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Rock wool is a type of mineral wool made from a mixture of rocks such as basalt, diabase and dolomite. Compared with plastic foam, rock wool has better effects in fire protection and sound insulation, and its insulation value is lower. Rock wool sandwich panels are used for roof, external wall or partition wall coatings of buildings with high fire risk, so that the material is not directly affected by water. In addition, the thermal conductivity value of the material is indirectly increased through capillary action.
The fibers in rock wool will not get wet, however, if the fibers come into contact with water, the air spaces between the fibers may fill with water, and wet rock wool cannot function as an insulation material. For air sound insulation, open-cell materials are used (e.g., glass wool, rock wool, sound-absorbing foam, etc.). Sound-absorbing materials are porous materials or fiber materials that perform their function by converting part of the sound energy into heat energy, by causing friction losses in the air entering the pores in their structure. Rock wool sandwich panels contribute relatively better to sound insulation than other types of panels. On the other hand, under conditions requiring high acoustic performance, rock wool boards should not be expected to have high load-bearing capacity values,
Due to its internal structure, rock wool board has a lower resistance value in the longitudinal direction compared to the transverse direction. However, its non-combustible characteristics allow various activities to improve its low mechanical values. As a simple method, rock wool sheets are divided into thin sheets, in other words, they are cut to the required thickness. The thin sheets are connected using adhesives to form panels. Therefore, while producing panels with high fire resistance, the mechanical properties are relatively improved.
Mineral wool is a fairly stable material because both the fibers and the bonding material can maintain their properties for a long time. Temperature has little effect on the mechanical properties of the material. Strength increases with density, however, it depends more on the internal structure. For the limit of 60-150kg/m³, the compressive strength is between 0.005 and 0.08N/mm². The tensile strength is low, usually between 0.001 and 0.01N/mm². The strength in the fiber direction is higher. Similarly, depending on the direction of the fibers, the shear strength varies between 0.03 and 0.20N/mm². In buildings where fire resistance is critical, rock wool boards composed of inorganic fibers are used as sandwich panel core materials. Also defined as combustibility, the fire resistance of a material is defined as fire performance. Fire testing is conducted through small-scale modeling of external walls and roof lines, where how much the fire spreads in the building. Materials are divided into 6 different fire grades from A1 to F. Other fire grades of materials are determined based on the amount of smoke and burning droplets caused by fire. Rock wool sandwich panels have better performance in fireproof external wall, roof or internal partition wall applications.
The fire resistance of rock wool sandwich panels varies between 30 and 120 minutes, depending on the type, thickness and joint details of the rock wool. The ignition temperature is 850°C. Compared with rigid foam, the structure of rock wool is open-cell. The open-cell structure of rock wool causes rock wool sheets to be more susceptible to water and vapor diffusion. However, since the metal surface does not allow diffusion, this risk is reduced in sandwich panels.
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