氟塑料热收缩管

本文着重描述PTFE、FEP、PFA、PVDF等氟塑料热收缩管的研制、性能和应用。由于PTFE与FEP、PFA、PVDF等热塑性氟塑料的加工方法不同,本文着重介绍PTFE和FEP二个产品,兼顾氟塑料     

纳米CaCO3对FEP非等温结晶动力学的影响

采用熔融共混法制备了聚全氟乙丙烯（FEP）/纳米碳酸钙（nano-CaCO3）复合材料,利用差示扫描量热法研究了FEP及其复合材料的非等温结晶行为,并通过Avrami方程修正的Jeziorny法、Ozawa法以及Mo法对其非等温结晶动力学进行了处理分析。结果表明,Jeziorny法及Mo法均适用于处理FEP和FEP/nano-CaCO3的非等温结晶过程,但Ozawa法不合适;在同一降温速率下,FEP/nano-CaCO3复合材料的初始结晶温度、最大结晶温度均比相应的纯FEP高,且半结晶时间延长,这说明nano-CaCO3对FEP具有一定的诱导和促进成核的作用,但由于FEP/nano-CaCO3复合材料的长链分子结构及大的空间位垒导致FEP的结晶总速率下降。     

复合聚全氟乙丙烯材料的介电及高频击穿性能研究

在聚全氟乙丙烯(FEP)中添加 TiO_2和 Al_2O_3,通过热压成型的方法制备了 FEP/TiO_2复合材料和 FEP/Al_2O_3复合材料,研究了氧化物添加量对复合材料介电常数、介电损耗和高频击穿性能的影响。结果表明,随氧化物含量的增加,复合材料的介电常数和介电损耗均增加;在同一添加量下,TiO_2对复合体系的介电性能影响较大。FEP/TiO_2复合材料的高频击穿性能随 TiO_2含量的增加而下降,在 TiO_2含量为4.0%(质量分数,下同)时,复合材料的损伤阈值已降为 FEP 材料损伤阈值的48.9 %。而 FEP/Al_2O_3复合材料的高频击穿性能随 Al_2O_3含量的增加而升高,当 Al_2O_3含量为1.2%时,复合材料的损伤阈值已增大到 FEP 材料损伤阈值的2倍,达到313 J/m~2。     

可熔性聚全氟乙丙烯色母粒的研制

通过TG、DSC、高精度测色仪及SEM测试分析,确定了FEP色母粒中载体树脂、颜料和分散助剂的成分及三者的配比,FEP色母粒的加工设备和工艺条件,并将色母粒法与直接着色法进行了对比.实验结果为FEP色母粒中,载体树脂为熔体指数在4.5～8.5g/10min的FEP粉料,颜料为可耐380℃以上高温的无机颜料,分散助剂为分散剂D(Tm=204℃,Td=427℃);为满足FEP着色成品介电性能要求,颜料含量不可过高,且分散要好,进而确定了颜料与分散剂D的最佳添加量;双螺杆挤出机加工FEP色母粒较单螺杆挤出机的剪切及塑化更充分,利于颜料进一步分散.实验表明颜料在FEP着色成品中分散效果,色母粒法远优于直接着色法.     

PPS对FEP／PPS复合材料结构与性能的影响

通过混炼工艺制备了聚全氟乙丙烯/聚苯硫醚(FEP/PPs)复合材料;研究了PPS用量对复合材料的微观结构、流动性能和力学性能的影响.结果表明:PPS的加入能显著改善FEP/PPS复合体系的流动性能,但FEP/PPS复合体系的拉伸强度却随PPS用量的增加而逐渐降低.FEP/PPS复合体系流动性改善的机理是弥散分布的PPS液相小颗粒为FEP基体提供了较大的剪切变形空间,而复合材料拉伸强度的降低主要来自于两者界面较差的相容性.     

FEP熔体流动性能和结晶性能的研究

应用熔体流动速率仪考察了口模半径、载荷及温度对聚全氟乙丙烯(FEP)流动性能的影响。结果表明:FEP熔体的表观黏度随着剪切速率、温度、载荷和口模半径的增加而降低,表现出假塑性流体行为。应用差示扫描量热法测定FEP的熔融和结晶温度及热焓,发现:与聚四氟乙烯(PTFE)相比,FEP熔点较低,熔融热较低,结晶度较小,而且熔融峰较宽。     

国外FEP和PFA薄膜的生产现状性能及应用

四氟乙烯-六氟丙烯共聚物薄膜氟化乙丙烯(FEP)即四氟乙烯-六氟丙烯共聚物的综合性能(化学稳定性、电气特性和抗粘性)与聚四氟乙烯(PTFE)相近。FEP 的最高长期使用温度为204℃。生产 FEP 的主要公司是美国 Du Pont公司、日本工业公司和德国 Hoechst公司。英国 ICI 公司取得了独创的 FEP 合成     

国外动态

阻燃聚烯烃可代替FEP用于电缆Dow公司推出一种新的阻燃聚烯烃配混料UnigardREDFDA1675NT,具有好的加工性能、电性能、耐湿性和韧性/柔软度,使其能够替代FEP氟聚合物用于PlenumCategory6通讯电缆的星形/十字形分离器。它是Dow公司计划今年商业化推出的几种无卤配混料中的第一种。该用途需要的是更轻更柔软的材料,而并不需要FEP的高强度和阻燃性。新的聚烯烃材料通过了ULNFPA262燃烧测试,其阻燃性能非常接近FEP材料,低烟密度和毒性水平与FEP相似。比FEP轻30%,转换成电缆则轻5%。不需要特别的模具,挤出速度会更快。新材料密度为…     

法国PEROLO制造MX65B75TG安全阀失效分析

介绍了MX65B75TG三氯氢硅罐车安全阀的性能和结构,通过安全阀的失效分析得出:密封圈FEP包覆层过薄,容易被介质冲刷磨损腐蚀失效,建议更换密封圈为全FEP的O形密封圈,或者加大FEP包覆层厚度。     

氟树脂性能与加工应用(续21)

叙述了聚全氟乙烯（FEP）树脂的压缩、注射、真空、传递和旋转成型的原理、方法、工艺和设备。     

聚全氟乙丙烯的着色及色母粒制备浅析

对聚全氟乙丙烯的着色进行了研究,分析认为先制备聚全氟乙丙烯色母粒再得到彩色树脂的方法优于直接着色,可使颜料在基体中获得更好的分散。重点讨论了制备聚全氟乙丙烯色母粒用载体树脂、颜料、分散剂及加工设备等几个方面的问题。     

聚全氟乙丙烯宽幅薄膜成型工艺的研究

聚全氟乙丙烯（简称FEP）以其高密度、高粘度及特有的高速剪切下的熔体破裂现象与通用塑料、工程塑料有着迥异的加工工艺及加工设备的要求。着重介绍了FEP宽幅薄膜成型工艺的研究内容,并对模具和设备的要求加以确定。通过解决研究中的几个技术难点,成功地获得了精度高、门幅宽、质量稳定的FEP薄膜。     

Surface modification of tetrafluoroethylene–hexafluoropropylene (FEP) copolymer by remote H2, N2, O2, and Ar plasmas

Tetrafluoroethylene–hexafluoropropylene (FEP) copolymer sheets were modified by remote H₂, N₂, O₂, and Ar plasmas, and the effects of the modification on adhesion between FEP sheets and copper metal were investigated. The four plasmas were able to modify the FEP surfaces' hydrophilicity. Defluorination and oxidation reactions on the FEP surfaces occurred with exposure to the plasma. The hydrophilic modification by H₂ plasma was best, followed by modification by O₂, Ar, and N₂ plasmas. The surface modification of FEP by all four remote plasmas was effective in improving adhesion with copper metal. The peel strength order of the FEP/Cu adhesive joints was H₂ plasma > Ar plasma > N₂ plasma > O₂ plasma. Mild surface modification is important for the adhesion improvement of FEP with Cu metal. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1258–1267, 2002     

Improvement of polymer electrolyte membrane by radiation-induced grafting of styrene onto FEP film with subsequent sulfonation

Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) film was homogeneously and highly grafted by styrene monomer under simultaneous irradiation with an electron beam, whereas preirradiation with an electron beam was insufficient to accomplish a high degree of grafting without activation of the styrene monomer. Following its subsequent sulfonation, the styrene-grafted FEP film exhibited considerably higher values of both the IEC and IC and less methanol crossover than the Nafion membrane. The grafting of styrene onto the FEP polymer is thought to be initiated by the abstraction of F atoms from the CF3 groups in the polymeric structure. It was estimated that two sulfonic acid groups can be attached to the benzene ring of one styrene molecule. The profile of sulfur across the FEP film, which is related to the concentration profile of sulfonic acid groups inside the styrene-grafted FEP film, became more and more homogeneous over a period of several hours, due to the step by step diffusion of monomers into the film, eventually showing a high IC value of 0.25 S/cm in the case of the 125 μm thick FEP film, whereas Nafion 117 (125 μm thickness) exhibited an IC value of 0.12 S/cm.     

Simulation of fuel ethanol production from potato tubers

Semi-continuous fuel ethanol production (FEP), based on the utilization of potato overstocks, including either acid (process I) or enzymatic (process II) hydrolysis of potato starch on the industrial scale was developed. The FEP simulations were developed by help of the Aspen Plus^® software using both experimental and literature data. The main goals were to analyze the influence of starch conversion kinetics on overall process design, to compare two FEP processes with respect to their technical benefits and limitations, to use the mass and energy balances for determining the consumption of materials and energy and to evaluate FEP environmental impact. From the technical assessment, both processes were shown to be feasible for producing high quality fuel ethanol. The analysis showed that the process I was less complex since it required fewest and smallest process equipment units than the process II, making it a competitive alternative for commercial FEP form potato overstocks.     

Low Dielectric Polyimide/Fluorinated Ethylene Propylene (PI/FEP) Nanocomposite Film for High-Frequency Flexible Circuit Board Application

The low dielectric polymer films have drawn great attention to the application as the dielectric insulating materials in high-frequency circuit boards, while the weak adhesion to the copper foils and the poor processability resulted from the fluorinated or rigid structures limited their high-frequency application. In this work, the low dielectric and high adhesive polyimide/fluorinated ethylene propylene (PI/FEP) nanocomposite film for high-frequency flexible circuit board application is developed. It is indicated that the fluorocarbon surfactants can significantly improve the dispersion of FEP in PI substrate, and thus, the PI/FEP nanocomposite film exhibits excellent mechanical properties, including the tensile strength increases to 46.6 MPa and the elongation at the break increases to 13.7%. Importantly, at the high-frequency of 10 GHz, the 60 wt% FEP filled PI nanocomposite film displays an ultralow dielectric loss (0.006) and a reduced dielectric constant (2.69). In addition, the high-frequency flexible circuit board with the PI/FEP film as the dielectric insulating layer has a high peel strength of 0.75 N mm⁻¹, indicating this PI/FEP nanocomposite film can meet the requirements of the high-frequency flexible circuit board application.     

Study of fretting wear behaviors of FEP

The fretting wear behaviors of perfluorinated ethylene–propylene copolymer (FEP) were studied on an SRV fretting wear tester with the plane contact of FEP against a bearing steel at room temperature of about 15°C. In our tests, the product of load (L) and total sliding distance (S) was preset to be a constant as the wear coefficient K_ω can be expressed as K_ω = W · P_m/(L · S), where W is the volume of material loss, P_m is the flow pressure of the softer material (FEP), L and S are the load and the total sliding distance, respectively. Under our test conditions, no wear of the bearing steel was observed when fretted against FEP. The sudden change of wear rate of FEP or its wear weight was governed by the critical PV value, an important parameter for polymers and polymer composites under sliding friction, which was the product of normal stress and average sliding speed. The critical PV value of FEP under study was 3 × 10⁴ Pa · m/s. It was also found that the topography of wear trace formed on FEP were fairly well corresponding with that of their transferred films on steel surface. Both on worn surface of FEP and on metal surface, three sharply defined regions, wear debris formation region, high-stress region, and slightly sliding wear region, can be distinguished. It indicated that the higher the normal stress, the more difficult the formation of thick transfer film. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1119–1125, 1998     

Calculations of antibody-antigen interactions: microscopic and semi-microscopic evaluation of the free energies of binding of phosphorylcholine analogs to McPC603

The study of antibody-antigen interactions should greatly benefitfrom the development of quantitative models for the evaluationof binding free energies in proteins. The present work addressesthis challenge by considering the test case of the binding freeenergies of phosphorylcholine analogs to the murine myelomaprotein McPC603. This includes the evaluation of the differentialbinding energy as well as the absolute binding energies andtheir corresponding electrostatic contributions. Four differentapproaches are examined: the Protein Dipoles Langevin Dipoles(PDLD) method, the semi-microscopic PDLD (PDLD/S) method, afree energy perturbation (FEP) method based on an adiabaticcharging procedure and a linear response approximation thataccelerates the FEP calculation. The PDLD electrostatic calculationsare augmented by estimates of the relevant hydrophobic and stericcontributions. The determination of the hydrophobic energy involvesan approach which considers the modification of the effectivesurface area of the solute by local field effects. The stericcontributions are analyzed in terms of the corresponding reorganizationenergies. This treatment, which considers the protein as a harmonicsystem, views the steric forces as the restoring forces forthe electrostatic interactions. The FEP method is found to giveunreliable results with regular cut-off radii and starts togive quantitative results only in very expensive treatment withvery large cut-off radii. The PDLD and PDLD/S methods are muchfaster than the FEP approach and give reasonable results forboth the relative and absolute binding energies. The speed andsimplicity of the PDLD/S method make it an effective strategyfor interactive docking studies and indeed such an option isincorporated in the program MOLARIS. A component analysis ofthe different energy contributions of the FEP treatment anda similar PDLD analysis indicate that electrostatic effectsprovide the largest contribution to the differential bindingenergy, while the hydrophobic and steric contributions are muchsmaller. This finding lends further support to the idea thatelectrostatic interactions play a major role in determiningthe antigen specificity of McPC603.     

Effect on Wettability of FEP Teflon Surface Morphology

Wettability of FEP Teflon® (a perfluorinated ethylene-propylene copolymer) is vastly improved by heterogeneous nucleation and crystallization in contact with gold, a high surface free energy substrate. The critical surface tension of wetting (γ_e) increases from 18.8 dynes/cm to 40.4 dynes/cm. We compute that this rise in γ_e results from a 20 percent increase in the surface density of gold-nucleated FEP Teflon®. The increase in critical surface tension from 18.8 dynes/cm to 20.6 dynes/cm, for as received FEP Teflon which had been crosslinked by helium in a glow discharge (CASING technique), suggests an increase of the surface density with crosslinking. The critical surface tension of the gold-nucleated FEP Teflon® is sharply decreased from 40.4 dynes/cm to 22.0 dynes/cm by short exposure to the CASING treatment in helium. The results of ATR infrared spectroscopy show that in the surface region of the polymer there are no chemical changes such as the presence of unsaturated groups or the introduction of polar groups by oxidation. We conclude from this study that wettability of the polymer surface is affected by the surface morphology.