| Flame retardant PVC flexible wires(ZR-BVR wire)are widely used in buildings because of its excellent flame retardant effect.With the change of ambient temperature and time,the ZR-BVR wires will aging,which not only increases the fire risk in the building,but also damages the fire resistance of the building.The specification JB/T8734.1-2016,GB/T19666-2005 specifies that the long-term allowable operating temperature of BVR wires shall not exceed 70?,but at the critical temperature of 70?,there is only one "not to be long" fuzzy regulation for its working time,therefore,in order to study In order to investigate the effect of thermal oxygen aging on the fire risk at critical temperature,the ZR-BVR wires sold on the market is chosen as the research object and 70 ? as the aging temperature.The effects of aging at critical temperature on the fire risk of the materials were studied by means of relevant instruments in five aspects: rate of water content,micromechanism,thermal decomposition performance,mechanical property and combustibility.Based on the analysis of the rate of water content,mechanical property,micromechanism,thermal decomposition performance and combustibility of the aged ZR-BVR wires insulation materials,it is concluded that the fire hazard of the ZR-BVR wire is increased by the thermal oxygen aging.During the aging of ZR-BVR wires,with the increase of the aging time,the color is deepened and the color becomes dull,the color fastness is changed,and a special smell is emitted during the aging process.At the same time,the water content of the material is reduced,so that the hardness of the material is increased,the brittleness is enhanced,the fracture is easy,and the mechanical property is obviously reduced.In addition,the insulation material of ZR-BVR wire is extruded at the age of 20 days,and the surface of the ZR-BVR wire insulation material is cracked at the age of 40 days,and an electric branch is generated inside the ZR-BVR wire insulating material at the age of 60 days,and the C = C bond is generated inside the insulating material of the ZR-BVR wires after aging,The thermal stability and thermal release of insulating materials increased first and then decreased with the aging time,and the fire risk increased with the prolongation of the time,and the peak spectra decreased at 1630 cm-1,and the thermal stability and thermal release of the insulating materials increased with the aging time.Under the same conditions,the pyrolysis temperature of the sample with wire core is 2? lower than that of the samples without wire core,and the initial pyrolysis time is about 8 seconds earlier.The macro-combustion performance tests show that the change of CO content mainly occurs in the decomposition stage,ignition stage,combustion stage,spreading stage and flame extinguishment stage of macro-combustion.With the increase of aging time,the emission of CO gas increases as a whole.ZR-BVR The fire risk of the wires combustion is increased,and the ZR-BVR wires is fully combusted under the action of a fire source to form a "Burr-like" structure,and the appearance diameter of the ZR-BVR wires after combustion is gradually smaller and larger with the increase of the aging time.The results obtained in this thesis can be used as the control parameters of the simulation model for the long-term accelerated aging life evolution and combustion law of ZR-BVR wire insulation materials at critical temperature.It is helpful to judge the fire risk in the actual use of ZR-BVR,and it is of great significance to reduce the probability of electric fire. |
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