Sharing of plastic tensile testing standards and test methods, mastering plastic tensile testing methods, understanding the basic structure and working principle of plastic tensile testing machines, and analyzing the material through the tensile stress-strain curve of the sample and various test data The tensile strength, yield strength, elongation at break and modulus of elasticity are evaluated.

(2) Experimental principle

Under the specified test temperature, humidity and tensile speed, a tensile load is applied to the longitudinal axis of the plastic sample to deform the sample until the material is broken. Record the maximum load when the sample is broken and the change in the distance between the corresponding markings. (On an electronic tensile machine with a microcomputer processor, as long as you enter the relevant data and requirements of the sample's specifications and dimensions, during the stretching process, the sensor transmits the force value to the computer, and the computer automatically records the stress-strain process through processing. And print out the stress-strain curve and each test data through the printer).

(3) Test equipment and tensile specimens

1. Test equipment

(1) Mechanical tensile testing machine

①There are special fixtures suitable for various types of samples.

② The moving speed of the fixture should be capable of multi-level or full speed adjustment to meet the needs of standard methods.

③The indicated value of the test data should be read within 10% to 90% of the dial of each level, but not less than 4% of the maximum load of the test. The error of the indicated value should be within 1%.

2. Tensile specimen

(1) Shape and size of sample 　 The standard method stipulates the use of four types of samples.

(2) Selection of samples

Thermosetting molding material: use I type.

Rigid board material: use type Ⅱ (can be larger than 170mm).

Rigid and semi-rigid thermoplastic molding material: use type 2, thickness d=(4±0.2)mm.

Soft board and sheet: use type Ⅲ, thickness d＜=2mm.

Plastic film: use type IV.

(3) Requirements for samples:

① The surface of the sample should be smooth, free of bubbles, cracks, delamination, no obvious impurities, processing damage and other defects. The test pieces with different orientations should be sampled separately along the vertical and horizontal directions.

②When the thickness of the hard plate d<10mm, the original thickness is used as the thickness of the sample; when the thickness d>10mm, it should be machined to 10mm from one side.

③To test the elastic modulus, use type II specimens with a thickness of 4-10mm or long specimens with a length of 200mm and a width of 15mm.

④There are no less than 5 samples in each group.

(4) Experimental steps

1. Experimental conditions

(1) Test speed (no load) 　 A: (10±5)mm/min, B: (50±5)mm/min, C: (100±10)mm/min or (250±50)mm/min .

① A speed is used for thermosetting plastics and hard thermoplastics.

② For rigid and semi-rigid thermoplastics (such as PP, PA, etc.) with large elongation, use B speed.

③ C speed is used for soft board, sheet and film. For relative elongation<100%, use (100±10)mm/min speed, and for relative elongation>100% use (250±50)mm/min speed.

(2) The tensile speed of 1～5mm/min can be used when determining the modulus, and the deformation should be accurate to 0.01mm.

2. Take the mechanical tensile testing machine as an example: adjust the test environment according to the GB1039-92 standard method to treat the sample or GB/T1040 to room temperature.

(1) Test environment 　 temperature: thermoplastic (25±2) ℃, thermosetting plastic (25±5) ℃. Humidity: Relative humidity (65±5)%.

(2) Sample pretreatment 　 Place the sample in a small environment so that its surface is exposed to the environment as much as possible. The processing time of samples with different thickness d is as follows: samples with d<0.25mm are not less than 4h; samples with 0.25mm2mm are not less than 16h.

(3) Measure the thickness and width of the sample, the molded sample and the plate sample are accurate to 0.05mm; the thickness of the sheet sample is 0.01mm; the thickness of the film sample is 0.01mm; each sample is within the distance from the marking line Measure three points and take the arithmetic average.

(4) When testing for elongation, the stretched parallel part of the sample shall be marked as a marking. This marking shall not affect the test result.

(5) When clamping the sample with the clamp, make sure that the center of the longitudinal axis of the sample coincides with the connecting line between the center of the upper and lower clamps, and the tightness is appropriate, so that the sample cannot slip off under force or be clamped too tightly in the clamp. Damage the sample at any place. To clamp the film sample, it is necessary to line the elastic sheet such as rubber in the clamp.

(6) Start the machine at the selected speed, and conduct a tensile test.

(7) After the specimen is broken, read the load and the elongation between gauge lengths, or read the load at yield. If the sample breaks at a position outside the gauge length, the test shall be invalidated and another sample shall be taken to make a new one.

(8) When determining the modulus, the load and corresponding deformation shall be recorded, and a stress-strain curve shall be drawn.

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