After the heat shrinkable sleeve is baked to the welding port, we have to carry out some tests to check whether it is qualified and meets the standard. One of the more important items is peel strength.

The peel strength test of the heat shrinkable sleeve filler material can reflect the advantages and disadvantages of its bonding performance from two aspects. One is the peel strength value, and the other is the peeling phenomenon, which reflects the adhesion between the heat shrinkable sleeve substrate and the glue, the glue and the reduced primer or overlap area, the primer and the steel pipe, and the cohesion of each layer of material. Divided into 5 categories:

1. Fully cohesive peeling. The peeling section is an adhesive layer, and the surface of the primer layer or the surface of the substrate is evenly occupied by the surface of the adhesive layer.

2. Partial cohesive peeling / partial non-cohesive peeling. The peeling section is divided into the adhesive layer, and part of it exhibits non-cohesive peeling from the primer or substrate (there is a peel strength value, but the adhesive layer is pulled away from the primer or substrate surface)

3. Completely non-cohesive peeling. That is, the peeling section is pulled away from the surface of the adhesive layer and the primer or the substrate.

4. Partial non-cohesive peeling / partial loss of adhesion. That is, the part of the peeling section is occupied by the primer, and the part is layered with the primer or the substrate.

5. Complete loss of adhesion. That is, the peel strength is zero, and the primer or substrate and the heat shrinkable sleeve material are in a layered state.

General peel strength test method:

First, cut the anticorrosive layer along the circumferential direction with a width of 20-30mm and a length of more than 100mm. When cutting, the anticorrosive layer should be cut through and the one end should be pryed up. Use a dynamometer to pull the anticorrosion layer at a rate of 10mm / min perpendicular to the surface of the steel pipe at a uniform speed, and record the value of the dynamometer. When measuring, a surface thermometer should be used to monitor the temperature of the outer surface of the anti-corrosion layer, and the peel strength test should be completed between 45-55 degrees Celsius.

The data value recorded by the dynamometer divided by the peeling width of the anticorrosive layer is the peeling strength in N / cm. The measurement results are expressed as the average of three measurements.

Normally, we measure the peel strength of the heat shrinkable sleeve, which is generally at a normal ambient temperature, about 24 degrees Celsius. It cannot be carried out at low or high temperatures.

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如何检测热缩套的剥离强度

热缩套烘烤到焊口处后，我们要对其进行一些测试，来检验是否合格，是否满足标准。其中比较重要的一项是剥离强度。

热缩套补口材料的剥离强度测试可以从两个方面反映出其黏结性能的优劣。一是剥离强度数值，二是剥离现象，反映了热缩套基材与胶、胶与还原底漆或搭接区、底漆与钢管等各界面的黏结性以及各层材料的内聚力，通常可以分为5类：

1，完全内聚剥离。 剥离断面为胶层，底漆表面或基材表面均匀胶层表面所占满。

2，部分内聚剥离/部分非内聚剥离。 剥离断面部分为胶层所占满，部分与底漆或基材呈现非内聚剥离（有剥离强度数值，但胶层与底漆或基材表面被拉开）

3，完全非内聚剥离。 即剥离断面从胶层与底漆或基材表面被拉开。

4，部分非内聚剥离/部分失黏。 即剥离部分断面为底漆所占满，部分与底漆或基材分层。

5，完全失黏。 即剥离强度为零，底漆或基材与热缩套材料呈分层状态。

一般剥离强度的测试方法：

首先先将防腐层沿环向划开宽度为20-30mm、长100mm以上的长条，划开时应划透防腐层，并撬起一端。用测力计以10mm/min的速率垂直于钢管表面匀速拉起防腐层，记录测力计的数值。测定时，应采用表面温度计监测防腐层的外表面温度，剥离强度检测应在45-55摄氏度之间完成。

测力计记录数据值除以防腐层的剥离宽度，即为剥离强度，单位为N/cm。测定结果以三次测定的平均值表示。

正常我们测定热缩套的剥离强度，一般要在正常的环境温度，大概24摄氏度左右。不能在低温或者高温下进行。