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1.
    
A potential application for conductive resins is in bipolar plates for use in fuel cells. The addition of carbon filler can increase the electrical and thermal conductivities of the polymer matrix but will also have an effect on the tensile and flexural properties, important for bipolar plates. In this research, three different types of carbon (carbon black, synthetic graphite, and carbon nanotubes) were added to polypropylene and the effects of these single fillers on the flexural and tensile properties were measured. All three carbon fillers caused an increase in the tensile and flexural modulus of the composite. The ultimate tensile and flexural strengths decreased with the addition of carbon black and synthetic graphite, but increased for carbon nanotubes/polypropylene composites due to the difference in the aspect ratio of this filler compared to carbon black and synthetic graphite. Finally, it was found that the Nielsen model gave the best prediction of the tensile modulus for the polypropylene based composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

2.
    
Microsized aluminum/epoxy resin composites were prepared, and the thermal and dielectric properties of the composites were investigated in terms of composition, aluminum particle sizes, frequency, and temperature. The results showed that the introduction of aluminum particles to the composites hardly influenced the thermal stability behavior, and decreased Tg of the epoxy resin; moreover, the size, concentration, and surface modification of aluminum particles had an effect on their thermal conductivity and dielectric properties. The dielectric permittivity increased smoothly with a rise of aluminum particle content, as well as with a decrease in frequency at high loading with aluminum particles. While the dissipation factor value increased slightly with an increase in frequency, it still remained at a low level. The dielectric permittivity and loss increased with temperature, owing to the segmental mobility of the polymer molecules. We found that the aluminum/epoxy composite containing 48 vol % aluminum‐particle content possessed a high thermal conductivity and a high dielectric permittivity, but a low loss factor, a low electric conductivity, and a higher breakdown voltage. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

3.
    
The influence of the carbon black content on the mechanical and electrical properties of polypropylene/carbon black composites prepared by different processing procedures was investigated. The formation of a continuous conducting network in the insulating matrix and, consequently, the percolation threshold depend strongly on the processing route and influence both the mechanical and electrical properties of the prepared composites. An interesting coincidence of the dependencies of conductivity and elongation at break on the filler content was found. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1903–1906, 2001  相似文献   

4.
    
The effective thermal conductivity behavior of vulcanized perfluoromethyl vinyl ether (PMVE) rubber filled with various inorganic fillers was investigated and analyzed with thermal conductivity models. Experimental results showed that there was no significant improvement in the thermal conductivity of PMVE rubber if the intrinsic thermal conductivity of the fillers was greater than 100 times that of the rubber matrix, and this agreed with the prediction of Maxwell's equation. The thermal conductivity of PMVE rubber filled with larger size silicon carbide (SiC) particles was greater than that of PMVE filled with smaller size SiC because of the lower interfacial thermal resistance, and there existed a transition filler loading at about 60 vol %. It was also found that flocculent graphite was the most effective thermally conductive filler among the fillers studied. A modified form of Agari's equation with a parameter independent on the units used was proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

5.
    
The crystallization behavior, structure, and morphology developed was investigated for polypropylene containing different fillers such as silica, calcium carbonate, talc, mica, graphite, etc. by using compression‐molded samples prepared at several cooling rates. It was observed that the crystallinity obtained for any given composition depended on the thermal conductivity of the filler and the PP composite containing it as well as the cooling rate to which it was subjected. These composites exhibited skin‐core type of morphology and the skin layer thickness was found to depend not only on the cooling rate but also on the type of filler, its thermal conductivity, etc. These various experimental findings were discussed in light of the phenomenological model described in our earlier work, which correlates thermal conductivity and degree of crystallinity for various compositions of PP containing additives. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 615–623, 2004  相似文献   

6.
    
The purpose of this study is to improve the several properties of composites consisting of a phenolic and fly ash or artificial Zeolite such as sodium type Zeolite (Na? Ze) or calcium type Zeolite(Ca? Ze). And it also includes the improvement in the flowability of molding compounds. The molding compounds were prepared from a phenol novolac, a curing agent, and several fillers. The flowability of the compounds containing fly ash and artificial Zeolite as a filler, mentioned above, was superior to that of the compounds containing glass fiber (GF), calcium carbonate (CaCO3), or talc as a filler. The phenolic composites were prepared from the above molding compounds by transfer molding. The phenolic composite containing Ca? Ze had most superior heat resistance, electrical insulation, and flexural strength, though in the lastly listed property it ranked next to the GF‐filled composite. The linear expansion coefficient of the composite containing Ca? Ze was as low as almost isotropic. The reasons of obtaining these excellent properties were thought to be as follows: (1) Ca? Ze could finely be dispersed in the phenolic resin to bring good impregnation. (2) The surface chemical and physical interaction between the resin and Ca? Ze was higher than that between the resin and the other fillers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   

7.
    
Thermally conductive resins are needed for bipolar plates in fuel cells. Currently, the materials used for these bipolar plates often contain a single type of graphite in a thermosetting resin. In this study, varying amounts of four different types of polyacrylonitrile carbon fillers (Ketjenblack carbon black, Thermocarb synthetic graphite, Fortafil 243 carbon fiber, and Panex 30 carbon fiber) were added to a thermoplastic matrix (Vectra A950RX Liquid Crystal Polymer), with the resulting resins tested for through‐plane and in‐plane thermal conductivity. There are two unique contributions of this work. The first contribution is the use of the Nielsen model for the through‐plane thermal conductivity as a function of the single filler volume fraction. The model fits the data for all composites well. The second contribution is the development of a new, accurate, empirical model to predict the in‐plane thermal conductivity for all resins containing synthetic graphite or carbon fiber. Both of these models will form the basis for the development of new thermal conductivity models for composites with multiple fillers for fuel cell bipolar plate applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007  相似文献   

8.
    
In recent years, rapid progress in the development of flexible electronic devices has increased the demand for materials with low Young's modulus and high thermal conductivities. In this study, we successfully fabricated such composites with polyrotaxane (PR) by applying highly concentrated graphene nanoplates (GNPs). A high thermal conductivity of 25 W m−1 K−1 was achieved along the in-plane direction of the composite while maintaining a low Young's modulus of 147 MPa at 35 vol% of GNPs. This thermal conductivity is higher than those achieved with PR composites containing 56 vol% of hexagonal boron nitride and 37 vol% of aligned carbon nanofiber/carbon nanotubes.  相似文献   

9.
    
Synergistic effect of copper and multiwalled carbon nanotube on thermal and mechanical properties of high‐density polyethylene (HDPE)‐matrix composite was evaluated. Attrition mill was employed to prepare the hybrid powder. Reinforcing the polymer‐matrix was carried out using different contents of simultaneously (Sim) and separately (Sep) milled powders as hybrid fillers. X‐ray diffraction and microscopy results show different trends of particle size for Sep and Sim affected by both milling time and volume fraction ratio. Thermal characterization indicates that conductivity was enhanced by 90% and thermal expansion was reduced to 53% of neat HDPE. Young's modulus and tensile strength were improved by 7.8 and 1.22 times of neat HDPE, respectively. Also, characteristics of Sim‐reinforced composites exhibited better correlated relation with milling time compared with erratic behavior of Sep. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45397.  相似文献   

10.
    
Crosslinked polyethylene is a promising polymer regarding its mechanical properties and wear resistance, predominantly used in pipework systems. However, it suffers from low thermal conductivity, which limits its application in geothermal heating/cooling systems. In this work, crosslinked high-density polyethylene (PEX) composites with spherical graphite (SG) as a reinforcing filler are examined in terms of their thermal and mechanical properties. Thermal conductivity measurements showed a significant improvement of the thermal conductivity of PEX with increasing filler content (40.6% augmentation for 5 wt% SG content), while the experimental data are in good agreement with the Chauhan theoretical model for spherical particles. Tensile tests revealed that the elastic modulus of PEX/SG composites presented a considerable improvement (23.6% augmentation for 5 wt% SG content). Various micromechanical models for the prediction of the composites' elastic behavior were applied to the experimental data, which present a satisfactory agreement with the Takayanagi I two-phase model for low concentrations of SG, and the Takayanagi II two-phase model for higher filler content.  相似文献   

11.
    
The temperature at which microcracking occurred in symmetrical cross‐ply carbon‐fiber/epoxy composite materials was predicted with a yield‐stress‐based failure model. A fracture mechanics analysis of the in situ strength of the ply groups in a composite material was combined with a compound beam determination of thermal stress development to create the predictive model. This approach, unlike many other models, incorporated the change in the material properties with temperature with the room‐temperature properties of the laminate to predict the low‐temperature behavior of the ply groups. Dynamic mechanical analysis was used to assess microcracking at cryogenic temperatures through the observation of discontinuities in the material properties during failure. Four different material systems were studied, and the model accurately predicted the onset temperature for microcracking in three of the four cases. It was shown that the room‐temperature properties of a fiber‐reinforced polymeric composite laminate, appropriately modified to account for property variations at low temperatures, could be used to predict transverse microcracking as a response to thermal stresses at cryogenic temperatures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1104–1110, 2004  相似文献   

12.
    
To determine the possibility of using starch as biodegradable filler in the thermoplastic polymer matrix, starch‐filled polypropylene (PP) composites were prepared by extrusion of PP resin with 5, 10, 15, and 20 wt % of potato starch in corotating twin‐screw extruder. The extruded strands were cut into pellets and injection molded to make test specimens. These specimens were tested for physicomechanical properties such as tensile and flexural properties, Izod impact strength, density, and water absorption. These PP composites were further characterized by melt flow index (MFI), vicat softening point (VSP), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) techniques. It was found that, with increase in starch content, tensile modulus, flexural strength, and flexural modulus of the PP composites increased along with the increase in moisture, water absorption, and density, while retaining the VSP; but, tensile strength and elongation, impact strength, hardness, and MFI of the PP composites also decreased. DSC analysis of the PP composite revealed the reduction in melting temperature, heat of fusion, and percentage of crystallization of PP with increase in starch content. Similarly, TGA traces display enhanced thermal degradability for PP as starch content increases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

13.
    
Polytetrafluoroethylene (PTFE) composites filled with Sr2Ce2Ti5O16 ceramic were prepared by a powder processing technique. The structures and microstructures of the composites were investigated by X‐ray diffraction and scanning electron microscopy techniques. Differential scanning calorimetry showed that the ceramic filler had no effect on the melting point of the PTFE. The effect of the Sr2Ce2Ti5O16 ceramic content [0–0.6 volume fraction (vf)] on the thermal conductivity, coefficient of thermal expansion (CTE), specific heat capacity, and thermal diffusivity were investigated. As the vf of the Sr2Ce2Ti5O16 ceramic increased, the thermal conductivity of the specimen increased, and the CTE decreased. The thermal conductivity and thermal expansion of the PTFE/Sr2Ce2Ti5O16 composites were improved to 1.7 W m?1 °C?1 and 34 ppm/°C, respectively for 0.6 vf of the ceramics. The experimental thermal conductivity and CTE were compared with different theoretical models. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

14.
    
Thermally conductive resins are needed for bipolar plates in fuel cells. Currently, the materials used for these bipolar plates often contain a single type of graphite in a thermosetting resin. In this study, varying amounts of two different types of polyacrylonitrile based carbon fibers, Fortafil 243 and Panex 30, were added to a thermoplastic matrix (Vectra A950RX Liquid Crystal Polymer). The resulting single filler composites were tested for thermal conductivity and a simple exponential thermal conductivity model was developed for the square root of the product of the in‐plane and through‐plane thermal conductivity . The experiments showed that the through‐plane thermal conductivity was similar for composites up to 40 vol % fiber. However, at higher loadings, the Panex 30 samples exhibited higher thermal conductivity. The experiments also showed that the in‐plane thermal conductivity of composites containing Panex 30 was higher than those containing Fortafil 243 for all volume fractions studied. Finally, the model agreed very well with experimental data covering a large range of filler volume fraction (from 0 to 55 vol % for both single filler systems). The model can be used with existing through‐plane thermal conductivity models to predict in‐plane thermal conductivity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5456–5462, 2006  相似文献   

15.
    
The pyrolysed oil shale (POS) obtained from the pyrolysis of bituminous rock was used as filler in poly(ethylene‐co‐vinyl alcohol) (EVAL). The effects of vinyl alcohol content in the EVAL and the particle size of pyrolysed oil shale in the mechanical properties were investigated. The EVAL was prepared by hydrolysis of poly(ethylene‐co‐vinyl acetate) (EVA) with 8 and 18 wt % of vinyl alcohol content. The composites were prepared in a rotor mixer at 180°C with concentration of pyrolysed oil shale up to 5 wt %. Stress–strain plots of compression‐molded composites showed a synergic behavior in the mechanical properties for low concentrations (1–5 wt %) of POS in all particle sizes and EVAL used. Such behavior indicates a close packing and strong interactions between the inorganic filler and the polymer. Increasing of the vinyl alcohol content of EVAL improved the compatibility between the polymer and filler, but decreasing the POS particle size had no effect on the properties. The modulus and the ultimate tensile strength also increased in all concentrations of POS for both EVAL. Mechanical properties and dynamic mechanical analysis also demonstrated the compatibility between EVAL and POS. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1658–1665, 2004  相似文献   

16.
    
Residual cellulose fibers from the paper industry have been used as reinforcements in recycled polypropylene (PP) composites. The main obstacle to obtaining good properties with this biocomposite is deficiencies in the compatibility between the nonpolar matrices and the polar cellulose fibers used as reinforcements. The aim of this work was to improve the compatibilization between these cellulose fibers and the PP matrix with four different methods: modification by the addition of polypropylene–maleic anhydride copolymer (PPgMA) during the process of blending, preblending modification of the cellulose with a solution of PPgMA, modification of cellulose by silanes (vinyltrimethoxysilane), and acetylation of cellulose. Blends with all of the differently modified celluloses were prepared with the cellulose content varied up to 40%, and then all of the blends were subjected to thermal (differential scanning calorimetry and thermogravimetric analysis) and thermomechanical (dynamic mechanical thermal analysis) analyses. The results showed that the addition of cellulose fibers improved the thermomechanical behavior of the PP, increasing the value of the log of the dynamic modulus, and affected the thermal and thermooxidative behavior. Moreover, an advantage of the use of a recycled PP containing a small quantity of ethyl vinyl acetate (EVA) as a prime material in the composition was the enhancement of mechanical properties. The use of these methods for the modification of cellulose led to more desirable thermal and thermooxidative stabilities. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2353–2360, 2003  相似文献   

17.
    
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  相似文献   

18.
    
To attain interface-engineered polypropylene/cellulose nanofibril (PP/CNF) composites with improved thermal and mechanical performance, PP was grafted with glycidyl methacrylate (GMA) and styrene via direct melt-mixing and GMA/styrene-grafted PP (PGMA) was reinforced with 1–10 wt% CNF content through a mass-producible melt-compounding process. The spectroscopic analyses confirmed the existence of specific hydrogen-bonding interactions between CNF and PGMA in the composites. The melt-rheological measurement revealed the occurrence of chemical reactions between the hydroxy group of CNF and the glycidyl group of PGMA of the composites. Accordingly, the dispersion and interfacial adhesion of CNF in the PGMA matrix was improved. β-form PP crystals were also developed by accelerating the crystallization of PGMA and PGMA/CNF composites, unlike PP with only α-form crystals. The storage modulus of PGMA/CNF composites was enhanced noticeably with increasing CNF content. Moreover, the impact strength of PGMA composite with 1 wt% CNF was found to be 29.2% higher than that of neat PP.  相似文献   

19.
    
Short bamboo fiber reinforced polypropylene composites were prepared by incorporation of various loadings of chemically modified bamboo fibers. Maleic anhydride grafted polypropylene (MA‐g‐PP) was used as compatibilizer to improve fiber–matrix adhesion. The effects of bamboo fiber loading and modification of the resin on the physical, mechanical, thermal, and morphological properties of the bamboo reinforced modified PP composites were studied. Scanning electron microscopy studies of the composites were carried out on the interface and fractured surfaces. Thermogravimetric analysis and IR spectroscopy were also carried out. At 50% volume fraction of the extracted bamboo fiber in the composites, considerable increase in mechanical properties like impact, flexural, tensile, and thermal behavior like heat deflection temperature were observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

20.
    
In this work, a new method to estimate the thermal conductivity of polymer composite was suggested. For this purpose, polymer composites composed of high‐density polyethylene (HDPE) and boron nitride (BN) were prepared by twin‐screw extruder melt‐mixing, followed by compression molding technique, and their microstructure was investigated by material simulation. Consequently, the Cf parameter of Agari and Uno equation, which represents an ease in forming conductive chains, was quantified by “Structure factor (related with conductive pathway)” and “Interfacial factors (related with thermal resistance)”, ultimately helping us evaluate the thermal conductivity of arbitrary composite system. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

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