Preparation of partially fluorinated aryl/alkyl vinylene ether polymers

A new class of partially fluorinated alternating aryl/alkyl vinylene ether (FAVE) polymers were prepared from addition polymerization of aryl trifluorovinyl ethers (TFVEs) with 1,4‐butanediol or 4‐hydroxybenzyl alcohol. Monodisperse FAVE telechelic polymers were also prepared possessing latent thermal reactivity which afforded chain‐extended perfluorocyclobutyl (PFCB) aryl ethers via step‐growth [2 + 2] cyclodimerization of the aryl TFVEs. Both linear and PFCB chain‐extended FAVE polymers produced thermally robust, optically transparent, flexible spin‐cast films. The FAVE polymers and their telechelic polymers were characterized using ¹⁹F NMR and ¹H NMR complemented with molecular weight analysis using gel permeation chromatography and thermal analysis employing differential scanning calorimetry and thermogravimetry. © 2013 Society of Chemical Industry     

含氟聚合物的研究进展

含氟聚合物因其具有优异的化学稳定性、耐热性、电绝缘性、自润滑性、不粘性、耐大气老化性等功能和特点,使其在工业的各个领域得到了广泛的应用。对近五年来含氟聚合物及含氟聚合物乳液的合成及表征的研究现状进行了综述。     

Scalable Aqueous Processing-Based Passive Daytime Radiative Cooling Coatings

Passive daytime radiative cooling (PDRC) can realize electricity-free cooling by reflecting sunlight and emitting heat to the cold space. Current PDRC designs often involve costly vacuum processing or a large quantity of harmful organic solvents. Aqueous and paint-like processing is cost-effective and environmentally benign, thereby highly attractive for green manufacturing of PDRC coatings. However, common polymers explored in PDRC are difficult to disperse in water, let alone forming porous structures for efficient cooling. Here, a simple “bottom-up” ball milling approach to create uniform microassembly of poly(vinylidene fluoride-co-hexafluoropropene) nanoparticles is reported. The micro- and nanopores among secondary particles and primary particles substantially enhance light scattering and results in excellent PDRC performance. A high solar reflectance of 0.94 and high emittance of 0.97 are achieved, making the coating 3.3 and 1.7 °C cooler than commercial white paints and the ambient temperature, under a high solar flux of ≈1100 W m⁻². More importantly, the volatile organic compound content in the aqueous paint is only 71 g L⁻¹. This satisfies the general regulatory requirements, which are critical to sustainability and practical applications.     

Influence of fluorinated segments of variable length on the thickening properties of a model HASE skeleton

Introduction of fluorocarbon segments in an associative thickener copolymer (ethyl acrylate (EA)/methacrylic acid/macromonomer) was achieved by the substitution of EA with either trifluoroethyl acrylate, 2‐perfluorobutylethyl acrylate, or 2‐perfluorooctylethyl acrylate. The thickening properties were evaluated by rheological flow experiments in aqueous medium as well as in 10 wt % of sodium dodecyl sulfate (SDS) aqueous solution. Whereas in the literature no particular attention is devoted to the impact of the ethylene moieties in hydrophobically modified alkali‐soluble emulsion (HASE) skeleton, our study reveals they contribute significantly to the performances when modified by an incompatible fluorocarbon segment. Moreover, the synthesis process has a huge influence by inducing a specific distribution of the fluorinated acrylates in the macromolecule. The amount of substitution is also important and even 20 mol % of EA substituted reveals a great impact on the rheological properties of the copolymer solutions. Whereas an SDS aqueous medium generally destroys almost all the hydrocarbon interactions from the macromonomer, the total replacement of ethyl groups by trifluoroethyl groups with a cosolvent process, leads to emulsions with an equivalent thickening effect than the reference hydrocarbon HASE used. This result is quite encouraging for research work on the synthesis of HASE with increased biocompatibility. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Depolymerization of clean unfilled PTFE waste in a continuous process

A continuous process is described whereby waste PTFE was converted into tetrafluoroethylene (C₂F₄, TFE), hexafluoroethane (C₂F₆, HFE), hexafluoropropylene (C₃F₆, HFP), and octafluorocyclobutane (c‐C₄F₈, OFCB). The waste PTFE was depolymerized inside a reactor that was heated by a radiofrequency induction generator. The reactor was capable of operating at various temperatures (600–900°C) as well as various reduced pressures (5–80 kPa). The depolymerization reaction conditions could be changed while the reactor was in operation in order to manipulate the reaction product composition. Under certain conditions, high yields of TFE (> 94%) and low concentrations of by‐products were formed. The PTFE was fed vertically downward from the hopper, with the screw feeder, into the reactor where the depolymerization process took place. The hot intermediate products were continuously evacuated through a self‐cleaning quench probe, where it was quenched to form the final products. The depolymerized products were analyzed with a gas chromatograph. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2752–2759, 2006     

Investigation of radiation grafting of vinyl acetate onto (tetrafluoroethylene–perfluorovinyl ether) copolymer films

A study has been made of radiation-induced grafting of vinyl acetate (VAc) on to (tetrafluoroethylene–perfluorovinyl ether) copolymer (PFA). Effects of grafting conditions such as inhibitor and monomer concentrations and irradiation dose on the grafting yield were investigated. In this grafting system, ammonium ferrous sulphate (Mohr′s salt) was added to the monomer-solvent mixture to minimize the homopolymerization of VAc and the most suitable concentration was found to be 2.0 wt%. It was found that the dependence of the initial grafting rate on monomer concentration is of the order 1.5. The degree of grafting tends to level off at high irradiation doses due to the recombination of formed free radicals without initiating graft polymerization. Some properties of the prepared graft copolymer such as swelling behaviour, electrical conductivity, thermal and mechanical properties were also investigated. The electrical conductivity was improved by hydrolysis of poly(vinyl acetate) in the grafted chains to their respective vinyl alcohols. The tensile properties were improved by grafting; however, the elongation percent decreased. The DTA data showed thermal stability of such graft copolymers for temperatures up to 300°C, but stability decreased at higher temperatures.     

氟聚合物耐磨自润滑涂层的性能与工程应用效果

目的介绍自主研发的氟聚合物耐磨自润滑涂层(简称为协合涂层)的基本性能、测试评价结果、工程应用效果及方向。方法采用TOKYO SEIMITSU Surfcom测量仪、SEM、电子探针线扫描分析、显微硬度仪、球盘式磨损试验仪、MM摩擦试验仪、Table摩擦磨损试验仪、CI4000氙灯老化测试仪及FY-10E盐雾试验箱等,对涂层的性能进行了表征,并且通过应用实例分析介绍了该涂层的主要应用情况。结果涂层厚度可控制在20~60μm,铝合金涂层硬度为400~600HV,钢铁材料涂层硬度为700~950HV,涂层摩擦系数小于0.15,磨损量小于50 mg/10 000 r,耐中性盐雾试验达336 h以上,抗光老化试验800 h,在165℃仍具有高温阻粘性能。涂层的综合防护性能突出,可满足耐磨、自润滑、耐腐蚀、耐温、阻粘等单一或综合功能性防护需求。结论氟聚合物耐磨自润滑涂层兼有阳极氧化膜或电镀层与控制渗入的低摩擦聚合物或润滑剂的优点,在铝合金和钢铁材料上的规模化应用表明,该涂层的性能和工艺技术状态稳定,具有广泛的工程应用价值。     

用电子转移活化再生原子转移自由基聚合制备含氟丙烯酸酯共聚物及其表征

在水分散介质中,以非离子乳化剂Tween-80和十二烷基磺酸钠作为复合乳化剂,通过电子转移活化再生原子转移自由基聚合,采用ab二次引发乳液聚合法制备了含氟丙烯酸酯三元共聚物,用傅里叶变换红外光谱、拉曼光谱、核磁共振波谱及凝胶渗透色谱等对其结构、组成和相对分子质量及其分布进行了表征。结果表明,含氟丙烯酸酯聚合物的分子结构及组成可控,转化率高达95%,相对分子质量分布较窄。优选憎水性配体和惰性乳化剂可提高反应的可控性。     

Surfactant-free emulsion polymerization of chlorotrifluoroethylene with vinylacetate or vinylidene fluoride

A surfactant-free emulsion process has been developed for the preparation of copolymers of chlorotrifluoroethylene with vinylacetate or vinylidene fluoride. A redox initiator system, consisting of sodium-meta-bisulfite, t-butylhydroperoxide, and ferrous sulfate heptahydrate, has been found to be effective in preparing self-emulsifying fluoropolymers with a monodisperse particle size distribution, having up to 45% polymer solids in water. Over the range studied in this investigation, the particle number and the ultimate particle size is linearly related to the quantity of initially charged redox catalyst. Under conditions of optimal catalyst concentrations, a greater number of particles is produced in the surfactant-free process than that which can be obtained using conventional fluorosurfactants. Particle number is defined at the earliest stage of polymerization and remains constant throughout the polymerization, unless surfactant is postadded to the surfactant-free latex at a very early stage in the polymerization. The aqueous phases of various latices have been purified by ion-exchange and dialysis, enabling the sulfonic acid-terminated fluoropolymer end groups to be quantified. The highest level of bound sulfonic acid is obtained at elevated temperatures. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2211–2225, 1998     

Use of the unique properties of fluoropolymers in the design of new,highly effective,ecologically friendly technologies for the fine purification of hydrogen halides and their aqueous solutions

A number of properties of fluoropolymers in aqueous solutions of hydrogen halides were investigated. The results enable fluoropolymers to be used in the purification of hydrogen halides and their aqueous solutions. The hydrophobicity of fluoropolymers and their diffusion permeability enable production of hydrogen halides of low moisture content. A second unit for hydroionic convection is based on hydroionic repulsion (determined by the hydrophobic properties of the fluoropolymer) and ionic elimination. The two units enable the highly effective, ecologically safe manufacture of highly pure hydrogen halides and their aqueous solutions to be carried out with minimum feedstock, cooling water, and power consumption. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1383–1387, 2001