Enhancing surface adhesion of polytetrafluoroethylene induced by two-step in-situ treatment with radiofrequency capacitively coupled Ar/Ar+CH_(4)+NH_(3) plasma

Although some progress in plasma modification of the polytetrafluoroethylene(PTFE) surface has been made recently,its adhesion strength still needs to be further improved.In this work,the surface of a PTFE sample was treated with a two-step in-situ method.Firstly,the PTFE surface was treated with capacitively coupled Ar plasma to improve its mechanical interlocking performance;then,Ar+NH_(3)+CH_(4) plasma was used to deposit an a-CNx:H cross-linking layer on the PTFE surface to improve the molecular bonding ability.After treatment,a high specific surface area of 2.20 and a low F/C ratio of 0.32 were achieved on the PTFE surface.Its surface free energy was increased significantly and its maximum adhesion strength reached77.1 N·10 mm^(-1),which is 56% higher than that of the single-step Ar plasma-treated sample and32% higher than that of the single-step Ar+CH_(4)+NH_(3) plasma-treated sample.

Free-radical evolution and decay in cross-linked polytetrafluoroethylene irradiated by gamma-rays

Electron spin resonance techniques were employed to investigate the effects of the absorbed dose and post-irradiation conditions on the evolution and decay of free-radicals in cross-linked polytetrafluoroethylene(XPTFE),induced byγ-ray radiation.Chain-end free-radicals,chain alkyl free-radicals,and tertiary alkyl free-radicals were detected when XPTFE was irradiated under Ar atmosphere.The corresponding peroxy free-radicals were formed upon exposure of irradiated XPTFE to air;the freeradicals concentration first increased linearly with increasing absorbed dose and then gradually saturated.The free-radicals yield under air atmosphere was greater than that under Ar,and the peroxy free-radicals were preserved for a relatively long time when irradiated XPTFE was stored under air atmosphere.The chain alkyl free-radicals may be converted to chain end free-radicals byβ-scission,while chain end free-radicals are more sensitive to oxygen than chain alkyl free-radicals.When the annealing temperature was raised above the a-transition temperature of XPTFE,the decay of the free-radicals was greatly affected and accelerated by the motion of the molecules over the long range.

Affinity Adsorption of Bilirubin on Cibacron Blue F3GA-modified Microporous Polytetrafluoroethylene Capillary

Bilirubin removal from human plasma was obtained via an affinity microporous polytetrafluoroethylene（MPTFE） capillary. The new adsorbent comprised grafted glycidyl methacrylate（GMA） via radiation-induced polymerization as hydrophilic coating and reactive sites; ethylenediamine（EDA） as a spacer arm; Cibacron Blue F3GA（CB F3GA） as an affinity ligand; MPTFE capillary as the supporting matrix. The average density of CB F3GA attachment to MPTFE capillaries was found to be 136.5 μmol/g. The capacity of bilirubin adsorbed on affinity MPTFE capillaries is 76.1 mg bilirubin/g polymer（at 25℃）. This new adsorbent has advantages over both membrane and traditional micro-column, and this system is stable and easy to operate. The results of blood tests suggest the CB F3GA affinity capillary has good blood compatibility.

Composites on Base of the Ultradispersed Polytetrafluoroethylene and Graphite Oxide Intercalated Compounds

Composites based on ultradispersed polytetrafluoroethylene and intercalated graphite oxide compounds with dodecahydro-closo-dodecaborates and methods of their fabrication have been developed. The fabricated composites have been characterized using XRD analysis, and optical microscopy. These composites are distinguished with completeness of their combustion, since the combustion products comprise gaseous boron fluorine-containing compounds of boron, boron trifluoride (BF3), and boron oxyfluoride ((BOF)3). Besides, these composites are characterized with increased energy capacity as compared to purely oxygen-containing compounds, since the heat of formation of boron fluorine-containing compounds is higher than that of boron oxide. Introduction of ultradispersed polytetrafluoroethylene imparts composites with hydrophobicity, thus improving their functioning properties.

The Application of Polytetrafluoroethylene (PTFE) Fiber Grafted Acrylic Acid as a Cation Exchanger for Removing Cu^(12)

The polytetrafluoroethylene fiber grafted acrylic acid was used as a cation exchanger. The exchange capacity of the cation fiber is 3.06 mmol/g. The maximum Cu2+ adsorption capacity is 107.48 mg/g. It could be desorbed completely by 1mol/L HCl.

Influence of external load on friction coefficient of Fe-polytetrafluoroethylene

A coarse-grained molecular dynamics simulation model was developed in this study to investigate the friction process occurring between Fe and polytetrafluoroethylene(PTFE).We investigated the effect of an external load on the friction coefficient of Fe–PTFE using the molecular dynamics simulations and experimental methods.The simulation results show that the friction coefficient decreases with the external load increasing,which is in a good agreement with the experimental results.The high external load could result in a larger contact area between the Fe and PTFE layers,severer springback as a consequence of the deformed PTFE molecules,and faster motion of the PTFE molecules,thereby affecting the friction force and normal force during friction and consequently varying the friction coefficient.

Dependence of Mechanical Performance of Polytetrafluoroethylene Filament on Elongation of Dispersion Particles

The effect of elongation of particles in dispersion powders on mechanical performance of polytetrafluoroethylene(PTFE)flat filament is analyzed.Morphology and elongation of particles in four different PTFE dispersion powders are analyzed.Meanwhile,the correlation between elongation and diameter of dispersion particles is discussed.Strength-elongation curves of PTFE flat filaments made of four different dispersion powders are obtained from measurements of mechanical behaviors.Experimental results show that PTFE flat filament manufactured with dispersion particles having appropriate elongation(0.55-0.60)shows excellent mechanical performance.This work could be regarded as a reference for manufacturing high performance PTFE flat filaments.

Preparation and Selectivity of Molecularly Imprinted Polymer Coating on the Micro Pore Membrane of Polytetrafluoroethylene

In order to obtain mechanically stable membrane for practical application, the imprinted polymer was synthesized in the pores of polyfluoromembrane, the binding and transport ability of the membrane were studied.

Effects of Stretching Parameters on Morphological and Mechanical Properties of Polytetrafluoroethylene Filaments

Comprehensive performances of polytetrafluoroethylene(PTFE) flat filaments used as suture materials in medical field can be affected significantly by morphological and mechanical characteristics.Due to low tensile strength and non-uniform morphology,PTFE flat filaments cannot be applied widely as medical sutures.In order to solve flaws above,PTFE flat filaments with constant linear density,550 dtex,are manufactured and dependences of morphology,frictional features and mechanical behaviors on stretching ratio and temperature are also analyzed.The results indicate that PTFE flat filaments with high tensile strength(1 922.0 cN) and excellent apparent performance can be manufactured at optimal stretching ratio and temperature,18.0 and350 ℃,respectively.

Composites on Base of the Ultradispersed Polytetrafluoroethylene and Chitosan Salts

Composites based on ultradispersed polytetrafluoroethylene and chitosan salts (nitrate, perchlorate and dodecahydro-closo-dodecaborate) and methods of their fabrication have been developed. For this purpose, the ultrasonic effect on the mixture of the aqueous gels of chitosan salts with dry UPTHE or UPTFE ethanol dispersion with propeller agitators. Introduction of ultradispersed polytetrafluoroethylene improving their functioning properties, namely high combustion efficiency and resistance to air moisture.

Effect of Expanded Polytetrafluoroethylene Combined with Autologous Ear Cartilage in Nasal Plastic Surgery

Objective:To explore the effect of combined application of expanded polytetrafluoroethylene and autologous ear cartilage in nasal plastic surgery.Methods:76 cases of nasal plastic surgery patients in our hospital from September 2019 to September 2020 were selected as the research objects and divided into experimental group(38 cases,treated with expanded polytetrafluoroethylene+autologous ear cartilage surgery)and control group(38 cases,treated with autologous ear cartilage surgery).The treatment effect,appearance score and complications were compared.Results:The total effective rate of the experimental group(97.37%,37/38)was higher than that of the control group(78.95%,30/38),P<0.05;After treatment,the appearance score of the experimental group was(8.97±0.37),which was significantly higher than that of the control group(P<0.05);The total incidence of complications in the experimental group(5.26%,2/38)was significantly lower than that in the control group(21.05%,8/38),P<0.05.Conclusion:In the process of nasal plastic surgery,the combined application of autologous ear cartilage surgery and expanded polytetrafluoroethylene has obvious effect,improves the appearance of patients,and has less postoperative complications,which is worthy of promotion.

Robust, breathable, and chemical-resistant polytetrafluoroethylene (PTFE) films achieved by novel in-situ fibrillation strategy for highperformance triboelectric nanogenerators

In the era of advanced wearable electronic devices,the triboelectric nanogenerators(TENGs)as energy harvesting and self-powered sensing units hold great promise.Selecting appropriate triboelectric material is the crucial factor to optimize the performance of TENG,while polytetrafluoroethylene(PTFE)stands out as a highly versatile option among the various materials.In this study,we present an ultrafine nanofibrous PTFE(NF-PTFE)films prepared by novel in-situ fibrillation strategy as the triboelectric material in TENG devices.The innovative processing methodology facilely addresses the dilemma between high porosity and fine pore size of traditional porous PTFE films,meanwhile achieves exceptional mechanical strength,hydrophobicity,air permeability,and chemical resistance of the films.With the integration of nanofibrous PTFE films into contact-separation mode TENG and droplet-based TENG,these devices realize the peak electrical output of 131 V/10.8μA and 54 V/14μA with great durability,which surpass the performance of TENGs using traditional expanded PTFE films.Furthermore,a smart glove capable of recognizing hand gestures is proposed,which demonstrates the versatility,flexibility,and practicality of this material for potential use in smart devices.This reported NF-PTFE film provides insights for the design of high-performance TENG device for advanced wearable electrical applications.

Tribological behavior of polydopamine/polytetrafluoroethylene coating on laser textured stainless steel with Hilbert curves

Shallow Hilbert curve patterns with easily programmable texture density were selected for laser texturing of stainless steel substrates.Two different texture path segment lengths(12 and 24 μm)and four different laser power percentages(5%,10%,15%,and 20%)were investigated.The textured and smooth substrates were coated with thin polydopamine/polytetrafluoroethylene(PDA/PTFE)coatings for tribological property assessment.The effects of texture density(texture area coverage)and laser power on the durability and friction of the coated surfaces were studied.Laser texturing the substrates improved the coating durability up to 25 times,reduced the friction coefficient,and prevented coating global delamination.The textures fabricated with a laser power of 15%and a texture path segment length of 12 μm yielded the best coating durability.The textures provided the interlocking for the PTFE coating and thus prevented its global delamination.Furthermore,the PTFE inside the texture grooves replenished the solid lubricant worn away in the wear track and prolonged the coating wear life.

IMPROVEMENT OF CREEP RESISTANCE OF POLYTETRAFLUOROETHYLENE FILMS BY NANO-INCLUSIONS

To improve creep resistance of directional polytetrafluoroethylene （PTFE） films, epoxy grafted nano-SiO2 is mixed with PTFE powder before sintering and calender rolling. The aligned macromolecular chains （especially those in amorphous region） of the composite films can be bundled up by the nanoparticles to share the applied stress together. In addition, incorporation of silica nanoparticles increases crystallinity of PTFE and favors microfibrillation of PTFE in the course of large deformation. As result, PTFE films exhibit lower creep strain and creep rate, and higher tensile strength and hardness. The work is believed to open an avenue for manufacturing high performance fluoropolymers by nano-inclusions.

Synergistic modification of the tribological properties of polytetrafluoroethylene with polyimide and boron nitride

Polytetrafluoroethylene(PTFE)blended with polyimide(PI)and filled with boron nitride(BN)is prepared through cold pressing and sintering for composites with remarkable wear resistance and reduced coefficient of friction(COF).The characterizations show that BN and PI at different levels,improve the hardness,dynamic thermo-mechanical modulus,thermal conductivity,and tribological properties of PTFE.PI boosts the dispersion and bonding of BN in PTFE.In dry sliding friction of a block-on-ring tribometer,the wear rate and COF of 10:10:80 BN/PI/PTFE reduce to almost 1/300 and 80%of those of pure PTFE,respectively,as the wear mechanism transition from being adhesive to partially abrasive.This occurs only when the additives BN and PI induce a synergistic effect,that is,at concentrations that are not higher than ca.10 wt%and 15 wt%,respectively.The obvious agglomeration at high percentages of added PI and severe conditions(400 N and 400 rpm)induce strong adhesive failure.The variations in the tensile properties,hardness,crystallization,and microstructure of the composites correspond to different effects.The multiple parameters of the plots of wear and friction are transformed into their contour curves.The mechanism transition maps aid in understanding the influence of various test conditions and composite compositions on the contact surfaces in the space-time framework of wear.

Preparation of microstructure-controllable superhydrophobic polytetrafluoroethylene porous thin film by vacuum thermal-evaporation

The three-dimensional porous network polytetrafluoroethylene （PTFE） thin films were achieved by a vacuum technique through evaporating the pure PTFE powders. The surfaces of PTFE thin films showed various morphologies by adjusting the evaporation temperature and the corresponding contact angle ranging from 133° to 155°. Further analyses of surface chemical composition and morphology by FTIR and FE-SEM revealed that the origin of hydrophobicity for the PTFE thin films could be ascribed to the fluorine-containing groups and the surface morphologies, indicating that abundant -CF2 groups and network structures with appropriate pore sizes played a vital role in superhydrophobicity. By characterization of UV-Vis, the films also showed high transmittance and antireflection effect. The films prepared by this simple method have potential applications such as waterproof membrane and self-cleaning coating.

Tensile ratcheting behaviors of bronze powder filled polytetrafluoroethylene

A series of tensile and ratcheting experiments for compacted polytetrafluoroethylene （PTFE） and bronze filled PTFE （PTFE/bronze） were conducted on dynamic mechanical analyzer （DMA-Q800）. The effects of mean stress, stress amplitude and temperature on the ratcheting behaviors of PTFE and PTFE/bronze were investigated. It is found that the stress-strain response of PTFE/bronze is nonlinear and its elastic modulus is higher than that of pure PTFE. For uniaxial ratcheting test, the dissipation strain energy density （DSED） decreases rapidly in the first l0 cycles and approaches a constant after 20 cycles. The ratcheting strain and the DSED corresponding to 100 cycles increase with increasing mean stress, stress amplitude and temperature. Additionally, the DSED and ratcheting strain of PTFE/bronze are much lower than those of pure PTFE under the same experimental conditions. It is also found that both pure PTFE and PTFE/bronze present cyclic hardening characteristics. Above all, the addition of bronze can improve both the uniaxial tensile property and the cyclic property of PTFE.

Interfacial interaction between human flbrinogen and polytetrafluoroethylene

One of the key problems in research and application of biomedical materials is thehemocompatibility of the materials.It is generally believed that the adsorption ofglycoproteins(e.g.fibrinogen,γ-globulin)onto the surface of the materials will resultin the formation of glycoprotein/platelet complex.The formed complex will be adhered tothe surface of the material and the intrinsic coagulation will be sped up.That will

Polytetrafluoroethylene-covered stent implantation with double guiding catheter technique for the treatment of type III coronary perforation after stenting

Coronary artery perforation is a life-threatening , complication during percutaneous coronary intervention （PCI） although it occurs rarely in contemporary era with incidence ranging from 0.1% to 0.8%. The overall mortality remains quite high and varied with thestype of perforation, with higher risk in type Ⅱ and Ⅲ

Proton Irradiation Effects on the Structural and Tribological Properties of Polytetrafluoroethylene

Polytetrafluoroethylene （PTFE） was irradiated with protons in a ground-based simulation facility to study the effects of proton irradiation on the structural and tribological properties of PTFE. The structural changes were characterized by X-ray photoelectron spectroscopy （XPS） and attenuated total-reflection FTIR （ATR-FTIR）, while the tribological properties were evaluated by friction and wear tests. It was found that proton irradiation induced the degradation of PTFE molecular chains, resulting in the increase of C concentration and the decrease in F concentration on the sample surfaces, and the surface chemical structure and morphology of the samples changed, which affected the friction coefficient and decreased the wear rate of the specimens as the friction and wear tests revealed.