The first thing to know is the definition of the casing, which is usually used in the basement of the building to protect the pipe or the iron ring that facilitates the installation of the pipe. Common types of casing are divided into two types: rigid casing and flexible waterproof casing. Mainly used in oil well casing and tubing seamless steel pipe. Casing can be widely used, because it has anti-extrusion, tensile, anti-internal pressure, good sealing and other characteristics, different types of casing has different functions, electronic professional production of various types of casing, according to customer needs for customized selection.

Understand the concept and basic characteristics of the casing, the next step requires us to have a deep understanding of some of the key words of the casing, the common casing keywords have shrinkage magnification, product specifications, flame retardant properties, shrinkage temperature and color, and then by the small series for these items for detailed introduction.

1, shrinkage heat shrinkage tube magnification

Shrinkage ratio generally refers to the ratio of casing inner diameter before and after non-restrictive (or free) shrinkage under certain conditions. Shrinkage ratio changes under certain conditions, the need for temperature to reach 200 ℃, the time takes 3 minutes to get the effect of shrinkage, shrinkage ratio and expansion ratio close, but slightly less than the expansion ratio.

2, Product specifications

Product specifications generally refer to the product of the maximum inner diameter and shrinkage ratio allowed after casing shrinkage. That should be difficult to understand, we give an example.

For example: the maximum inner diameter allowed after shrinkage is 2mm (that is, the shrinkage of the inner diameter ≤2), the shrinkage ratio is 2, then the specification of this casing is: Φ4; If the shrinkage ratio is 3, the specification of this casing is: Φ6; If the shrinkage ratio is 2.5, the specification of this casing is: Φ5.

3. Flame Retardant Properties

Flame Retardant performance casing products have a significant delay in the nature of flame spread, test casing flame retardant properties are common in two ways:

(1) Oxygen Index Determination method

The double-walled heat shrinkable tube is mainly aimed at the flame retardant test method of the high pressure parent row series casing.

(2) Vertical combustion hair

Mainly for the conventional casing flame retardant test method, but also UL224 flame retardant standard determination method.

4. Shrinkage temperature

The shrinkage temperature has two types, the initial shrinkage temperature and the complete shrinkage temperature, and the initial shrinkage temperature is the temperature when the casing begins to shrink. The complete shrinkage temperature is the lowest temperature at which the casing can shrink completely, and the shrinkage temperature of the casing can be determined by doing the shrinkage curve experiment.

5. Color

The casing is varied in color and can be understood according to the table below.

PTFE's Chinese name is PTFE. It is a kind of chemical material containing PTFE high temperature division. It is widely used in packaging, electrical and electronic, chemical energy, corrosion-resistant materials. Because of pronunciation, it is also known as Teflon, Tiefurong, Teflon, Tefflon and so on (all for the Teflo of the translation). The second is the FEP:FEP Chinese name is vinyl fluoride propylene copolymer (perfluorinated ethylene propylene high temperature heat shrinkable tube copolymer). FEP is a copolymerization of polyethylene and six fluorine propylene.

The difference between PTFE and FEP:

①FEP, F46 (vinyl fluoride propylene copolymer) Casing material non-stick coating in baking melt flow to form porous film, with excellent chemical stability, excellent non-stick characteristics, the maximum use temperature of 200 ℃, melting point of 270 ℃, can be injection molding, extrusion molding.

②PTFE (PTFE) Casing material non-stick coating can be used continuously in 260 ℃, with a maximum use temperature of 290-320 ℃, very low coefficient of friction, good wear resistance and excellent chemical stability. Cannot be molded, can squeeze molding or make paint.

Therefore, PTFE material is much more practical than FEP. The reason is very simple because of its characteristics, PTFE temperature resistance, anti-corrosion performance, anti-viscosity performance is better than FEP. However, due to the cost problem, if the requirements are not too high, but only friction resistance, the FEP material is a good choice.

套管的日常应用与铁氟龙PTFE套管与FEP套管材料的对比

首先要知道套管的定义，套管通常用在建筑地下室，用来保护管道或者方便管道安装的铁圈。常见的套管种类分为两种：刚性套管和柔性防水套管。主要用于油井用套管和油管的无缝钢管。套管之所以能够得到广泛的应用，因为其具备抗挤、抗拉、抗内压、密封性好等特点，不同类型的套管具备不同的功能，电子专业生产各类套管，可根据客户需求进行定制选择。

了解了套管的概念和基本特点，下一步需要我们对套管的一些关键词进行深入了解，常见的套管关键词有收缩倍率、产品的规格、阻燃性能、收缩温度和颜色，接下来由小编针对这几项作详细介绍。

1、收缩热缩管倍率

收缩倍率一般指在一定条件下非限制性（或称自由）收缩前后套管内径的比值。收缩倍率在一定条件下发生变化，需要温度达到200℃，时间需要3分钟就可以到手收缩的效果，收缩倍率与扩张倍率接近，但会稍小于扩张倍率。

2、产品规格

产品规格一般是指套管收缩后允许的最大内径与收缩倍率的乘积。这么说应该不好理解，我们举例说明下。

例如：收缩后允许的最大内径为2mm(即收缩后内径≤2)，收缩倍率为2，则此套管的规格为：Φ4；若收缩倍率为3，则此套管的规格为：Φ6;若收缩倍率为2.5，则此套管的规格为：Φ5。

3、阻燃性能

阻燃性能套管产品具有的明显推迟火焰蔓延的性质，测试套管的阻燃性能常见的有两种方法：

（1）氧指数测定法

双壁热缩管　主要是针对高压母排系列套管的阻燃测试方法。

（2）垂直燃烧发

主要针对常规套管的阻燃测试方法，也是UL224阻燃标准测定方法。

4、收缩温度

收缩温度有起始收缩温度和完全收缩温度两种，起始收缩温度是套管开始收缩时的温度；完全收缩温度是套管可以完全收缩的最低温度，通过做收缩曲线实验可以来测定套管的收缩温度。

5、颜色

套管的颜色多样，可以根据以下表格作了解。

PTFE中文名字叫聚四氟乙烯。是一种含聚四氟乙烯高温分化学材料。它广泛应用于包装，电子电气，化工能源，耐腐蚀材料。因为发音的缘故，又被称作铁氟龙、铁富龙、特富龙、特弗隆等等（都为teflo的译音）。其次是FEP：FEP中文名字叫氟化乙烯丙烯共聚物（全氟乙烯丙烯高温热缩管共聚物）。FEP是聚四乙烯和六氟丙烯共聚而成的。

PTFE与FEP的区别：

①FEP、F46（氟化乙烯丙烯共聚物）套管材料不粘涂料在烘烤时熔融流动形成无孔薄膜，具有卓越的化学稳定性、极好的不粘特性，最高使用温度为200℃，熔点为270℃，可以注塑，挤压成型。

②PTFE（聚四氟乙烯）套管材料不粘涂料可以在260℃连续使用，具有最高使用温度290-320℃，极低的摩擦系数、良好的耐磨性以及极好的化学稳定性。不能注塑，可以挤压成型或做涂料。

所以说PTFE材质比FEP要实用许多。原因很简单就是因为其特性，PTFE的耐温性能，防腐性能，防粘性能都要比FEP好。然而由于成本问题，如果对要求不是太高，只是耐摩擦的话，FEP材料倒是一个不错的选择。