GB/T 38711-2020Test method for reheating shrinkage of ultrathin glass - Laser method (English PDF)

3.1 Ultra-thin glass

Flat glass products with a thickness of not more than 1.1mm.

3.2 Reheating shrinkage

The glass sample is reheated and cooled according to a certain heating, heat preservation, and cooling process, and the glass structure is loosened and the size is relatively

The rate of change of shrinkage from the original length.

6.1 Shape and size

The sample is required to be rectangular, and the recommended size is not less than 270mm in length, 20mm to 25mm in width, and the two end faces in the long direction are ground flat

Polished, two sides are parallel and four corners are perpendicular.

6.2 Number of samples

The number of samples is 2.

7.1 Environmental placement

The instrument device is placed on the marble countertop experiment table or shock-absorbing table, before the test, the sample is placed in the measurement environment for 1h.

7.2 Reference calibration

Follow the steps below.

a) Use the quartz calibration sample of the same material as the bracket and undergoing strict heat treatment, and its length and thickness are similar to the glass sample.

b) Use a vernier caliper that meets the requirements of GB/T 21389 to measure the length L0 of the quartz calibration sample, and keep the result to 0.00001m.

c) The quartz calibration sample is placed on the quartz holder and placed in the heating furnace.

d) Compact the end of the quartz mandrel (in the furnace) on the end of the quartz calibration sample, and apply 80g counterweight.

e) Adjust the three-way adjustment platform of the rangefinder so that the spot of the laser sensor is aligned with the outer end of the quartz ejector furnace.

f) Adjust the front and rear positions of the three-way adjustment platform to make the laser sensor within the measuring range.

g) Set the test temperature system, including parameters such as heating rate, holding temperature, holding time, and cooling rate.

For example. heat up to the set holding temperature at a rate of 3°C/min (the holding temperature of different glass varieties is different, and it is recommended that the holding temperature ratio is

The glass transition temperature Tg should be lower than 100°C), keep the temperature for 30min at the holding temperature, so that the glass is heated evenly, and then

The temperature is lowered to.200°C at a rate of 3°C/min, and the measuring device is naturally cooled to room temperature.

h) The measuring device loaded with the quartz calibration sample is allowed to stand for 30 minutes in the experimental environment. After the laser sensor shows a stable value, read and

Record the value D0 of the laser sensor.

i) According to step g) temperature system, heat, heat and cool the quartz calibration sample, and read and record after returning to room temperature for 2 hours

The laser sensor shows the value D1.

j) Calculate the reference correction value SJ of the reheating shrinkage rate of this device according to formula (1).

7.3 Sample test

Test the glass sample according to 7.2.The measurement results of the two samples are recorded as S1 and S2 respectively, and the arithmetic mean SC is calculated according to formula (2).

When the relative deviation is greater than 3%, samples should be prepared and tested again.

7.4 Calculation of results

The total reheat shrinkage rate S of the glass sample is calculated according to formula (3).