-BN-S)的面内热导率[20]
Figure 6. (a) Models of the transfer of heat flow in PI/GF, PI/AlN, and PI/GF/AlN composites; Influence of filler content on the thermal diffusivity and thermal conductivity of PI/GF/AlN composites: (b) AlN; (c) GF[49]; (d) Mechanochemical-assisted fabrication of PI-BN-B composite films and effects on BN; (e) In-plane thermal conductivities of PI composite film (PI-BN-B) from mechanochemical-assisted fabrication and the control PI composite film (PI-BN-S) from in-situ polymerization[20]
图 7 (a) ae-BN/PI和h-BN/PI复合材料的结构模型;(b) 在室温下ae-BN/PI和h-BN/PI复合材料的平面内导热率[51];(c) PI复合材料的导热模型示意图,特别是复合材料的声子传输模型示意图(c')和界面态((c''), (c'''));(d) 具有不同填料含量的复合材料的平面内导热率[52]
δ—Distance factor
Figure 7. (a) Structure models of ae-BN/PI and h-BN/PI composites; (b) In-plane thermal conductivity of ae-BN/PI and h-BN/PI composites at room temperature[51]; (c) Schematic diagram of the heat dissipation model for PI composites, specifically, the schematic diagram for phonon heat conduction model of composites (c'), and the interfacial state ((c''), (c''')); (d) In-plane thermal conductivity of composites with different filler contents[52]
图 8 (a) PI/3DSG复合材料的制备工艺;(b) 复合材料的热流模型;(c) 不同填料含量的PI/3DSG复合材料的导热系数和热扩散系数;(d) 纯PI和PI复合材料的导热性能和提升率[41]
SiCNWs—Silicon carbide nanowire; GSs—Graphene sheets; 3DSG—Three-dimensional SiCNWs@GSs
Figure 8. (a) Preparation process of the PI/3DSG composites; (b) Model of heat flow for the composites; (c) Thermal conductivity and thermal diffusivity of PI/3DSG composites with various filler contents; (d) Thermal conductivity and thermal conductivity enhancement of neat PI and PI composites[41]
图 9 (a) PI/CNT@CF复合材料的制备和表征:通过单向冷冻干燥制备PI/CNT@CF气凝胶和热压制备PI/CNT@CF复合材料的示意图;(b) PI/CF和PI/CNT@CF复合材料中热流的平面内传递示意图;(c) 不同填料质量分数的PI/CF和PI/CNT@CF复合材料的平面内导热系数;(d) 纯PI和PI/CNT@CF复合材料在加热过程中的热膨胀系数(CTE)值(温度范围为25~235℃)[55]
Figure 9. (a) Preparation and characterization of PI/CNT@CF composites: Schematic of the preparation of PI/CNT@CF aerogels by the unidirectional freeze-drying and fabrication of PI/CNT@CF composites by hot-pressing; (b) Schematic diagram of the in-plane transfer of heat flow in the PI/CF and PI/CNT@CF composites; (c) In-plane thermal conductivity of PI/CF and PI/CNT@CF composites with different filler mass fractions; (d) Coefficient of thermal expansion (CTE) values of pure PI and PI/CNT@CF composites in the heating process (Temperature range of 25-235℃)[55]
图 10 (a) BNNS及聚酰亚胺/氮化硼/碳纳米管@碳化聚乙烯醇(PI/BNNS/CNT@αPVA)复合膜的制备示意图;(b) BNNS为30wt%的PI/BNNS/CNT@αPVA复合膜的SEM图像;(c) PI及其复合膜的表面温度随时间的变化;(d) PI、PI/BNNS和PI/BNNS/CNT@αPVA膜的红外热图像;(e) PI、PI/BNNS和PI/BNNS/CNT@αPVA膜的热传导机制示意图[62]
Figure 10. (a) Schematic illustration for the exfoliation of BNNS and the fabrication of polyimide/boron nitride/carbon nanotubes@carbonized polyvinyl alcohol (PI/BNNS/CNT@αPVA) composite films; (b) SEM images PI/BNNS/CNT@αPVA films with BNNS of 30wt%; (c) Surface temperature variations of films versus time; (d) Infrared thermal images of PI, PI/BNNS and PI/BNNS/CNT@αPVA films with different BNNS loading; (e) Schematic illustration of heat conduction mechanism of PI, PI/BNNS and PI/BNNS/CNT@αPVA films[62]
DI water—Deionized water; SDS—Sodium dodecyl sulfate; BNNS—Boron nitride nanosheet; BA—Boric acid
图 11 (a) 制备PI/定向BNNSs复合材料的示意图;(b) PI/取向BNNSs纳米复合材料的热流图;(c) PI/定向BNNSs-12.4的扫描电镜断裂图像;(d) 比较PI/取向BNNSs和PI/随机BNNSs复合材料的热导率增强作为BNNSs加载的函数;(e) 纳米复合材料的表面温度随时间的变化[66]
Figure 11. (a) Schematic illustration of preparing PI/oriented BNNSs composites; (b) Diagram of in-plane transfer of heat flow in the PI/oriented BNNSs nanocomposites; (c) SEM fracture images of PI/oriented BNNSs-12.4; (d) Comparison of thermal conductivity enhancement between the PI/oriented BNNSs and the PI/random BNNSs composites as a function of BNNSs loading; (e) Surface temperature variations of nanocomposites versus time[66]
表 1 本征导热聚酰亚胺的导热性能
Table 1. Thermal conductivity of various intrinsic thermally conductive polyimide
类型 化学结构 导热率/(W·(m·K)–1) 参考文献 非晶型聚酰亚胺调控分子链结构 6FDA/TFB/BAPP 0.40 [6] 非晶型聚酰亚胺分子链取向、分子
间相互作用PPD/BIA/BPDA 2.13 [9] 非晶型聚酰亚胺分子链取向、分子
间相互作用ODPA/BAPP 0.98 [10] 非晶型聚酰亚胺分子间相互作用 PMDA/ODA/4NADA 0.58 [12] 液晶型聚酰亚胺调控分子链结构 ODA/TPE-Q/HQDA/PEPA λ∥=2.11, λ⊥=0.32 [14] Notes: FDA—4, 4'-(hexafluoroisopropylidene) diphthalic anhydride; TFB—2, 2'-bis(trifluoromethyl)-benzidine; BAPP—2, 2-bis(4-(4-aminophenoxy)-phenyl) hexafluoropropane; BPDA—3, 3', 4, 4'-biphenyldianhydride; PDA—p-phenylene diamine; PMDA—Pyromellitic dianhydride; PPD—p-phenylenediamine; BIA—2-(4-aminophenyl)-5-amino-benzimidazole; ODPA—4, 4′-oxydiphthalic anhydride; 4NADA—2, 4, 5, 7-tetraamino-1, 8-dihydroxyanthracene-9, 10-dione monomers; PEPA—4-phenylethynyl phthalic anhydride; HQDA—4, 4′-(p-phenylenedioxy)bis[phthalic anhydride]. 表 2 填充型导热聚酰亚胺的导热性能
Table 2. Thermal conductivity of polyimide composites with different fillers
类型 填料 添加量 导热率/(W·(m·K)–1) 参考文献 共价键改性 ODA改性MWCNT 3wt% 0.4397 [23] 共价键改性 EPPOSS改性Gh-BN 0.3wt% 0.36 [27] 非共价键改性 TMN改性LC-GeF 15wt% λ∥=4.21, λ⊥=0.63 [24] 杂化填料 h-BN-ND 40wt% 0.98 [35] 杂化填料 f-MWCNT-g-rGO 40wt% 1.60 [36] 磁取向 PDA改性GF 30wt% λ∥=2.532, λ⊥=0.425 [43] 磁取向 mf-BN 30wt% 1.246 [44] 电取向 h-BN 14.2vol% 0.59 [46] 应力取向 GF/AlN 11wt% 11.19 [49] 应力取向 BN 20wt% 14.7 [20] 真空抽滤 ae-BN 30vol% 6.57 [51] 真空抽滤 h-BN@PDA 20vol% 3.01 [52] 模板法 GWFs 12wt% 3.73 [54] 模板法 3DSG 11wt% 2.63 [41] 模板法 CNT@CF 20wt% 4.25 [55] 静电纺丝法 mBN 30wt% 0.696 [61] 静电纺丝法 BNNS, CNT 30wt% 8.40 [62] 隔离结构 BN 30wt% λ∥=2.81, λ⊥=0.73 [65] 隔离结构 BNNSs 12.4vol% 4.25 [66] Notes: MWCNT—Carbon nanotube; TMN—Polyethylene glycol trimethylnonyl ether; LC-GeF—Graphene fluoride; EPPOSS—Epoxidized polyhedral oligomeric silsesquioxanes; Gh-BN—KH550 modified hexagonal boron nitride; ILFG—Ionic liquid functionalized graphene; h-BN—Hexagonal boron nitride; ND—Nanodiamond; f-MWCNT—Urea functionalized multi-walled carbon nanotubes; rGO—Reduced graphene oxide; First GF in Table 2—Reduced GO/γ-FeOOH/γ-Fe2O3 hybrid nanoparticle; mf-BN—Fe3O4 nanoparticles was attached to the surface of the h-BNs with hydroxyl groups; GF in GF/AlN—Graphene flakes; AlN—Polyhedral aluminum nitride; ae-BN—Polydisperse hexagonal boron nitride; GWFs—Graphene woven fabrics; 3DSG—A rigid three-dimensional structure composed of silicon carbide nanowire@graphene sheets; CNT@CF—Grafted carbon nanotubes onto carbon fiber surface; BNNS—Boron nitride nanosheet; mBN—Micrometer boron nitride. -
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