Tensile Characteristics of Rubber Material of Firefighting Supplies According to Test Piece Shape

Abstract

Currently, rubber materials are widely utilized in firefighting supplies. They are utilized as rubber packing, such as air respirators, rubber bands, such as pipe windows, and rubber packing, such as fire extinguishers. EPDM initially utilized the rubber packing material, but because of aging and curing, it is difficult to maintain air tightness in the cracked gap; therefore, it has been replaced with NBR and utilized until now. In addition, among the material's physical properties, tensile properties are required, and the form usually adopted as a tensile test specimen is generally an aging form. However, rubber utilized in firefighting supplies employs rubber packing or rubber ring products. Currently, tensile tests are conducted by manufacturing a sample as a dumbbell from a separately manufactured sample without conducting a tensile test with a rubber ring-type specimen. Furthermore, questions often arise about the tensile properties of rubber rings. Therefore, this study tested the tensile properties with a ring-shaped specimen. In KS M ISO 37, it is generally known that an annular-type test piece is desirable for tensile strength measurement. An annular-type test piece has a lower value than an annular-type test piece, and an annular test piece with an elongation rate is almost the same value as an annular-type test piece. Therefore, the test was conducted to find the difference between the test piece as a dumbbell and the actual ring-shaped specimen. As a result of the tensile test, the tensile strength was found to be lower in the range of 11.8-15.5% in the ring-shaped test piece than in the age-shaped test piece, and the elongation rate was lower in the range of 4.1-40.1% than in the age-shaped test piece. This is thought to be because the stress of the stretched high-ring-shaped specimen is not equal to the cross-sectional area of the specimen. However, the tensile property value of the rubber material was satisfied with both types of test pieces with the reference value required for approval.