GB/T 39937-2021Plastics - Extruded sheets of polypropylene (PP) - Requirements and test methods (English PDF)

4.3.2.2 Maximum shrinkage for thermoforming applications

For sheets for thermoforming applications, under the conditions specified in Table 3, measure the maximum shrinkage in the extrusion direction according to 5.10, and the result should not exceed the table

The value given in 3.

Table 3 Maximum shrinkage for thermoforming applications

4.3.3 Hygienic performance

According to the requirements of relevant laws, regulations and national standards.

5.1 Sample

5.1.1 Sample preparation

The sample should be cut separately from the longitudinal direction (extrusion direction, the same below) and the transverse direction (perpendicular to the extrusion direction, the same below), and the cutting should be evenly distributed on the plate.

Take a sample. For plates in the form of coils, 2m should be taken from the end of the coil to prepare samples. There should be no damage on the surface of the specimen that can cause the notch effect.

Injuries and defects. During the preparation process, if there are burrs or flashes on the sample, they should be removed without damaging the surface of the sample. When needed,

Use sandpaper with a particle size of 220 or finer to smooth the length of the test sample. Samples with a thickness of more than 4.2mm are undergoing 5.5~

During the test in 5.7, one-sided processing shall be carried out in accordance with the requirements of ISO 2818 to make the thickness reach 4.0mm+/-0.2mm.

5.1.2 State adjustment

All samples should be placed at the standard temperature of 23°C specified in ISO 291 for at least 16h. If there is no significant difference in the test results, you can provide

Both parties need to negotiate to determine the use of a shorter state adjustment time.

5.1.3 Test

Unless otherwise specified, the test should be carried out at the 23°C standard temperature specified in ISO 291.

5.2 Delivery conditions

Check visually to ensure that there is no mechanical damage or other obvious defects. If necessary, it can be inspected by ultrasonic or X-ray methods.

5.3 Appearance

Whenever possible, a suitable light source should be used to inspect visible defects through transmitted light. Otherwise, the reflected light with sufficient brightness should be used. According to the supply

The requirements (which can be a written specification or a reference sample) and the corresponding category to identify all deficiencies that need to be negotiated by both parties.

5.4 Dimensions

5.4.1 Thickness

The calibrated equipment that meets the requirements of Table 4 shall be used to measure the thickness h.

5.4.2 Length and width

Appropriate calibrated equipment or meters should be used for measurement, accurate to 1mm. Measure the surface along the cutting edge.

5.4.3 Right angle

For a flat sheet, use the difference between the diagonal lengths to represent the right angle |d1-d2|, as shown in Figure 1.Should use a scale or

The tape measure is accurate to 1mm.

5.4.4 Curvature of coil

Lay the coil flat and measure its curvature along a straight edge. Use appropriate calibrated equipment or meters to measure with an accuracy of 1mm.

5.5 Tensile yield stress and tensile yield strain

According to the test specified in ISO 527-2, at least 5 type 1B specimens are cut from the longitudinal and transverse directions to determine the tensile yield stress sigmay and

Tensile yield strain epsilony, test speed is 50mm/min+/-5mm/min.

5.6 Tensile modulus of elasticity

According to the test specified in ISO 527-2, at least 5 type 1B specimens are cut from the longitudinal and transverse directions to determine the tensile elastic modulus Et.

The inspection speed is 1.0mm/min+/-0.2mm/min.

5.7 Notched impact strength of simply supported beams

For plates with thickness hn >= 4mm, the notched impact strength acn of the sample should be in accordance with ISO 179-1/1eA or ISO 179-2/

1eA is measured, and at least 10 samples are cut from the vertical and horizontal directions.

5.8 Melt mass flow rate (MFR)

Measured according to ISO 1133, the temperature is 230 degrees C, and the load is 2.16kg.

5.9 Heat resistance

Measured in accordance with ISO 4577.

5.10 Determination of thermal behavior

Measured in accordance with ISO 11501.Cut at least three samples, the size is 100mmx100mm, in the center and two sides of the plate respectively

Sampling should be taken at least 50mm away from the edge of the plate. Make one or more pairs of marks in the extrusion direction of the sample. Measure the mark at room temperature

The initial length, L0, is accurate to 0.1mm. Sprinkle a layer of kaolin on the sample and lay it flat on the kaolin bed in a circulating air oven. test

The temperature and duration of the test are shown in Table 5 and Table 6.