Pavel Stoklasek

Cross-linked low density polyethylene mechanical properties after temperature load at 110, 180 and 220 °C

Radiation processing of polymers is a well-established and economical commercial method of precisely modifying the properties of polymers, especially mechanical properties. The mechanical properties of modified low density polyethylene samples by beta rays were measured at the ambient temperature and after temperature load above the pure low density polyethylene melting temperature. The tested samples showed significant changes of mechanical behaviour before and after temperature load. From this point of view, new applications could also be seen in areas with service temperatures higher than their former melting point, especially for application with short time exposure of temperature load.

Effect of High Doses Beta Irradiation on the Micromechanical Properties of Surface Layer of Glass-Filled Polypropylene

The presented article deals with the research of micro-mechanical properties in the surface layer of modified Polypropylene filled by 25% of glass fibers. These micro-mechanical properties were measured by the Depth Sensing Indentation - DSI method on samples which were non-irradiated and irradiated by different doses of the β - radiation. Radiation doses used were 0, 66 and 99 kGy for filled Polypropylene with the 6% cross-linking agent (triallyl isocyanurate). The change of micromechanical properties is greatly manifested mainly in the surface layer of the modified polypropylene where a significant growth of microhardness values can be observed.

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 Electrical, Mechanical and Surface Properties of Thermoplastic Polyester Elastomer Modified by Electron Beta Radiation

The main advantages of Thermoplastic Polyester Elastomers (TPE-E) are their elastomer properties as well as their ability to be processed in the same way as thermoplastic polymers (e.g., injection moulding, compression moulding and extrusion). However, TPE-Es’ properties, mainly their mechanical properties and thermal characteristics, are not as good as those of elastomers. Because of this TPE-Es are often modified with the aim of improving their properties and extending their range of application. Radiation cross-linking using accelerated electron beams is one of the most effective ways to change virgin polymers’ properties significantly. Their electrical (that is to say permittivity and resistivity measurements), mechanical (that is, tensile and impact tensile tests), as well as surface (that is, nano-indentation) properties were measured on modified/cross-linked TPE-E specimens with and/or without a cross-linking agent at irradiation doses of 0, 33, 66, 99, 132, 165 and 198 kGy. The data acquired from these procedures show significant changes in the measured properties. The results of this study allow the possibility of determining the proper processing parameters and irradiation doses for the production of TPE-E products which leads to the enlargement of their application in practice.

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.

Local mechanical properties of irradiated cross-linked filled poly (butylene terephthalate) (PBT)

MEYS, Ministry of Education, Youth and Science; MSMT-7778/2014, National Landcare Programme; LO1303, National Landcare Programme; CEBIA-Tech, ERDF, European Regional Development Fund; CZ.1.05/2.1.00/03.0089, ERDF, European Regional Development Fund

INFLUENCE OF BETA RAYS ON POLYPROPYLENE

The polypropylene samples for testing were injection moulded and subsequently irradiated by beta radiation at the dose of 15 and 33 kGy with the kind help of BGS Germany. Temperature stability, tensile test, bending test and Charpyimpact test were applied. The influence of beta irradiation low doses on thermal and mechanical properties was subsequently compared. Just dose of irradiation 15 kGy improves tensile and bending properties of polypropylene which expands usage of this material in new applications, especially in automotive.

Physical Properties of Polyamide 11 after Radiation Cross-Linking by Accelerated Electrons

Radiation processing of polymers is a well-established and economical commercial method of precisely modifying the properties of polymers, especially physical properties. The physical properties of modified polyamide 11 samples by beta rays were measured at the ambient and elevated temperature. The tested samples showed significant changes of physical properties between ambient (23°C) and elevated (80°C) temperature. From this point of view, new applications could also be seen in areas where more expensive materials are used, especially for application in automotive industry.

Influence of Beta Rays on Nylon 6 Mechanical Properties

Radiation cross-linking of polymers is a good modification method of modifying the properties of polymers, especially mechanical properties. The mechanical properties of non-irradiated and irradiated nylon 6 samples by beta rays were measured at the ambient and elevated temperature for comparison. The tested samples showed noticeable changes of mechanical behavior between ambient (23°C) and elevated (80°C) temperature and between non-irradiated and irradiated samples. It is possible to use these results in the practice because they clearly shows that radiation cross-linking influences the mechanical properties in most ways positively.

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.