Vapor grown carbon nanofiber (VGCNF)/polymer conductive composites are elegant materials that exhibit superior electrical, electromagnetic interference (EMI) shielding effectiveness (SE) and thermal properties compared to conventional conductive polymer composites. This article reviews recent developments in VGCNF/polymer conductive composites. The article starts with a concise and general background about VGCNF production, applications, structure, dimension, and electrical, thermal and mechanical properties. Next composites of VGCNF/polymer are discussed. Composite electrical, EMI SE and thermal properties are elaborated in terms of nanofibers dispersion, distribution and aspect ratio. Special emphasis is paid to dispersion of nanofibers by melt mixing. Influence of other processing methods such as in-situ polymerization, spinning, and solution processing on final properties of VGCNF/polymer composite is also reviewed. We present properties of CNTs and CFs, which are competitive fillers to VGCNFs, and the most significant properties of their composites compared to those of VGCNF/polymer composites. At the conclusion of the article, we summarize the most significant achievements and address the future challenges and tasks in the area related to characterizing VGCNF aspect ratio and dispersion, determining the influence of processing methods and conditions on VGCNF/polymer composites and understanding the structure/property relationship in VGCNF/polymer composites. 相似文献
Electromagnetic interference shielding effectiveness (EMI SE) of multifunctional Fe3O4/carbon nanofiber composites in the X-band region (8.2–12.4 GHz) is studied. Here, we examine the contributing effects of various parameters such as Fe3O4 content, carbonization temperature and thickness on total shielding efficiency (SEtotal) of different samples. The maximum EMI SE of 67.9 dB is obtained for composite of 5 wt.% Fe3O4 (0.7 mm thick) with the dominant shielding by absorption (SEA) of electromagnetic radiation. The enhanced electromagnetic shielding performance of Fe3O4/carbon nanofiber composites is attributed to the increment of both magnetic and dielectric losses due to the incorporation of magnetite nanofiller (Fe3O4) in electrically conducting carbon nanofiber matrix as well as the specific nanofibrous structure of carbon nanofiber mats, which forms a higher aspect ratio structure with randomly aligned nanofibers. Furthermore, we prove that the addition of elastomeric polydimethylsiloxane (PDMS) as a coating for carbon nanofiber composite strengthens the composite structure without interfering with its electromagnetic shielding efficiency. 相似文献
The microstructure, electromagnetic interference (EMI) shielding effectiveness (SE), DC electrical conductivity, AC electrical conductivity and complex permittivity of nanostructured polymeric materials filled with three different carbon nanofillers of different structures and intrinsic electrical properties were investigated. The nanofillers were multiwall carbon nanotubes (MWCNT), carbon nanofibers (CNF) and high structure carbon black (HS-CB) nanoparticles and the polymer was acrylonitrile-butadiene-styrene (ABS). In addition, the EMI SE mechanisms and the relation between the AC electrical conductivity in the X-band frequency range and the DC electrical conductivity were studied. The nanocomposites were fabricated by solution mixing and characterized by uniform dispersion of the nanofillers within the polymer matrix. It was found that, at the same nanofiller loading, the EMI SE, permittivity and electrical conductivity of the nanocomposites decreased in the following order: MWCNT > CNF > CB. MWCNT based nanocomposites exhibited the lowest electrical percolation threshold and the highest EMI SE owning to the higher aspect ratio and electrical conductivity of MWCNT compared to CNF and HS-CB. The AC conductivity in the X-band frequency range was found to be independent of frequency. 相似文献
The influence of the dispersion of vapor-grown carbon nanofibers (VGCNF) on the electrical properties of VGCNF/Epoxy composites has been studied. A homogenous dispersion of the VGCNF does not imply better electrical properties. In fact, it is demonstrated that the most simple of the tested dispersion methods results in higher conductivity, since the presence of well-distributed nanofiber clusters appears to be a key factor for increasing composite conductivity.PACS: 72.80.Tm; 73.63.Fg; 81.05.Qk. 相似文献
Vapour grown carbon nanofibre (VGCNF)/rubbery epoxy (RE) composites were produced, by either mechanical mixing, three-roll milling (RM) or combined ultrasonication/mechanical mixing. Incorporation of VGCNFs resulted in significant enhancements in the thermal and electrical conductivities of the material. Appropriate selection of processing technique and parameters can help to maximise the potential of VGCNF additions by improving their dispersion in the matrix. The composites produced by RM have superior transport properties compared with those produced by other techniques. The thermal conductivity of such composites at 40 wt.% VGCNFs reached 1.845 W/m K, a 10-fold increase compared to RE alone. The thermal conductivity data of VGCNF/RE composites best fits to the Hatta–Taya model. The lowest electrical percolation threshold is at 2 wt.%, obtained for composites produced by RM. The thermal conductivity of VGCNF/glassy epoxy (GE) composites at 12 wt.% is 10% lower than the corresponding RE composite but its electrical conductivity is 2 orders of magnitude higher than the corresponding RE composite. VGCNFs at 40 wt.% increase the compressive strength of rubbery epoxy by ~5× but the compressive modulus of 40 wt.% VGCNF/RE composite is 12 times lower than that of 12 wt.% VGCNF/GE composite, demonstrating highly compliant nature of RE composites. 相似文献
An in situ polymerization method to prepare thermoplastic polyurethanes (TPU)/graphene and TPU/graphite composites have been studied to clarify the influence of intrinsic filler properties and dispersion level on the morphology and properties of the TPU. Two types of graphene, one high-aspect ratio and one low, and graphite flake at various loadings were studied. Rotational rheology experiments on the suspensions of filler in polyol were used to characterize the agglomeration level of the filler after the dispersive mixing step and an effective aspect ratio reflective of the dispersion level was obtained. Variations in the glass transition temperature and thermal transitions of the TPU composites were related to the agglomeration level and intrinsic filler properties. 相似文献
Novel foam composites comprising functionalized graphene (f‐G) and polyvinylidene fluoride (PVDF) were prepared and electrical conductivity and electromagnetic interference (EMI) shielding efficiency of the composites with different mass fractions of f‐G have been investigated. The electrical conductivity increases with the increase in concentration of f‐G in insulating PVDF matrix. A dramatic change in the conductivity is observed from 10?16 S · m?1 for insulating PVDF to 10?4 S · m?1 for 0.5 wt.% f‐G reinforced PVDF composite, which can be attributed to high‐aspect‐ratio and highly conducting nature of f‐G nanofiller, which forms a conductive network in the polymer. An EMI shielding effectiveness of ≈20 dB is obtained in X‐band (8–12 GHz) region and 18 dB in broadband (1–8 GHz) region for 5 wt.% of f‐G in foam composite. The application of conductive graphene foam composites as lightweight EMI shielding materials for X‐band and broadband shielding has been demonstrated and the mechanism of EMI shielding in f‐G/PVDF foam composites has been discussed.
Graphene sheets with different oxygen contents were prepared to functionalize the electrically insulating polymethylmethacrylate (PMMA). The influences of surface chemistry of graphene on rheological, electrical and electromagnetic interference (EMI) shielding properties of its PMMA composites were investigated. The appearance of frequency-independent storage modulus at low frequency suggests a solid-like viscoelastic behavior and the formation of an interconnected network of graphene in the matrix. Due to the favorable interfacial interactions arising from polarity matching, the graphene with a C/O ratio of 13.2 (graphene-13.2) shows a better dispersion in PMMA than those with lower C/O ratios, and thus its PMMA composites exhibit lower rheological and electrical percolation thresholds. The EMI shielding properties of the graphene/PMMA composites exhibit similar dependence on the oxygen content of graphene. A high EMI shielding effectiveness of ~30 dB was obtained for the PMMA composite with 4.2 vol.% of graphene-13.2 with microwave absorption as the dominant EMI shielding mechanism. 相似文献
In this article, carbon nanofiller, in particular graphite, has been reviewed for the preparation of polymer-based composites. The dispersion of graphite relies on fabrication methods employed such as solution mixing, melt blending, and in situ polymerization. The consequences of surface modification on thermal, mechanical, and electrical characteristics were explored. Moreover, the properties and parameters involved in feature enhancement of graphite-based materials have been highlighted. Topical development in field of thermal, mechanical, and other physical properties of polymer/graphite composites was investigated. Furthermore, worth of materials regarding electrodes, resistors, dye-sensitized solar cells, electromagnetic interference shielding, packaging, and flame retardant applications has been discussed. 相似文献
Electrical, morphological and rheological properties of polyethylene (PE)/multi-walled carbon nanotube (MWCNT) and poly(phenylene sulfide) (PPS)/MWCNT composites were studied with the MWCNT content using vector network analyzer, scanning electron microscopy and rotational rheometry. From the results of electrical conductivity and electromagnetic interference shielding efficiency (EMI SE) of the PE/MWCNT and PPS/MWCNT composites, the electrical percolation threshold of the composites has found to be 5 and 3 wt% MWCNT, respectively. From the results of the EMI SE of the composites, it was suggested that the increase in homogeneous dispersion of the MWCNT in the PPS matrix has been attributed to the increase in connectivity of the MWCNT-MWCNT network structure of the composite. Therefore, the higher values of the EMI SE with the MWCNT content were observed in the PPS/MWCNT than the PE/MWCNT composites. From the results of the rheological properties of the PE/MWCNT and PPS/MWCNT composites, the increase in the complex viscosity was observed for the PPS/MWCNT than the PE/MWCNT composites. The increase in complex viscosity maybe due to the increase in homogeneous dispersion of the MWCNT in the PPS matrix than that in the PE matrix. From the results of the rheological properties of the PE/MWCNT and PPS/MWCNT composites, it was suggested that the homogeneous dispersion of the MWCNT in the polymer matrix has affected the increase in complex viscosity of the PPS/MWCNT composite. This result of rheological behavior is consistent with the results of the EMI SE of the PE/MWCNT and PPS/MWCNT composites. 相似文献
Harmful electromagnetic radiations that are generated from different electronic devices could be absorbed by a light weight and mechanically flexible good electromagnetic interference (EMI) shielding polymer nanocomposite. On the other hand, different electronic wastes (“e-wastes”) which are generally polymer building materials generated from wastes of dysfunctional electronic devices are not naturally biodegradable. Our recent effort has been employed to produce bio-degradable EMI shielding polymer nanocomposite. For that purpose, we had prepared a 50:50 ratio polylactic acid/thermoplastic polyurethane polymer nanocomposite by mixing the conducting carbon black with the blend following the facile and industrially feasible solution mixing method. Morphological characterizations by scanning electron microscopy and transmission electron microscopy analysis revealed the co-continuous morphology of the neat blend as well as polymer nanocomposites with the preferential distribution of conductive filler on a particular polymer phase. The polymer nanocomposites gave good mechanically with improved thermal properties. We got EMI shielding effectiveness around −27 dB with a low percolation threshold at around 30 wt% filler loading in the polymer nanocomposite at the X-band frequency domain (8.2–12.4 GHz). Later we had studied the biodegradability of the PLA/TPU along with their composites (TXPXCX) by employing the respirometry method and got a satisfactory result to ensure their biodegradability. 相似文献
The length of multi-walled carbon nanotubes (MWCNT) has an important influence on the properties of polymer/MWCNT composites. This study aims to examine the influence of the length of MWCNT on the mechanical properties, distribution, melting and crystallization behavior, and electromagnetic interference shielding effectiveness (EMI SE) of PP/MWCNT composites. The test results show that MWCNT of a short length contribute to better mechanical properties and have a better dispersion in the matrix. MWCNT also serve as a nucleating agent for PP, thereby increasing the crystallization temperature (Tc). In particular, short MWCNT provide PP/MWCNT composites with a greater degree of cyrstallinity. The conjunction of 8 wt% long MWCNT in PP/MWCNT composites results in an optimal electrical resistivity of 65.02 Ω-cm, and an average EMI SE of ?29.47 dB. The polymer/MWCNT composites have properties that can be adjusted by using different lengths of MWCNT, which is advantageous for application in diverse products. 相似文献