The so-called brittle temperature is a measure of the mechanical behavior of plastics at low temperatures. 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. Below the embrittlement temperature, the molecular segment loses activity and is in a rigid fixed state. The fracture caused by force is brittle fracture, and the elongation is almost zero.
It can be known from GB∕T 5470-2008 "Test method for impact embrittlement temperature of plastics" that plastics need to be bent at low temperature under impact conditions or not in various applications. The orientation created during processing, the thermal history, the force applied to the material during impact, and especially the rate of force application, all affect the brittleness of the polymer. The embrittlement temperature can be used to predict the low temperature behavior of plastic materials when the applied deformation conditions are similar to those specified in the test method. The embrittlement temperature test measures the temperature at which a polymer loses its toughness and becomes "glassy".
The relationship between the minimum installation and laying temperature of the cable and the low temperature embrittlement temperature of the PVC cable material must be inseparable. However, there is no authoritative report on the corresponding relationship. Generally speaking, when the temperature is 5°C higher than the embrittlement temperature, the probability of cracking of the impact specimen is zero. Theoretically speaking, if the impact force during installation and laying is less than the test impact force, the construction can be carried out. But here involves the support of various cable models and construction specifications as well as practical test data.
If we want to really understand the relationship between the installation and laying temperature and the low temperature embrittlement temperature of the material, it is a relatively large research topic. It is necessary to sample and test from various links such as materials, cables, construction (or imitation construction), and systematically find the critical damage. This requires a lot of financial, material and human support. In turn, once it is figured out, it will be a great feedback to the enterprise.
If there is no authoritative data to support it, the installation and laying temperature is given based on the GB/T12706 standard which is 20°C higher than the jacket embrittlement temperature. Although the installation and laying temperature with a difference of 20°C is not so accurate, and the safety margin is very large, there will never be a cracking quality problem due to the construction temperature. It is also possible to have a difference of 15°C for the installation and laying temperature, but the cable type and construction must be strictly controlled.