Electric cables can contribute to the spread of fire through the insulating layer. This paper focuses on their properties characterizing the initiation of fire. Samples of ethylene-based cable insulation were tested using a cone calorimeter by exposing them to external heat flows of six different values (25 kW m−2 – 50 kW m−2). Time to initiate flame burning was observed. The critical heat flux (depending on the method of calculation was in the range 2.94 kW m−2 – 4.59 kW m−2) and the thermal response parameter (342 kW s−0.5 m−2) was calculated from the time of initiation and external heat flow dependence.
Ivan Hrušovský, Jozef Martinka, Peter Rantuch and Karol Balog
The potential of vegetable oils to undergo violent thermal oxidation is long-known problem. The process of this oxidation is investigated by the means of differential thermal analysis. Polyurethane foam was saturated with Tung oil rich in unsaturated fatty acids at three different mass rations, and airflow at three different rates is introduces to the sample to ensure sufficient volume of air for oxidation. The samples were thermally stressed both dynamically and isothermally. The results were compared to results of standard differential Mackey test.
Ivan Hrušovský, Peter Rantuch, Jozef Martinka and Simona Dzíbelová
The decomposition stages of spruce wood sawdust were analyzed by means of sequential differential calorimetry. Two stages of decomposition were identified and activation energy of one stage was calculated using the Kissinger method. The DTA was conducted by means of SEDEX safety calorimeter. Sample was analyzed under three heating rates of 10, 20 and 45 °C/h in temperature range from room temperature to 400 °C. The calculated activation energy for the last and most clear decomposition peak was 122.63 KJ/mol. The results are comparable with the data calculated by J.V. Rissanen et al., who calculated activation energy for Spruce hemicellulose as 120 KJ/mol.
Jozef Martinka, Peter Rantuch, Igor Wachter and Karol Balog
This paper deals with the fire risk of a selected halogen-free electrical cable. The research was objected to a three-core power electric cable for a fixed installation CHKE J3x1.5 (cross section of each copper core was 1.5 mm2) with a declared class of reaction to fire B2ca, s1, d1, a1. The electrical cable was manufactured and supplied by VUKI, a. s., Slovakia. The fire risk of the electric cable was evaluated based on the heat release rate, total heat release, smoke release rate, total smoke release and effective heat of combustion. These parameters were measured using a cone calorimeter at 50 kW m−2 (specimens and cone emitter were placed horizontally during the test). The measured electrical cable showed a maximum heat release rate of nearly 150 kW m−2, a maximum average heat emission rate of almost 100 kW m−2, a total heat release of almost 130 MJ m−2, a maximum smoke release rate of almost 2.5 s−1, a total smoke release of more than 800 m2 m−2, an effective heat of combustion (cable as a whole) of nearly 9 MJ kg−1 and an effective heat of emission (polymeric parts of the cable) of 26.5 MJ kg−1.
Peter Rantuch, Igor Wachter, Ivan Hrušovský and Karol Balog
This contribution is aimed to compare the values of the ignition activation energies of two types of polyamide – Slovamid 6 FRB and Slovamid GF 50 LTS. Samples were isothermally stressed at five different temperatures between 500 °C a 550 °C, while the time to initiation of the flame combustion was monitored. Subsequently from the measured times were compiled Arrhenius plots under which activation energy of ignition of both polymers were calculated. The values of activation energies were 106 kJ.mol−1 and 158.0 kJ.mol−1 for Slovamid 6 FRB 4 and Slovamid 6 GF 50 LTS.
Peter Rantuch, Igor Wachter, Jozef Martinka and Marcel Kuracina
This article deals with the activation energy of ignition calculation of plastics. Two types of polyamide 6 and one type of polypropylene and polyurethane were selected as samples. The samples were tested under isothermal conditions at several temperatures while times to ignition were observed. From the obtained data, activation energy relating to the moment of ignition was calculated for each plastics. The values for individual plastics were different. The highest activation energies (129.5 kJ.mol−1 and 106.2 kJ.mol−1) were achieved by polyamides 6, while the lowest was determined for a sample of polyurethane.
Martina Hladová, Jozef Martinka, Peter Rantuch and Aleš Nečas
Formaldehyde is a toxic chemical commonly found in the environment. Owing to its increased usage, its incidence has also increased, and there is a need to determine the concentration of formaldehyde for the pollution control purposes. In general, spectrophotometric methods are easy to perform, low-cost, selective and sensitive, but every spectrophotometric method has its advantages and disadvantages, which are an important factor when selecting the method for determination of formaldehyde. Therefore, the aim of the research described in this paper was to compare the current spectrophotometric methods and to summarize their advantages and disadvantages.
Denis Benko, Jozef Martinka, Tomáš Štefko, Igor Wachter and Peter Rantuch
The aim of the research was to determine the fire risk of selected flammable liquids (alcohols). Four alcohols, methanol, ethanol, propanol, and butanol, were chosen for the research. Flammable liquids were examined in a cone calorimeter at 0 and 5 kW.m−2 heat fluxes. Both, the cone calorimeter and test procedure, were in accordance with ISO 5660-1:2015. The fire risk was evaluated mainly on the basis of heat release rate, effective heat of combustion and carbon monoxide yield. Comparison of the achieved parameters of selected alcohols shows that the fire risk of the investigated alcohols increases with increasing the molar mass of alcohol and applied heat flow.
Jozef Martinka, Peter Rantuch, Martina Hladová, Janka Sulová, Aleš Nečas, Denis Benko and Karol Balog
This scientific study deals with investigation of the heat of combustion and effective heat of combustion of selected electrical cables. Two different electrical cables for rated voltage of 0.6/1 kV were investigated. Both cables were power three-core with cross-section area of each core of 1.5 mm2. The cores of both cables were made of a bar cooper wire. Insulations of conductors of both cables were made of silane cross-linked polyethylene without any inorganic filler, while the bedding and outer sheath were made of polyethylene-based copolymer (the beddings were filled with two fillers - aluminium hydroxide and calcium carbonate, while the outer sheath were filled only with aluminium hydroxide). Reaction to fire class of both cables was B2ca, s1, d0, a1. The main difference in the investigated cables was that the core of one of them was wrapped in a glass mica tape (this cable showed circuit integrity maintenance under fire conditions during 180 minutes). The heat of combustion and effective heat of combustion were determined by the oxygen bomb calorimeter according to the ISO 1716:2018 standard. The highest effective heat of combustion showed the insulation of wires (for both cables 42.47 ± 0.03 MJ/kg), lower value showed outer sheath (interval form13.61 to 15.26 MJ/kg) and the lowest value was determined for bedding (interval from 4.69 to 6.39 MJ/kg). The effective heath of combustion per unit of length of both investigated cables lies in the interval from 1.37 to 1.38 MJ/m. Therefore, there is no significant difference in effective heats of combustion of the electrical cables investigated.
Lukáš Satin, Lukáš Likavčan, Miroslav Košík, Peter Rantuch and Jozef Bílik
All plastics products are made of the essential polymer mixed with a complex blend of materials known collectively as additives. Without additives, plastics would not work, but with them, they can be made safer, cleaner, tougher and more colourful. Additives cost money, but by reducing production costs and making products live longer, they help us save money and conserve the world's precious raw material reserves. In fact, our world would be a lot less safe, a lot more expensive and a great deal duller without the additives that turn basic polymers into useful plastics. One of these additives is sodium bicarbonate. Influence of sodium bicarbonate on properties of the product made of polystyrene was observed in the research described in this paper. Since polystyrene is typically used as a material for electrical components, the mechanical properties of tensile strength and inflammability were measured as a priority. Inflammability parameters were measured using a cone calorimeter.