SU-8 Composite Based “Lube-tape” for a Wide Range of Tribological Applications (original) (raw)
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Tribology of Self-lubricating SU-8+PFPE Composite based Lub-tape
Procedia Engineering, 2013
Despite the fact that the SU-8 is a useful material for micro-fabrication of MEMS devices using the photolithography process, its poor tribological properties restrict its wider applications. It was postulated in our previous study that adding perflouropolyether (PFPE) lubricant to SU-8 possibly promoted chemical reaction between the molecules and also formed the boundary lubrication, which enhanced the wear durability of SU-8 by more than four orders of magnitude. The same SU-8+PFPE composite were used to fabricate a stand-alone laminate film called "Lub-tape", which has two layers of ~90 μm thickness each. The top and bottom layers were made of SU-8+PFPE composite and pristine SU-8, respectively. The lub-tape has reduced the initial coefficient of friction by ~7 times and increased wear life by more than five orders of magnitude of SU-8. It can also improve the tribology of any given surface. The Lub-tape can be used to protect all surfaces against friction and wear.
Tribology Letters, 2014
In an earlier work, we demonstrated the development of SU-8 composites using perfluoropolyether (PFPE) as lubricant filler which reduced friction coefficient by *7 times and enhanced wear life of SU-8 by more than four orders of magnitude. In this work, we have investigated the role of chemical bonding between SU-8 and PFPE molecules using two types of PFPE lubricants (i.e., Fomblin Ò Z-dol and Z-03) in improving the tribological properties of the composite. Z-dol has polar (-OH) end groups whereas Z-03 has non-polar (CF 3 ) end groups. SU-8 with Z-dol (SU-8 ? Z-dol) films yielded *8 times greater wear life than SU-8 with Z-03 (SU-8 ? Z-03) films and more by four orders of magnitude than pure SU-8. The nature of the films was analyzed in detail by chemical and physical characterization techniques like X-ray photoelectron spectroscopy, water contact angle and thermo-gravimetric analysis. The results validated the role of polar end functional group of Z-dol in covalent binding with SU-8 upon UV plasma treatment that resulted in improved tribological properties.
Lubrication Mechanism of SU-8/Talc/PFPE Composite
Tribology Letters, 2017
SU-8, a very promising structural polymer for the next-generation 3D fabrication of micro-electromechanical systems (MEMS), has extremely poor tribological properties. The improvement in tribological properties has been recently addressed by developing SU-8/talc (30 wt%) /perfluoropolyether (PFPE) (30 wt%) composite. This composite showed wear durability approximately five orders of magnitude greater in comparison with that of pure SU-8. This drastic increment was found to be because of the in situ lubrication mechanism provided by the PFPE liquid droplets present in the composite. In this present investigation, the lubrication mechanism for SU-8/talc (30 wt%)/PFPE (10, 20 and 30 wt%) composites was further investigated by varying sliding speed (0.1-1.0 m/s) and normal load (2 N and 4 N) using silicon nitride ball of 4 mm diameter as the counterface. The data show that the coefficient of friction and interfacial shear strength follows linear relations with the logarithm of the sliding velocity. Normal load has effect on marginally reducing the coefficient of friction.
An in-situ heating effect study on tribological behavior of SU-8+PFPE composite
Wear, 2013
SU-8 polymer is an emerging structural material for micro-fabrication of MEMS/NEMS devices using photolithography process. However, poor tribological properties of SU-8 restrict its wide applications as a very reliable MEMS material. In our earlier work [1], we have developed SU-8 composites which reduced friction and enhanced wear life of SU-8 by more than four orders of magnitude. The improvements in the properties were attributed to the self-lubricating nature of the composite by continuous supply of the lubricant into the worn areas, the lubricious nature of the filler lubricant perfluoropolyether (PFPE), and possible chemical bonding between SU-8 and PFPE. In this current work, we further investigated the effect of in-situ heating on the tribological performances of the SU-8þ PFPE composite. In-situ heating from room temperature (25 1C) to 100 1C showed a strong effect on the tribological behavior of SU-8þPFPE composite by reducing its initial and steady-state friction coefficients by $ 2 and $ 7 times, respectively. Wear life (n) increased by more than three times due to in-situ heating. Greater surface area coverage by the spreading of PFPE lubricant and migration of PFPE from the bulk to surface are found responsible for this superior tribological performance of the composite at high temperatures.
SU8 nanocomposite coatings with improved tribological performance for MEMS
Surface & Coatings Technology, 2006
The increasing interests in micro-electro-mechanical systems (MEMS) has raised the requirement for photoresist materials with improved friction and wear properties for mechanically loaded 3D shaped microstructures. In this work, SU8 photoresist layers reinforced with different amounts of silica nanoparticles were produced and thermally treated. Dry sliding tests indicate that SU8 composite epoxies produced in the form of thin films exhibit similar or even better tribological properties than bulk epoxies. The SU8 nanocomposites exhibit reduced wear rates and frictional coefficient compared to the un-reinforced material. Further, nanoparticle content, heat treatment and nature of the sliding counter piece were found to affect wear and friction. The tribological behaviour was discussed in terms of mechanical properties and contact pressures.
Use of Nanotechnology in Reduction of Friction and Wear
The potential opportunities promised by nanotechnology for enabling nanopolymer composites as lubricants. Lubricants are required to reduce the all basic issues of friction, wear and adhesion in any fast moving interacting surfaces where rapid actuation is required. When the traditional fluid and grease lubricants fail the applications of polymer composites are enhanced which have a superior tribological performance to conventional polymer composites. This review provides an insight into the capabilities offered by nanopolymer composites to use as lubricants. It discusses polymer-based nanocomposite materials, nanoscale fillers and provides examples of the actual and potential uses of polymer nanocomposites as lubricant.
In Situ Lubrication of SU-8/Talc Composite with Base Oil (SN150) and Perfluoropolyether as Fillers
Tribology Letters, 2016
In this paper, pure SU-8 and SU-8/talc (30 wt%) composite were filled with two liquid lubricants, hydrocarbon base oil (SN150) and perfluoropolyether (PFPE) in different weight percentages (2, 10, 20 and 30 wt%). The composite coatings in the thickness range of *150 lm were prepared on glass substrate using spin-coater. Pure SU-8 and its self-lubricated composites were examined using pin-on-disk tribometer, 3D optical profilometer, optical microscope, micro-hardness tester, thermogravimetric analyzer and goniometer. From tribological tests, it was observed that the coefficient of friction reduced by *9-10 times after adding lubricant fillers and the wear life was [4 9 10 5 cycles for the SU-8/talc (30 wt%) with 30 wt% PFPE at 6 N normal load and 0.28 m/s sliding speed compared with zero life for without PFPE. The corresponding specific wear rate was 6.4 9 10-8 mm 3 /N-m. From surface characterization, it was observed that the surface changed from hydrophilic to hydrophobic in nature after adding PFPE, but SN150 oil-filled composite shows hydrophilic nature at higher wt%. The wear mechanism for SN150-filled composite was by delamination at high load and higher wt% of the liquid, whereas for PFPE-filled composite, it was of abrasive type. There were improvements in the elastic modulus, hardness and thermal decomposition temperature for SU-8 composites with liquid fillers over pure SU-8, and the benefit was more for composites that also contained 30 wt% of talc.
Tribology Letters, 2007
The tribological behavior of polyphenylene sulfide (PPS) composites filled with micro and nano CuO particles in waterlubricated sliding condition were studied. Pin-on-disk sliding tests were performed against a steel counterface of surface roughness 0.09-0.11 lm. The lubrication regimes were established from friction data corresponding to various combinations of loads and sliding speeds. Later experiments were performed using the sliding speed of 0.5 m/s and contact pressure of 1.95 MPa, which corresponded to boundary lubrication regime. Micro CuO particles as the filler were effective in reducing the wear of PPS but nano CuO particles did not reduce wear. The steady state wear rate of PPS-30 vol.% micro CuO composite was about 10% of that of unfilled PPS and the coefficient of friction in this case was the lowest. The examination of the topography of worn pin surfaces of nano CuO-filled PPS by SEM revealed grooving features indicating three-body abrasion. The transfer films formed on the counterfaces during sliding were studied by optical microscopy and AFM. The wear behavior of the composites in water-lubricated sliding is explained using the characteristics of worn pin surfaces and transfer films on the counterface.
Journal of Synthetic Lubrication, 2000
High-temperature polymers are generally preferred for those tribology applications where cost is secondary and performance is the primary considesation. Since frictional heat dissipation limits the usefulness of polymers because of theis poor thermal conductivity, high-temperatuse polymers are prejerred in applications which have harsh operating conditions. In this paper, a high-temperature polymer, polyethersulphone (PES), was selected jor some adhesive weas studies, along with two PES composites containing 18% glass-fibre (GF) reinforcement and two solid lubricants, i.e., PTFE and MoS, (2% each). Adhesive weas studies of these materials on two pin-on-disc machines indicated that neat PES was not a good tribo-material. However, incorporation of GF and solid lubricants enhanced the wear perjofbr-mance by an order of two. PTFE was found to behave better than MoS,. However, afer long sliding duration both the luhric/yzts ye$ormed almost equally well. The topography of the s u~a c e of the pins and the disc was studied using SEM to investigate the wear mechanisms.