Lubricant Spin-Off from Magnetic Recording Disks

As the rotation rate of magnetic recording disks increases over the next few years, lubricant spin-off from the disk surface may be significant. Lubricant thickness was measured as a function of spin time at 10000 rpm on typical carbon overcoated magnetic recording disks initially lubricated with 10–135 Å of perfluoropolyether Zdol. The viscosity of the lubricant film increased as the film thickness decreased with spin time. Lubricant spin-off in response to air shear stress on the free surface was approximately described by viscous flow. The rate of lubricant removal by evaporation was compared to the spin-off removal rate in films between 10 and 50 Å thick. Dispersion interaction and chemisorption are expected to retain a molecularly thin film of lubricant on the disk surface.     

Studies on the interactions between ZDOL perfluoropolyether lubricant and the carbon overcoat of rigid magnetic media

Current high performance magnetic storage devices, i.e., hard disk drives, typically operate at elevated temperatures of nominally 45–60°C. As a consequence, understanding the thermal response of the materials used in the construction of the drive becomes imperative. In this report, we focus on the thermal behavior of a common perfluoropolyether lubricant (ZDOL) used on the carbon-overcoated, hard disk. In particular, we show that evaporative loss of this disk lubricant, as well as bonding of the lubricant to the carbon-overcoated disk, can occur at the temperatures encountered in the hard-disk drive. Surface energy measurements show that the interaction of the hydroxyl-terminated perfluoropolyether ZDOL occurs principally through the end-groups. On unannealed disks, the interaction between this “mobile” lubricant and the carbon overcoat is characterized by hydrogen bonding with the strength of these interactions being only slightly stronger than the intermolecular hydrogen bonding characteristic of bulk ZDOL. Upon annealing at temperatures in the range of 60–150°C, the ZDOL lubricant becomes “bonded” to the disk. The surface energy of the bonded lubricant is substantially lower than the mobile lubricant reflecting the increased interaction strength that occurs as a result of bonding. Since the bonded state is the lower energy state, transitions from the mobile state to the bonded state are thermodynamically favored. The kinetics of this bonding transition, as well as the kinetics of lubricant evaporation were studied as a function of temperature. Using a model of two competing reaction channels, the activation energies for both lubricant bonding and lubricant evaporation were determined to be 3.6 kcal/mole and 5.4 kcal/mole respectively. Ab initio quantum chemical modelling was used to investigate possible interaction sites on the carbon surface. Both experiment and theory indicate that interaction of the hydroxyl-terminated ZDOL to the carbon overcoat occurs via hydrogen bonding to oxygenated species on the carbon overcoat, with a binding energy of 5–8 kcal/mole. An esterification reaction between the hydroxyl end-groups of ZDOL with carboxyl groups on the carbon surface as a result of annealing is shown to be consistent with the both the surface energy data and the kinetic data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Perfluoropolyether polymers by UV curing: design,synthesis and characterization

Perfluoropolyether (PFPE) structures can be functionalized with acrylic groups using appropriate hydrogenated acrylic monomers: the macromers obtained are highly reactive under UV irradiation, and fluorinated polymers can be obtained. In the first part of this work is described the synthesis of new PFPE (meth)acrylic oligomers by extending OH‐terminated fluorinated chains with urethane groups and reactive acrylic functions. The photopolymerization reaction of each product is then reported followed by the characterisation of the main thermal, mechanical and surface properties of UV‐cured coatings. The polymers have good thermal resistance and fair mechanical and chemical resistance. More interestingly they show very low refractive index and low surface tension. For these latter properties the products can be advantageously used in highly demanding applications such as photonic devices and nano‐patterning. Copyright © 2011 Society of Chemical Industry     

Synthesis and properties of cyclotriphosphazene and perfluoropolyether‐based lubricant with polar functional groups

A novel hard disk lubricant IDL2 was synthesised by reacting sodium 4‐((2,2‐dimethyl‐1,3‐dioxolan‐4‐yl)methoxy)phenoate with hexachlorocyclotriphosphazene, followed by treatment with 1H,1H‐perfluoro‐3,6,9‐trioxatridecan‐1‐ol in the presence of sodium hydride and subsequent hydrolysis using sulfuric acid. The chemical structure of IDL2 was confirmed by proton nuclear magnetic resonance (¹H NMR), phosphorus‐31 (³¹P) NMR spectroscopy and mass spectrometer. The thermal property of IDL2 was analysed using thermal gravimetric analysis (TGA) and it shows better thermal stability than two commercial lubricants Z‐DOL and Z‐Tetraol with two and four terminal hydroxy groups, respectively. IDL2 was found to have comparable hydrophobicity to commercial lubricants Z‐DOL, A20H and Z‐Tetraol with water contact angles in the range of 78 – 85°, revealing that IDL2 has analogous surface energy to these commercial lubricants. IDL2 exhibits comparable friction coefficient to A20H and Z‐Tetraol, but much lower than Z‐DOL. More interestingly, it has a much high bonding ratio when compared with commonly used commercial lubricants under the same testing conditions due to the presence of two polar hydroxy groups, which enhance the interaction between lubricant and substrate. These promising properties of IDL2 show that it would be very potential for real application as a hard disk drive lubricant. Copyright © 2016 John Wiley & Sons, Ltd.     

Density and viscosity of linear perfluoropolyethers under high pressures

New experimental data on the density and viscosity of linear, unbranched perfluoropolyethers are presented at temperatures from 273 to 333 K and pressures up to 180 MPa. The measurements were carried out by a high-pressure burrette apparatus and a falling-cylinder viscometer. The uncertainties of the measurements are estimated to be less than 0.09% for the specific volume and 2.5% for the viscosity. The P-V data at each temperature are correlated satisfactorily by the Tait equation. The viscosity data are also analyzed and correlated with pressure or molar volume by several empirical and theoretical equations.     

全氟聚醚的研究进展

介绍全氟聚醚的四种不同分子结构及光催化聚合和阴离子催化聚合两种合成方法，着重介绍以六氟环氧丙烷为原料的阴离子催化聚合法，由于催化剂体系及反应条件的不同，使产物聚合度不同。同时综述全氟聚醚的性能及应用。     

亲水拒油含氟整理剂的合成及其在棉织物上的应用

以F113和全氟聚醚酰氟为原料,合成了全氟聚醚二酰基过氧化物,并用来引发二甲基二烯丙基氯化铵聚合,得到含有全氟烷氧基(末端基团)的二甲基二烯丙基氯化铵聚合物Pf通过传统的轧-烘-焙过程将其整理到棉织物上.通过测试水和正十二烷在整理后织物上的接触角对该聚合物的亲水拒油性能进行评价.结果表明:聚合物Pf具有良好的亲水拒油性,对水的接触角为0°,对正十二烷的接触角为116.3°,同时整理后的棉织物具有很好的亲水拒油耐洗性.     

The Effect of Solvents on the Perfluoropolyether Lubricants Used on Rigid Magnetic Recording Media

The adsorption characteristics and tribological properties of the perfluoropolyether (PFPE) lubricants Zdol and Z-Tetraol on amorphous nitrogenated CN_x carbon are investigated as a function of solvent used to apply the lubricants. The solvents used in these studies include perfluorohexane, CF₃CHFCHFCF₂CF₃ and C₄F₉OCH₃. Deposition studies indicate that the applied thickness of PFPE films is strongly solvent-dependent that can be related to differences in the solubility parameters between the various lubricants and solvents. The results of ab initio computations on the molecular electronic structure of the solvent molecules show that their solvent power is correlated to their polarity and in particular to the acidity of the protons on the CF₃CHFCHFCF₂CF₃ and C₄F₉OCH₃ molecules. Tribological reliability, as measured by contact start-stop testing, slider-disk clearance, lubricant pickup by the slider, lubricant smearing on the disk surface, etc., is independent of solvent and is limited to the physical properties of the adsorbed lubricant film. The kinetics of lubricant mobility are charateristic of confined liquids that are independent of solvent as shown by lubricant flow profiles, bonding kinetics, and contact angle goniometry.     

耐摩擦型全氟聚醚硅氧烷的制备与性能

以K型全氟聚醚醇、K型三羟基全氟聚醚、双端Z型全氟聚醚醇、烯丙基氯和三甲氧基硅烷为原料,氯铂酸为催化剂,通过硅氢加成制备了三类全氟聚醚硅氧烷。用FTIR、~1HNMR对K型全氟聚醚硅氧烷的结构进行了表征,并利用接触角和耐摩擦实验对全氟聚醚硅氧烷的耐摩擦性能进行了测试,考察了全氟硅氧烷链结构、含量、相对分子质量和硅氧烷水解促进剂对涂层耐摩擦性能的影响。结果表明:质量分数为0.1%的三类全氟聚醚硅氧烷涂层对水和正十六烷的接触角均分别高于113.1°和65.2°,具有良好的疏水疏油性能。双端Z型全氟聚醚硅氧烷(Mn=2 500)的耐摩擦性能最好,在负载质量为1 035 g时,经钢丝绒循环摩擦2 500次后,水接触角仍可保持100°以上。在K型全氟聚醚三硅氧烷(Mn=2 800)喷涂液中,添加质量浓度为0.5 mg/L的乙酸和质量分数为0.5%的异丙醇混合硅氧烷水解促进剂,可将涂层的耐摩擦性能从1 000次提升到1 100次。