Relationship between low temperature embrittlement temperature of PVC cable material and minimum installation and laying temperature of cable
The so-called embrittlement temperature ( brittle temperature) , Refers to a measure of the mechanical behavior of plastics at low temperature. When the sample is impacted by a hammer with a certain energy, the temperature when the cracking probability of the sample reaches 50%, that is, the embrittlement temperature. It can also be understood as the boundary point between the glass state and the high elastic state, which is lower than the embrittlement temperature, the molecular segments lose their activity and are in a rigid and fixed state, and the fracture under stress is brittle fracture with almost zero elongation. In GB/T 5470- 2008 'Test Method for impact embrittlement temperature of plastics' can be known that plastics need to be bent at low temperature under or without impact in various uses. The orientation generated during processing, thermal history, the force exerted on the material during impact, especially the force application speed, will all affect the brittleness of the polymer. When the applied deformation conditions are similar to those specified in the test method, embrittlement temperature can be used to predict the low temperature behavior of plastic materials. The embrittlement temperature test is used to measure the temperature at which the polymer loses its toughness as 'glass. The relationship between the minimum installation and laying temperature of cables and the low temperature embrittlement temperature of PVC cable materials is definitely inseparable. However, there has been no authoritative report on the correspondence. Generally speaking, when the embrittlement temperature is higher than 5℃, the probability of cracking of impact samples is zero. Theoretically, if the impact force during installation and laying is less than the test impact force, it can be constructed. However, there are various cable models and construction specifications involved here, as well as the support of practical testing data. If you want to really understand the relationship between the installation temperature and the low temperature embrittlement temperature of the material, it is a relatively large research topic, which needs to be from materials, cables, construction (Or imitation construction) Such as sampling tests in various links, systematically finding the critical point of damage, which requires a lot of financial, material and human support. On the other hand, once it is clear, it will be a great feedback to the enterprise. If there is no authoritative data to support it, the installation and laying temperature will be given based on the higher than the embrittlement temperature of the sheath in GB/T12706 standard. Although the installation and laying temperature with a difference of 20 ℃ is not so accurate and has a large safety margin, there will never be any cracking quality problem due to the construction temperature. It is also possible when the difference of 15℃ is the installation and laying temperature, but the cable model and construction must be strictly controlled.