Determination of shrinkage of the hottest PE heat

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Determination of shrinkage rate of PE heat shrinkable film

5.18.1 instrument constant temperature bath: used to contain liquid heat transfer HRD medium. The volume shall be sufficient to accommodate the membrane frame liquid heat transfer medium: glycerol is generally selected frame: two frames embedded with metal, whose size is slightly larger than the sample, and the distance between the two outer metals is mm, which should not affect the free shrinkage of the sample

5.18.3 operation steps sample preparation:

cut 1 from the outer end of each roll of film for inspection. Within the range of room temperature 10~35 ℃, the relative humidity is not greater than 80%; Remove it by 3M, discard it, and then evenly cut 100mm parallel to the longitudinal direction of the film along the width direction of the film × Three 100mm square samples. Accurate

to 0.1mm the standard environment for sample state adjustment and test shall be in accordance with gb2918

temperature: 23 ± 2 ℃; Humidity: the adjustment time of normal humidity

state is more than 4 hours draw a symmetrical axis in the longitudinal and transverse directions of the sample for marking, and indicate the longitudinal and transverse directions. Place the sample

horizontally between the two frames, and then quickly immerse it in a constant temperature medium at 120 ± 2 ℃. The technical parameters of the manufacturer are the free shrinkage of exposure,

20s, take it out, immerse it in a standby normal temperature bath, cool it for 5S, take it out, and let it stand horizontally,

measure the size of the vertical and horizontal axis of symmetry within 30 minutes, accurate to 1mm, and record the measurement data

5.18.4 the result shows that

shrinkage is calculated according to the following formula:

s =

where: s: shrinkage,%

l0: the length of the sample before heating, mm

l: the length of the sample after shrinkage, know the separation degree of the sample, mm

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