Preparation and tribological properties of carbon fibre reinforced poly(vinylidene fluoride) composites

Abstract

The current study examines the tribological performance of poly(vinylidene fluoride) (PVDF) and carbon fibre reinforced poly(vinylidene fluoride) (CF/PVDF) under dry sliding condition. Different contents of carbon fibres (CFs) were employed as reinforcement. All filled and unfilled polyimide composites were tested against CGr15 ball and representative testing was performed. The effects of CF content on tribological properties of the composites were investigated. The worn surface morphologies of neat PVDF and its composites were examined by scanning electron microscopy and the wear mechanisms were discussed. Moreover, all filled PVDFs have superior tribological characteristics to unfilled PVDFs. The optimum wear reduction was obtained when the content of CF is 20 vol.-%.     

The effect of carbon fiber content on the friction and wear properties of carbon fiber reinforced polyimide composites

The current study examines the tribological performance of polyimide and carbon fiber reinforced polyimide (CF/PI) under dry sliding condition. Different contents of carbon fibers were employed as reinforcement. All filled and unfilled polyimide composites were tested against CGr15 ball and representative testing was performed. The effects of carbon fiber content on tribological properties of the composites were investigated. The worn surface morphologies of neat PI and its composites were examined by scanning electron microscopy and the wear mechanisms were discussed. Moreover, all filled polyimides have superior tribological characteristics to unfilled polyimides. The optimum wear reduction was obtained when the content of carbon fiber is 20 vol %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrical characteristics of fluorinated carbon black‐filled poly(vinylidene fluoride) composites

Dispersion and electrical properties of fluorinated carbon black‐filled poly(vinylidene fluoride) (PVDF) composites were studied as a function of the fluorine content. It was found that with increasing the fluorine content carbon particles tend to stick together to form large aggregates. The percolation concentration increases to a high concentration, whereas the percolation process becomes gradual. The temperature dependence of resistivity measurements show that the fluorinated carbon black‐filled PVDF composites exhibit a high PTC intensity and a low NTC effect. These phenomena were discussed in terms of thermodynamic interactions between fluorinated carbon and the PVDF matrix. The dielectric behavior was also investigated in this study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1063–1070, 2001     

VGCF填充PVDF/PMMA复合材料导电性能的研究

以气相生长碳纤维（VGCF）为导电填料,聚偏氟乙烯（PVDF）、聚甲基丙烯酸甲酯（PMMA）为基体制备复合型导电高分子材料。考察了填料用量、基体种类、配比以及PVDF结晶行为对复合材料导电性能的影响。结果表明,VGCF填充PMMA、PVDF、PVDF／PMMA（50／50）体系的渗滤阔值分别为5、4、3phr的填料用量。VGCF的加入会导致PVDF／PMMA体系发生微观相分离,而且VGCF会选择性富集在PVDF的非晶相中,所以PVDF／PMMA／VGCF体系的导电性呈现双重渗滤现象,该体系的体积电阻率不仅取决于富集相中VGCF的含量,而且还与PVDF相的连续性及其结晶行为密切相关。     

The Effect of Carbon Fiber Content on the Mechanical and Tribological Properties of Carbon Fiber-Reinforced PTFE Composites

Blending polytetrafluorothylene (PTFE) to carbon fiber at different compositions was produced in a corotating twin screw extruder where PTFE acts as the polymer matrix and carbon fiber as the dispersed phase. The effects of carbon fiber content on mechanical and tribological properties of the composites were investigated. The worn surface morphologies of neat PTFE and its composites were examined by scanning electron microscopy (SEM) and the wear mechanisms were discussed. The presence of carbon fiber dispersed in the PTFE continuous phase exhibited superior tribological characteristics to unfilled PTFE. The optimum wear reduction was obtained when the content of carbon fiber is 30 vol%.     

Carbon black–filled immiscible blends of poly(vinylidene fluoride) and high density polyethylene: Electrical properties and morphology

The electrical conductivity, current-voltage characteristics and morphology of carbon black–filled immiscible blends of poly(vinylidene fluoride)(PVDF) and high density polyethylene (HDPF) were investigated. Carbon black (CB) had stronger affinity to HDPE than to PVDF, resulting in its selective localization in the HDPE phase. The CB content and PVDF/HDPE volume ratio were the two main factors influencing the electrical conductivity, current-voltage characteristics, and morphology. At a fixed PVDF/HDPE volume ratio of 1/1, a percolation threshold of 0.037 volume fraction of CB was observed, and that value was much lower than that for conventional CB-filled polymer composites. At a fixed CB content (10 wt% CB), a maximum electrical conductivity was observed at a PVDF/HDPE volume ratio of 2.75. An increase in CB content in the composites with a fixed PVDF/HDPE volume ratio (1/1) and an increase in PVDF content in composites with a fixed CB content (10 wt%) greatly decreased the domain size of the PVDF phase. A positive-temperature-coefficient effect was used to determine the location of CB in the blends.     

Poly(vinylidene fluoride)/thermoplastic polyurethane flexible and 3D printable conductive composites

This work focus on the development of polymeric blends to produce multifunctional materials for 3D printing with enhanced electrical and mechanical properties. In this context, flexible and highly conductive materials comprising poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) filled with carbon black-polypyrrole (CB-PPy) were prepared by compression molding, filament extrusion and fused filament fabrication. In order to achieve an optimal compromise between electrical conductivity, mechanical properties and printability, blends composition was optimized and different CB-PPy content were added. Overall, the electrical conductivities of PVDF/TPU 50/50 vol% co-continuous blend were higher than those found for PVDF/TPU 50/50 wt% (i.e., 38/62 vol%) composites at same filler content. PVDF/TPU/CB-PPy 3D printed samples with 6.77 vol% filler fraction presented electrical conductivity of 4.14 S m⁻¹ and elastic modulus, elongation at break and maximum tensile stress of 0.43 GPa, 10.3% and 10.0 MPa, respectively. These results highlight that PVDF/TPU/CB-PPy composites are promising materials for technological applications.     

Conductive network formation and electrical properties of poly(vinylidene fluoride)/multiwalled carbon nanotube composites: Percolation and dynamic percolation

Conductive network formation and its dynamic process for multiwalled carbon nanotubes (MWNTs) and carboxyl‐tethered MWNT (MWNT‐COOH) filled poly(vinylidene fluoride)(PVDF) systems were investigated. Based on real‐time tracing the variation of electrical resistivity of systems with isothermal treatment time, the conductive network formation was evaluated. It was found that the conductive network formation was temperature and time dependent. The percolation time, characterized at a certain annealing time where the electrical resistivity started to decrease drastically, decreased with the increase of the filler concentration or the annealing temperature. However, the values of the percolation time and the activation energy of conductive network formation for the PVDF/MWNT‐COOH system were higher than those of the PVDF/MWNT system, indicating that the interaction between MWNTs and PVDF molecules played an important role in the conductive network formation of the composites. Furthermore, a modified thermodynamic percolation model was proposed to predict the percolation time of PVDF/MWNT composites. It was found that the calculated results fit the experimental data very well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Melt processible fluoropolymer composites

A series of melt-processible fluoropolymer compounds including ethylene-tetrafluoroethylene (ETFE), poly(vinylidene fluoride) (PVF₂), ethylene-chlorotrifluoroethylene copolymer (ECTFE), perfluoroalkoxy modified tetrafluoroethylene (PFA), and fluorinated ethylene-propylene copolymer (FEP) containing reinforcing glass fiber, milled glass fiber, carbon fiber, minerals, poly(tetrafluoroethylene) (PTFE) lubricant powder, graphite powder and MoS₂ were prepared and characterized. The mechanical, physical, thermal, and tribiological properties of these composites were compared and ranked for suitability in various applications. These composites represent the first comprehensive evaluation of reinforced and filled meltprocessible fluoropolymer composites.     

Compatibilization of PVDF/PA6 Blend by the Addition of a Third Polymer PTFE

The compatibilization of poly(vinylidene fluoride) (PVDF) with polyamide 6(PA6, higher acrylonitrile content) blend was improved by adding poly(methyl methacrylate) (PTFE). It was confirmed by characterizing the mechanical and tribological properties of the blends. More homogeneous morphology was formed when PTFE was added into PVDF/PA6 blend, which was shown in scanning electron microscopy (SEM). The surface tension of blends was increased due to the higher polar surface tension of PTFE. As the content of PTFE was increased further, the tensile strength of the blend was slightly decreased.     

Optical Properties of Composites Based on Poly(o-phenylenediamine), Poly(vinylenefluoride) and Double-Wall Carbon Nanotubes

In this work, synthesis and optical properties of a new composite based on poly(o-phenylenediamine) (POPD) fiber like structures, poly(vinylidene fluoride) (PVDF) spheres and double-walled carbon nanotubes (DWNTs) are reported. As increasing the PVDF weight in the mixture of the chemical polymerization reaction of o-phenylenediamine, the presence of the PVDF spheres onto the POPD fibers surface is highlighted by scanning electron microscopy (SEM). The down-shift of the Raman line from 1421 cm⁻¹ to 1415 cm⁻¹ proves the covalent functionalization of DWNTs with the POPD-PVDF blends. The changes in the absorbance of the IR bands peaked around 840, 881, 1240 and 1402 cm⁻¹ indicate hindrance steric effects induced of DWNTs to the POPD fiber like structures and the PVDF spheres, as a consequence of the functionalization process of carbon nanotubes with macromolecular compounds. The presence of the PVDF spheres onto the POPD fiber like structures surface induces a POPD photoluminescence (PL) quenching process. An additional PL quenching process of the POPD-PVDF blends is reported to be induced in the presence of DWNTs. The studies of anisotropic PL highlight a change of the angle of the binding of the PVDF spheres onto the POPD fiber like structures surface from 50.2° to 38° when the carbon nanotubes concentration increases in the POPD-PVDF/DWNTs composites mass up to 2 wt.%.     

Tribological properties of SiO2 nanoparticle filled–phthalazine ether sulfone/phthalazine ether ketone (50/50 mol %) copolymer composites

SiO₂ nanoparticle filled–poly(phthalazine ether sulfone ketone) (PPESK) composites with various filler volume fractions were made by heating compression molding. The tribological behavior of the PPESK composites was investigated using a block‐on‐ring test rig by sliding PPESK‐based composite blocks against a mild carbon steel ring. The morphologies of the worn composite surfaces, wear debris, and the transferred films formed on the counterpart steel surface were examined with a scanning electron microscope, whereas the chemical state of the Fe element in the transfer film was analyzed with X‐ray photoelectron spectroscopy. In addition, IR spectra were taken to characterize the structure of wear debris and PPESK composites. It was found that SiO₂ nanoparticle filled–PPESK composites exhibit good wear resistance and friction‐reduction behavior. The friction and wear behavior of the composites was improved at a volume fraction between 4.2 and 14.5 vol % of the filler SiO₂. The results based on combined SEM, XPS, and IR techniques indicate that SiO₂ nanoparticle filled–PPESK composite is characterized by slight scuffing in dry sliding against steel and polishing action between composite surface and that of the countpart ring, whereas unfilled PPESK is characterized by severe plastic deformation and adhesion wear. In the former case a thin, but not complete, transfer film was formed on the surface of the counterpart steel, whereas in the latter case, a thick and lumpy transfer film was formed on the counterpart steel surface. This accounts for the different friction and wear behavior of unfilled PPESK and SiO₂ nanoparticle filled–PPESK composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2136–2144, 2002     

Dielectric properties of Ag@C/PVDF composites

The core–shell Ag@C nanoparticles were prepared by hydrothermal method. The silver cores with diameters from 100 to 120 nm are each covered with a carbon shell about 60–80‐nm thick. Ag@C/poly(vinylidene fluoride) (PVDF) composites were prepared by the solution cast method. Transmission electron microscopy showed that the Ag@C core–shell nanoparticles were dispersed homogenously in the PVDF matrix with little agglomeration. The crystallization behavior and dielectric properties of the Ag@C/PVDF composites as a function of frequency and temperature were studied. The differential scanning calorimeter measurements showed that the crystallinity of the Ag@C/PVDF composites decreased with the increasing content of the Ag@C nanoparticles. The dielectric tests showed that the permittivity of the Ag@C/PVDF composites increased obviously over that of the pure PVDF with increasing content of Ag@C particles because of the enhanced interfacial polarization. The tan δ of the composites remained at a low level (～0.08 at 1000 Hz). Furthermore, the permittivity and the tan δ of the composites increased with increasing temperature. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Integration of PDA Chemistry and Surface‐Initiated ATRP to Prepare Poly(methyl methacrylate)‐Grafted Carbon Nanotubes and Its Effect on Poly(vinylidene fluoride)–Carbon Nanotube Composite Properties

Poly(methyl methacrylate)‐grafted carbon nanotubes (PMMA@MWCNTs) are nondestructively prepared via the integration of mussel‐inspired polydopamine (PDA) chemistry and the surface‐initiated atom transfer radical polymerization (ATRP) method. The structures and properties of the poly(vinylidene fluoride)‐based (PVDF‐based) nanocomposites filled with pristine MWCNTs and PMMA@MWCNTs are investigated. The results show that the encapsulation of PMMA on the MWCNTs surface not only improves the dispersibility of MWCNTs in the PVDF matrix but also enhances the interfacial interaction between MWCNTs and PVDF. The addition of PMMA@MWCNTs nanofillers to PVDF can effectively induce the crystal structure of PVDF to transform from the α‐phase to the β/γ ‐phase, and nearly 100% β/γ ‐phase PVDF formed when the nanofiller loading is higher than 5 wt%. Compared with the MWCNTs/PVDF composites, the PMMA@MWCNTs/PVDF composites exhibit obvious improvement in the percolation threshold because the PMMA shells hinder the direct contact of the MWCNTs. Moreover, the loss tangent of the PMMA@MWCNTs/PVDF composites is effectively suppressed due to the reduced leakage current in the composites and the enhanced interfacial strength between the nanofiller and the matrix.     

Self-assembly and conductive network formation of vapor-grown carbon fiber in a poly(vinylidene fluoride) melt

The construction of vapor-grown carbon fiber (VGCF) conductive networks through the self-assembly process in a poly(vinylidene fluoride) (PVDF) melt was investigated. Depending on real-time tracing of the variation of electrical resistivity with isothermal treatment time, the properties and possible assembly mechanism of PVDF/VGCF composites were evaluated. It was found that the self-assembly velocity of VGCFs in the matrix increased with annealing temperature. Scanning electron microscopy showed that the coagulation of VGCFs formed the conductive paths in the matrix after annealing. The value for the activation energy of conductive network formation was about 144 kJ/mol, which was higher than the value for the activation energy of zero-shear-rate viscosity () of the pure polymer (62 kJ/mol), but was close to the value for the activation energy of of VGCF filled PVDF composites (135 kJ/mol). These results indicated that the conductive network of the composites was related to the interaction between PVDF molecules and VGCFs. According to a thermodynamic percolation model, a self-assembly velocity model for conductive network formation was proposed, and the result indicated that self-assembly velocity was a function of annealing time and temperature.     

Dielectric properties of poly(vinylidene fluoride) composites based on Bucky gels of carbon nanotubes with ionic liquids

“Bucky gels” of carbon nanotubes were successfully prepared by grinding multi‐walled carbon nanotubes (MWNTs) and ionic liquids (ILs) for several hours. A series of poly(vinylidene fluoride) (PVDF) composites with Bucky gels was obtained through simple melt compounding. The Raman spectrum showed significant interaction among the ILs, MWNTs, and PVDF. The dielectric behavior of the PVDF composites based on unmodified and IL‐modified MWNTs was studied from 40 Hz to 30 MHz. The addition of ILs significantly enhanced the dielectric property of the PVDF/IL/MWNT ternary composites, which was much higher than that of the sum of PVDF/IL and PVDF/MWNT binary composites. The SEM results revealed that both MWNTs and ILs uniformly dispersed throughout the PVDF/IL/MWNT composites because of the strong interaction between them. The DSC and XRD results showed that the addition of ILs in the composites changed the crystallinity and crystal form of the PVDF. POLYM. COMPOS., 36:94–101, 2015. © 2014 Society of Plastics Engineers     

The Effect of Arylboronic Acid Treatment of Carbon Fiber on the Mechanical and Tribological Properties of PA66 Composites

PA66 composites filled with surface-treated carbon fiber were prepared by twin-screw extruder in order to study the influence of carbon fiber surface arylboronic acid treatment on the mechanical and tribological behavior of the PA66 composites (CF/PA66). The mechanical property, friction and wear tests of the composites with untreated and treated carbon fiber were performed and the worn surface morphology was analyzed. The results show that the worn surface area of the treated carbon fiber was far smoother than that of the untreated carbon fiber and there formed a bonding adhesion on the carbon fiber surface after treatment. The tensile strength of CF/PA66 composites with surface arylboronic acid treatment was improved. The friction coefficient and wear of arylboronic acid treated CF/PA66 composites were apparently lower than that with untreated carbon fiber. In conclusion, the surface treatment favored the improvement of the higher interface strength and so had good effect on improving the tribological properties of the composites.     

聚偏氟乙烯/氟橡胶合金/炭黑三元复合体系电热性能

以聚偏氟乙烯(PVDF)/氟橡胶(F2 6 )合金为基体,研究了两种不同炭黑类型及用量、不同环境温度、不同热历程及辐照交联对复合物PTC(正电阻温度系数)导电特性的影响。结果表明,聚偏氟乙烯/氟橡胶/炭黑三元复合体系具有强PTC特性,可用于制作电致发热稳定性良好的、自限温度 135± 5℃、具有商业用途的自控温型伴热带     

钛酸钾晶须和硫酸钙晶须增强PA66/PVDF的摩擦学行为研究

制备了钛酸钾晶须（PTW）和硫酸钙晶须（CSW）增强聚酰胺66（PA66）/聚偏氟乙烯（PVDF）复合材料,通过摩擦磨损试验机研究了不同含量晶须对PA66/PVDF摩擦磨损性能的影响,并采用扫描电子显微镜、傅里叶变换外光谱仪观察了复合材料的微观结构、磨损表面和转移膜形貌。结果表明,PTW的加入使得共混物的自润滑性与耐磨性均降低,CSW有效地提高了PA66/PVDF的摩擦学性能;摩擦前后复合材料表面并未发生化学变化。     

A study of the mechanical and electrical properties of a polymer/carbon black binder system used in battery electrodes

The effects of carbon black content and crosslinking on the mechanical and electrical properties of a fluorinated elastomer, FC2178 (Dyneon Corp., Oakdale, MN), poly(vinylidene fluoride‐co‐hexafluoropropylene), were investigated and compared to those of poly(vinylidene fluoride) (PVDF). Attention was given to changes in mechanical and electrical properties of the polymers when under cyclic deformation. To describe the mechanical properties of the carbon‐filled polymers in a way that is independent of the chemical details, two mechanical models were used to fit cyclic stress–strain experiments. The linear model was used to determine the effect of crosslinking on the mechanical properties of crosslinked FC2178 films. However, when carbon black was added to the polymer films, the linear model no longer fit the data well. In particular, the cyclic stress–strain curves for carbon‐filled polymers showed non‐linear regions and displayed the characteristic of ‘memory.’ A non‐linear element was added in parallel with the existing elements of the linear model to successfully describe the effects of the added carbon black. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1891–1899, 2003