高导热高介电BT/SiC/PA6复合材料的制备及性能研究

以聚酰胺(PA6)为基体,氮化硅(SiC)为导热填料,钛酸钡(BT)为介电填料,通过热压法制备出系列复合材料;研究了不同粒径填料的搭配对材料导热与介电性能的影响。结果表明:在填充量较低时,使用混合粒径导热填料能产生一定的级配效应,从而提高复合材料的导热性能。总填充量为26%时,以4∶1的比例,用粒径为0.5~0.7μm和3μm的SiC共同填充PA6,制备获得了最高导热系数为0.9198W/(m·K)的复合材料,而不同粒径、不同功能的混合功能填料还能产生协同效应,进一步提升材料的导热性能并使材料同时获得较好的介电性能,当SiC填充量为20%,BT填充量为20%时,复合材料的导热系数达到1.1110W/(m·K),介电常数到达16(100Hz),损耗保持在0.075(100Hz)左右。     

可控热膨胀聚合物复合材料的挑战和机遇(英文)

负热膨胀(negative thermal expansion,NTE)材料可作为填料制备可控热膨胀复合材料.高质量聚合物复合材料的研发面临诸多挑战,包括NTE 填料与基体材料的相容性,NTE相的稳定性,颗料形貌和尺寸的控制及其对混合稗度的影响.本文对影响聚合物复合材料成型中存在的诸多可能存 在的问题进行了述评,讨论了对有望用作填料的NTE材料的要求,即对NTE填料颗粒尺寸和相容性进行合成控制.通过晶体前驱体到目标NTE相 的拓扑转变,可实现对颗粒尺寸的最优控制.     

The synergistic effects on enhancing thermal conductivity and mechanical strength of hBN/CF/PE composite

In this work, a simple and novel method was applied to prepare polymer composites by taking the advantage of melt flow shear force driving orientation of the fillers. By using this method, hexagonal boron nitride/polyethylene (hBN/PE) and hexagonal boron nitride/carbon fibers/polyethylene (hBN/CF/PE) composites were fabricated to be possessed of high thermal conductivity and mechanical properties. A high thermal conductivity of 3.11 W/mK was realized in the composite containing 35 wt% hBN and 5 wt% CF, which was over 1,200% higher than that of unfilled PE matrix. Under this component, the compressive strength and modulus of hBN/CF/PE composite were determined to be 30.1 and 870.9 MPa, respectively, which were far higher than that of unfilled PE accordingly. The bending performance was also somewhat enhanced. Meanwhile, the bulk resistivity of the composite material reached 2.55 × 10¹¹ Ω·cm, which was basically the same as that of pure PE. The novel composites with high thermal conductivity, excellent mechanical properties, and controllable electrical insulation could be a potential thermal management material for electrical and electronics industries.     

Synergistic effects of carbon fillers in electrically and thermally conductive liquid crystal polymer based resins

Adding conductive carbon fillers to insulating thermoplastic resins increases composite electrical and thermal conductivity. Often, as much of a single type of carbon filler is added to achieve the desired conductivity, while still allowing the material to be molded into a bipolar plate for a fuel cell. In this study, varying amounts of three different carbons (carbon black, synthetic graphite particles, and carbon fiber) were added to Vectra A950RX Liquid Crystal Polymer. The resulting single filler composites were tested for electrical resistivity (1/electrical conductivity) and thermal conductivity. In addition, the effects of single fillers and combinations of two different carbon fillers were studied via a factorial design. The results indicated that for the composites containing only single fillers, synthetic graphite, followed by carbon fiber, cause a statistically significant decrease in composite electrical resistivity. Composites containing only synthetic graphite, followed by carbon black, and then carbon fiber cause a statistically significant increase in thermal conductivity. For the combinations of two different fillers, the composites containing carbon black/synthetic graphite and synthetic graphite/carbon fiber had a statistically significant and positive effect on thermal conductivity. It is possible that thermally conductive pathways are formed that “link” these carbon fillers, which results in increased composite thermal conductivity. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Melt mixing of carbon fibers and carbon nanotubes incorporated polyurethanes

Polyurethane composites filled with carbon fibers (CF) and carbon nanotubes (CNT) were prepared by mixing and injection molding, and its mechanical as well as their thermal properties were investigated. Dynamic mechanical analysis (DMA), thermogravimetry analysis (TGA), and thermal conductivity tests were done, and the properties were evaluated as a function of the filler concentration. The storage modulus of the composites increased with fillers concentration, which also mean the increase of the stiffness, suggest a good adhesion between the polyurethane matrix and the fillers. Addition of more CF and CNT to the composites broadened and lowered the peak of tan δ specifies that the polyurethane composite became more elastic because there is a good adhesion between the fillers and the matrix. The addition of carbon fillers improves the thermal stability of the polyurethane. The inclusions of CNT show a better thermal stability when compared with CF. The addition of carbon fillers also increased the thermal conductivity of the polyurethane composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

低界面热阻改性氮化铝和多壁碳纳米管充填PVDF构建杂化三维网络及其导热性能强化

通过对多壁碳纳米管(MWCNT)和氮化铝(AlN)颗粒进行不同的改性,提高其分散性以及与聚偏氟乙烯(PVDF)基体的界面相容性,降低界面热阻。通过溶液共混后再用热压法将填料与基体的混合物压制成致密的薄膜,提高PVDF的导热性能。TEM测试证明改性后的填料分散性能提高,SEM证明两种填料成功地在PVDF基体中构成三维杂化网络结构。当填料含量50%时,a-AlN-PVDF复合薄膜的热导率达到原膜的300%、断裂强度变为原膜的92%。当MWCNT与AlN的体积比为1∶1、改性混合填料的质量分数为50%时,热导率变为原膜的565%,断裂强度变为原来的51%。     

Porous boron nitride nanofibers/PVA hydrogels with improved mechanical property and thermal stability

Polyvinyl alcohol (PVA) hydrogel is a promising material possessing good chemical stability, high water absorption, excellent biocompatibility and biological aging resistant. However, the poor mechanical performance of PVA hydrogel limits its applications. Here we report the utilization of one-dimensional (1D) BN nanofibers (BNNFs) as nanofillers into PVA matrix to prepare a novel kind of BNNFs/PVA composite hydrogel via a cyclic freezing and thawing method. For comparison, the composite hydrogels using spherical BN nanoparticles i.e. BN nanospheres (BNNSs) as fillers were also prepared. The mechanical properties, thermal stabilities and swelling behaviors of the composite hydrogels were investigated in detail. Our study indicates that the mechanical properties of the hydrogels can be improved by adding of BNNFs. After loading of BNNFs into PVA with content of 0.5?wt%, the compressive strength of the composite hydrogel increases by 252% compared with that of pure PVA hydrogel. The tensile performance of BNNFs/PVA composite hydrogels has also been improved. Impressive 87.8% increases in tensile strengths can be obtained with 1?wt% BNNFs added. In addition, with the increase of BNNFs content, the thermal stability and the swelling ratio of hydrogels are increased gradually. The swelling ratio of hydrogel increases by 56.3% with only 1?wt% BNNFs added. In comparison, the improvement effects of the BNNS fillers on the mechanical strengths and swelling ratios are much weaker. The enhanced effects of BNNFs can be ascribed to the strong hydrogen bond interaction between BNNFs and PVA. The high aspect ratios of the nanofibers should also be took into account.     

Enhanced thermal conductivity of boron nitride epoxy‐matrix composite through multi‐modal particle size mixing

Castable particulate‐filled epoxy resins exhibiting excellent thermal conductivity have been prepared using hexagonal boron nitride (hBN) and cubic boron nitride (cBN) as fillers. The thermal conductivity of boron nitride filled epoxy matrix composites was enhanced up to 217% through silane surface treatment of fillers and multi‐modal particle size mixing (two different hBN particle sizes and one cBN particle size) prior to fabricating the composite. The measurements and interpretation of the curing kinetics of anhydride cured epoxies as continuous matrix, loaded with BN having multi‐modal particle size distribution, as heat conductive fillers, are highlighted. This study evidences the importance of surface engineering and multi‐modal mixing distribution applied in inorganic fillered epoxy‐matrix composite. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Polymer derived ceramics with β-eucryptite fillers: A novel processing route to negative and near zero expansion materials

A polymer derived ceramic with near-zero or negative thermal expansion was manufactured from a powder mixture consisting of β-eucryptite fillers having a negative thermal expansion, and a polymethylsilsesquioxane preceramic polymer. The composite starting material was manufactured by ball-milling and warm-pressing and pyrolysis in inert atmosphere. The thermal expansion behavior of the composite material was controlled via the filler volume fraction and via the pyrolysis temperature. An influence of the filler material on the pyrolysis process was found.     

Microstructure Development,Wear Characteristics and Kinetics of Thermal Decomposition of Hybrid Nanocomposites Based on Poly Aryl Ether Ketone,Boron Carbide and Multi Walled Carbon Nanotubes

In the present study a high performance polymer poly aryl ether ketone (PAEK) is reinforced with micro and nano boron carbide (B₄C) and functionalized multi walled carbon nanotubes (F-MWCNT) to investigate the individual and hybrid effect of the fillers. Optical microscopy and transmission electron microscopy suggested the dispersion of micro and nano fillers respectively in PAEK matrix. The inclusion of B₄C nano fillers increased the hardness of the composites which aided the wear resistance of the composites. The morphological features of the worn surface of the samples are analyzed using scanning electron microscopy. It is found from the izod impact test analysis that the impact strength of the composite enhanced by the F-MWCNT inclusion. The thermal properties of PAEK in the composites are studied using differential scanning calorimetry and it revealed dominant effect of F-MWCNT influencing the thermal transitions than the B₄C particles. The kinetics of thermal degradation of various composites is analyzed using Coats–Redfern method. The positive influence of B₄C in the matrix indicates that the thermal degradation is delayed due to the higher activation energy it possesses. The overall results shows that the hybrid nanocomposite exhibits better properties compared to individual micro and nano composites.     

Cure kinetics of a polymer‐based composite friction material

In the present article, cure kinetics of a commercially available composite friction material used in railroad vehicles is investigated using the rheometer measurements. Effect of ingredients of friction material compound, including rubber matrix, phenolic resin, and fillers, on overall cure kinetics of friction compound is also investigated by comparing the cure kinetics of friction material and rubber matrix compound. A phenomenological model and an Arrhenius‐type equation is developed for cure kinetics and induction time of both friction material and rubber matrix. The parameters of the models are extracted from experimental data, using the rheometer at different temperatures and utilizing appropriate optimization method. The good agreement between experimental measurement and models prediction indicates the good performance of the models developed in this study. The results demonstrate that phenolic resin and fillers have dominant effects on the overall cure behavior of the friction material compound. A comparison between the present results and other published data based on the differential scanning calorimetry (DSC) shows a reasonable agreement as well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 100: 9–17, 2006     

Thermal conductivity augmentation of composite polymer materials with artificially controlled filler shapes

Plastics or polymers of high thermal conductivity are highly desired in various industries. Adding fillers of high thermal conductivity to the base materials is a solution to make composite plastics of high thermal conductivity. Previous researches were focused on increasing the thermal conductivity of the composite materials by increasing the filler content and the thermal conductivity of the fillers. Relatively little attention was paid to the optimization of filler shapes. In this study, the effects of the filler shapes on the thermal conductivity of the composite materials are investigated, where the filler shapes are artificially designed. Heat conduction between the base materials and the artificially designed fillers is modeled. It is found that the filler shapes have great impacts on the effective thermal conductivity of the composite materials. Of the various shapes, the double Y shaped fillers are found to be the best choice for composite materials in which the fillers are distributed randomly. In future industrial applications, new filler shapes, such as double Y, Y, quad Y shaped, I and T shapes should be specially produced to replace the traditional fillers shapes: particles, fibers or slices. At last, composite materials made of paraffin wax and steel fillers of ten shapes are fabricated to simulate and validate the results. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39550.     

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.     

Properties of nylon-6-based composite reinforced with coconut shell particles and empty fruit bunch fibres

Novel natural fibre composites of nylon-6 reinforced with coconut shell (CS) particles and empty fruit bunch (EFB) fibres have been investigated. Fillers were alkali treated before melt compounding with nylon-6. Mechanical, thermal and rheological properties of composites were measured. Tensile modulus was found to improve with both fillers up to 16% for nylon-6/CS composite and 10% for nylon-6/EFB composite, whereas a moderate increase in tensile strength was observed only with CS composites. Differences in the strengthening mechanisms were explained by the morphology of the two fillers, empty fruit bunch fibres having a weaker cellular internal structure. Observation of composite morphology using SEM showed that both fillers were highly compatible with nylon-6 due to its hydrophilic nature. Both fillers were found to cause a slight drop in crystallinity of the nylon matrix and to lower melt viscosity at typical injection moulding strain rates. Moisture absorption increased with addition of both fillers.     

Mechanical Properties of Melt-processed Blend of Amorphous Corn Flour Composite Filler and Styrene-Butadiene Rubber

The corn flour composite fillers were prepared by blending corn flour with rubber latex, dried, and cryogenically ground into powders, which were then melt-blended with rubber polymers in an internal mixer to form composites with enhanced mechanical properties. The composites prepared with melt-blending method were compared to those prepared with a freeze-drying method. The composite fillers prepared with styrene-butadiene were compared to those made with carboxylated styrene-butadiene matrix. Dynamic effects showed that the corn flour composite fillers produced composites with good tensile strength, elongation ratio, and toughness at 500 mm/min strain rate. Tear resistance of different composites was also studied.     

Preparation and heat resistance of hollow glass microbead/silicone rubber composite coating

Hollow glass microbead/silicone rubber composite coatings were prepared to improve the heat-resistance and mechanical properties of silicone rubber-based composites, using CE modified SR as the matrix and HGM as the filler. The microscopic morphology and thermal stability of the composites were characterized by scanning electron microscopy (SEM) and thermogravimetric analyzer (TGA), respectively. The results showed that the thermal stability of the composites increases with the increase of filler content. For the composite sample with a HGM mass content of 16.7%, the initial decomposition temperature (T₅) is 408°C, which is 84°C higher than that of silicone rubber. The low density and high sphericity of HGM make it easier to uniformly disperse in the polymer matrix. In addition, compared to silica, which is commonly used as an inorganic filler, the lower thermal conductivity of HGM is also beneficial for achieving better thermal shielding effect. It is confirmed that the insufficient thermal stability of the polymer matrix above 400°C can be compensated for by the properly dispersed inorganic fillers. Therefore, the thermal stability of the composite is improved by the synergistic effect of modified heat-resistant matrix and inorganic filler.     

Elastic moduli of particulate composites with graded filler‐matrix interfaces

The elastic response of plane‐array models of composites reinforced by particles or aligned fibers having graded interfaces with the matrix is analyzed. Such microstructure is representative of a new class of polymer matrix composite materials in which the filler is nanometer‐sized. In such materials, the polymer chains in the matrix are preferentially oriented close to the interface with the relatively rigid fillers, this leading to a graded interfacial layer about each inclusion. The composite elastic moduli are determined based on the properties and geometry of the interfacial graded layer as well as on the moduli of the filler and the matrix, and the volume fraction of filler. Conversion curves are constructed allowing for an equivalence to be established between the present case and that of similar composites without graded interfaces. Based on these conversion curves, standard homogenization algorithms can be applied to determine the overall elastic properties of such composite. The fillers are considered to be stiffer than the matrix, both rigid and of finite stiffness. Results for both sliding and bonded interfaces are presented. The effect of anisotropic material properties in the graded region on the composite moduli is also investigated. The results of the model are compared with published experimental data.     

Epoxy composites based on inexpensive char filler obtained from plastic waste and natural resources

In this study, plastic [polyethylene terephthalate (PET)] waste was recycled as raw material for the preparation of diglycidyl ether of bisphenol A‐type epoxy composite materials. The other inexpensive fillers used to prepare the composites were wood shavings char and pine cone char (PCC), obtained from natural resources. The thermogravimetric analysis showed that plastic waste char (PWC) and PCC can significantly improve the thermal stability of neat epoxy resin at temperatures above 300°C. The best thermal and electrical conductivity results were obtained with PWC. The residual weight of the composite with 30 wt% PWC was 69%. Surface hardness, Young's modulus, and tensile strength of the composites were higher than those with a pure epoxy polymer matrix. The composite morphology was characterized by X‐ray diffraction and scanning electron microscopy. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Mechanical and morphological characterization of PVC plastisol composites with almond husk fillers

The present study develops new composite materials derived from environmentally friendly material, based on lignocellulosic fillers combined with a thermoplastic matrix. Almond husk, obtained as a by‐product of the agri‐food industry, has been used as a filler, combined with PVC thermoplastic matrix. This composite type (lignocellulosic material/thermoplastic matrix) is the object of this work for the advantages that it offers in environmental protection terms. With a view to identifying the degree of influence of filler amount, plasticizer concentration, and filler particle size on the properties of this new composite, we tested its mechanical properties and analyzed tensile fracture surfaces using scanning electron microscopy. POLYM. COMPOS., 28:71–77, 2007. © 2007 Society of Plastics Engineers     

超细改性矿物粉体增强硅橡胶

采用材料物理化学和复合材料的方法,系统地研究了８种矿物及其超细粉体和改性粉体与硅本的相互作用。结果表明,湍石、石英和硅灰石对硅橡胶基体具有较好的增强作用。粒径小、比面积大、长径比大等粉体性质好的填料,其增强性能高。界面粘附功与界面张力比值大的复合材料的力学性能好。具有表面活性基团（通过表面改性）、表面缺陷和一的表面羟基是提高粉体增强性能的重要因素。复合粉体的增强性能与粉休性质、混炼胶中的结合橡胶、