炭黑对ASA/天然石墨复合材料的电磁屏蔽性能影响

通过熔融共混方法制备导电高分子复合材料丙烯腈-苯乙烯-丙烯酸酯共聚物(ASA)/天然石墨(NGR)/炭黑(CB),采用电磁屏蔽测量仪、四探针电阻率测量仪和动态热机械分析仪对复合材料的电性能和力学性能进行详细研究.结果 表明,ASA/NGR复合材料的体积电阻率随着炭黑含量增加而增加;同时在30 MHz～1500 MHz范...     

Carbon‐fiber‐reinforced acrylonitrile–styrene–acrylate composites: Mechanical and rheological properties and electrical resistivity

The aim of this study was to improve the mechanical properties of an acrylonitrile–styrene–acrylate copolymer (ASA) with the help of carbon fibers (CFs). Additionally, the effects of the CFs on the morphology, rheological properties, dynamical mechanical properties, electrical resistivity, and heat resistance of the ASA composites were studied with scanning electron microscopy, rotational rheometry, and dynamic thermomechanical analysis (DMA). The mechanical properties of the ASA composites were enhanced largely by the CFs. The maximum tensile strength of the ASA/CF composites reached 107.2 MPa. The flexural strength and flexural modulus also reached 162.7 MPa and 12.4 GPa, respectively. These findings were better than those of neat ASA; this was attributed to the excellent interfacial adhesion between the CFs and ASA resin. Rheological experiments proved that the viscosity and storage modulus (G′) values of the ASA/CF composites did not increase until the CF content reached 20%. The DMA outcomes confirmed that the glass‐transition temperature of the ASA composites was elevated from 120.6 to 125°C. Importantly, the G′ values of the composites with 20 and 30% CFs showed a large increase during heating. In addition, the ASA/CF composites exhibited excellent conductivity and heat resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43252.     

Processing and properties of polymer composites containing aligned functionalized carbon nanofibers

AC electric field was used to align functionalized carbon nanofibers (CNFs), carboxylic acid-functionalized CNFs (O-CNFs) and amine-functionalized CNFs (A-CNFs), in an epoxy resin. The resulting composites were characterized for dispersion and alignment structure as well as for their mechanical and electrical properties in the CNF alignment direction. Optical images of the composites revealed uniform distribution and alignment of the CNFs in the direction of the electric field. Due to the similarity in the alignment structure, it was observed that alignment of the functionalized CNFs was independent of the functional groups attached to the CNFs. Compression tests (parallel to the direction of the aligned A-CNFs) of A-CNF/epoxy composites showed an increase of 19% in compressive modulus and 9% in compressive strength at a CNF concentration of 4.5 wt.%, with respect to the neat composite. Electrical resistivity of composites measured parallel to the direction of aligned CNFs (containing up to 4.5 wt.% O-CNFs and A-CNFs) were found to be approximately three orders of magnitude lower than composites with non-aligned CNFs. The electrical resistivity percolation threshold for composites with aligned O-CNFs and A-CNFs occurred at approximately 0.75 wt.%. Discussion regarding the contribution of CNF type towards the mechanical and electrical properties is also presented.     

Cellulose nanofibril‐reinforced polypropylene composites for material extrusion: Rheological properties

Polypropylene (PP) is not typically utilized in 3D printing material extrusion because PP shrinks and warps during the printing process. Cellulose nanofibrils (CNF) have the potential to make PP 3D printer processable and also enhance mechanical properties of PP printed parts. The rheological behavior of CNF‐PP composites during material extrusion requires study because it is different from injection molding and compression molding processes. This study revealed the effects of CNF contents (3 and 10 wt%) and maleic anhydride polypropylene (MAPP) coupling agent on the rheological properties of CNF–PP composites. Morphological analysis showed that CNF agglomerated during spray drying and a spherical structure was formed. Rheological tests showed that the elastic modulus, complex viscosity, viscosity, and transient flow shear stress of PP were increased by the addition of 10 wt% CNF, while the creep strain of PP was reduced. The damping factor and stress relaxation time remained the same when 10 wt% CNF was added to the PP. Incorporation of MAPP into the CNF–PP composites impacted the rheological properties of the CNF–PP composites. Flexural strength and modulus of PP were improved by 5.9% and 26.8% by adding 10 wt% CNF compared to the control. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Cellulose NANOFIBER‐polyethylene nanocomposites modified by polyvinyl alcohol

The uniform dispersion of cellulose nanofibers (CNFs) in non‐polar polymer matrices is a primary problem to overcome in creating novel nanocomposites from these materials. The aim of this study was to produce CNF‐polyethylene (PE) nanocomposites by melt compounding followed by injection molding to investigate the possibility of using polyvinyl alcohol (PVA) to improve the dispersion of CNF in the PE matrix. The tensile strength of CNF‐ filled composites was 17.4 MPa with the addition of 5 wt % CNF–PVA, which was 25% higher than the strength of neat PE. The tensile modulus of elasticity increased by 40% with 5% CNF–PVA addition. Flexural properties also significantly increased with increased CNF loading. Shear viscosity increased with increasing CNF content. The elastic moduli of the PE/CNF composites from rheological measurements were greater than those of the neat PE matrix because of the intrinsic rigidity of CNF. Melt creep compliance decreased by about 13% and 45% for the composites with 5 wt % CNF and 10 wt % CNF, respectively. It is expected that the PVA carrier system can contribute to the development of a process methodology to effectively disperse CNFs containing water in a polymer matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42933.     

ASA/graphite/carbon black composites with improved EMI SE,conductivity and heat resistance properties

Composites, comprised of acrylonitrile styrene acrylate copolymer (ASA)/graphite (GR) with high electromagnetic interference shielding effectiveness (EMI SE), were fabricated by the introduction of carbon black (CB). The effects of CB on properties such as EMI SE, morphology, heat resistance, rheological and mechanical performance of the composites were characterized using a scanning electron microscope (SEM), rotational rheometer, electromagnetic shielding measuring instruments. The graphite and carbon black exhibited positive synergistic action, which promoted the complete formation of conductive networks in ASA matrix. The EMI SE and electrical conductivity of the ASA/GR/CB composites increased with higher CB loadings. In the frequency range of 30–3000 MHz, the maximum EMI SE of ASA composites with 50 % fillers reached 40 dB, but with 40 % fillers this property reached its maximum value of 50 dB. The flexural strength of ASA/GR/CB composites started to decline as CB loading exceeded 5 %. The heat resistance of the composites was improved due to the addition of CB. In this respect, the vicar softening temperature (VST) of the composites with 40 % fillers increased from 115.1 to 132.7 °C, and the VST of the composites with 50 % fillers was elevated from 125.4 to 138.9 °C.     

Thermal characterization of carbon‐nanofiber‐reinforced tetraglycidyl‐4,4′‐diaminodiphenylmethane/4,4′‐diaminodiphenylsulfone epoxy composites

The thermal properties of carbon nanofibers (CNF)/epoxy composites, composed of tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) resin and 4,4′‐diaminodiphenylsulfone (DDS) as a curing agent, were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis, and dynamic mechanical thermal analysis. DSC results showed that the presence of CNF had no pronounced influence on the heat of the cure reaction. However, the incorporation of CNF slightly improved the thermal stability of the epoxy. Furthermore, the storage modulus of the TGDDM/DDS epoxy was significantly enhanced, whereas the glass‐transition temperature was not significantly affected, upon the incorporation of CNFs. The storage modulus of 5 wt % CNF/epoxy composites at 25°C was increased by 35% in comparison with that of the pure epoxy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 295–298, 2006     

CNT基木塑复合材料的力学性能、电磁屏蔽性能

采用碳纤维(CF)和碳纳米管(CNT)通过模压工艺制备出具有电磁屏蔽功能的丙烯酸酯木塑复合材料。借助材料试验机、动态热机械分析仪、微欧计和电磁屏蔽测量仪等详细研究CNT质量分数对丙烯酸酯木塑复合材料弯曲性能、动态力学性能、电阻率和电磁屏蔽效能的影响。结果表明,添加质量分数为2%的CNT,使得复合材料的弯曲强度和弯曲弹性模量分别增加了10%和16%。复合材料的储能模量也在CNT质量分数为2%时达到最大值,之后储能模量随着CNT的增加而逐渐下降,损耗因子在CNT质量分数多于2%时也逐渐增加。复合材料的吸水率和导电性能随着CNT含量的增加而增加。同时复合材料的电磁屏蔽效能也随着CNT含量增加而递增。在30~1 500 MHz范围内,电磁屏蔽效能从27 d B增加到40 d B。结果证明,当CNT质量分数在2%时,丙烯酸酯木塑复合材料具有较佳的力学性能和较好的电磁屏蔽效能(30 d B),能满足商业要求。     

The effect of surface chemistry of graphene on rheological and electrical properties of polymethylmethacrylate composites

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.     

Effects of particle size and electrical resistivity of filler on mechanical,electrical, and thermal properties of linear low density polyethylene–zinc oxide composites

The effects of particle size and electrical resistivity of zinc oxide (ZnO) on mechanical properties, electrical and thermal conductivities of composites made with linear low density polyethylene (LLDPE) were investigated. Micron sized (mZnO), submicron sized (sZnO), and nano sized (nZnO) powders having resistivities of 1.5 × 10⁶, 1.5 × 10⁹, and 1.7 × 10⁸ were used to prepare composites with 5–20 vol % filler. The tensile strength was lowered and the modulus of elasticity of the composites was increased with ZnO addition. Rather than the particle size of the ZnO, its initial resistivity and aspect ratio affected the resistivity of composites. The resistivity of the LLDPE was lowered from 2.3 × 10¹⁶ Ω cm down to 1.4 × 10¹⁰ Ω cm with mZnO addition. Thermal conductivity of the composites was increased with ZnO addition 2.5–3 times of the polymer matrix. The composites can be used for electrostatically dissipating and heat sink applications due to their decreased electrical resistivity and increased thermal conductivity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2734–2743, 2013     

Influence of carbon nanofiber structure on properties of linear low density polyethylene composites

Three types of carbon nanofibers (MJ, Pyrograf®III PR‐19 and PR‐24) were incorporated into linear low density polyethylene (LLDPE) using intensive mixing. The electrical volume resistivity of composites decreased with the addition of CNFs from over 10¹² Ω cm for pure LLDPE to less than 10⁴ Ω cm for carbon nanofibers (CNF) contents of 15 wt% or more. Tensile modulus increased from 110 MPa for pure LLDPE to 200 MPa and 300 MPa for 15 wt% MJ and 15 wt% PR composites, respectively. However, the tensile strength remained fairly unchanged at about 20 MPa. Strain‐to‐failure decreased from 690% for pure LLDPE to 460% and 120% for 15 wt% MJ and 15 wt% PR composites, respectively. It was inferred that the interfacial interactions of LLDPE matrix with MJ fibers is better than that with PR fibers, resulting from the rougher surface of MJ fibers. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Highly dispersed and electrically conductive polycarbonate/oxidized carbon nanofiber composites for electrostatic dissipation applications

The influence of low cost, commercially oxidized carbon nanofibers (ox-CNFs) on the morphological, thermal, mechanical and electrical properties of polycarbonate (PC) composites was examined. Using a simple solution mixing process leads to good dispersion and high packing density of CNFs in the resultant composites. The composite materials exhibit a dramatic improvement in the DC conductivity; for example, increasing from 2.36 × 10⁻¹⁴ S/m for PC to ca. 10⁻² S/m for the composite at only 3.0 wt.% of CNFs, and exhibits a very fast static charge dissipation rate. Dynamic mechanical analysis showed a remarkable increase in storage modulus (282%) at 165 °C, compared to pure PC. Thermogravimetric analysis showed that thermal stability of the composites increased by 54 °C compared to the pure PC. To our knowledge, the measured electrical conductivity and thermal properties for PC/CNF are the highest values yet reported for PC/CNF composites at comparable loadings. The AC/DC conductivity is shown to play an important role to predict the state of dispersion.     

Mechanical and thermal transmission properties of carbon nanofiber‐dispersed carbon/phenolic multiscale composites

The present article reports the development and characterization of carbon nanofiber (CNF)‐incorporated carbon/phenolic multiscale composites. Vapor‐grown CNFs were dispersed homogeneously in to phenolic resin using an effective dispersion route, and carbon fabrics were subsequently impregnated with the CNF‐dispersed resin to develop carbon fiber/CNF/phenolic resin multiscale composites. Mechanical and thermal transmission properties of multiscale composites were characterized. Elastic modulus and thermal conductivity of neat carbon/phenolic and multiscale composites were predicted and compared with the experimental results. It was observed that incorporation of only 1.5 wt % CNF resulted in 10% improvement in Young's modulus, 12% increase in tensile strength, and 36% increase in thermal conductivity of carbon/phenolic composites. Fracture surface of composite samples revealed the formation of stronger fiber/matrix interface in case of multiscale composites than neat carbon/phenolic composites. Enhancement of above properties through CNF addition has been explained, and the difference between the predicted values and experimental results has been discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Desirable electrical and mechanical properties of continuous hybrid nano-scale carbon fibers containing highly aligned multi-walled carbon nanotubes

The continuous highly aligned hybrid carbon nanofibers (CNFs) with different content of acid-oxidized multi-walled carbon nanotubes (MWCNTs) were fabricated through electrospinning of polyacrylonitrile (PAN) followed by a series of heat treatments under tensile force. The effects of MWCNTs on the micro-morphology, the degree of orientation and ordered crystalline structure of the resulting nanofibers were analyzed quantitatively by diversified structural characterization techniques. The orientation of PAN molecule chains and the graphitization degree in carbonized nanofibers were distinctly improved through the addition of MWCNTs. The electrical conductivity of the hybrid CNFs with 3 wt% MWCNTs reached 26 S/cm along the fiber direction due to the ordered alignment of MWCNTs and nanofibers. The reinforcing effect of hybrid CNFs in epoxy composites was also revealed. An enhancement of 46.3% in Young’s modulus of epoxy composites was manifested by adding 5 wt% hybrid CNFs mentioned above. At the same time, the storage modulus of hybrid CNF/epoxy composites was significantly higher than that of pristine epoxy and CNF/epoxy composites not containing MWCNTs, and the performance gap became greater under the high temperature regions. It is believed that such a continuous hybrid CNF can be used as effective multifunctional reinforcement in polymer matrix composites.     

Hyperbranched polyol/carbon nanofiber composites

Carbon nanofiber (CNF) and carbon nanotube (CNT) composites have enhanced mechanical and electrical properties that make these composites desirable for antistatic and electronic dissipation technology. These applications require a homogenous dispersion of CNFs within a polymer matrix. To improve the compatibility/dispersability of CNFs within a polymer matrix, a hyperbranched polyol CNF composite was synthesized by the chemical modification of oxidized CNFs with glycidol and boron trifluoride diethyl etherate. The resulting polyol CNFs were characterized by TGA, FTIR, TEM/SEM and XPS. The hydroxyl groups were reacted with heptafluorobutyryl chloride to determine the amount of oxidized groups in the sample. The resulting composite was characterized by FTIR and elemental analysis. The amount of hydroxyl groups increased by 550% for the polyol CNFs as compared to the oxidized CNFs and an improvement in dispersion ability was observed.     

Rheological Analyses of Carbon Nanofiber/Polypropylene Composites

Rheological properties of carbon nanfiber/polypropylene composites were investigated. CNFs synthesized at 600°C were thermally modified at 2200°C. These CNFs with a curl/twisted morphology were incorporated into polypropylene (PP) by intensive mixing. The untreated CNF composites showed higher dynamic moduli, G′ and G″, than the heat-treated CNF composites. Also, stress relaxation results indicated that untreated CNF composites were relaxed in a longer time than heat-treated CNF composites. These results support that the untreated CNF composites needed less CNFs to perform CNF-CNF network than the heat-treated CNF composites did. It is suggested that structural changes can be verified by rheological analyses.     

Electrical conductivity and EMI shielding effectiveness of polyurethane foam–conductive filler composites

The morphological, electrical, and thermal properties of polyurethane foam (PUF)/single conductive filler composites and PUF/hybrid conductive filler composites were investigated. For the PUF/single conductive filler composites, the PUF/nickel‐coated carbon fiber (NCCF) composite showed higher electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) than did the PUF/multiwall carbon nanotube (MWCNT) and PUF/graphite composites; therefore, NCCF is the most effective filler among those tested in this study. For the PUF/hybrid conductive fillers PUF/NCCF (3.0 php)/MWCNT (3.0 php) composites, the values of electrical conductivity and EMI SE were determined to be 0.171 S/cm and 24.7 dB (decibel), respectively, which were the highest among the fillers investigated in this study. NCCF and MWCNT were the most effective primary and secondary fillers, and they had a synergistic effect on the electrical conductivity and EMI SE of the PUF/NCCF/MWCNT composites. From the results of thermal conductivity and cell size of the PUF/conductive filler composites, it is suggested that a reduction in cell size lowers the thermal conductivity of the PUF/conductive filler composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44373.     

Preparation and characterization of low‐density polyethylene/thermoplastic starch composites reinforced by cellulose nanofibers

In the current study, the effect of extracted cellulose nanofibers (CNFs) on rheological and mechanical properties and biodegradability of polyethylene/starch blend was investigated. The CNFs were extracted from wheat straws using a chemo‐mechanical method. Polyethylene/starch blend was reinforced by different amounts of CNF (6–14 wt%) using an internal mixer followed by a single screw extruder. The flow properties of nanocomposites were investigated by determining Melt Flow Index (MFI) and viscosity. Due to the weak interaction of cellulosic nanofibers and polymers, the flow behavior of nanocomposites was undesirable. Tensile tests were performed to evaluate the mechanical performance of nanocomposites. By increasing the CNF content, the tensile strength and elongation at break declined; whereas, the Young's modulus was improved. The biodegradation of cellulose nanocomposites was investigated by water absorption and degradability tests. Both experiments confirmed the progressive effect of cellulose nanofibers on the degradation of the composites. POLYM. COMPOS., 36:2309–2316, 2015. © 2014 Society of Plastics Engineers     

Effects of filler–filler and polymer–filler interactions on rheological and mechanical properties of HDPE–wood composites

High‐density polyethylene (HDPE)–wood composite samples were prepared using a twin‐screw extruder. Improved filler–filler interaction was achieved by increasing the wood content, whereas improved polymer–filler interaction was obtained by adding the compatibilizer and increasing the melt index of HDPE, respectively. Then, effects of filler–filler and polymer–filler interactions on dynamic rheological and mechanical properties of the composites were investigated. The results demonstrated that enhanced filler–filler interaction induced the agglomeration of wood particles, which increased the storage modulus and complex viscosity of composites and decreased their tensile strength, elongation at break, and notched impact strength because of the stress concentration. Stronger polymer–filler interaction resulted in higher storage modulus and complex viscosity and increased the tensile and impact strengths due to good stress transfer. The main reasons for the results were analyzed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

炭纳米纤维添加剂对炭/炭复合材料力学性能影响

采用等温CVI工艺制备出5种不同炭纳米纤维含量（质量分数分别为0，5％，10％，15％和20％）的炭／炭复合材料。发现添加炭纳米纤维的炭／炭复合材料具有很高的力学性能，在加入炭纳米纤维为5％时，相对于没有添加炭纳米纤维的炭／炭复合材料，弯曲强度增大了76．3％，弹性模量增大了55．5％，但添加量增大到20％时，强度和模量都逐渐降低。