Lenka Hylova

Mechanical Properties Changes of Irradiated Thermoplastic Elastomer

Some polymers need a cross-linking agent for the controlled cross-linking process of polymers with a tendency to degradation during the radiation cross-linking process. While, on the other hand, other polymers do not need a cross-linking agent—predominantly there are cross-linking polymers. The Thermo-Plastic Elastomer (TPE) that was used belongs to this group of predominantly cross-linking polymers; however, this agent is added because of faster reaction times and smaller irradiation doses. Microindentation–tensile and tensile impact tests were carried out on a thermoplastic sample—with, and without, a cross-linking agent. Small changes were measured between these materials at low radiation doses, (up to 66 kGy); nevertheless, at higher doses, the influence of the cross-linking agent on the mechanical properties is significant.

The Effect of Irradiation on Mechanical and Thermal Properties of Selected Types of Polymers

This article deals with the influence of electron-beam radiation on the micro-mechanical, thermo-mechanical, and structural properties of selected polymers. In the search for the desired improvement of polymers, it is possible to use, inter alia, one particular possible modification—Namely, crosslinking—Which is a process during which macromolecular chains start to connect to each other and, thus, create the spatial network in the structure. In the course of the treatment of the ionizing radiation, two actions can occur: crosslinking and scission of macromolecules, or degradation. Both these processes run in parallel. Using the crosslinking technology, standard and technical polymers can acquire the more “expensive” high-tech polymeric material properties and, thus, replace these materials in many applications. The polymers that were tested were selected from across the whole spectra of thermoplastics, ranging from commodity polymers, technical polymers, as well as high-performance polymers. These polymers were irradiated by different doses of beta radiation (33, 66, 99, 132, 165, and 198 kGy). The micro-mechanical and thermo-mechanical properties of these polymers were measured. When considering the results, it is obvious that irradiation acts on each polymer differently but, always when the optimal dose was found, the mechanical properties increased by up to 36%. The changes of micro-mechanical and thermo-mechanical properties were confirmed by structural measurement when the change of the micro-hardness and modulus corresponded to the crystalline phase change as determined by X-ray and gel content.

Study of nano-creep of unfilled and filled cross-linking polypropylene

Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behavior. This paper describes the effect of electron beam irradiation on the nanoindentation creep of unfilled and glass fiber filled polypropylene (25%). nanoindentation creep were measured by the DSI (Depth Sensing Indentation) method on samples which were non-irradiated and irradiated by different doses of the β – radiation (0, 30, 45 and 60 kGy). The purpose of the article is to consider to what extent the irradiation process influences the resulting nanoindentation creep measured by the DSI method. The unfilled and filled polypropylene tested showed significant changes of indentation creep. The measured results indicate, that electron beam irradiation is very effective tool for improvement of creep properties of unfilled and filled polypropylene. The nanoindentation creep after irradiated unfilled Polypropylene was decreased up to 16 % (filled polypropylene was decreased up to 9%) compared to non-irradiated surface. These changes were examined and confirmed by Gel content.

Study of Tensile Properties of Recycled Polypropylene with Glass Fibers at Different Temperature

This research paper studies the influence of preparation method of recycled polymer material with glass fibers on the tensile properties of the final product. The recycled material was made from polypropylene, which originally contained 30 % of glass fibers. It was divided into fractions using size of the crushed particles. These fractions ranged from large particles, similar to the original material, to small dust particles. Measurements were performed at various temperatures. It was found that the mixture of dust particles showed a large decrease in measured properties. It is mainly due to shortening of the large glass fibers, so that it no longer fulfills its function as reinforcing filler. Conversely, mixture with larger particles did not show a significant decrease in properties compared to the original material.

Impact Resistance Study of High-Density Polyethylene through Drop-Weight and Tensile Impact Tests

This study deals with high-density polyethylene (HDPE) which was put to the drop weight and tensile impact tests. HDPE is a semicrystalline thermoplastic polymer which is used in common applications such as packaging, consumer goods and car tanks. The injection moulded HDPE samples were subjected the drop weight impact test at different potential energies and the results were subsequently evaluated and discussed. The second test was performed on pendulum test machine where impact resistance in tensile was studied. It was found out that HDPE is a low-cost material with high-performance properties in the field of the impact resistance which was evaluated in penetration and tensile test where the plastic deformation creates.

The Influence of Nanofillers on HDPE Creep Properties

Nowaday´s trend is the effort to replace metal materials with the polymers, which already have the irreplaceable place in the field of the construction of various applications. Development offices effort is to achieve the best polymer quality for which various ways of modification are used. Besides common fillers and e.g. modification using beta radiation, there is a possibility to modify these properties (creep resistance, hardness, tensile strength) with the nanofillers, which have also the irreplaceable place in the field of development. This article deals with the possibilities of use of the nanofillers in HDPE material and primarily with the influence on creep properties of thus modified matrix. The influence of nanofillers shows a considerable influence in various materials, which should contribute to better resistance during these long-term tests.

Testing device design for validation of synchronization between high speed camera and drop weight test machine

High-speed cameras are expanding into science laboratories in many disciplines. For example, they can be used for monitoring of the impact testing course, widely spread in evaluation of materials. Usually, they exhibit a slight delay between the trigger pulse was applied and the recording was started. For many applications, this delay may be critical. The authors of this paper have faced two problems: the need to determine the delay in total and the need to check whether it varies in time or not. Therefore, the hereby described device was designed. It allows measurement of the delay of the cameras start in the range from 1 to 999 ms with the step of 0.1 ms.

Evaluation of Mechanical Properties of Surface Layer Injection Molded Polypropylene by Nanoindentation Test

The influence of beta radiation on the changes in the structure and selected properties (mechanical and thermal) polymers were proved. The use of low doses of beta radiation for polypropylene and its influence on the changes of micro, macro mechanical properties was thoroughly studied. The specimens of polypropylene were made by injection molding technology and irradiated by low doses of beta radiation (0, 15 and 33 kGy). The changes in the microstructure and micromechanical properties of surface layer were evaluated using WAXS and instrumented nano hardness test. The results of the measurements showed considerable increase in mechanical properties (indentation hardness, indentation elastic modulus) when the beta radiation are used.

Micro-Hardness of Irradiated Polyamide

The influence of beta radiation on the changes in the structure and selected properties (mechanical and thermal) was proved. Using high doses of beta radiation for glass fiber filled polyamide (PA) and its influence on the changes of micromechanical properties of surface layer has not been studied in detail so far. The specimens of glass fiber filled PA were made by injection moulding technology and irradiated by low doses of beta radiation (0, 132, 165 and 198 kGy). The changes in the microstructure and micromechanical properties of surface layer were evaluated using WAXS and instrumented microhardness test. The results of the measurements showed change some in micromechanical properties (indentation hardness) when high doses of beta radiation are used.