Polytetrafluoroethylene Micropowder Research Articles

Preparation of PTFE-TIO2-GO/EP superhydrophobic costing and its performance study

For many years, the issue of microbial adhesion has presented difficulties in both daily life and business. In this paper, superhydrophobic coatings were produced by adding epoxy resin (EP), butyl acetate, titanium dioxide (TiO2) nanoparticles, polytetrafluoroethylene micropowder (PTFE), and graphene oxide (GO) sequentially into a mug and mixing well, and then modifying the microscopic particles by using perfluorooctyltriethoxysilane (POTS), and lastly producing the superhydrophobic coatings applied via spraying on the aluminum sheet surface. The micro morphology of the samples was analysed by SEM and EDS, the molecular makeup of the samples was analysed by FTIR and the molecular stability, mechanical stability and algae resistance were tested, and finally the the rust unwillingness of the coatings was investigated by using an electrochemical workstation (Tafel and EIS). The outcomes demonstrated that the best GO to nanoparticle mass ratio of 10% was chosen to achieve a contact angle of 167.5° and a sliding angle of 2.5°. The coating contact angle was still superior to 150° after 7 days of immersion in strong acids and bases as well as 3.5 wt% Nacl and after 8 hours of immersion in boiling water. After 800 abrasion tests the contact angle was still 150.6°. Algae resistance tests showed that the coatings had good resistance to algae adhesion.

3D printed stretchable coaxial fiber grid for dual-mode multifunctional tactile sensor array

Tactile sensors play a critical role in the Internet of Things (IoT) and wearable devices. However, although current tactile sensors can precisely measure pressure, the simple fabrication of stretchable high-performance tactile sensors with a broad measuring range and multifunctions is still challenging. Herein, an ink-direct writing 3D printing method is developed to fabricate novel stretchable dual-mode tactile sensors with coaxial fiber structure. The 3D printed coaxial fibers have an outer skin composed of silicone rubber and polytetrafluoroethylene micropowders thixotropic agent and an inner core of an ionic conductive solution composed of polyvinyl alcohol and sodium chloride. The coaxial fibers exhibit excellent electrical conductivity (0.54 S cm−1) and outstanding stretchability, as high as 390 %. The intersection of the two fibers constitutes a dual-mode tactile sensor which can operate in triboelectric or capacitive modes with complementary measurement ranges from 0.0003 to 0.4517 N. Besides, by combining the signals from the two modes, the sensor can identify the material that comes into contact with the sensor. A 3D printed network of tactile sensor arrays made of warp-weft interwoven coaxial fibers is able to accurately detect the locations of multi-point contact with the array. This dual-mode multifunctional tactile sensor can be widely used in various applications such as the IoT and wearable devices.

Effect of radiation sensitizer on the friction, mechanical and thermal degradation properties of electron beam cured FKM-PTFE composite

Friction coefficient behaviour of electron beam cured vinylidene fluoride-hexafluoropropylene copolymer fluorocarbon rubber (FKM) with 30% loading of polytetrafluoroethylene micro-powder (PTFEMP) irradiated at 250 kGy dose were studied by using a pin-on-disk tribometer for a total testing distance of 360 m in dry conditions at a sliding speed and applied normal load (FN) of 0.05 m/s and 1 N respectively. The same tests were done on the 70/30 blend added with radiation sensitizers n,n-1,3 phenylene bismaleimide (HVA2), trimethylol propane triacrylate (TMPTA) and tripropylene glycol diacrylate (TPGDA). The average friction coefficient (μ) value of all the composites with sensitizer decreased with the TMPTA system recording the lowest μ value which reduced by almost half compared to the pure composite due to better crosslinking density of the vulcanizate. Analysis of the friction coefficient curve behaviour showed an initial low value but displaying an increasing trend versus distance in the TMPTA and TPGDA composites while HVA2 composite recorded an initial high value but showed a reducing trend versus distance. HVA2 composite also recorded the best tensile strength results due to its influence in promoting better synergistic effect and miscibility of PTFEMP filler in FKM matrix.

Neutron Nanomediators for Non-Invasive Temperature Mapping of Fuel Cells

Polymer electrolyte fuel cells (PEFCs) have gained significant attention in the past century for their ability to convert hydrogen chemical energy into electrical energy. However, the technology still requires refinement due to losses in polarization, ohmic resistance, and mass transport that result in heat generation, negatively affecting the device water management and durability. To better understand these processes, researchers initiate studies to improve knowledge of the temperature at the cell structure core. However, current methods using micro-thermocouples [1] are highly invasive, impeding cell operation and limiting data accuracy.The project aims to overcome the latter problem using ferromagnetic nanoparticles for non-invasive temperature mapping on these devices. A key part of this novel method is the application of Neutron Imaging through a polarized beam [2], which allows to detection of the temperature distribution on the surrounding nanosensors. The dispersed ferromagnetic nanomediators, in these conditions, depolarize the incoming neutron beam due to the random magnetic field produced by the nanoparticles themselves. Furthermore, as the temperature rises toward the Curie temperature (Tc), the nanosensors tend to lose their magnetic preferential orientation, influencing the neutron beam polarization gradually less as the ambient temperature increases.This project includes identifying a suitable material, synthesizing nanoparticles through solution techniques [3], and performing physical and magnetic ex-situ characterizations. By dispersing them in Polytetrafluoroethylene micro-powders, nickel, iron, and Nd2Fe14B alloys were initially studied at different concentrations, grain sizes, and magnetic environments, showing promising signal detection (η) and absolute thermal variation (Δη) results.

Preparation and properties of PTFE@TiO2/epoxy superhydrophobic coating

The problem of bacterial adhesion has been a challenge in everyday life and industry for decades. In this paper, polytetrafluoroethylene(PTFE) micropowder, titanium dioxide(TiO2) nanopowder, ethyl acetate and epoxy resin were sequentially added to a beaker and stirred well, then the nanoparticles were modified using perfluorooctyltriethoxysilane (POTS), and finally superhydrophobic coatings were fabricated on the surface of an aluminium sheet by spraying process. Characterisation was carried out using scanning electron microscopy and contact angle measurement, and the coating wettability, chemical stability and mechanical stability properties were investigated, and finally the coating was tested for antimicrobial properties. The study suggests that the hydrophobicity of the sample was optimal at a contact angle of 163.3° and a rolling angle of 3.2° when the ratio of PTFE micropowder to nano-TiO2 by mass was 1:4 and the ration between POTS and nanoparticles by mass was 12%. The contact angles were 137.8° and 143.6° after 25 and 32 hours of soaked in an anhydrous solution with a pH of 14 and 1, respectively. Most importantly, it exhibits good antimicrobial properties.

Design and Fabrication of a New Filament, PLA with PTFE as Fillers, for Water Repellent Surfaces

The use of additive manufacturing by fused deposition is a versatile, cost-effective and simple prototyping and manufacturing technique that is generating and accelerating a revolution in equipment and filaments. However, materials are limited to a small number of polymers. It is a scientific challenge to bring new characteristics and properties to the parts obtained. In this work, a new filament has been designed with the combination of PLA (poly lactic acid) as matrix and PTFE (polytetrafluoroethylene) as filler. This filament has improved the water repellency of the parts obtained. Cleaning, demoulding, anti-adherence, anti-frost, anti-humidity and anti-bacterial applications can be deployed with this new filament. Extruded filaments have been obtained with PLA beads and PTFE micropowder. Flat test tubes have been produced with this filament. The experiments included PTFE fillers (1% to 40% by weight). The surfaces have been characterised by sliding angle (SA) and static contact angle (CA) tests, surface roughness (Sa and Sz), flatness error and % water adsorption. The results indicate, as expected, that the higher the fluoropolymer content, the higher the hydrophobicity, reaching values of 125° for CA and 9° for SA, and the % adsorption decreases. In terms of roughness, the surfaces are less rough when the PTFE load increases. On the other hand, the flatness is a property strongly affected by the % PTFE load and at values higher than 15% it produces intense warping and deformation of the specimens. Finally, the PTFE loading thresholds in the PLA matrix have been obtained below which the wettability and dimensional reproduction properties are balanced and optimal.

Surface modification by microencapsule coating and grafting to prepare high hydrophilic polytetrafluoroethylene micropowder

Due to the hydrophobic nature and high gravimetric density, it is very difficult to obtain water dispersible polytetrafluoroethylene (PTFE). In this work, high hydrophilic PTFE microparticle was successfully prepared by grafting poly(acrylic acid) MAA and BA onto the surface of PTFE micropowder via an in-situ polymerization of melamine formaldehyde resin (MFR) coating processing method. The functional groups and surface microstructures of the MFR/acrylate modified PTFE micropowder were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM), the hydrophilic performance was characterized by water contact angle measurement. The results revealed that the hydrophilicity of the PTFE micropowder was greatly enhanced by grafting of the MFR/acrylate complex systems, and the contact angle decreased from 132.8° for pristine PTFE to 73.2° for sample of MFR1PTFE60MAA5BA2.5. The obtained micropowder could be well dispersed in water to form homogeneous suspension with high stability. Compared with the other methods to improve the hydrophilicity of PTFE microparticle, furthermore, this microcapsule grafting method is more convenient and efficient, which could promote the application of PTFE micropowder in waterborne coating fields.

3D Printing of a Polydimethylsiloxane/Polytetrafluoroethylene Composite Elastomer and its Application in a Triboelectric Nanogenerator.

Silicone rubber elastomers are broadly used in various fields, where the three-dimensional (3D) printing of silicone rubber elastomers is important for the free construction of complex structures. Herein, a series of polydimethylsiloxane/polytetrafluoroethylene composite inks for direct-ink-writing 3D printing are developed. The inks are prepared by directly mixing a silicone rubber liquid precursor with polytetrafluoroethylene micropowder. The polytetrafluoroethylene micropowder serves as a thixotropic agent to regulate the rheological properties of the polydimethylsiloxane precursor to fulfill the requirement of 3D printing and endow the composite material with high electron affinity. The printed polydimethylsiloxane/polytetrafluoroethylene composite elastomer exhibits excellent elasticity and cyclic stability. A high-performance triboelectric nanogenerator is constructed with the 3D-printed polydimethylsiloxane/polytetrafluoroethylene composite as the triboelectric layer and elastic structure. This work establishes a new method of 3D printing polydimethylsiloxane-based elastomers and thus provides a new technique for constructing complex structures in flexible devices.

Pentadecafluorooctanoic-acid-free polytetrafluoroethylene and mechanism of PFOA formation by \u03b3-irradiation

Low-molecular-weight (Mw) polytetrafluoroethylene (PTFE) micropowder is added to wax for use in automotive equipment and printing machines and is produced by radiation-initiated degradation under atmospheric conditions. However, pentadecafluorooctanoic acid (PFOA) is produced as a by-product in concentrations greater than 25 ppb, which is problematic because PFOA does not degrade in the environment. Herein, we clarify the PFOA-formation mechanism and develop a manufacturing process for a novel low-Mw PTFE micropowder that does not contain PFOA (less than 5 ppb). The process uses combined irradiation and heat treatment in an oxygen-free atmosphere. Furthermore, PFOA-free PTFE micropowder can be produced on the 10-kg scale.

Grafting Polytetrafluoroethylene Micropowder via in Situ Electron Beam Irradiation-Induced Polymerization.

Decreasing the surface energy of polyacrylate-based materials is important especially in embossed holography, but current solutions typically involve high-cost synthesis or encounter compatibility problems. Herein, we utilize the grafting of polytetrafluoroethylene (PTFE) micropowder with poly (methyl methacrylate) (PMMA). The grafting reaction is implemented via in situ electron beam irradiation-induced polymerization in the presence of fluorinated surfactants, generating PMMA grafted PTFE micropowder (PMMA–g–PTFE). The optimal degree of grafting (DG) is 17.8%. With the incorporation of PMMA–g–PTFE, the interfacial interaction between polyacrylate and PTFE is greatly improved, giving rise to uniform polyacrylate/PMMA–g–PTFE composites with a low surface energy. For instance, the loading content of PMMA–g–PTFE in polyacrylate is up to 16 wt %, leading to an increase of more than 20 degrees in the water contact angle compared to the pristine sample. This research paves a way to generate new polyacrylate-based films for embossed holography.

Self-lubricating layer consist of polytetrafluoroethylene micropowders and fluorocarbon acrylate resin formation on surface of geotextile

In this study, the self-lubricating layer consist of polytetrafluoroethylene (PTFE) micropowders and two types fluorocarbon acrylate resin were formed on the surface of geotextile, to improves the evenness and decreases the frictional angle value of geotextile surface. The surface and cross section morphology of geotextile were examined by scanning electron microscopy (SEM). It was determined that composite resin emulsion was evenly coated on the surface of geotextile, to form a even and complete self-lubricating layer, and it was strongly combined with the geotextile due to formation of the transition layer. The tensile fracture stress and strain values of samples were evaluated by mechanical properties measurement, the tensile fracture stress of the untreated and treated sample was approximately 5329 kN/m and 5452 kN/m while the elongation at the yield of them was approximately 85% to 83.9%, respectively. In addition, the frictional angle values of municipal solid waste (MSW)/geotextile interface was measured by the tilt table test, the values of untreated sample was 28.1° and 24.2° under the dry and moist condition, the values of treated sample was 16.2° and 9.8°, respectively.

Trimethyl borate‐treated polytetrafluoroethylene micropowders with improved hydrophilic and adhesive properties based on coordination bond theory

Based on coordination bond theory, the current study proposes a novel method to modify the surface of the polytetrafluoroethylene (PTFE) micropowders. The samples were treated with trimethyl borate in the n‐hexane solution, and this improves the hydrophilic and adhesive properties of PTFE micropowders. The surface properties of treated samples were evaluated by using X‐ray photoelectron spectrometry, contact angle measurement, settling velocity measurement, and adhesive property measurement. Trimethyl borate treatment led to an evident increase in the hydrophilic and adhesive properties of PTFE micropowders. The water contact angle of PTFE micropowders decreased from 115° to 85.4°, while the ethanol contact angle of PTFE micropowders decreased from 39.8° to 11.2° owing to the combination of the trimethyl borate with PTFE micropowders as indicated by the X‐ray photoelectron spectrometry spectra. Furthermore, the settling velocity of powders dispersed in ethanol/water (1/10) solution (pH = 8.5) improved (with a settlement ratio exceeding 20% in 60 minutes), and the fracture stress of the powders/resin composite membrane increased from 4.68 to 6.67 MPa while the elongation at the yield of membrane increased from 25.4% to 31.5%.

Formulation and Characterization of PAI-PTFE-cg Antifriction Coatings

Polytetrafluoroethylene (PTFE) powder is used as a solid lubricant in commercial antifriction coatings. However, most of the matrix polymers are usually not compatible with virgin PTFE resulting in low dispersion and mechanical film stability and adhesion. In our research PTFE TF 2025 was irradiated by g-beam generating PTFE micropowder with persistant radicals and functional groups. These functional groups are able to perform a chemical grafting (cg) of polyamideimide (PAI) and modified PTFE-micropowder by reactive extrusion in melt. Based on grinded extrudates PAI-PTFE-cg dispersions were formulated followed by characterizing dispersion as well as film properties. It was found, that PAI-PTFE-cg dispersion comprises very small PTFE-particles at higher g-irradiation doses in homogeneous dispersions. In addition, all samples showed outstanding film flexibility. Basic tribological properties under mixed lubrication were studied by using a ring-on-disk tribometer. Finally, diluted dispersions were applied to a multi-surface sliding bearing (four segments) for testing in a hydrodynamic plain test bench.

Hydrophobic composite coatings with photocatalytic self-cleaning properties by micro/nanoparticles mixed with fluorocarbon resin

A newly developed hydrophobic composite coating was fabricated by incorporating modified TiO2 nanoparticles and hydrophobic material polytetrafluoroethylene (PTFE) micropowders dispersed in fluorocarbon resin. Moreover, the surface characteristics and self-cleaning properties of the newly developed composite material were examined. The material was found to exhibit sufficient hydrophobicity with a water contact angle of 133°. The surface free energy of the composite coating was 4.11mJ/m2. Scanning electron microscopy results revealed a micro/nanocomposite structure composed of PTFE micropowders and TiO2 nanoparticles, which was verified by X-ray photoelectron spectroscopy results. Through ultraviolet irradiation the modified TiO2-PTFE/FEVE composite coating successfully removed oleic acid absorbed on its surface. These results showed that the functional composite coating had a sufficiently hydrophobic surface with an efficient self-cleaning effect.

Superhydrophobic PVDF–PTFE electrospun nanofibrous membranes for desalination by vacuum membrane distillation

In this study, a superhydrophobic nanofibrous membrane was prepared on the basis of an electrospun polyvinylidene fluoride (PVDF)–polytetrafluoroethylene (PTFE) nanofibrous scaffold coupled with a microporous PTFE substrate. The PVDF–PTFE nanofibrous scaffold was fabricated by electrospining of PVDF–PTFE blend solutions, it was observed that by changing the PTFE micro-powder content in the dope solutions from 0wt.% to 12wt.%, the water contact angle (WCA) and the liquid entry pressure (LEPw) of the membrane vary from 130.4° and 84kPa to 152.2° and 137kPa, respectively. The superhydrophobic PVDF–PTFE nanofibrous membrane was then tested for desalination by vacuum membrane distillation (VMD), a stable flux of 18.5kg/m2h and salt rejection higher than 99.9% was presented throughout the entire testing period of 15h, indicating the great potential of the PVDF–PTFE nanofibrous membranes in VMD. For further application of the PVDF–PTFE nanofibrous membranes in VMD, a mathematical model was presented to predict the vapor flux of the novel membrane under various operation conditions. A good agreement between the experimental and theoretical values for vapor fluxes was obtained; the results indicated that the VMD flux increased with the increase of feed temperature and flow rate and decreased with the increase of permeate pressure.

Water dispersible polytetrafluoroethylene microparticles prepared by grafting of poly(acrylic acid)

Due to the hydrophobic nature and high gravimetric density, it is very difficult to obtain water dispersible polytetrafluoroethylene (PTFE) powder. In this work, hydrophilic PTFE microparticles were successfully prepared by grafting of poly(acrylic acid) onto PTFE micropowder via a pre-irradiation method. The as-obtained hydrophilic PTFE microparticles were analyzed by FT-IR, 1H NMR, CA, SEM and TGA. After neutralization by sodium hydroxide, the water contact angle decreased from 145.69° for pristine PTFE to 63.38° for PTFE-g-NaAA. The obtained micropowder can be easily dispersed in water to form a dispersion with very high stability. Furthermore, the presence of grafted PAA shows no obvious influence on degradation temperature of PTFE backbones.

Conferring polytetrafluoroethylene micropowders with hydrophilicity using dopamine chemistry and the application as water‐based lubricant additive

AbstractThe hydrophilicity of polytetrafluoroethylene (PTFE) micropowders was easily achieved by modifying the surface with thin polydopamine(Pdop) layer deposited through spontaneous oxidative polymerization of dopamine. Compared with the pure PTFE, the Pdop modified PTFE(PTFE@Pdop) possesses excellent hydrophilic property such as low active ratio, and good dispersivity in water. The quantity of coating and the surface amphiphilic properties were readily controlled by adjusting the deposition time. The tribological properties of the as‐prepared PTFE@Pdop micropowders as additives in water were evaluated. The results confirmed that the PTFE@Pdop exhibited good antiwear and friction reduction properties even under low concentration in water. The simplicity of the method makes large‐scale production of hydrophilic PTFE possible and may be extended as a powerful route for modification of other organic solid lubricating materials that can be exploited as water‐based lubricant additives. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Physical and tribological properties of PTFE micropowder-filled EPDM rubber

The physical and tribological properties of ethylene–propylene–diene–rubber (EPDM) filled with polytetrafluoroethylene (PTFE) micropowders, i.e. MP1100 and MP1200 having chemically similar but distinctive microstructural morphology have been investigated. EPDM–PTFE micropowder blends filled with MP1200 having a solid granular structure, showed poor tensile strength and elongation at break but significantly improved tribological properties. It attained both the lowest steady-state friction coefficient and specific wear rate. However, EPDM–PTFE blends containing a fine agglomerated PTFE micropowder of MP1100 showed enhanced physical properties. Its increasing tensile strength and elongation at break with PTFE micropowder loading compared to MP1200-filled EPDM blend was essentially due to its characteristic morphology, which enhanced its dispersion and compatibility with EPDM. It showed specific wear rate similar to MP1200-filled EPDM but resulted in high friction coefficient. Scanning electron microscopy (SEM) of the PTFE micropowders and the corresponding PTFE micropowder-filled EPDM blends suggest that agglomerates morphology, dispersion and interfacial compatibility with EPDM are the key factors influencing physical and tribological properties of these compounds.

Functionalization of irradiated PTFE micropowder with methacryl‐ or hydroxy groups for chemical coupling of PTFE with different matrix polymers

AbstractThis article describes the modification of electron beam irradiated polytetrafluoroethylene (PTFE) material (500 kGy) into a functionalised micropowder, bearing methacrylate or hydroxy groups. The aim of this work is to achieve compatibilization of modified PTFE in a variety of matrix polymers, such as elastomers and duromers. It is well known that irradiation of high molecular PTFE in the presence of air, followed by annealing with water vapor, leads to a functionalization of the PTFE micropowder, containing carboxylic acid groups. For sufficient stability of the coupling of the functional groups that are to be introduced via these acid groups, a transformation into amide groups is necessary, and can be performed by the reaction of the electron beam irradiated PTFE with ε‐caprolactam in the first step. The corresponding acid‐terminated PTFE–oligoamide is then reacted with functional epoxy monomers, like glycidol or glycidyl methacrylate, to obtain the functionalised PTFE micropowders (PTFE‐OH and PTFE‐MA). As the number of COOH groups in the electron beam irradiated PTFE is not very high, IR‐spectroscopic identification of the functional groups is not very distinct. To find evidence for the existence/reactivity of the additionally introduced functional groups, model reactions have been performed, where PTFE‐MA is reacted with methyl methacrylate/AIBN. IR spectroscopic analysis of the reaction products shows characteristic absorption bands of PMMA, indicating successful graft polymerization of PMMA to PTFE‐MA. For PTFE‐OH, reaction with cyclohexylisocyanate leads to a bisurethane adduct, which shows a strong urethane absorption in the IR spectrum. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2819–2824, 2006

Friction and wear of blended polyoxymethylene sliding against coated steel plates

Measurements were made of the dynamic friction coefficients and specific wear rates of several thermoplastics rubbing against relatively soft coatings on steel plates. Polyoxymethylene (POM)-based composites were investigated using reciprocating, line contact tests against two types of corrosion-protected steel plates (electro-deposited cathodic epoxy layers, called “E-coatings”, and galvanised plates). In addition to virgin POM, composites containing glass fibres, polytetrafluoroethylene (PTFE) fibres, PTFE micro-powder, and high-viscosity silicon oil were investigated. Sliding speeds ranged from 0.05 to 0.3 m/s, and normal loads ranged from 5 to 30 N. The E-coating failed at high loads and velocities. The beneficial effects of lubricating additives in tests with uncoated steel counterfaces were also observed with the coated steel surfaces. POM with glass fibre additives was found to be more abrasive than the base material. The considered non-conformal contact produced similar friction and wear trends than those obtained for the conformal contact.