Schott Robax vidros especiais vidros vidro para lareira vidro resistente ao fogo vidros para churrasqueira vidro cerâmica 16 4. 4.3 Thermal properties 4.3.1 Coefficient of mean linear thermal expansion 4.3.2 Specific heat 4.3.3 Thermal conductivity 4.3.4 Resistance to thermal gradients (RTG) 4.3.5 Resistance to thermal shock (RTS) 4.3.6 Temperature/time loading The RTG value is a measure of how well a material can resist temperature differences on a restricted area, e.g. the temperature difference between the hot area in the center of a panel and the cold edge area (room temperature). No breakage caused by thermal stress occurs at a maximum temperature of Tmax ≤ 700 °C. The RTS value is a measure of the panel’s ability to withstand a sudden thermal shock. No breakage caused by thermal stress occurs at a maximum temperature of Tmax ≤ 700 °C. The temperature/time loading limits determine the permissible temperature for set usage times at which no breakage caused by thermal stress occurs. The pairs of values in the following table are relevant for the practical usage of glass ceramic as a vision window for stoves and room heaters. The temperature values refer to the hottest points on the outside of the panel. It must be ensured that these temperature/time loading limits are not exceeded. Taking resistance to thermal gradients and thermal shock into account, the following apply: Usage temperature Usage time 560 °C 5,000 h 610 °C 1,000 h 660 °C 100 h 710 °C 10 h 760 °C 5h
(20-700 °C) (0 ± 0.5) x 10-6/K cp(20-100 °C) approx. 0.8 x 103 J / (kg x K) (90 °C) approx. 1.6 W / (m x K) Schott Robax vidros especiais vidros vidro para lareira vidro resistente ao fogo vidros para churrasqueira vidro cerâmica 17 4. The chemical composition of ROBAX® complies with the requirements for a glass ceramic in accordance with EN 1748 T2. ROBAX® is made of ecologically safe raw materials. The glass can be reused through recycling of the material (see point 8). Glass grain hydrolytic resistance class according to ISO 719: HGB 1 2 g of glass grains are heated with 50 ml of water for one hour in a boiling water bath. Then the alkali (sodium, potassium) given off is titrated with hydrochloric acid (HCI). On the basis of the acid usage or alternatively alkali leached out, the glasses are classified into the five hydrolytic classes below: 4.4 Chemical properties 4.4.1 Chemical composition 4.4.2 Hydrolytic resistance Hydrolytic class Possible description HGB 1 high-resistance glass HGB 2 resistance glass HGB 3 medium-resistance glass HGB 4 low-resistance glass HGB 5 very low-resistance glass