Analysis and Comparative Assessment of Basic Tribological Properties of Selected Polymer Composites

Phenomena occurring in the contact area between two mating bodies are characterised by high complexity and variability. Comparisons are usually made between parameters such as the coefficient of friction, friction force, wear and temperature in relation to time and friction path. Their correct measurement enables the proper evaluation of tribological properties of materials used in the friction pair. This paper concerns the measurements of basic tribological parameters in the friction of selected polymer composites. Knowing the tribological properties of these composite materials, it will be possible to create proper operating conditions for kinematic friction pairs. This study investigated the coefficients of friction, friction force and temperatures of six polymer composites: cast polyamide PA6 G with oil, PA6 G with MoS2, polyoxymethylene POM with aluminium, polyethylene terephthalate PET with polytetrafluoroethylene PTFE, PTFE with bronze, and PTFE with graphite. The friction surface was also examined using an optical system and computer software for 3D measurements. As a result, PA6-G with oil was found to be the best choice as a composite material for thin sliding coatings.

The Effect of Sizes of the Cast Polyamide 6 Rods upon Tensile-Impact Strength

We have studied the tensile-impact strength of the magnesium catalysed cast polyamide 6 (PA6) rods according to the EN ISO 8256:2004 standard. The purpose of our investigation was to follow: the mechanical properties of rods are mapped beside same casting technological process in case of different diameters. We have compared the received results with each other than have sought disparities. We examined cylindrical product (rod) in seven dimensional steps in diameter ranging from 40 mm to 300 mm. We have determined that the semi-finished products can be divided into two groups typically in case of their tensile-impact strengths in this size range. The tensile-impact strength is higher in case of the rods with a diameter of less than 100 mm and it is smaller in the larger dimension range. Therefore, the smallest tensile-impact strength can be established in case of the natural semifinished PA6 rods that each rod accomplishes independently of size. However, a range can be determined, which the tensile-impact strength values of product are separated according to the manufacturing size

Accuracy estimation in drilling small holes on engineering plastics by a mathematical approach

Engineering plastics have wide applications in different fields of industry due to their light weight and easy shaping. In manufacturing multi-component products, assembly is an inevitable stage and drilling is one of the necessary processes before joining of the components of these products. In this study, two of the most common types of engineering plastics, polyacetal (POM) and cast polyamide (castamide), were drilled with twist drills of 0.5 mm and 1 mm diameters, under different cutting speeds and feeds. In determining the accuracy of the drilled small holes, a mathematical approach was used in which least square circle method was applied and radial error of the each drilled hole was obtained. Thus, the hole accuracy could be determined without measuring equipment such as coordinate measurement machine. It has been seen that POM gave better hole accuracy than cast polyamide due its thermal and tribological properties. The effects of feed and cutting speed on the radial error were also investigated. POM did not show apparent difference in radial error according to the cutting parameters while cast polyamide showed lower radial error in higher feeds with 0.5 mm of drill tool and lower radial error with 1 mm of drill tool. Additionally, the radial error could be reduced with decrease of spindle speed at higher feed.