Tribological Properties Of Polymers Research Articles

Influence of Polymer Flow on Polypropylene Morphology, Micro-Mechanical, and Tribological Properties of Injected Part

This research investigates the micro-mechanical and tribological properties of injection-molded parts made from polypropylene. The tribological properties of polymers are a very interesting area of research. Understanding tribological processes is very crucial. Considering that the mechanical and tribological properties of injected parts are not uniform at various points of the part, this research was conducted to explain the non-homogeneity of properties along the flow path. Non-homogeneity can be influenced by numerous factors, including distance from the gate, mold and melt temperature, injection pressure, crystalline structure, cooling rate, the surface of the mold, and others. The key factor from the micro-mechanical and tribological properties point of view is the polymer morphology (degree of crystallinity and size of the skin and core layers). The morphology is influenced by polymer flow and the injection molding process conditions. Gained results indicate that the indentation method was sufficiently sensitive to capture the changes in polypropylene morphology, which is a key parameter for the resulting micro-mechanical and tribological properties of the part. It was proven that the mechanical and tribological properties are not equal in varying regions of the part. Due to cooling and process parameters, the difference in the indentation modulus in individual measurement points was up to 55%, and the tribological properties, in particular the friction coefficient, showed a difference of up to 20%. The aforementioned results indicate the impact this finding signifies for injection molding technology in technical practice. Tribological properties are a key property of the part surface and, together with micro-mechanical properties, characterize the resistance of the surface to mechanical failure of the plastic part when used in engineering applications. A suitable choice of gate location, finishing method of the cavity surface, and process parameters can ensure the improvement of mechanical and tribological properties in stressed regions of the part. This will increase the stiffness and wear resistance of the surface.

Tribological properties of carbon nanotube/polymer composites:A mini-review

With the development of modern industry, the requirements for mechanical equipment are increasingly stringent, and increasing attention has been paid to reducing wear or lubrication in the movement of mechanical structural parts. Polymers are widely used in the field of mechanical structural parts due to their high processing performance and comprehensive performance. However, the relatively weak mechanical and tribological properties of polymers limit their further application in mechanical equipment lubrication. Incorporation of fillers is a common method to improve the friction properties of polymers. Among various fillers, carbon nanotubes (CNTs) are considered the ideal fillers to significantly improve the tribological properties of polymers. Therefore, this paper reviews the tribological properties of carbon nanotube modified polymer materials. The tribological wear mechanism of polymers and the influence of friction-reducing fillers on the tribological properties of polymers and the related lubrication mechanism explanation are outlined, and the factors influencing the tribological properties of composites by carbon nanotubes and the related lubrication mechanism explanation are analyzed. The presented review will be beneficial for the production of high-performance polymer nanocomposites.

AFM Characterization of Temperature Effect on the SU-8 Mechanical and Tribological Properties.

This study presents the effect of temperature on the mechanical and tribological properties of SU-8 polymer. The temperature of investigated samples increasing during testing and the variation of mechanical and tribological properties were monitored. The samples for tests were SU-8 hard baked at different temperatures. The hard bake temperature changes the mechanical and tribological properties of polymers. The aim of this research work is the reliability design improvement of SU-8 microstructures from electro-thermally actuated devices where a thermal gradient produces the softening and modification of SU-8 behavior. As a function of the hard baked temperature, different mechanical and tribological properties were experimentally determined using the atomic force microscopy (AFM) technique. The mechanical properties of interest are the modulus of elasticity and hardness. The investigated tribological properties involve the adhesion and friction forces. The modulus of elasticity and hardness decrease if the operating temperature increases based on the thermal relaxation of material and their viscoelastic behavior. The adhesion force between AFM tip and investigated samples increases if the operating temperature increases, respectively. The same evolution was experimentally observed in the case of friction force. Moreover, for the same testing temperature, the modulus of elasticity and hardness increase, and the adhesion and friction forces decrease if the SU-8 is hard baked at high temperature.

The effect of environmental humidity/water absorption on tribo-mechanical performance of polymers and polymer composites – a review

Purpose The mechanical and tribological properties of polymers and polymer composites vary with different environmental conditions. This paper aims to review the influence of humidity/water conditions on various polymers and polymer composites' mechanical properties and tribological behaviors. Design/methodology/approach The influence of humidity and water absorption on mechanical and tribological properties of various polymers, fillers and composites has been discussed in this paper. Tensile strength, modulus, yield strength, impact strength, COF and wear rates of polymer composites are compared for different environmental conditions. The interaction between the water molecules and hydrophobic polymers is also represented. Findings Pure polymer matrices show somewhat mixed behavior in humid environments. Absorbed moisture generally plasticizes the epoxies and polyamides and lowers the tensile strength, yield strength and modulus. Wear rates of PVC generally decrease in humid environments, while for polyamides, it increases. Fillers like graphite and boron-based compounds exhibit low COF, while MoS2 particulate fillers exhibit higher COF at high humidity and water conditions. The mechanical properties of fiber-reinforced polymer composites tend to decrease as the rate of humidity increases while the wear rates of fiber-reinforced polymer composites show somewhat mixed behavior. Particulate fillers like metals and advanced ceramics reinforced polymer composites exhibit low COF and wear rates as the rate of humidity increases. Originality/value The mechanical and tribological properties of polymers and polymer composites vary with the humidity value present in the environment. In dry conditions, wear loss is determined by the hardness of the contacting surfaces, which may not effectively work for high humid environments. The tribological performance of composite constituents, i.e. matrix and fillers in humid environments, defines the overall performance of polymer composite in said environments.

Growth of ultra-dense MoS2 nanosheets on carbon fibers to improve the mechanical and tribological properties of polyimide composites

To enhance the interface bonding of polyimide (PI)/carbon fiber (CF) composites, CFs were functionalized by introducing a polydopamine (PDA) transition layer, whose active groups provide absorption sites for the growth of molybdenum disulfide (MoS2) nanosheets and improve the bonding strength with PI. Uniform and dense MoS2 nanosheets with thicknesses of 30–40 nm on the surface of the PDA@CF were obtained via a subsequent hydrothermal method. As a result, the interface between the CF and the PI matrix becomes more compact with the help of the PDA transition layer and MoS2 nanosheets. This is beneficial in forming PI/CF-MoS2 composites with better thermal stability, higher tensile strength, and enhanced tribological properties. The lubricating and reinforcing effects of the hybrid CF-MoS2 in the PI composite are discussed in detail. The tensile strength of the PI/CF-MoS2 composite increases by 43%, and the friction coefficient and the wear rate reduce by 57% and 77%, respectively, compared to those of the pure PI. These values are higher than those of the PI/CF composites without MoS2 nanosheets. These results indicate that the CF-MoS2 hybrid material can be used as an additive to improve the mechanical and tribological properties of polymers.

Impact of 3D-printing structure on the tribological properties of polymers

Purpose The purpose of this paper is to examine the impact of three-dimensional (3D)-printing process settings (particularly print orientation) on the tribological properties of different polymers. Design/methodology/approach In this study, fused deposition modelling 3D-printing technology was used for fabricating the specimens. To evaluate the influence of print orientation, the test pieces were manufactured horizontally (X) and vertically (Z). The tribological properties of various printed polymers, which are polylactide acid, high tensile/high temperature-polylactide acid and polyethylene terephthalate-glycol have been studied. The tribological tests have been carried out under reciprocating sliding and dry condition. Findings The results show that the presence of various orientations during the 3D-printing process makes a difference in the coefficient of friction and the wear depth values. Findings suggest that printing structure in the horizontal orientation (X) assists in reducing friction and wear. Originality/value To date, there has been very limited research on the tribology of objects produced by 3D printing. This work was made as an attempt to pave the way for future research on the science of tribology of 3D-printed polymers.

THE ANALYSIS OF THE INFLUENCE OF GAMMA IRRIADIATED POLYSULFONES ON THE STATIC FRICTION COEFFICIENT

The paper presents the results of studies on the effects of gamma irradiation on the static friction coefficient of thermoplastic polymer – polysulfone. These polar polymers belong to the group of amorphous thermoplastics and are widely used for various applications, e.g., automotive and electronic industries (dielectrics in capacitors), waste water recovery, medical uses (hemodialysis membranes), requiring autoclave, and steam sterilization. Polysufones are known for their toughness and stability at high temperatures. The aim of this study is to analysed changes in the static coefficient of friction in association with a contact pressure (in the range 0.2 – 0.8 MPa) depending on the ionizing radiation dose of PSU (in the range 50-150 kGy). Additionally, microhardness, and wear intensity were measured, because tribological properties of polymers as well as mechanical properties that influence their durability and applications. The studies confirmed that the static coefficient of friction increases with an increase in contact pressure (in the test range). The research has shown that mechanical (microhardness) and tribological (static coefficient of friction and tribological wear) improve as the radiation dose of irradiated material increase. Moreover, the tribological wear increases with increasing the sliding velocity. This gamma irradiated polymer is characterized by higher microhardness, a static coefficient of friction, and a higher wear rate compared to PSU in the initial state, because of changes in structure. It requires further research.

Polimer Yatak Malzemelerin Tribolojik Özelliklerinin Deneysel İncelenmesi

Polimer Yatak Malzemelerin Tribolojik Özelliklerinin Deneysel İncelenmesi

Молекулярная масса и трибологические свойства полимеров

Молекулярная масса и трибологические свойства полимеров

Effect of inorganic constituent on nanomechanical and tribological properties of polymer, quasi-ceramic and hybrid coatings

This study investigates the variations in nanomechanical properties of coatings made of a pristine polymeric backbone and those containing silicone segments. Four different coatings with varying degrees of inorganic segments were prepared and analyzed. The four coatings were 1) a pure epoxy polymer coating, 2) a hybrid coating consisting of epoxy and silicone, 3) a ceramer coating consisting of organo-silicone and 4) a quasi-ceramic coating consisting of specialty silicone composition. The molecular bonding characteristics of the coatings were characterized with FTIR spectroscopy. The coatings were also tested using nanoindentation and nanoscratch methods to investigate mechanical and tribological properties. The scratched surface was investigated using scanning electron microscopy and atomic force microscopy. The hybrid coating displayed superior nanomechanical properties compared to the pure polymer coating, and the coating containing high silicone levels displayed better hardness. Atomic force microscopy showed that the epoxy-based polymer coating consisted of a smooth surface that was compressed when scratched using a nanoindenter. The hybrid coating had rough surface that was damaged and partially recovered after the scratch test. The ceramer and quasi-ceramic coatings displayed brittle failure.

Effect of Surface Fluorination and Sulphonation on the Adhesion and Tribological Properties of Polymers

Effect of Surface Fluorination and Sulphonation on the Adhesion and Tribological Properties of Polymers

Influence of test conditions on the tribological properties of polymers

The tribological problems of polymers have received more attention because of their suitability for fabricating machine elements in food industry, which require self lubrication environment. In this investigation, we studied and explored the influence of test speed and load values on the friction and wear behaviour of PTFE, POM and PEI polymers. Friction and wear tests of PTFE, POM and PEI vs steel were carried out at dry condition on a pin‐on‐disc arrangement. Tribological tests were carried out at room temperature, under 5, 10 and 15 N loads and at 0.5, 0.75 and 1 m/s speeds. The specific wear rates were deduced from mass loss. The results showed that, for all the polymers used in this investigation, the coefficient of friction increases linearly with the increase in load. Moreover, for the load and speed range of this investigation, the wear rate showed very little sensitivity to the applied load and large sensitivity to test speed, particularly at high load values.

Epoxy nanocomposites with high mechanical and tribological performance

Small ceramic particles are known to enhance the mechanical and tribological properties of polymers. Introduced into an epoxy resin, the filler morphology, size, particle amount and the dispersion homogeneity influence extensively the composite's performance. In the present study, various amounts of micro- and nano-scale particles (calcium silicate CaSiO 3, 4–15 μm, alumina Al 2O 3, 13 nm) were systematically introduced into an epoxy polymer matrix for reinforcement purposes. The influence of these particles on the impact energy, flexural strength, dynamic mechanical thermal properties and block-on-ring wear behavior was investigated. If the nanoparticles were incorporated only, they yield an effective improvement of the epoxy resin at a nanoparticle content of already 1–2 vol.% Al 2O 3. Choosing the nanocomposite with the highest performance as a matrix, conventional CaSiO 3 microparticles were further added in order to achieve additional enhancements in the mechanical properties. In fact, synergistic effects were found in the form of a further increase in wear resistance and stiffness. Several reasons to explain these effects in terms of reinforcing mechanisms were discussed.

Impact and wear resistance of polymer nanocomposites at low filler content

AbstractIt is well known that inorganic filler particles enhance the mechanical and tribological properties of polymers. The stiffness, toughness, and wear performance of the composites are extensively determined by the size, shape, volume content, and especially the dispersion homogeneity of the particles. In the present study, various amounts of micro‐ and nano‐scale particles (titanium dioxide TiO2, 200–400 nm, calcium silicate CaSiO3, 4–15 μm) were introduced into an epoxy polymer matrix for its reinforcement. The influence of these particles on the impact strength, dynamic mechanical thermal properties, and block‐on‐ring wear behavior was investigated. Using only the nano‐particles, the results demonstrate the best improvement in stiffness, impact strength, and wear resistance of the epoxy at a nano‐particle content of 4 vol% TiO2. Therefore, this nanocomposite was used to act as a matrix for the CaSiO3 micro‐particles, in the hope of finding synergistic effects between the micro‐ and the nano‐particles. Results show, in fact, a further improvement of wear resistance and stiffness, whereas the impact strength suffers. Geometrical properties of the particles, the homogeneous dispersion state, energy dissipating fracture mechanisms, and a transition of wear mechanisms mostly contribute to the increase in performance.

The effect of refractive index on the friction coefficient of DLC coated polymer substrates

Abstract This paper describes the enhanced mechanical performance that can be achieved by the application of diamond-like carbon (DLC) coatings to polymer substrates. The polymers coated are silicone and polyethylene, and the effect on the friction coefficient is studied. Film adhesion is found to depend on the DLC film refractive index ( n ), whereas the friction is largely independent of n in the range studied. Films were deposited from a He/C 2 H 2 mixture at 20 Pa (0.15 Torr) on to the polymer substrates placed on a 10-cm-diameter electrode driven at 13.56 MHz. Film growth was monitored by in-situ ellipsometry (at 675 nm), which was performed on a glass slide placed near the polymer substrate. Friction measurements were obtained using a pin-on-disk tribometer, and measurements were carried out using a stainless-steel pin at a linear speed of 6 cm s −1 . Film adhesion was evaluated using a pull-adhesion tester. It was found that DLC coatings adhere well to the polymer substrates and can significantly reduce the friction coefficient of polymers such as silicone. Higher refractive index films (which are harder and have a higher mechanical strength) were found to have a poorer adhesion and provide a slightly increased friction on the polymer surface when compared to lower-index films. This study indicates that DLC may be used to enhance the tribological properties of polymers with potential applications in the biomaterials and light-engineering industries.