Enhancement of polymer hydrophobicity by SF6 plasma treatment and argon plasma immersion ion implantation

In this study sulphur hexafluoride (SF₆) plasmas and argon plasma immersion ion implantation (ArPIII) techniques have been applied to improve the hydrophobicity of poly(tetrafluoroethylene) (PTFE), polyurethane and silicone surfaces. As evaluated by water contact angle measurements, all the treatments resulted in a significant enhancement in the hydrophobicity of the polymers. However, exposure of the treated samples to air induced a strong variation in their hydrophobicity as a consequence of post‐plasma reactions between atmospheric species and remnant surface free radicals. X‐ray photoelectron spectroscopy results strongly suggest that for polyurethane and silicone the surface fluorination by SF₆ plasmas and the creation of new carbon bonds and radicals are the main agents for hydrophobicity enhancement. The PTFE exposed to ArPIII revealed increases in the contact angles after exposure to air. A significant incorporation of oxygen and the formation of new carbon bonds were revealed by XPS measurements. Copyright © 2003 John Wiley & Sons, Ltd.     

Computer Simulation of Surface Tension for Complex Emulsion System

The computer simulation of surface tension for the complex emulsion systems of polytetrafluoroethylene (PTFE) modified polyacrylate were carried out in this paper. A mathematical model was founded using statistical method.The effects of the components and their proportions have been discussed in detail. The surface tension of 21 samples have been simulated, and the error value of the simulation is 0.2–5.0%. The study results show that the mathematics model can accurately simulate the effects of the experimental parameters mentioned above on the surface tension.     

填充聚四氟乙烯复合材料在水润滑条件下的摩擦磨损特性研究

采用MPX-200型摩擦磨损试验机研究了水润滑条件下不同含量的炭纤维、二硫化钼和三氧化二铝填充聚四氟乙烯复合材料与不锈钢配副时的摩擦磨损性能,通过方差和极差分析方法对材料的耐磨性进行研究,并利用原子力显微镜观察分析磨损表面及其磨屑形貌.结果表明:采用模压法制备填充聚四氟乙烯复合材料是可行的,在水润滑条件下复合材料具有优良的摩擦磨损性能,其C∶MoS2∶Al2O3∶PTFE合适的配比为5∶5∶5∶85或15∶10∶5∶70.     

PTFE Electrospun Stent Graft——Preparation,Properties and Its Industrialization Prospect

Stent graft(SG), isolating the diseased vessels from the normal blood circulation and preventing the rupture of the aneurysm wall in minimally invasive surgery, is normally composed of a metallic stent and a cover with a textile structure. In this study, the electrospinning method was used to prepare a new type of cover, and the preparing conditions and the performance of the SG were investigated. The polytetrafluoroethylene(PTFE) and polyethylene oxide(PEO) were blended at the ratios of 99:1, 98:2, 97:3 and electrospun to form precursor membranes. Then they were dried in a vacuum and sintered at different temperatures under different time periods to obtain PTFE membrane, which was compounded with a stent. Their morphology, mechanical properties, water permeability and biological properties were studied. The results showed that when the membrane was sintered at 380℃ for 10 min, it had the best tensile properties. The integral water permeability of the PTFE electrospun SG was close to 0. The hemolysis rate of the SG was 2.84%, and human umbillical vein endothelial cells(HUVECs) can adhere and proliferate well on the surface of the PTFE membranes. The PTFE electrospun SG had great potential for clinical application and industrialization.     

Transcrystallization of PTFE fiber/PP composites (I) crystallization kinetics and morphology

Transcrystallization of polypropylene (PP) on the polytetrafluoroethylene (PTFE) fiber was investigated. Both nucleation rate and crystal growth rate were determined by a polarized optical microscope. Based on the theory of heterogeneous nucleation, it has been found that the induction time can correlate well with the nucleation rate in determining the interfacial free energy difference function Δσ. The ratio of Δσ in the bulk matrix to that at the interface is 1.63 which implies the transcrystalline growth is favorable from a thermodynamic point of view. No difference in crystal growth rate of PP has been found in either spherulites or transcrystalline layers. On the basis of regime theory, a transition between regimes II and III was observed at ΔT = 48K. From the morphology studies, it has been found that the thickness of the transcrystalline layer increases with crystallization temperature, from 30 to 120 μm in the temperature range of 110–140°C. The growth of transcrystalline layer is hindered by the spherulites nucleated in the bulk. Moreover, the radius of spherulites adjacent to the transcrystalline layer is much smaller than that distant to the fiber. No significant increase in nucleation density at fiber ends is observed. Effect of internal stresses of fibers on the fiber's nucleating ability is not pronounced. © 1996 John Wiley & Sons, Inc.     

Novel preconcentration technique using bis(2-ethylhexyl) hydrogen phosphate (HDEHP) loaded porous polytetrafluoroethylene (PTFE) filter tube as a sorbent: Its application to determination of In(III) in seawater by ICP-MS with air segmented discrete sample introduction

Novel preconcetration method involving porous polytetrafluoroethylene (PTFE) filter tube impregnated bis(2-ethylhexyl) hydrogen phosphate (HDEHP) as a sorbent was studied to establish it as a practical preconcentration method for ultra trace analysis with ICP-MS. A 1 ng portion of In(III) in 1000 ml of matrix free solution or 700 ml of synthetic seawater was quantitatively complexated with HDEHP adsorbed onto porous PTFE filter tube by passing the solution through the micro pore of the filter tube. Preconcentrated In(III) was then quantitatively recovered provided that the elution, which consists of a cyclical filtering 0.1 ml of 8 mol dm⁻³ hydrochloric acid through the filter tube for 1 min; therefore, up to 10000- and 7000-fold of enrichment was attained for matrix free solution and synthetic seawater, respectively. To introduce a 0.1 ml of the eluted solution to ICP-MS, flow injection method with air segmented discrete sample introduction (ASDI) was also studied by using manually operated simple valve system. By using ASDI, good linearity of calibration curve (r = 0.99997) was observed from 0.01 to 5.0 ng ml⁻¹ of In(III). Good reproducibility was also shown in measurements of 0.1 ml of 5 ng ml⁻¹ of In(III) (R.S.D. = 1.9%, n = 5). The average recovery and R.S.D. of the results for the five duplicates determination of 0.1 ng of In(III) spiked to 200 ml of synthetic seawater were 99 and 2.4%, respectively. The method was applied to the determination of In(III) in coastal seawater sampled at north east of Hachijyo Island, Japan; using 200 ml of sample, 2000-fold preconcentration of In(III) was performed within 30 min for five samples. The analytical detection limit and the blank were 9.8 and 21 pg l⁻¹, respectively. The average concentration was determined to be 96 pg l⁻¹, and R.S.D. of the results was 3.7% (n = 3).     

The effect of temperature-induced phase transition of PTFE on the dynamic mechanical behavior and impact-induced initiation characteristics of Al/PTFE

PTFE is a semi-crystalline polymer which can undergo two phase transitions at 19°Ϲ and 30°Ϲ. To investigate influence of temperature-induced phase transition of PTFE on the mechanical behavior and impact-induced initiation characteristics of Al/PTFE, the dynamic mechanical analysis, split Hopkinson pressure bar test and drop-weight test were conducted at different temperatures. The correlation between fracture modes and ignition mechanism were analyzed associated with microstructures and reaction phenomena. The results show that with the temperature elevated, the mechanical behavior and reactive characteristics of Al/PTFE manifested a bilinear temperature dependence. Al/PTFE went through a gradual transition from brittleness to ductility. The ignition energy declined, explosion flare enhanced and reaction time prolonged consistent with the change of mechanical properties. The shock pressure and ignition time under drop-weight tests were far from the requirement of shock-induced reaction, indicating that it is fracture-induced reaction dominates the ignition of Al/PTFE at low strain rate.     

An overview of sample preparation and extraction of synthetic pyrethroids from water,sediment and soil

The latest developments in sample preparation and extraction of synthetic pyrethroids from environmental matrices viz., water, sediment and soil were reviewed. Though the synthetic pyrethroids were launched in 1970s, to the best of authors’ knowledge there was no review on this subject until date. The present status and recent advances made during the last 10 years in sample preparation including conservation and extraction techniques used in determination of synthetic pyrethroids in water, sediment and soil were discussed. Pre- and post-extraction treatments, sample stability during extraction and its influence upon the whole process of analytical determination were covered. Relative merits and demerits including the green aspects of extraction were evaluated. The current trends and future prospects were also addressed.     

粘结剂对模压成型各向异性粘结NdFeB磁体表面磁粉吸附的影响

采用模压成型方法制备各向异性粘结NdFeB磁体,并研究了其经交流退磁及热退磁后磁体的表面剩磁大小对磁粉吸附程度的影响。考察了分别以环氧树脂（epoxy resin）和聚四氟乙烯（PTFE）为粘结剂时,其对各向异性粘结NdFeB的热退磁效果、尺寸精度、磁性能和力学性能的影响。通过试验发现,以聚四氟乙烯为粘结剂的磁体在取向成型后能够在高于NdFeB合金居里点（312℃）的温度（360-380℃）进行热退磁处理,达到良好的热退磁效果,使得磁体的表面剩磁降低到5 mT以下,以满足磁体表面防腐处理和尺寸精度的要求。     

Investigation of transfer film of PTFE/bronze composites on 2024Al surface

Polytetrafluoroethylene (PTFE) composites filled with 10–30% volume content of bronze powder were prepared through molding and sintering process. Transfer films of these composites were prepared on surface of 2024 Al bar through friction method under certain condition. Roughness, morphology, andelement of these transfer films were investigated using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) methods. Tribological propertiesof these transfer films sliding against GCr15 steel ball were tested using a DFPM reciprocating tribometer. Worn surfaces were observed and analyzed using SEM and EDS methods. It was found that uniformity and continuity of the transfer films were obviously improved by the increase of bronze content of the composites. Transfer films with better uniformity and continuity holds longer wear life. Considerably lower friction coefficient and longer wear life of these transfer films indicate that the transfer films prepared in the experiment could effectively prevent direct contact of metal friction pair and thus protect them from heavy wear. SEM and EDS analyses of the worn surfaces indicate that adhesion wear and fatigue wear were main wear modes of the transfer film. Copyright © 2009 John Wiley & Sons, Ltd.