test device
1. Constant temperature bath
Used to contain liquid heat transfer medium, the volume should meet the test requirements.
2. Liquid heat transfer medium
The selection of heat transfer medium should be based on the principle of no impact on the sample.
3. Framework
Two frames embedded with metal mesh, with the outer dimensions of the metal mesh being more than 10mm larger than the sample. The distance between the two metal mesh should be 1mm-3mm, and it should not affect the free shrinkage of the sample.
4. Sample
Using a steel ruler, blade, or tool with an accuracy of 0.5mm, cut three 100mm * 100mm specimens and mark the longitudinal and transverse directions of the film.
Test steps
Place the sample between two frames, quickly immerse it in the medium of a constant temperature bath at (140 ± 2) ℃, and start timing. During the test, the sample should be kept uniformly heated and freely contracted. After 20 seconds, remove the sample and immerse it in the medium of a constant temperature bath for cooling. After 5 seconds of cooling, remove it and let it stand horizontally for 10 minutes. Measure the longitudinal and transverse dimensions of the sample separately.
calculate
Calculate the shrinkage rate according to the following formula, and take the arithmetic mean of three samples as the result.
S=（（L1-L2）/L1）*100
Among them: S - shrinkage rate,%;
L1- length of sample before heating, in millimeters (mm);
L2- The length of the specimen after shrinkage, measured in millimeters (mm).

WRS-01 heat shrink tester, also known as heat shrink tester, shrinkage rate tester, etc., is suitable for testing the thermal shrinkage performance of materials. It is suitable for testing the thermal shrinkage performance of various films in liquid media at various temperatures, such as PE heat shrink film for overall packaging of alcoholic beverages, cans, mineral water, and various beverages, as well as PVC, POF, OPS, PET and other materials with thermal shrinkage performance suitable for various packaging such as shrink film, flexible packaging composite film, PVC polyvinyl chloride hard sheet, solar cell backsheet, and other materials with thermal shrinkage performance. The specific technical parameters are as follows:

Sample size: ≤ 140mm × 140mm;
Temperature range: Room temperature -200 ℃;
Temperature control accuracy: ± 0.5 ℃;
Heating medium: oil bath;
Dimensions: 480 (L) × 360 (W) × 270 (H) mm;
Weight: 18Kg;
Working temperature: 23 ℃± 2 ℃;
Relative humidity: 50% ± 5%;
Working power supply: AC220V50Hz;
Standard configuration: host, sample tray, sample clamp, thermal oil