Huseyin Unal

Friction and wear behaviours of some industrial polyamides against different polymer counterparts under dry conditions

Purpose – The present study aims to find out the best polymer/polymer pair in electrical insulating applications. Moreover, the effects of different polymer counterpart and applied load on the friction and wear behaviour of PA 46 + 30%GFR and unfilled PA 66 thermoplastic polymers are to be studied.Design/methodology/approach – Friction and wear tests vs PA 46 + 30%GFR and PPS + 30%GFR polymer composites were carried out on a pin‐on‐disc arrangement and at a dry sliding conditions. Tribological tests were performed at room temperature under 20, 40 and 60 N loads and at 0.5 m/s sliding speed.Findings – The results showed that, the coefficient of friction decreases with the increasing of load (up to 40 N) for PA 46 + 30%GFR composite and polyamide (PA) 66 polymer used in this study. However, above 40 N applied load the coefficient of friction increases. The specific wear rate for PA 46 + 30%GFR and PA 66 against PPS + 30%GFR polymer composite counterpart are about in the order of 10−13 m2/N while the specifi...

Influence of Process Parameters on the Mechanical and Foaming Properties of PP Polymer and PP/TALC/EPDM Composites

In this study, PP and Talc/EPDM/PP composite materials are used. Foaming process is achieved by a conventional injection molding method. The influence of injection pressure and melting temperature on the average cell dimension, cell number, skin layer thickness, foam density and mechanical properties of investegated foam materials were evaluated. It is observed that cell density is increased by the increment of injection pressure. However, the values of skin layer thickness, density, cell diameter and charpy impact strength are decreased. In addition, the values of skin layer thickness, cell density, density and impact strength are increased with the increment of melting temperature.

Extension in Shelf Life of Fresh Food Using Nanomaterials Food Packages

In this study, the use of nanocomposite polyethylene films to extend shelf life of food products and to enhance its barrier and mechanical properties was investigated. Nanocomposite was designated 80%wt LLDPE, 14.28%wt PE-g-MA, and 5.72%wt organoclay and package films were prepared on the “cast-film” line. The physical and chemical properties of these films were determined and evaluated. The results showed that an “exfoliated/intercalated” mixture was obtained, with un pronounced change in mechanical properties and transparencies, while oxygen permeability is decreased by 42% and the shelf-lives of foods extended up to twofold.

Tribological performance of industrial polyamide-imide and its composite under different cooling conditions

Abstract Polyamide-imide (PAI) polymer is a high-temperature resistant polymer, which is used as contact breaker material because of its high electrical insulation property. The working conditions of contact breakers arise from the wear and friction problem conditions of these materials. Therefore, the tribological behavior of PAI polymer is important. In this study, the friction and wear performance of pure PAI polymer and PAI composite [PAI+12% graphite+3% polytetrafluoroethylene (PTFE)] were studied in two different cooling environmental conditions (with and without air cooling). Wear tests were carried out with the configuration of a polymer pin, on a rotating AISI 316 L stainless steel disc. Test conditions were atmospheric conditions, 50 N, 100 N, and 150 N loads and 0.5, 1.0, 2.0 and 3.0 m/s sliding speeds. For sliding without air cooling and sliding with air cooling, the results show that the coefficient of friction and wear rates for pure PAI and PAI+12% graphite+3% PTFE composite, slightly decrease and increase with the increase in applied load and sliding speed values, respectively. In addition, for the range of loads and sliding speeds of this study, low coefficients of friction and high specific wear rates are registered at sliding under air cooling conditions. Finally, the wear mechanism includes adhesive and abrasive processes.

Development of thermal residual strains in a single sided composite patch

The use of composite patching to reinforce aircraft structure is on the increase as it offers advantages over those of rivet fastened metal patches in application. The objective of this research is to determine the thermal residual strains in graphite/epoxy composites on Al-2024 T3 substrate. To realize this, four specimens were produced, of which one was instrumented by bonding several strain gauges on the patch and Al-substrate. Thermal and thermal residual strains were measured as a function of operating temperatures via those gauges.

Comparison of tribological performance of PEEK, UHMWPE, glass fiber reinforced PTFE and PTFE reinforced PEI composite materials under dry and lubricated conditions

Abstract In this study, the tribological performance of poly-ether-ketone (PEEK), ultrahigh molecular weight polyethylene (UHMWPE), glass fiber reinforced poly-tetra-fluoro-ethylene (PTFE) and PTFE reinforced poly-ether-imide (PEI) composite materials, under dry and lubricated conditions, were compared and evaluated. Wear tests were carried out on a pin-disc arrangement and under 50, 100 and 150 N applied loads and 0.5 m/s sliding speed conditions. The results show that the coefficient of friction and specific wear rates for these materials decreases with the increase in applied load values. Finally, the wear rates for PEEK, UHMWPE polymers, PTFE+20% glass fiber reinforced (GFR) and PEI+10% PTFE composites under dry and lubricated conditions are in the order of 10-14 and 10-15, respectively. The results suggested that it is convenient to use PTFE+20% GFR composites for machine components with low processing and product costs.

The effect of applied load and sliding speed on the tribological properties of Nylon 6 and ultra-high-molecular-weight polyethylene

Purpose – The purpose of the study was to find the best performance polymer material to be used in railway car bogies. Design/methodology/approach – Wear tests and optical and scanning electron microscopy were used. Findings – The friction coefficients of ultra-high-molecular-weight polyethylene (UHMWPE) and Nylon 6 polymers, as opposed to AISI 4140 steel, reduced with the increment of applied loads. With the increment of sliding speed, the friction coefficient increased in both UHMWPE and Nylon 6 polymers. The specific wear rate of the UHMWPE polymer was determined to be about 10-14 m2/N, whereas the rate of Nylon 6 was determined to be 10-13 m2/N. Practical implications – The aim of the study was to find the best performance polymer material to be used in railway car bogies. Originality/value – The friction and wear performance of UHMWPE and Nylon 6 engineering polymers were studied and compared to their AISI 4140 steel counterparts. It is an original work and it is not published in any media.

Mechanical, electrical and tribological properties of graphite filled polyamide-6 composite materials

Abstract In this study, the influence of adding graphite filler, on the mechanical, electrical and tribological properties of nylon-6 composites, is studied. Graphite fillers with different percentages, varying between 5 and 15 wt% were added to nylon-6 polymer material. Nylon-6 composite samples were prepared by the injection molding process. Tensile, impact, electrical and tribological tests were carried out and the dielectric permittivity tangent loss factor, tensile strength, modulus of elasticity, elongation at break, impact strength, specific wear rate and coefficient of friction properties were obtained. The results showed that the tensile strength, elongation at break, impact strength, and specific wear rate of nylon-6 composites, decrease with the increase in graphite filler weight ratio, while the modulus of elasticity, hardness, real part of dielectric permittivity, imaginary part of dielectric permittivity and dielectric loss, increase with increase in the filler weight ratio. Furthermore, it is observed that a rise in the relaxation time of ionic polarization is proportional to the increase in the amount of graphite in the medium and the dielectric conductivity and loss decrease proportionally after approximately 10 KHz. Finally, the maximum improvement in properties, in total, is recorded following the addition of 5 to 10 wt% graphite filler.

Evaluation of the sliding performance of polyamide, poly-oxy-methylene and their composites

Abstract The friction and wear performance of cast polyamide, unfilled poly-oxy-methylene, 10 wt.% graphite filled polyamide 6, 10 wt.% graphite filled poly-oxy-methylene, and 10 wt.% graphite plus 6% wax filled polyamide 6 sliding against stainless steel under dry sliding conditions were studied. The aim was to evaluate the tribological behavior of the above materials which enables suggesting alternative material for costly cast polyamide polymer in industrial applications. Tribological tests were carried out using a pin-on-disk arrangement at a sliding speed of 0.5–2.0 m s−1 and under applied loads of 50 to 150 N. The results showed that the friction coefficient of the tested materials decreases with the increase in applied load as well as with the decrease in sliding speed values. Furthermore, the lowest wear rate is 2.24−15 m2 N−1 for 10 wt.% graphite filled polyamide 6 composite. This suggests its use instead of cast polyamide polymer. Finally, it is concluded that the wear mechanism includes transfer film and deformation.

Influence of micro- and nanofiller contents on friction and wear behavior of epoxy composites

Abstract In this study, the influence of micro- and nanofiller contents on the tribological performance of epoxy composites was studied. The fillers are micro-Al2O3, micro-TiO2, and micro-fly ash and nano-Al2O3, nano-TiO2, and nanoclay fillers. The microfillers were added to the epoxy by 10%, 20%, and 30% by weight. The nanofillers were added to the epoxy by 2.5%, 5%, and 10%. Friction and wear tests were conducted using the pin-on-disc arrangement. Tribo elements consisted of polymer pin and DIN 1.2344 steel counterface disc. A load value of 15 N, a sliding speed of 0.4 m/s, a sliding distance of 2000 m, and dry atmospheric conditions were applied to test conditions. The results show that the friction coefficients and the specific wear rates of the nanofilled composites increase as the filler content increases. For microfiller-filled epoxy composites, these values decrease as filler content increases. The tribological performance of epoxy composites is enhanced by the addition of microfillers, and the higher enhancement is reached with the addition of 30% fly ash filler. Finally, the pin and disc worn surface images show the presence of adhesive and some abrasive wear mechanisms.