The effect of filler concentration on the electrical,thermal, and mechanical properties of carbon particle and carbon fiber‐reinforced poly(styrene‐co‐acrylonitrile) composites

Composite materials of poly (styrene‐co‐acrylonitrile) (luran) matrix with carbon fibers (CF)/carbon particles (CP) were prepared and their properties were evaluated. The mechanical and thermal properties of these composites were studied by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Although, by increasing the filler concentration no significant difference was found in melting and crystallization temperatures of the luran. The storage and tensile modulus of the composites increased linearly with filler concentration up to 40 wt % that was approximately three times higher than that of the virgin luran. There is a shift in glass transition temperature of the composite with increasing the filler concentration and the damping peak became flatter that indicated the effectiveness of the filler–matrix interaction. The volume resistivity and thermal conductivity (TC) of the composites were also measured. At a given carbon filler content the CF–Luran composites have much less volume resistivity as compared to CP–Luran composites. The decreased percolation threshold and volume resistivity in case of CF–Luran composites indicated that conductive paths existed in the composites. The conductive pathways were probably formed through interconnection of the carbon fillers. The volume resistivity was also decreased as a function of temperature. The thermal conductivity was increased linearly as a function of temperature with increasing filler concentration up to 40% of CF and CP. This increase was more profound in case of CF–Luran as compared to CP–Luran composites. This was owing to greater thermal networks of fibers as compared to particles. POLYM. COMPOS., 28:186–197, 2007. © 2007 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     

Hybrid particulate and fibrous injection molded composites: Carbon black/carbon fiber/polypropylene systems

The electrical properties of injection molded composite systems based on a polypropylene matrix and two types of carbonaceous fillers—carbon black (CB) and carbon fibers (CF)—were investigated. In addition to conductivity as a function of system compositions, conductivity profiles were studied. Inhomogeneous spatial distribution of CB particles in moldings containing either CB as a single filler or in combination with CF was found. Furthermore, unexpected fiber orientation transverse to the melt flow direction and disappearance of skin‐core orientation pattern, typical for injection molded fiber filled composites, were observed in the two filler samples. An amplification of the shear‐thinning behavior, characteristic for the polypropylene (PP) matrix, imposed by the inhomogeneity of the CB distribution resulting in flattening of the advancing melt front and velocity profile is suggested as underlying the observed phenomena. POLYM. COMPOS., 26:454–464, 2005. © 2005 Society of Plastics Engineers     

Comparative study of EMI shielding effectiveness for carbon fiber pultruded polypropylene/poly(lactic acid)/multiwall CNT composites prepared by injection molding versus screw extrusion

The electrical conductivity and electromagnetic interference (EMI) shielding effectiveness of the composites of polypropylene/poly(lactic acid) (PP/PLA) (70/30, wt %) with single filler of multiwall carbon nanotube (CNT) or hybrid fillers of nickel‐coated carbon fiber (CF) and CNT were investigated. For the single filler composite, higher electrical conductivity was observed when the PP‐g‐maleic anhydride was added as a compatibilizer between the PP and PLA. For the composite of the PP/PLA (70/30)/CF (20 phr)/CNT (5 phr), the composite prepared by injection molding observed a higher EMI shielding effectiveness of 50.5 dB than the composite prepared by screw extrusion (32.3 dB), demonstrating an EMI shielding effectiveness increase of 49.8%. The higher values in EMI shielding effectiveness and electrical conductivity of the PP/PLA/CF (20 phr)/CNT (5 phr) composite seemed mainly because of the increased CF length when the composites were prepared using injection molding machine, compared with the composites prepared by screw extrusion. This result suggests that the fiber length of the conductive filler is an important factor in obtaining higher values of electrical conductivity and EMI shielding effectiveness of the PP/PLA/CF/CNT composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45222.     

碳纤维增强聚丙烯复合材料的制备及性能

采用硝酸液相氧化法改性短切碳纤维(NCF),用以制备聚丙烯(PP)复合材料。以纤维含量和纤维种类为变量,通过万能力学试验机、熔体流动速率试验机、差示扫描量热、X射线衍射、扫描电子显微镜等研究它们对材料力学性能、流动性能、熔融温度以及结晶性能的影响。实验结果表明,纤维的含量影响纤维在基体中的分布,进而显著影响材料的性能,且含量在10%至20%区内时具有较好的增强效果;NCF与PP的界面具有更强的粘附力,这提升了复合材料的力学强度,降低了材料的断裂伸长率,降低了材料的熔融流动速率,提升了材料的结晶温度与结晶度,略微降低了材料的熔融温度;纤维含量与纤维种类均对材料的结晶晶型无明显影响。     

碳纤维/空心玻璃微珠/聚丙烯三元复合体系的制备及力学性能研究

以聚丙烯(PP)为基体、碳纤维(CF)为增强材料、空心玻璃微珠(HGB)为增韧剂制备了CF/HGB/PP三元复合体系,研究了CF、HGB含量对复合体系力学性能的影响,并对复合体系的微观结构进行了分析。结果表明:当CF含量为5份、HGB含量为15份时,CF/HGB/PP三元复合体系的综合力学性能最佳,其拉伸强度和缺口冲击强度分别比纯PP提高了46.5%和17.6%。     

Synergistic effects of carbon fillers on tensile and flexural properties in liquid‐crystal polymer based resins

One emerging market for thermally and electrically conductive resins is bipolar plates for use in fuel cells. Adding carbon fillers to thermoplastic resins increases the composite thermal and electrical conductivity. These fillers have an effect on the composite tensile and flexural properties, which are also important for bipolar plates. In this study, various amounts of three different types of carbon (carbon black, synthetic graphite particles, and carbon fibers) were added to Vectra A950RX liquid‐crystal polymer. In addition, composites containing combinations of fillers were also investigated via a factorial design. The tensile and flexural properties of the resulting composites were then measured. The objective of this study was to determine the effects and interactions of each filler with respect to the tensile and flexural properties. The addition of carbon black caused the tensile and flexural properties to decrease. Adding synthetic graphite particles caused the tensile and flexural modulus to increase. The addition of carbon fiber caused the tensile and flexural modulus and ultimate flexural strength to increase. In many cases, combining two different fillers caused a statistically significant effect on composite tensile and flexural properties at the 95% confidence level. For example, when 40 wt % synthetic graphite particles and 4 wt % carbon black were combined, the composite ultimate tensile and flexural strength increased more than what would be expected from the individual additive effect of each single filler. It is possible that linkages were formed between the carbon black and synthetic graphite particles that resulted in improved ultimate tensile and flexural strength. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

聚乳酸/碳纤维复合材料的3D打印线丝制备及其性能研究

本研究用高混机充分混合碳纤维(CF)和聚乳酸(PLA),再通过单螺杆挤出机制备出聚乳酸/碳纤维(PLA/CF)复合材料线丝,并成功地制备3D打印试样。通过测试PLA/CF复合材料线丝的力学性能,热性能,断面形态,发现PLA/CF复合材料线丝的耐热性高于纯PLA线丝,并且CF含量为1%的复合材料线丝的断裂强度可达70 MPa,高于纯PLA线丝的断裂强度,证明CF对PLA本体有增强效果。但随CF含量增加,断裂强度却有一定程度的下降,这可能是高含量CF的分散和复合材料的界面等因素影响的结果。     

短碳纤维增强聚丙烯复合材料性能的研究

本文研究了单螺杆挤出机加工短碳纤维增强聚丙烯复合材料（ＣＦＲＰＰ）的性能。结果表明，经表面处理的短碳纤维与ＰＰ复合，得到的材料其拉伸强度、冲击强度和热变形温度有明显提高，成型收缩率显著减小、电性能与半导体相近。本文还结合拉伸断面的电镜照片，比较分析了表面处理前后短碳纤维增强ＰＰ复合材料力学性能的变化。     

Effects of carbon fillers on the thermal conductivity of highly filled liquid‐crystal polymer based resins

The thermal conductivity of insulating polymers can be increased by the addition of conductive fillers. One potential market for these thermally conductive resins is for fuel cell bipolar plates. In this study, various amounts of three different carbon fillers (carbon black, synthetic graphite particles, and carbon fiber) were added to Vectra A950RX liquid crystal polymer. Because the resulting composites were anisotropic, they were tested for both through‐plane and in‐plane thermal conductivities. The effects of single fillers and combinations of the different fillers were studied via a factorial design. Each single filler caused a statistically significant increase in composite through‐plane and in‐plane thermal conductivities at the 95% confidence level, with synthetic graphite causing the largest increase. All of the composites containing combinations of the different fillers caused statistically significant increases in the composite through‐plane and in‐plane thermal conductivities. It is possible that thermally conductive pathways were formed that linked these carbon fillers, which resulted in increased composite thermal conductivity. Composites containing 70, 75, and 80 wt % synthetic graphite and the composite containing all three fillers (2.5 wt % carbon black, 65 wt % synthetic graphite, and 5 wt % carbon fiber) had in‐plane thermal conductivities of 20 W m^?1 K^?1 or higher, which is desirable for bipolar plates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of carbon fiber modification with multiwall CNT on the electrical conductivity and EMI shielding effectiveness of polycarbonate/carbon fiber/CNT composites

The effect of carbon fiber (CF) modification with multiwall carbon nanotube (CNT) on the electrical, mechanical, and rheological properties of the polycarbonate (PC)/CF/CNT composite was investigated. The CF and multiwall CNT (MWCNT) were treated with sulfuric acid and nitric acid (3:1 wt %) mixture, to modify the CF with the CNT. For the PC with acid-treated CNT (a-CNT) modified acid-treated CF (a-CF) (PC/a-CF/a-CNT) composite, the electrical conductivity, and the electromagnetic interference shielding effectiveness (EMI SE) showed the highest values, compared with those of the PC/a-CF and PC/a-CF/CNT composites. The EMI SE of the PC/a-CF (10 wt %)/a-CNT (0.5 wt %) composite was found to be 26 (dB at the frequency of 10.0 GHz, and the EMI SE was increased by 91.2%, compared to that of the PC/a-CF composite at the same amount of total filler content. Among the composites studied in this work, the PC/a-CF/a-CNT composite also showed the highest values of relative permittivity (ε_r) and dielectric loss factor. The above results suggest that the CF modification with the a-CNT significantly affected the electrical conductivity and EMI SE of the composite, and the hybrid fillers of the a-CNT and a-CF resulted in good electrical pathways in the PC/a-CF/a-CNT composite. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47302.     

聚偏氟乙烯/鳞片石墨/碳纤维高导热复合材料的制备

以聚偏氟乙烯（PVDF）树脂为基体,天然鳞片石墨（FG）、碳纤维（CF）为填料,采用熔融共混法制备了PVDF/FG/CF复合导热材料,并研究了FG、CF含量及其改性对复合材料导热性能和力学性能的影响。结果表明,复合材料的热导率随FG含量的增加而增大,力学性能随着FG含量的增加而降低;CF的加入提高了复合材料的力学性能,但热导率略有降低;对CF进行表面氧化处理将使得复合材料的热导率以及力学性能有所提高,当CF含量为5 %、FG含量为50 %时,复合材料的热导率为11.4 W/(m·K),拉伸强度为48 MPa,断裂伸长率为11 %。     

Study of plastic compounds containing polypropylene and wood derived fillers from waste of different origin

The scope of the article was to study the perspectives of the using of wood derived fillers (WDF) from waste of different origin as fillers of polypropylene. The WDF used in this study was hard wood flour (HW), birch veneer polishing dust (VD) and tetra‐pack carton cellulose fiber (TC). Some mechanical strength parameters, water uptake in the static and cyclic test and resistance to fungal decay of polypropylene (PP) composites containing these three types of WDF were studied and compared with similar loading (40 wt %) talc‐filled PP. Composites containing TC and VD fibers as filler showed the highest flexural strength at three test temperatures (?40, +20, and +40°C) and flexural modulus and tensile strength at plus temperatures. On the other hand talc‐filled PP exhibited greatest flexural modulus at minus temperature, greatest impact strength at room temperature and best flow ability. Significant difference was observed between PP composites with HW and VD fillers regarding water uptake in cyclic tests, however flexural strength and modulus change of composites were reversible after drying. No weight loss of WDF/PP composites was observed after 6 week exposure to brown‐ and white‐rot fungi, however, degradation of the surface of samples was detected by SEM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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.     

Self-healing interfaces of poly(methyl methacrylate) reinforced with carbon fibers decorated with carbon quantum dots

Fiber-polymer matrix interfacial debonding is often observed when mechanical loads are applied to fiber reinforced polymer composites. These defects usually end-up leading to a catastrophic fracture of the composites. In this work, carbon quantum dots (CDs) were incorporated on the surface of carbon fibers (CF), and poly(methyl methacrylate) (PMMA) composites with these modified fibers were able to restore their original properties after been previously damaged. To this end, CDs were synthesized and used to decorate the surface of CF. These decorated CF were then incorporated into PMMA by using a high intensity mixer. The prepared composites were submitted to dynamic mechanical, three-point bending and self-healing tests. Fluorescent CDs with diameters of 10 nm and functional groups, such as amine and carboxylic groups were successfully synthesized by the microwave pyrolysis method. The deposition of CDs on the surface of CF was evaluated and quantified by UV–vis spectroscopy and 1.2 wt.% of CDs on CF was determined. Composites with different surface treatments (including the presence of CD) did not show significant differences in strength, stiffness and damping, suggesting that the surface treatments on CF did not lead to major changes in the degree of interfacial interaction. Self-healing tests showed that damaged composites with CD decorated CF were able to restore their original properties, while no self-healing effect was noted in composites with no CD on CF. The observed self-healing behavior between PMMA and CF decorated with CD is due to the interactions between chemical groups on the surface of the CD and PMMA. Thus, damages related to fiber-matrix interfacial detachments can be repaired through reversible interactions based on CD.     

Recycled polypropylene reinforced with curaua fibers by extrusion

Curaua fibers were studied as reinforcing agents for postconsumer polypropylene. The composites were processed by extrusion. The composite properties were investigated by mechanical tests, thermal methods, melt flow index, surface morphology, and water uptake. The variables studied were as follows: fiber contents (10 to 40 wt %), fiber surface treatment, initial fiber length, and modification of the polypropylene matrix. The treatment of the fiber with 5 wt % NaOH aqueous solution did not improve fiber‐matrix adhesion and the composites using 20 wt % of untreated curaua fibers presented the better mechanical properties. Feeding the extruder with fibers having shorter lengths (0.01–0.4 mm) produced better fiber dispersion, improving the mechanical properties of the composites. Composites prepared using fibers without surface treatment with postconsumer polypropylene and with polypropylene modified with maleic anhydride showed mechanical properties and water uptake similar to composites using the same polymer reinforced with other lignocellulosic fibers. The extrusion process caused also partial fibrillation of the fibers, improving their aspect ratio. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

短切CF增强TPEE热塑性复合材料的注射成型及力学性能研究

以热塑性聚酯弹性体(TPEE)为基体材料,8 mm短切碳纤维(CF)为增强材料,制备CF/TPEE复合材料。材料通过双螺杆挤出系统混合塑化、挤出造粒后,再经过注塑成型制备成标准拉伸试样,通过力学性能测试及微观结构观察,系统研究了碳纤维含量和等离子表面处理对CF/TPEE复合材料拉伸性能的影响。结果表明,当碳纤维含量为20%时,CF/TPEE复合材料的拉伸强度最大,为39.08 MPa;相比于纯TPEE,其拉伸强度提高了217%;经过等离子表面处理后,拉伸强度进一步提高了5%。结合拉伸后断面的SEM图发现,注塑试样表层碳纤维取向度高,而近中区和中心层取向度相对较低,这是注射CF/TPEE复合材料拉伸性能提高效应不明显的主要原因。     

Melt spinning of conductive textile fibers with hybridized graphite nanoplatelets and carbon black filler

In this study, two different carbon fillers: carbon black (CB) and graphite nanoplatelets (GNP) are studied as conductive fillers for the preparation of conductive polypropylene (PP) nanocomposites. In order to obtain a homogenous dispersion of GNP, GNP/PP composites were prepared by two different methods: solid state mixing (SSM) and traditional melt mixing (MM). The result shows that MM is more efficient in the dispersion of GNP particles compared to SSM method. PP nanocomposites containing only one conductive filler and two fillers were prepared at different filler concentrations. Based on the analysis of electrical and rheological properties of the prepared nanocomposites, it shows that a hybridized composite with equal amounts of GNP and CB has favorable processing properties. Conductive fibers with a core/sheath structure were produced on a bicomponent melt spinning line. The core materials of these fibers are the hybridized GNP/CB/PP nanocomposite and the sheath is pure polyamide. It was found that GNPs were separated during melt and cold drawing which results in the decrease of conductivity. However, the conductivity could partly be restored by the heat treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2579–2587, 2013     

Effect of the delignification of wood fibers on the mechanical properties of wood fiber–polypropylene composites

The effect of the delignification of hornbeam fibers on the mechanical properties of wood fiber–polypropylene (PP) composites was studied. Original fibers and delignified fibers at three levels of delignification were mixed with PP at a weight ratio of 40:60 in an internal mixer. Maleic anhydride (0.5 wt %) as the coupling agent and dicumyl peroxide (0.1 wt %) as the initiator were applied. The produced composites were then hot‐pressed, and specimens for physical and mechanical testing were prepared. The results of the properties of the composite materials indicate that delignified fibers showed better performance in the enhancement of tensile strength and tensile modulus, whereas the hardness of the composites was unaffected by delignification. Delignified fibers also exhibited better water absorption resistance. Notched impact strength was higher for delignified fiber composites, but it was reduced at higher delignification levels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4759–4763, 2006     

Water absorption and dimensional stability of short kenaf fiber‐filled polypropylene composites treated with maleated polypropylene

The purpose of this research was to investigate the water absorption behavior and associated dimensional stability of kenaf‐polypropylene‐filled (PP/KF) composites. Composites with different fiber loadings, ranging from 0 to 40 wt %, were prepared with a twin‐screw extruder followed by hot press molding. The influence of the compatibilizer was also studied for PP/KF composite with 5 wt % maleated PP (MAPP). Water absorption testing was carried out at room temperature for 7 weeks. Tensile, flexural, and impact tests were also performed on control, wet, and re‐dried specimens. Increasing the fiber content resulted in higher water absorption and thickness swelling. The inferior mechanical properties of the wet composites were attributed to the effect of water, which deteriorates the interfacial properties of composites. On re‐drying, all properties were almost recovered because of the recovery of interfacial area as evident in scanning electron micrographs. Incorporation of the MAPP significantly improved the compatibility between the fiber and matrix and the mechanical properties of the composites compared with those without MAPP. It also diminished the water absorption as well as the related thickness swelling in the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010