QC/T 1045-2016Heat-shrinkable tubing for protection of automotive pipes (English PDF)

3.1 General requirements

3.1.1 Specifications

Heat-shrinkable tubing for automotive pipe is divided into single wall tubing and double wall tubing. Single wall tubing has a maximum operating temperature of 105°C. Double wall tubing has a maximum operating temperature of 125°C.

The double wall tubing is composed of an inner wall (hot melt adhesive) and an outer wall (heat shrinkable material). […]

4.4 Wall thickness and concentricity

Measure the wall thickness with a thickness gauge with an accuracy of 0.01 mm. First lift the pressure column, carefully place the specimen on the pressure pin, and then release the pressure column. The pressure column is pressed against the pressure pin with a force of (0.25±0.02) N. Read the wall thickness value. Measure at least 10 times at different locations to find the maximum wall thickness M1 and the minimum wall thickness M2.

Place the specimen in an aging chamber heated to (150±2)°C. After (600±5) s non-limiting shrinkage, the maximum wall thickness and minimum wall thickness of the specimen after shrinkage shall be measured as described above.

Calculate the concentricity according to formula (1).

where,

Ec - concentricity value;

M2 - minimum wall thickness, mm;

M1 - maximum wall thickness, mm.

4.5 Longitudinal shrinkage

Measure the length of the specimen before shrinkage L1 and the length of the specimen after shrinkage L2 using a steel ruler with a precision of 1 mm or other measuring tools of the same precision. The shrinkage condition is: place the specimen in a (150±2)°C aging oven, and perform (600±5) s non-limiting shrinkage.

Calculate the longitudinal shrinkage according to formula (2).

where,

LC - longitudinal shrinkage;

L2 - specimen length after shrinkage, mm; […]

5.1 Sampling method and determination of rejection

The products shipped to the same user at one time shall be one batch, in batches with minimum packaging. Each batch of products shall be randomly sampled according to Table 5. If the user deems it necessary, determine the sample size of each batch according to the agreement between the parties. If the performance is unqualified, the unqualified performance shall be doubled and sampled again. If it is still unqualified, this batch of products shall be rejected.

5.2 Exit-factory inspection

Before the product leaves the factory, the manufacturer shall carry out the exit-factory inspection according to the test methods of 4.2 and 4.3. The exit-factory inspection shall meet the requirements of 3.1.

5.3 Type test

When any of the following conditions occurs, the type test shall be carried out in accordance with all test methods of 4.2 to 4.12. Type test shall meet the requirements of 3.2.

- trial model identification for new product; […]