GB/T 1843-2008Plastics - Determination of izod impact strength (English PDF)

5.1 Testing machine

5.1.1 For the principle, characteristics, identification of the testing machine, please refer

to GB/T 21189-2007.

5.1.2 Some plastics are very sensitive to clamping force. When testing such materials, a standardized clamping force method shall be used and the clamping force shall be noted in the test report. The clamping force can be controlled by a calibrated torque wrench or a pneumatic or hydraulic device on the screw tightened by the vise.

5.2 Micrometer and gauge

Measure the main dimensions of the specimen, using a micrometer or gauge which has an accuracy of 0.02 mm. In order to measure the dimension of the notched specimen bN, a measuring probe which has a width of 2 mm ~ 3 mm and a shape suitable for the shape of the notch shall be installed on the micrometer.

6.1 Preparation

6.1.1 Molded and extruded materials

The materials shall be prepared in accordance with the relevant material standards. If there is no such standard or otherwise specified, the specimens shall be directly compression molded or injection molded in accordance with the corresponding standards of GB/T 9352-2008, GB/T 17037.1-1997, GB/T 5471-2008 or ISO 10724-

1:1998, or machined from compression molded or injected sheets. The specimens may also be cut from type A multi-purpose specimens conforming to GB/T 11997-2008.

6.1.2 Sheets

The specimens shall be machined from sheets in accordance with ISO 2818:1994, using type A notches whenever possible. During testing, the machined surface of the unnotched specimen shall not be in tension.

material is to be obtained, specimens with notches of Type A and Type B shall be tested.

6.3.3 Sheets, including long fiber reinforced materials

The recommended thickness h is 4 mm. If the specimen is cut from a sheet or component, its thickness shall be the same as the original thickness of the sheet or component, which shall not exceed 10.2 mm.

When the thickness of the sheet is uniform and contains only one regularly distributed reinforcement material, when its thickness is greater than 10.2 mm, it shall be machined from one side of the sheet to 10.2 mm ± 0.2 mm. When testing unnotched specimens, in order to avoid surface effects, the original surface of the specimen shall be in tension during the test.

During the test, the side of the impact specimen is impacted; the impact direction is parallel to the plane of the sheet. Only when h = b = 10 mm can the test be carried out parallel or perpendicular to the sheet surface (see Figure 1).

6.4 Number of specimens

6.4.1 Unless otherwise specified in the standard of the test material, a group of specimens shall be 10. When the coefficient of variation (see ISO 2602:1980) is less than 5%, 5 specimens can be tested.

6.4.2 If the laminated material is tested in the vertical and parallel directions, 10 specimens shall be tested in each direction.

6.5 State conditioning

Unless otherwise specified in the standard of the test material, the test shall be conditioned for at least 16 hours at 23 °C and 50% relative humidity in accordance with

GB/T 2918-1998, or according to the conditions agreed upon by the relevant parties.

The conditioning time of the notched specimen shall be calculated after the notch processing.

7.4 Determine the friction loss and corrected absorbed energy according to GB/T

21189-2007.

7.5 Lift and lock the pendulum. Install the specimen as shown in Figure 1 and meet the requirements of 5.1.2. When measuring the notched specimen, the notch shall be on the side of the pendulum impact edge.

7.6 Release the pendulum. Record the impact energy absorbed by the specimen. Make

necessary corrections for its friction loss (see 7.4).

7.7 The following characters are used to name the four types of impact:

C - Complete failure: The specimen is broken into two or more sections.

H - Hinge failure: An incomplete failure in which the specimen is not connected by a very thin rigid surface.

P - Partial failure: Incomplete failure except hinge failure.

N - No failure: No failure, only bending deformation; stress whitening may occur.

8.1 Unnotched specimen

The Izod unnotched impact strength aiU is calculated according to formula (1), in kilojoule per square meter (kJ/m2):

Where:

Ec - Corrected specimen fracture absorption energy, in joule (J);

h - Specimen thickness, in millimeter (mm);

b - Specimen width, in millimeter (mm).

d) Description of the material properties and shape, i.e., finished product, semi- finished product, test piece or specimen, including main dimensions, shape, processing method, etc.;

e) Impact velocity;

f) Nominal energy of the pendulum;

g) If a uniform clamping force is used, indication of the clamping force (see 5.1.2);

h) Method of specimen preparation;

i) Direction of specimen cutting (if the material is a finished or semi-finished product);

j) Number of specimens;

k) Conditioning used and standard test environment, as well as special treatments required by the test material and product standards;

l) Type of failure observed;

m) Individual test results, as follows (see also Table 2):

1) Grouped into three types of failure:

C: Complete failure, including hinge failure H;

P: Partial failure;

N: No failure - no failure occurred.

2) Select the failure type that occurs most frequently and record the average value x of the impact strength of this failure type; record the corresponding failure type with the letter C or P;

3) If the most common failure type is N, only record the letter N;

4) For the failure type that occurs less frequently, add the letter C, P or N between the two brackets, only when the number of occurrences is higher than 1/3 (otherwise insert a "*" sign).

n) Standard deviation of the mean value if necessary;

o) Test date.

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