Casing can be seen everywhere in our daily life and has a wide range of applications. In the process of using casing, we need to understand some professional knowledge of casing, which will also play a significant role in the later use.
First of all, we need to know the definition of casing, which is usually used in the basement of the building to protect the pipeline or to facilitate the installation of iron rings. There are two kinds of common casing: rigid casing and flexible waterproof casing. It is mainly used for seamless steel pipes of casing and tubing for oil wells. The reason why casing can be widely used is that it has the characteristics of anti-collapse, anti-tension, anti-internal pressure and good sealing. Different types of casing have different functions. Electronic professional production of various types of casing can be customized according to customer needs.
Understanding the concept and basic characteristics of casing, we need to further understand some key words of casing. Common key words of casing include shrinkage ratio, product specifications, flame retardant performance, shrinkage temperature and color. Next, we will introduce these key words in detail by Xiaobian.
1. Shrinkage tube ratio
Shrinkage ratio generally refers to the ratio of inner diameter of casing before and after unconstrained (or free) shrinkage under certain conditions. The shrinkage ratio changes under certain conditions. It takes temperature to reach 200 C and time to reach the hand shrinkage effect in 3 minutes. The shrinkage ratio is close to the expansion ratio, but slightly smaller than the expansion ratio.
2. Product Specification
Product specifications generally refer to the product of the maximum diameter allowed after casing shrinkage and shrinkage ratio. It's hard to understand that. Let's give an example.
For example, the maximum allowable inner diameter after shrinkage is 2 mm (i.e. the inner diameter after shrinkage is less than 2) and the shrinkage ratio is 2, then the specification of the casing is 4; if the shrinkage ratio is 3, the specification of the casing is 6; if the shrinkage ratio is 2.5, the specification of the casing is 5.
3. Flame Retardant Property
There are two common methods to test the flame retardant performance of casing products, which have the property of obviously delaying flame spread.
(1) Determination of oxygen index
The double-wall heat-shrinkable tube is mainly aimed at the flame retardant test method of high-pressure bushing series.
(2) Vertical combustion
It is mainly aimed at the flame retardant test method of conventional casing, and is also the standard test method of UL224 flame retardant.
4. Shrinkage temperature
There are two kinds of shrinkage temperature: the initial shrinkage temperature and the complete shrinkage temperature. The initial shrinkage temperature is the temperature when the casing starts to shrink. The complete shrinkage temperature is the lowest temperature at which the casing can shrink completely. The shrinkage temperature of the casing can be measured by shrinkage curve experiment.
The casing is of various colors, which can be understood according to the following table.
The Chinese name of PTFE is PTFE. It is a high temperature differentiation chemical material containing PTFE. It is widely used in packaging, electronic and electrical, chemical energy, corrosion resistant materials. Because of the pronunciation, it is also called Teflon, Teflon, Teflon and so on. Secondly, FEP: FEP Chinese name is ethylene fluoride propylene copolymer (perfluoroethylene propylene high temperature heat shrinkable pipe copolymer). FEP is a copolymerization of polytetraethylene and hexafluoropropylene.
The difference between PTFE and FEP:
(1) The non-stick coatings of FEP and F46 (vinyl fluoride propylene copolymer) casing materials melt and flow during baking to form a porous film, which has excellent chemical stability and excellent non-stick properties. The highest use temperature is 200 C, and the melting point is 270 C. They can be injected and extruded.
(2) PTFE (polytetrafluoroethylene) casing material non-stick coating can be used continuously at 260 C, with the highest temperature of 290-320 C, very low friction coefficient, good wear resistance and excellent chemical stability. It can not be injected. It can be extruded or painted.
So PTFE material is much more practical than FEP. The reason is very simple because of its characteristics, PTFE's temperature resistance, anti-corrosion performance, anti-sticking performance are better than FEP. However, due to the cost problem, FEP material is a good choice if the requirement is not too high, but friction resistance.