高分子复合材料导热性能研究

以Al2O3、MgO和BN三种无机填料作为尼龙6(PA6)的导热填料,研究填料的种类、填充量、粒径大小和粒径配比等对复合材料热导率的影响。结果表明:PA6基复合材料的热导率随导热填料填充量的增加而增大,随导热系数大的填料填充量的增加增大较快;导热系数大的填料的粒径对复合材料的导热系数的影响比较明显;导热系数大的填料,不同粒径的复配可以显著提高复合材料的导热系。     

高导热绝缘尼龙复合材料的制备和性能

以尼龙6 (PA6)为基体,采用两种不同粒径的氧化铝(Al203)按1∶1混合后,再与高导热填料氮化铝(AlN)复配成导热填料,采用熔融挤出法制备PA6/Al20JAlN导热绝缘复合材料.研究了复配填料含量为60％时,复配填料中AlN含量对复合材料力学性能、导热性能和结晶性能的影响.采用扫描电子显微镜(SEM)对复合材料的微观形貌进行了表征.结果表明,复合材料的热导率随着复配填料中AlN含量的增加而增大.复合材料的拉伸强度和弯曲强度随复配填料中AlN含量的增加先增大再减小,AlN含量占复配填料的50％时,复合材料拉伸强度和弯曲强度分别达到最大值83.09 MPa和137.14MPa.复合材料的结晶度和熔融温度没有显著变化.扫描电镜显示填料与基体的相容性较好.     

导热尼龙6材料的制备与性能

以氧化铝(Al2O3)和碳化硅(Si C)为导热填料,采用熔融挤出法先制备了氧化铝或碳化硅单独填充导热尼龙6材料,然后再把氧化铝和碳化硅按一定比例复配,制备了复配导热尼龙6材料。研究了复合材料的导热性能、机械性能、流动性、热性能和扫描电子显微镜(SEM)照片。结果表明,复合材料的导热系数随着填料含量的增加而增大。当60%的碳化硅填充PA6材料时,导热PA6材料的导热系数最高在1. 229 W/(m·K);当氧化铝和碳化硅复配时,对导热PA6材料的导热系数提高无明显效果。     

导热硅橡胶的老化性能研究

热老化是影响导热硅橡胶使用寿命的主要因素之一。该文分别采用氧化铝、氮化硼和石墨烯作为导热填料制备导热硅橡胶,研究其热老化性能。通过研究不同导热系数的导热硅橡胶复合材料热氧老化过程中交联密度和导热系数的变化,提出了不同导热系数的样品在热氧老化过程中导热系数变化的机理。     

球形氧化铝填充聚氨酯制备导热塑料

以聚氨酯为基材,球形氧化铝为导热填料,制备了填充型热固性塑料,研究了氧化铝填充量、表面处理对复合材料导热性能的影响,比较了不同粒径氧化铝填充的导热塑料的导热性能,并进行了两者复配研究。结果表明:聚氨酯复合材料的导热系数是导热通道的形成与界面层阻碍效应相互作用的结果;当氧化铝填充总量为600质量份且m(BAK–0100):m(BAK–0300)为1:2,并经过占总填料质量1.5%的KH560改性后,所得材料的导热系数高达2.51 W/(m·K)。     

具有高各向同性导热性能的PA6/Al_2O_3/BN复合材料

以不同粒径的球形氧化铝(α-Al_2O_3)和少量二维氮化硼(BN)为填料,聚酰胺6 (PA6)为基体,通过熔融共混法制备了PA6/Al_2O_3/BN导热复合材料,并使用激光散射仪等对其各向导热性能进行了研究。由于两种填料粒子间的协同作用,复合材料的导热性能相对仅以氧化铝为填料时得到了明显的提升。研究还发现氧化铝粒子能降低BN在垂直于热压方向的取向系数,从而使复合材料导热系数的各向异性指数得到降低,材料在平行于热压方向上(Through-plane)也兼具较好的导热性能。在填料总体积分数为47%时(其中氧化铝为40%、BN为7%),PA6/Al_2O_3/BN复合材料在平行及垂直于热压方向(In-plane)的导热系数最高分别达到了2.32 W/(m·K)和2.90 W/(m·K),较之使用50% Al_2O_3的PA6/Al_2O_3复合材料,其导热系数在各方向上分别提升了26.78%、58.47%。此外,红外热图测试进一步表明了PA6/Al_2O_3/BN复合材料较好的散热性能。     

BN填充PA6基导热绝缘复合材料导热性能研究

以聚酰胺6（PA6）为基体, 氮化硼（BN）作为导热填料,经双螺杆挤出机熔融共混,模压成型制得导热绝缘复合材料。研究了BN含量、粒径、形状和不同BN粒径复配对复合材料导热性能的影响,并研究了BN含量和粒径对复合材料绝缘性能的影响。结果表明,在各种粒径下,复合材料热导率均随BN填充量的增加而增大;在BN粒径为5 μm、填充量为25 %（体积分数,下同）时,复合材料热导率达到1.2187 W/(m·K);在BN填充量相同时,填料粒径对复合材料热导率的影响不是简单的单调规律,呈现50、100 μm时较小,1、5、15 μm时较大,150 μm时最大的规律;片状BN填料比球状BN填料更有利于提高复合材料的热导率;2种不同粒径填料复配所填充的复合材料的热导率大于单一粒径填充的复合材料;5 μm与150 μm粒径BN复配,在填充量为20 %,配比为1:3时,复合材料的热导率最大,达到1.3753 W/(m·K),为纯PA6的4.9倍;在不同BN含量和粒径下,复合材料体积电阻率均能达到10000000000000 Ω·cm以上,满足绝缘性能。     

甲基乙烯基硅橡胶导热复合材料的研究与制备

以甲基乙烯基硅橡胶为基体树脂,不同粒径碳化硅(SiC)和碳纤维(CF)复配作为填料,经开炼后模压硫化成型制得高导热复合材料。利用热流法导热系数测试仪(DRL-II)、扫描电子显微镜(SEM)对复合材料的导热性能、微观结构、力学性能进行了表征。结果表明：碳化硅和碳纤维能够均匀的分散在基体树脂中,不同粒径的碳化硅复配能使复合材料的导热性能进一步提高,导热系数达到1.28w/(m.k)。加入碳纤维不仅能使基体内部形成串联的导热网链,进一步提高基体树脂的导热性能,使复合材料的导热系数达到1.88w/(m.k),同时提高了复合材料的拉伸强度。     

不同粒径氮化硼填充环氧树脂/玻璃纤维

以聚砜改性环氧树脂为基体,通过高温模压制备了环氧树脂/玻璃纤维/氮化硼复合材料,研究了不同粒径及不同氮化硼导热粒子用量对复合材料导热性能、力学性能和电性能的影响。结果表明,大粒径粒子有利于复合材料力学性能的提高,小粒径有利于导热性能的提高;随着氮化硼用量的增加,复合材料的导热性能升高,力学性能呈现先增后降趋势,当氮化硼用量为10 %（质量分数,下同）时,复合材料的冲击强度和弯曲强度均达到最佳,当氮化硼用量为20 %时,复合材料仍保持较好的电性能。     

填料形状对聚酰胺6基复合材料导热性能的影响

首先分别以膨胀石墨(EG)、氮化硼(BN)、氧化铝(Al_2O_3)、氧化锌晶须(T-ZnO_W)为填料,采用熔融共混法制备了聚酰胺6(PA6)基导热复合材料,研究了填料形状对复合材料导热性能的影响;在此基础上,再以EG为主填料,分别与BN、Al_2O_3、T-ZnO_W复配填充改性PA6,考察了复配填料形状、含量对复合材料导热性能的影响。结果表明,片状EG较其他填料对PA6树脂的热导率具有更好的提升效果;复配填料中小粒径填料Al_2O_3有助于打开并进入EG的片层结构,形成更加完善的导热网络,发生协同效应;当复配填料总含量固定为20%(体积分数,下同),BN或Al_2O_3或T-ZnO_W含量分别为7.5%、5%、2.5%时,复合材料的热导率分别达到最大值:3.05、3.10、2.84 W/(m·K)。     

Thermal and electrical properties of aluminum nitride/boron nitride filled polyamide 6 hybrid polymer composites

The effects of boron nitride (BN) and aluminum nitride fillers on polyamide 6 (PA6) hybrid polymer composites were investigated. In particular, the thermal and electrical conductivity, thermal transition, thermal degradation, mechanical and morphological properties and chemical bonds characteristic of the materials with crystal structure of BN and aluminum nitride (AlN) filled PA6 prepared at different concentrations were characterized. Thermal conductivity of hybrid systems revealed a 1.6-fold gain compared to neat PA6. The highest thermal conductivity value was obtained for the composite containing 50 vol% additives (1.040 W/m K). A slight improvement in electrical conductive properties of composites appears and the highest value was obtained for the 50 vol% filled composite with only an increase by 3%. The microstructure of these composites revealed a homogeneous dispersion of AlN and BN additives in PA6 matrix. For all composites, one visible melting peak around 220°C related to the α-form crystals of PA6 was detected in correlation with the X-ray diffraction results. An improved thermal stability was obtained for 10 vol% AlN/BN filled PA6 composite (from 405.41°C to 409.68°C). The tensile strength results of all composites were found to be approximately 22% lower than pure PA6.     

Synergistic enhancement of thermal conductivity by addition of graphene nanoplatelets to three-dimensional boron nitride scaffolds for polyamide 6 composites

Three-dimensional boron nitride/graphene nanoplatelets (3D-BN-GNP) scaffolds were fabricated using an ice-templating method and polyamide 6 (PA6)-based composites were prepared by vacuum impregnation of caprolactam monomers into the scaffolds, followed by polymerization. The BN sheets in the PA6/3D-BN and PA6/3D-BN-GNP composites display a predominant parallel alignment along the ice-crystal formation constructing thermally conductive paths. The addition of few GNPs assists the dispersion of BN sheets in the PA6/3D-BN-GNP composites and repair the broken thermal paths caused by local agglomeration of the BN sheets. Consequently, GNPs play a morphology-promoted synergistic role in the enhancement of the thermal conductivity of the PA6/3D-BN-GNP composites. The PA6/3D-BN-GNP composite prepared with 23.40 wt% BN sheets and 2.60 wt% GNPs exhibits the highest thermal conductivity of 2.80 W m⁻¹ K⁻¹, which is 833% and 33% higher than the values recorded for the pure PA6 and the PA6/3D-BN composite at BN loading of 26.18 wt%, respectively. Infrared imaging analysis revealed that the surface of the PA6/3D-BN-GNP composite has a fast response to heating and cooling, suggesting the potential of the composites in thermal management applications.     

Study on thermal conductive PA6 composites with 3-dimensional structured boron nitride hybrids

To develop thermally conductive PA6 composites with the aim of decreasing filler content, structure-complexed fillers were fabricated. This research presented an effective approach by noncovalent functionalization of poly(dopamine) (PDA) followed by silver nanoparticles decoration to fabricate 3-dimensional (3-D) structured boron nitride hybrids (BN@PDA@AgNPs). BN hybrids were then introduced into PA6 to prepare thermally conductive PA6 composites. The results demonstrated that PA6/BN hybrids (PMB) composites exhibited higher thermal conducivity compared with PA6/BN composites, which revealed more effective construction of thermal conductive network in the composites with the addition of 3-D structured fillers. The effects of BN hybrids with different loadings on thermal stability, mechanical property, as well as electrical resistance of the composites were also analyzed. Overall, the prepared PMB composites exhibited outstanding performance in thermal conductivity, thermal stability, mechanical property, while retaining good electrical insulating property, which showed a potential application in electronic packaging fields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47630.     

PA6/BN/MgO导热复合材料的制备与性能研究

以聚酰胺6（PA6)为基体,以氮化硼（BN）、氧化镁（MgO）为导热填料制备了PA6/BN/MgO导热复合材料。固定填料含量为50%（质量分数,下同）不变,考察MgO/BN配比的变化对复合材料热导率、力学性能和熔体流动性的影响。结果表明,材料的热导率、拉伸强度和弯曲强度随着MgO/BN配比的增大而减小,冲击强度和断裂伸长率随着MgO/BN配比的增大而增大,材料熔体流动性则呈现了随MgO/BN配比的增大先增大后减小的趋势。     

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.     

Phase morphology evolution and thermally conductive networks of immiscible polymer blends

The selective distribution of fillers in multi-phase polymer blends was dramatically studied to deal with thermal management fields issues. Concerning thermodynamic and kinetic effects of fillers on immiscible polymer blends, the compatibilization of fillers on phase morphology evolution and final construction of thermal conductive pathways were rarely discussed. In this work, BN fillers and polar dispersed phase were introduced into PE through various processing methods. The result showed that filler-coated shell was formed around the larger-sized dispersed phase, thereby forming more thermal conductivity network with other fillers in the two-step processing composites. When the BN content was 20 phr, the thermal conductivity was 0.8271 W/(m·K) for PE/PA6/BN-two steps composites, which was 95.48% higher than that of PE/PA6 composites. From the perspective of the regulation of the morphological structure of the dispersed phase, this study can provide methods and basic data for improving the thermal conductivity of incompatible polymer blends.     

Reinforced thermal conductivity and mechanical properties of in situ microfibrillar composites through multistage stretching extrusion

To surmount difficulty of the melt processing and deterioration of mechanical properties of polymer composites induced by high fraction of the reinforced fibers and thermal conductive fillers, polyethylene (PE)/boron nitride (BN)/polyamide 6 (PA6) and PE/BN/poly(‐hydroxybenzate‐co‐DOPO‐benzenediol dihydrodiphenyl ether terephthalate) (PHDDT) in situ microfibrillar composites were prepared through multistage stretching extrusion. The experimental results showed that both the tensile and impact strength of the PE/BN/PA6 and PE/BN/PHDDT composites were improved. Meanwhile, the thermal conductivities of the PE/BN, PE/BN/PA6, and PE/BN/PHDDT composites were also reinforced. Based on the equation proposed by Y. Agari, the new modified equations can well predict the thermal conductivity of the composites prepared through multistage stretching extrusion with different number of laminating‐multiplying elements. In addition, it was found that PHDDT can act as a “processing aid” to reduce the viscosity of the PE/BN composites. POLYM. COMPOS., 38:2663–2669, 2017. © 2015 Society of Plastics Engineers     

In situ Polymerization of Polyamide 6/Boron Nitride Composites to Enhance Thermal Conductivity and Mechanical Properties via Boron Nitride Covalently Grafted Polyamide 6

Polyamide 6/boron nitride (PA6/BN) composites were synthesized via anionic ring-opening polymerization using ε-caprolactam as the monomer and functional boron nitride (f-BN) as the thermal conductive filler. Besides the homopolymerized PA6, some PA6 molecule chains would grow from the f-BN sheets through the “grafting from” strategy. Compared with unfunctional hexagonal BN (h-BN), the introduction of f-BN not only improved the dispersion of f-BN in the matrix but also enhanced the interface bonding between f-BN and PA6. The homogeneous dispersion of f-BN in the PA6/f-BN composite favored the formation of the continuous thermal conductive paths or network at a low f-BN loading, and the good interface bonding reduced the phonon scattering in the interface, which improved the thermal conductivity (TC) of the PA6/f-BN composite by 66.0% compared with that of the pure PA6, when only 5 wt% f-BN was added. In contrast, with the same content of unfunctional h-BN loading, the TC of the corresponding composite merely improved by 29.7%. Moreover, Young's modulus and yield strength of PA6/f-BN composites had increased obviously with the introduction of f-BN, whereas those of PA6/h-BN composites showed small fluctuation with the same contents of BN. POLYM. ENG. SCI., 60:710–716, 2020. © 2020 Society of Plastics Engineers