改性BN/聚丙烯复合材料的制备及导热性能研究

本文在氮化硼(BN)表面通过原位分散聚合苯乙烯引入PS,以此改善BN在聚苯乙烯(PS)基体中的分散,实现改性BN在PS相中的选择性分散。通过引入另一种聚丙烯(PP)相构建共混物的双连续结构,来增强复合材料的导热性。由于改性BN在PS相中的选择性分散,双连续PS/PP(60/40)相有利于PS的热导率的进一步增强。此外,含14.5wt%改性BN的PS/PP共混物的热导率比纯PP高2倍,比PP/BN高30%。     

聚丙烯/碳纤维/氮化硼导热绝缘复合材料的制备

研究聚丙烯(PP)/碳纤维(CF)/氮化硼(BN)复合材料的导热绝缘性能。结果表明,CF的含量达15%时,PP/CF复合材料的体积电阻率大幅度下降,出现逾渗现象;基于PP/CF(15%)填加不同含量的BN,当BN的含量达到20%。PP/CF/BN复合材料的热导率达0.939 5 W/(m·K),比纯PP提高近4倍,其体积电阻率为1.3×1014Ω·cm。     

聚丙烯/高密度聚乙烯/氮化硼导热复合材料的制备及性能研究

以聚丙烯（PP）/高密度聚乙烯（HDPE）共混物为基体，六方氮化硼（h-BN）为导热填料，聚丙烯接枝马来酸酐（PP-g-MAH）为相容剂，通过熔融共混法制备PP/HDPE/h-BN和PP/HDPE/h-BN/PP-g-MAH导热复合材料。采用导热系数仪、场发射扫描电镜、万能试验机、热分析仪等测试导热复合材料，研究不同含量的h-BN、PP-g-MAH对复合材料导热性、力学性能、结晶性能和耐热性的影响。结果表明：随着h-BN含量的增加，PP/HDPE/h-BN复合材料的弯曲强度、热导率和耐热性提高。当h-BN含量为20%，复合材料的弯曲强度达到41.02 MPa；当h-BN含量为25%，复合材料热导率达到0.372 1 W/（m·K）。h-BN对PP的结晶具有促进作用，提升PP的结晶速率和结晶温度。PP、HDPE与h-BN质量比为64∶16∶15时，添加5%的PP-g-MAH，增强了h-BN和基体材料的界面相容性，复合材料的弯曲强度达到42.72 MPa，拉伸强度达到26.64 MPa，热导率达到0.356 1 W/（m·K）。     

CB结构度对隔离型PP/PE–UHMW/CB导电复合材料的影响

通过乙醇辅助超声分散–热压法制备了具有隔离结构的聚丙烯(PP)/超高分子量聚乙烯(PE–UHMW)/炭黑(CB)导电复合材料。利用偏光显微镜和扫描电子显微镜分析了所制备的导电复合材料的结构与形貌,并研究了不同结构度的CB对复合材料逾渗行为的影响。结果表明,所制备的隔离型导电复合材料中,CB被PE–UHMW所隔离,高结构度CB主要分布在PP与PE–UHMW的界面处,而低结构度CB在PP与PE–UHMW的界面处及PP基体中均有分布。相比传统熔融法,采用上述方法制备的隔离型导电复合材料具有较低的逾渗值和更好的导电性能。其中,由高结构度CB制备的导电复合材料具有更低的逾渗值。     

共混顺序对石墨烯微片在PP/PA6/SEBS共混物中的选择性分布和迁移的影响

研究了聚丙烯（PP）/聚酰胺6（PA6）/氢化苯乙烯-丁二烯嵌段共聚物（SEBS）/石墨烯微片（GNPs）纳米复合材料在不同共混顺序下的微观形貌、导电及导热性能,分析了GNPs在复合体系中的选择性分布和迁移及其对复合材料性能的影响。结果表明,在PP/PA6/SEBS/GNPs共混体系中,GNPs在界面张力的作用下趋向于分布在PA6中;当GNPs先加入PP中复合,再与PA6共混时,GNPs从PP相向界面处迁移,有利于GNPs在界面上搭建较多的导热网络,从而提高复合材料的导热性能;GNPs的含量为7 %时,其热导率最高可达0.83 W/（m·K）;SEBS的加入改善了PP和PA6之间的相容性,消除了两相间部分界面空隙。     

微纳层叠共挤对EPDM/PP热塑性弹性体力学性能的影响

利用自制的微纳层叠共挤成型装备预制EPDM/PP多层复合材料,通过动态硫化制备共挤和共混2种EPDM/PP热塑性弹性体,测试EPDM/PP热塑性弹性体的力学性能,并利用扫描电子显微镜观察EPDM/PP热塑性弹性体相态结构。结果表明:共挤法能够明显减小橡胶相颗粒粒径的大小,且粒径均匀,并提高了橡胶相颗粒的分散均匀性,共挤法制备的EPDM/PP热塑性弹性体的力学性能总体优于共混法。     

环氧树脂/氧化锌晶须/氮化硼导热绝缘复合材料的研究

以环氧树(脂EP)为基体,分别以氧化锌晶(须ZnOw)和ZnOw/氮化硼(BN)混合物为导热填料,制备了EP导热绝缘复合材料。研究了填料含量对复合材料导热性能、电绝缘性能及力学性能的影响,并利用扫描电镜对复合材料的断面形貌进行了观察。结果表明:随着导热填料含量的增大,复合材料的导热系数和介电常数增大,体积电阻率下降,而拉伸强度呈先增大后减小的趋势;在填料含量相同的情况下,EP/ZnOw/BN复合材料比EP/ZnOw复合材料具有更好的导热性能;当填料体积分数为15%时,EP/ZnOw/BN复合材料的热导率为1.06W/(mK)而,EP/ZnOw复合材料的热导率仅为0.98W/(mK)。     

环氧树脂/玻璃布/BN导热复合材料的制备与性能研究

采用高温模压成型法制备环氧树脂(EP)/玻璃布/氮化硼(BN)导热复合材料。探讨了BN用量和偶联剂处理对复合材料力学性能、导热性能和介电性能等影响。结果表明:当w(BN)=15%时,复合材料的冲击强度较高;导热性能随着BN用量的增加而增大;当w(BN)=25%时,改性复合材料的热导率为0.901 2 W/(m.K),此时复合材料仍保持较低的介电常数和介电损耗。当BN用量相同时,偶联剂表面处理可有效改善复合材料的力学性能和导热性能。     

PP/EPDM/纳米TiO_2复合材料的制备与热性能

采用熔融共混法制备了PP/EPDM/纳米TiO_2复合材料,并对其结晶行为和热稳定性进行了研究。通过Jeziorny法和莫志深模型对复合材料的非等温结晶动力学进行表征,并利用Kissinger法和Friedman法计算结晶活化能。结果表明,三元乙丙橡胶(EPDM)包裹在纳米TiO_2表面所形成的核壳结构虽然延缓了复合体系的结晶过程,但并没有影响PP基体的结晶能力。纳米TiO_2作为导热填料使复合材料的特征温度T_(5%)、T_(10%)、T_(max)比PP分别提高了33.34、21.55、7.92℃,说明纳米TiO_2能够增强体系的热导率,增加内部的热传导作用,从而有效地提高了基体的热稳定性。     

性能均衡的尼龙6基导热复合材料的结构设计

聚合物基导热复合材料以其独特的优势,如耐环境性和易于加工成型等特点而被广泛的关注和研究。将与尼龙6(PA6)具有部分相容性的尼龙11(PA11)引入尼龙6/氮化硼(PA6/BN)复合材料中,并对其导热性能和力学性能进行了研究。结果发现,在PA6/PA11/BN复合材料中,氮化硼选择性分布在PA6连续相中,PA11相起到体积排除的作用,使得BN在PA6中更有效地形成导热通路,可在较低粒子含量下显著提高复合材料热导率。同时,韧性较高的尼龙11亦起到改善复合材料力学性能的作用。当PA6/PA11体积比为7/3、氮化硼体积分数为20%时,PA6/PA11/BN复合材料热导率达到1.96 W/(m·K),与同等BN含量的PA6/BN复合材料的热导率相比提高了约13.7%,且复合材料的断裂伸长率和拉伸强度也同时得到提高,分别提高了86.72%和13.95%。该研究为制备兼具优异导热性能和力学性能的新型聚合物基导热复合材料提供了一种思路。     

具有“沙袋”结构的PP/EPDM/CB导电复合材料的形态构建及性能研究

提出通过构建类似拳击训练沙袋的硬核-软壳分散相结构来同时实现导电高分子复合材料的高电导率和高韧性这一设想,并通过两步熔融共混法构建了这种具有“沙袋”分散相结构的聚丙烯（PP）/三元乙丙橡胶（EPDM）/炭黑（CB）导电复合材料,其中,CB粒子选择性分布于EPDM分散相中。通过定量计算发现,无论从热力学角度还是动力学角度,CB粒子均倾向于选择性分布在EPDM中,这也阐明了“沙袋”分散相结构的形成机理。此外,性能测试表明,这种具有“沙袋”分散相结构的导电复合材料的体积电导率和缺口冲击强度随炭黑含量的增加呈现反常的同步增长。     

Enhanced thermal conductivity of PE/BN composites through controlling crystallization behavior of PE matrix

In this article, in order to enhance the thermal conductivity of the polyethylene (PE)/boron nitride (BN) composites through controlling the crystallization behavior of the PE matrix, the crystallization and melting behavior of the PE in the PE/BN composites was investigated. When the BN content was more than 10 wt%, an extra weak exothermic peak (T _h) at 130°C was observed. Moreover, after the annealing of the PE/BN composites at 130°C, the extra weak melting peaks (T _mh) of the PE in the PE/BN composites were also observed and shifted to the high temperature with increasing annealing time, which proved that the T _h was induced by PE crystallization. Meanwhile, the results of temperature‐dependent absorbance IR spectra of the PE/BN composites showed that the crystallization peak (729 cm⁻¹) remarkably appeared at 130.2°C, indicating that the crystallization of the PE in the PE/BN composites can occur at 130.2°C. When the annealing time and temperature were 20 min and 130°C, the thermal conductivity of the PE/BN composite was 16% higher than that of the unannealed PE/BN composites. In addition, the results of the wide angle X‐ray diffraction (WAXD) showed that the BN particles had no influence on the PE crystalline form in the PE/BN composites. POLYM. COMPOS., 38:2806–2813, 2017. © 2015 Society of Plastics Engineers     

Polypropylene/poly(lactic acid)/carbon nanotube semi-biodegradable nanocomposites: The effect of sequential mixing approach and compatibilization on morphology,rheology and electrical conductivity

Semi-biodegradable polypropylene (PP)/poly(lactic acid) (PLA) (50:50 vol%) blend loaded with 0.6 vol% of pristine carbon nanotube (CNT) were prepared by melt compounding the components using different sequential mixing strategies: (i) all components together (PP/PLA/CNT); (ii) PP first mixed with CNT (PP@CNT/EVA) and (iii) EVA first mixed with CNT (EVA@CNT/PP). The composites presented co-continuous structure and the CNT selectively localized inside the PP phase or at the interface, regardless the order of the CNT addition into the mixing. These features were confirmed by selective extraction experiments and morphological studies: optical, scanning electron, and transmission electron microscopy. However, the preferential localization at the interface was predicted from wetting coefficient, determined from interfacial energy. Higher electrical conductivity values were achieved by using the one-step mixing approach, were all components were mixed together, whose value of around 10⁻⁴ S/m was achieved by adding 0.6 vol% of CNT to the blend. The compatibilization with polypropylene-g-maleic anhydride increased the melt viscosity of the blend and composite but did not affect the conductivity or the tensile properties of the CNT-based composite.     

Enhanced Electrically Conductive Polypropylene/Nano Carbon Black Composite

In this work, a porous polypropylene (PP)/nano carbon black (CB) composite was facilely fabricated via immiscible co-continuous polymer blend and subsequent dissolution process. The porous structure was generated from co-continuous polymer blend, which was exploited as the substrate for depositing nano CB. The interconnected micro pores of the co-continuous polymer blend and nano pores derived from agglomerated CB resulted in a significant enhancement of conductivity. Comparing with the conventional carbon composite obtained through dual-percolation method, the electrical conductivity of PP/CB composite increased 10 orders of magnitude with CB loading ranged from 1 wt% to 5 wt%. Moreover, it was found that the percolation threshold of PP/CB composite decreased nearly 80% compared with that of as-mixed sample. The enhanced conductivity and much lower percolation make this novel method a potential way for fabricating porous conductive materials for advanced application.     

Largely improved toughness of PP/EPDM blends by adding nano-SiO2 particles

As a part of long-term project aimed at super polyolefin blends, in this work, we report the toughness and phase morphology of polypropylene (PP)/EPDM/SiO₂ ternary composites. Two processing methods were employed to prepare PP/elastomer/filler ternary composites. One was called one-step processing method, in which the elastomer and the filler directly melt blended with PP matrix. Another one was called two-step processing method, in which the elastomer and the filler were mixed first, and then melt blended with pure PP. Two kinds of PP (grafted without or with maleic anhydride (PP-g-MA)) and SiO₂ (treated with or without coupling agent) were used to control the interfacial interaction among the components. The dependence of the phase morphology on interfacial interaction and processing method was investigated. It was found that the formation of filler-network structure could be a key for a simultaneous enhancement of toughness and modulus of PP and its formation seemed to be dependent on the work of adhesion (W_AB) and processing method. As the W_AB of PP/EPDM interface was much lower than that of PP/SiO₂ and EPDM/SiO₂, and the two-step processing method was used, the formation of filler-network structure was favorable. In this case, a super toughened PP ternary composite with the Izod impact strength 2-3 times higher than PP/EPDM binary blend and 15-20 times higher than pure PP could be achieved.     

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.     

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。     

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     

Improvement in thermal conductivity and mechanical properties of ethylene‐propylene–diene monomer rubber by expanded graphite

Thermally conductive fillers are usually employed in the preparation of rubber composites to enhance thermal conductivity. In this work, ethylene‐propylene‐diene monomer rubber (EPDM)/expanded graphite (EG) and EPDM/graphite composites with up to 100 phr filler loading were prepared. Compared to EPDM/graphite compounds with the same filler loading, stronger filler network was demonstrated for EPDM/EG compounds. Thermal conductivity and mechanical properties of EPDM/graphite and EPDM/EG composites were compared and systematically investigated as a function of the filler loading. The thermal conductivity of both EPDM/graphite and EPDM/EG composites increased with increasing volume fraction of fillers, and could be well fitted by Geometric Mean Model. The thermal conductivity as high as 0.910 W · m⁻¹ · K⁻¹ was achieved for the EPDM/EG composite with 25.8 vol% EG, which was ∼4.5 times that of unfilled EPDM. Compared to EPDM/graphite composites, EPDM/EG composites exhibited much more significant improvement in thermal conductivity and mechanical properties, which could be well correlated with the better filler‐matrix interfacial compatibility and denser structure in EPDM/EG composites, as revealed in the SEM images of tensile fracture surfaces. POLYM. COMPOS., 38:870–876, 2017. © 2015 Society of Plastics Engineers     

Influences of compatibilization and compounding process on electrical conduction and thermal stabilities of carbon black‐filled immiscible polypropylene/polystyrene blends

The influences of styrene–butadiene–styrene (SBS) copolymer compatibilizer and compounding process on the electrical conduction and thermal stabilities of carbon black (CB)‐filled immiscible polypropylene (PP)/polystyrene (PS) (1/1) blends were investigated. The immiscible CB/PP/PS composite with CB homogeneously located in the PS phase exhibited the highest resistivity and the fastest variation amplitudes of electrical resistivity (ρ) and rheological parameters upon annealing. An optimal content of 5 vol% SBS could significantly lower ρ of the composites by partially trapping CB particles in the PP/PS interfacial region and by reducing the phase size. The compatibilizer markedly slowed down the variation amplitudes of ρ and rheological parameters and the phase coalescence of the composites submitted to thermal annealing. The (SBS/CB)/PP/PS composite with CB located at the PP/PS interface and in the PP phase prepared by blending a (SBS/CB) masterbatch with PP and PS exhibited lower ρ and better thermal stability in comparison with the CB/SBS/PP/PS composite with CB mainly within the PS phase and partially at the PP/PS interface prepared by direct blending. Spreading and wetting coefficients were used to explain the CB distribution and the phase morphology of the composites. © 2012 Society of Chemical Industry