František Greškovič

Evaluation of Process Wear of Selected Tool Steels for Injection Molds

The aim of this contribution is to test the suitability of selected types of tool steels used for manufacturing of injection molds. Experiments were realized by the simulation of adhesive wear using laboratory equipment Amsler, which allows the testing of grinding pairs. Evaluated grinding pairs consisted of tool steel and two types of roundels. Tested polymeric materials were based on pure PA6 and PBT filled with short glass fibers, prepared by mixing process in twin screw extruder. The wear of five types of tool steels were evaluated by weight decrease before and after the experiment, while changing the friction coefficient of grinding pairs, material of grinding pairs and sensing the roughness of steel before and after wear.

Preparation and Characterization of Polypropylene/MMT Nanocomposites

In this paper, study of preparation and testing of polymer nanocomposites (PNC) based on polypropylene matrix and montmorillonite nanofillers is described. Samples were prepared by twin-screw extrusion and injection molding to final shape. Changes of basic properties of these PNC ́s were tested and described in main part of this article.

Possibility of Increasing the Mechanical Strength of Carbon/Epoxy Composites by Addition of Carbon Nanotubes

The development of nanoparticle reinforced polymer composites is presently seen as one of the most promising approaches in the field of future engineering applications. The unique properties of at least some of these nanoparticles (e.g., CNTs or carbon black) and the possibility of combining them with conventional reinforcements (e.g., carbon-, glass-or aramid-fibers) has led to an intense research in the field of nanocomposites. This study presents mechanical properties of two carbon composites made from bisphenol A epoxy resin (E) and 3 layers of 160 g/m2 carbon cloth with twill (TC) and plain (PC) weave as a reference and three-composite system that consists from carbon fiber reinforced epoxy matrix and 1% of multi-wall carbon nanotubes dispersed in epoxy resin. Used hardener H507 was based on cycloaliphatic polyamine with absence of nonylphenol. Samples were also tempered at 80 oC (for 12hours) for improvement of their thermal resistance.

Analysis of the Mechanical Properties Change of PA6/MMT Nanocomposite System after Ageing

The paper deals with the influence of environmental degradation on the change of the mechanical properties of polymer nanocomposites. The tested material was polyamide (PA) filled with nanoclay fillers Cloisite 30B, Cloisite 93A and Cloisite Na + in a volume of 2, 4 and 6 wt%. Test samples were produced by injection molding and were subjected to 540 hours and 1080 hours of UV radiation. The change of mechanical properties of PA6/MMT nanocomposite systems after the ageing in the UV chamber was studied by tensile test and Charpy impact resistance test. Article also compares structure of PA6/MMT nanocomposite.

Analysis of Short Glass Fiber Orientation in Injection Moulded Components

Fiber reinforced polymer composites are common materials used to produce parts for structural applications. The attractiveness of these materials is a result of the combined advantages of the fiber reinforcing effect and the high production rates achievable by technologies such as injection molding. The fiber orientation in short fiber reinforced thermoplastics depends on injection moulding technology parameters. The aim of this paper is to propose possibilities for comparing fiber orientation of the real sample and the result from simulation software.