CALCULATION OF MOLECULAR INTERNAL ROTATING STERIC FACTOR OF FLUOROPOLYMERS BY RADIATION CROSSLINKING METHOD

In this paper, the relationship between radiation crosslinking parameter β and the molecular internal rotating steric factor (σ) for fluoropolymers were studied. An expression calculating the molecular internal rotating steric factor of fluoropolymers, σ=1.44+(β-0.206)/1.946, was established. σ value obtained by this method is in agreement with that given in the literature.

Photocuring Behaviors of UV-Curable Perfluoropolyether-Based Fluoropolymers with and without Tertiary Amine

UV-curable perfluoropolyether (PFPE)-based fluoropolymer (PFPE-DMA) was synthesized and the photocuring behaviors of PFPE-DMA/HDDA systems with and without tertiary triethyl amine (TEA) were investigated using photo-DSC under air and nitrogen atmospheres. Photo-DSC analysis revealed that N2 purging and the presence of TEA mitigated oxygen inhibition in the photopolymerization of the UV-curable free-radical PFPE-DMA/ HDDA system. In addition, TEA synergistically acted as a coinitiator or photosynergist under nitrogen atmosphere, which increased the cure rate and percentage conversion for the photopolymerization of PFPE-DMA/ HDDA. TEA acted as both oxygen scavenger and photosynergist. The results presented here demonstrate that investigating the photocuring behaviors of PFPE-DMA/HDDA systems is very helpful to determine the optimal curing conditions for the PFPE-DMA fluoropolymer.

EFFECT OF IRRADIATION TEMPERATURE ON GENERAL EQUATION OF SOL FRACTION-DOSE RELATIONSHIP FOR FLUOROPOLYMERS

In this paper, the effect of irradiation temperature on sol fraction-dose relationship of tluoropolymers was studied. It was found that the increasing of irradiation temperature can result in the decreasing of β value of fluoropolymer, which increases the crosslinking probability of fluoropolymer. The relationship between crosslinking parameter β and irradiation temperature (T_i)of fluoropolymer is established as follows:β=2.2×10^(-3) T_g+4×10^(-4)(T_g-T_i)+0.206.values of some tluoropolymers calculated from the above expression are in agreement with the experimental values.

Fluorinated semi-interpenetrating polymer networks for enhancing the mechanical performance and storage stability of polymer-bonded explosives by controlling curing and phase separation rates

Herein, the effect of fluoropolymer binders on the properties of polymer-bonded explosives(PBXs) was comprehensively investigated. To this end, fluorinated semi-interpenetrating polymer networks(semiIPNs) were prepared using different catalyst amounts(denoted as F23-CLF-30-D). The involved curing and phase separation processes were monitored using Fourier-transform infrared spectroscopy, differential scanning calorimetry, a haze meter and a rheometer. Curing rate constant and activation energy were calculated using a theoretical model and numerical method, respectively. Results revealed that owing to its co-continuous micro-phase separation structure, the F23-CLF-30-D3 semi-IPN exhibited considerably higher tensile strength and elongation at break than pure fluororubber F2314 and the F23-CLF-30-D0 semi-IPN because the phase separation and curing rates matched in the initial stage of curing.An arc Brazilian test revealed that F23-CLF-30-D-based composites used as mock materials for PBXs exhibited excellent mechanical performance and storage stability. Thus, the matched curing and phase separation rates play a crucial role during the fabrication of high-performance semi-IPNs;these factors can be feasibly controlled using an appropriate catalyst amount.

New superhydrophobic composite coatings on Mg-Mn-Ce magnesium alloy

A novel combined method for the formation of composite coatings on the Mg-Mn-Ce alloy is developed.Ceramic like matrix was formed on the Mg alloy surface by the plasma electrolytic oxidation.Then the samples were subsequently processed by dip-coating in an alcohol suspension of superdispersed polytetrafluoroethylene and spraying with the tetrafluoroethylene telomers solution.SEM,OSP,and SPM was used to study structure of formed surfaces.It was established by measurements of CA and CAH,as well as surface free energy calculations that formed coatings demonstrate superhydrophobic properties due to the presence of an irregular hierarchical surface structure and low surface free energy of fluoropolymers.The coating preserves its hydrophobic properties after exposure to high and low temperatures,for a long time as well as being in corrosive environments.EDS and XRD data analysis confirmed the presence of organofluorine compounds in the composite layers,including in the form of crystalline polytetrafluoroethylene.Using potentiodynamic polarization test and EIS,it was found that the resulting coatings significantly increase the corrosion resistance of Mg material.These data are also confirmed by salt spray tests for 40 days.Incorporation of fluoropolymers additionally decrease coatings coefficient of friction.

In Situ Formed Tribofilms as Efficient Organic/Inorganic Hybrid Interlayers for Stabilizing Lithium Metal Anodes

The practical application of Li metal anodes(LMAs)is limited by uncontrolled dendrite growth and side reactions.Herein,we propose a new friction-induced strategy to produce high-performance thin Li anode(Li@CFO).By virtue of the in situ friction reaction between fluoropolymer grease and Li strips during rolling,a robust organic/inorganic hybrid interlayer(lithiophilic LiF/LiC_(6)framework hybridized-CF_(2)-O-CF_(2)-chains)was formed atop Li metal.The derived interface contributes to reversible Li plating/stripping behaviors by mitigating side reactions and decreasing the solvation degree at the interface.The Li@CFO||Li@CFO symmetrical cell exhibits a remarkable lifespan for 5,600 h(1.0 mA cm^(-2)and 1.0 mAh cm^(-2))and 1,350 cycles even at a harsh condition(18.0 mA cm^(-2)and 3.0 mAh cm^(-2)).When paired with high-loading LiFePO4 cathodes,the full cell lasts over 450 cycles at 1C with a high-capacity retention of 99.9%.This work provides a new friction-induced strategy for producing high-performance thin LMAs.

Synthesis of poly[methyl(3,3,3-trifluoropropyl)siloxane]-b-poly(ethylene oxide) block copolymers

A series of new amphiphilic poly[methyl（3,3,3-trifluoropropyl）siloxane]-b-poly（ethylene oxide） （PMTFPS-b-PEO） diblock copolymers with different ratios of hydrophobic segment to hydrophilic segment were prepared by coupling reactions of end-functlonal PMTFPS and PEO homopolymers. Copolymers were shown to be well defined and narrow molecular weight distribution （MWD） （1.07-1.3） by characterizations such as gel permeation chromatography （GPC） and ^1H-nudear magnetic resonance （^1H-NMR）.

Thermal and combustion behavior of Al-MnO_(2) nanothermite with poly(vinylidene fluoride-co-hexafluoropropylene) energetic binder

Fluoropolymers get increasing attention in energetic materials application due to the high fluorine content.To explore the effect of poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF-HFP))on Al/MnO_(2) nanothermite,the samples with different contents are prepared and characterized by SEM,TGDSC,XRD,and their ignition and combustion behavior are tested and recorded.The results show that P(VDF-HFP)as an energetic binder can combine the nanothermite components together,even exist in the gaps.The integrity of energetic materials has been improved.Thermal analysis shows that the addition of P(VDF-HFP)greatly changes the thermal reaction processes,and the exothermic peaks appear early,but the utilization of fuel and oxidizer is not efficient from the XRD results.Furthermore,the appropriate addition of P(VDF-HFP)can directly reduce the ignition energy threshold and increase the combustion time,which is necessary for the potential ignition charge application.The possible reasons for above phenomena are discussed and analyzed.This research provides a reference for improvement of thermitebased ignition charge formulation.

Grafting of Hexafluoropropylene onto Polytetramethylene Glycol by Radical Reaction

A well-defined modification of polytetramethylene glycol （PTMG） was realized by radical grafting with hexafluoropropylene （HFP）. The structure of grafted product was confirmed by means of IR, ^1H NMR and ^13C NMR. The effects of the amount of initiator, reaction time and temperature on the grafting HFP onto PTMG were investigated.

Morphologies and Superhydrophobicity of Hybrid Film Surfaces Based on Silica and Fluoropolymer

Fluoropolymer and different kinds of silica particles were used for controlling surface chemistry and morphology, respectively. A superhydrophobic surface originated from strawberry-like or quincunx-shaped composite silica particles was obtained. The dual size particles are obtained by utilizing the graft of different modified silica particles with epoxy functional group and amine functional group, This makes the surface of film form a composite interface to have irregular binary structure which plays an essential role in trapping air between the substrate surface and the liquid droplets to be necessary for high contact angle and low contact angle hysteresis. The maximum contact angle for water on the hybrid film is about 174±2° and the contact angle hysteresis is less than 2°. The surface morphologies, roughness and the wettability on the surface of films containing different structural silica particles were compared. It was shown that the hierarchical irregularly structure with a low roughness factor and high air-trapped ratio is indispensable for superhydrophobic surface. Although this structural surfaces based on composite silica particles play a vital role in governing the surface wettability, it is necessary to combine with a low surface energy to make the surface superhydrophobic.

Scalable Synthesis of LiF-rich 3D Architected Li Metal Anode via Direct Lithium-Fluoropolymer Pyrolysis to Enable Fast Li Cycling

Lithium metal anode holds an important position in fast-charging batteries.But lithium dendrite issues tend to exacerbate at high currents.Li F can be considered as an effective way to improve the Li metal surface electrochemical stability to achieve high power and high energy.However,most of reported work are relying on in situ formation of a 2D Li F on Li metal in liquid electrolyte,which limits the scalability and plated Li quantity.Here,we address this challenge and report a scalable synthesis of Li F-rich 3D architected Li metal anode via a direct pyrolysis of molten lithium and fluoropolymer to enable fast Li charging with high current density(20 mA cm-2)and high areal capacity(20 m Ah cm-2).The 3D structure is synthesized by the pyrolysis of fluoropolymer with Li metal and results show high similarity to the pristine electrolyte-derived solid-electrolyte-interphase(SEI).This concept using pyrolysis of fluoropolymer with Li-containing active materials could be also extended to modify Li metal oxide cathode(e.g.,Li Ni0.5Mn1.5O4)for mixed conductive interphase and engineer Li solid ion conductors(e.g.,Li garnet-type oxides)for interface stabilization andframework design.

Fluorinated Surfactants and Fluorinated Polymer Materials(Ⅱ):Environmental and Safety Issues

The environmental and safety issues of perfluorooctane sulfonyl fluoride/perfluorooctane sulfonic acid/ perfluorooctane sulfonates (PFOS) were introduced in detail by summarizing several published reviews, including their production, occurrence and emission in environment, exposure and intake to human being, supervision and emission reduction, long-distance transport, bioaccumulation and excretion, degradation and toxicity. Opinion with respect to safety issues of PFOS was also proposed in view of surfactant working field in order to upgrade their application value. The overreaction in the current state for the fear of “fluorine” was concerned. For fire-fighting foams, the issue of “safety” needs to be critically weighed.

Fluorinated Surfactants and Fluorinated Polymer Materials(Ⅰ): General Review

Fluorinated surfactants and fluorinated functional materials were introduced. Their fundamental concept, classification and structure, major physicochemical properties, industrial production methods, as well as applications in industrial and high technological fields were summarized. Their current environmental problems and the countermeasures in this field were also briefed.

Study of high-speed interaction processes between fluoropolymer projectiles and aluminum-based targets

The experimental results and numerical modeling of penetration process of fluoropolymer projectiles in aluminum-based targets are presented. Analysis of mathematical models for interaction of elastoplastic projectile and target without taking additional energy released during interaction of fluoropolymer and aluminum into consideration is carried out. Energy fraction which is spent effectively on the increase in cavity volume is determined. The experimental and calculated results of penetration by combined and inert projectiles are compared.

Fluorinated Hyperbranched Poly(urea-urethane)s Containing Reactive Groups: Synthesis, Characterization and Application on Cotton Fabric

A series of hyperbranched poly(urea-urethane)s (HPUs) containing short fluoroalkyl chain and reactive groups (HPUFs) capable as hydrophobic and oleophobic coating materials were synthesized. The obtained polymers were characterized by FTIR(fouier transform-infrared spectroscopy), 1H NMR(nuclear magnetic resonance), 13C NMR, 19F NMR, GPC(gel permeation chromatography), TGA(thermogravimetric analyzer), and XPS(X-ray photoelectron spectroscopy) analyses. Highly hydrophobic and oleophobic cotton fabrics could be achieved from these fluorinated hyperbranched polymers by solution-immersion coating method. The static contact angles reached to 143°, 114°, and 92° for water, hexadecane, and decane, respectively. The water and oil repellency ratings were 90 and 6, respectively, and still kept 80 and 5, respectively, after 10 soaping cycles at 50℃.

Coacervation Microencapsulation of CaCO₃Particles with a Fluoropolymer by Pressure-induced Phase Separation of Supercritical Carbon Dioxide Solutions

We report a method for the coacervation micro-encapsulation of several forms of CaCO3 microparticles with the fluoropolymer poly(heptadecafluorodecyl acrylate) (poly (HDFDA)) by pressure-induced phase separation of a supercritical CO2 solution.? A suspension of CaCO3 in CO2 and dissolved poly(HDFDA) were mixed in supercritical CO2.? After the system pressure was slowly decreased to atmospheric pressure, the microcapsules were obtained.? Coacervation was achieved by the precipitation of poly(HDFDA) during the decrease in the pressure of CO2;the solubility of poly(HDFDA) in CO2 decreased with the pressure.? The structure and morphology of the microparticles were investigated by using a scanning electron microscope (SEM) and an electron probe microanalyzer (EPMA) equipped with a wavelength dispersive X-ray spectroscope (WDX).

Chemical and Morphological Surface Modification of Epoxy Based Thermosets

Recently developed low fluorine containing polymers are advanced materials which confer advantageous properties to surfaces at a lower cost than conventional fluoropolymers (like PTFE), and are also more easily processable. Fluoropolymer surfaces are characterized by a low surface energy, high oleo and hydrophobicity, low coefficients of friction, among many other properties. This makes them desired materials in microelectronics, antifogging, antifouling and medical applications, to name a few. Fluorinated compounds are not easily coupled with macromolecules or common organic systems, and great efforts are made to compatibilize fluorinated species with hydrocarbon polymers. In this work, two chemical routes were explored in order to incorporate perfluorinated alkyl chains in an epoxy-amine based thermoset. On one side, a perfluoroalkyl thiolated molecule was used as a stabilizing ligand for silver nanoparticles, which were incorporated in the matrix polymer. On the other hand, fluorinated chains containing epoxy functionalities, were used as the matrix modifier. In the first case, fluorinated chains covering the nanoparticles, were mixed with the matrix, while in the second case, the fluoroalkyl chains were chemically linked to the network. Fluorine migration to the air—polymer interface was confirmed by X-Ray photoelectron spectroscopy (XPS). The materials hydrophobicity was then studied in terms of their contact angle with water (CA), as a function of the surface composition and the topography. Scanning electron microscopy (SEM) and atomic force microscopy (AFM), operated in moderate and light tapping modes, were used to morphologically describe the surfaces. An exhaustive surface analysis was made in order to explain the different hydrophobicity grades found.

Fluorinated Surfactants and Fluorinated Polymer Materials(Ⅲ): Personal Opinion on the Problems of PFOS

As surfactant researchers, we have discussed the current problems of PFOS in China from our personal standpoint. The difficulties in both elimination and investigation on PFOS are analyzed. The production, application, biodegradation and regulation for some other important fluorinated alkylated substances are also briefly introduced. Finally, the objective and tasks for surfactant researchers are pointed out.

Continuous Synthesis of Main-Chain-type Fluorinated Graft Copolymers via Successive Flow START Polymerization and Cu(0)-Mediated RDRP

Fluorinated polymers are receiving more and more attention worldwide due to their unique chemical properties,and modified fluorinated polymers with different topologies are persued for enriching and enhancing their performance in a variety of application fields.In this work,main-chain-type semifluorinated graft copolymers are produced steadily in continuous tube reactors via photocontrolled step transferaddition and radical-termination(START)polymerization and Cu(0)-mediated reversible deactivation radical polymerization(Cu(0)-RDRP)at room temperature for the first time.Specifically,semifluorinated alternating copolymer(AB)n B is prepared by START polymerization of 1,6-diiodoperfluorohexane(A)and 1,7-octadiene(B)in the first quartz pipeline under irradiation with purple LED light at 20℃.The(AB)nB with periodic C―I bonds is then flowed into the second copper pipeline directly and acts as the macroinitiators for Cu(0)-RDRP of methyl acrylate(MA)to obtain corresponding graft copolymer(AB)n B-g-PMA.This work provides a new strategy for continuous synthesis of fluorinated graft copolymer materials.

The progress on antifouling organic coating: From biocide to biomimetic surface

The advancement in material science and engineering technology has led to the development of antifouling(AF) coatings which are cheaper, durable, less toxic, and safe to the environment. The use of AF coatings containing tributyltin compounds was prohibited at the beginning of 2003, this necessitated the development of environmentally friendly coatings. The fouling release coating(FRC) lacks biocides and has low surface energy, low elastic modulus with smooth surface properties, hence a better release effect to fouling organisms. Several functional coatings have been recently developed based on fouling release(FR) technology to combat the effects of biofouling. Here, we provide a brief overview of innovative technologies and recent developments based on FRCs, including silicone, modified fluorinated polymer,cross-linked coatings, amphiphilic copolymer coating, hydrogel coatings, and biomimetic coatings. We also highlight the key issues and shortcomings of innovative technologies based on FRCs. This may give new insights into the future development of marine AF coatings.