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What TPU test pieces consist of and what are they used for
May 13 , 2022

A TPU physical properties test pieces consist of abrasion test particles, crescent, dog bone, test coupons. Different part be used to do different properties test.

The main physical properties of TPU are: hardness, tensile strength, 100% modulus, elongation at break, tear strength, compression set, resilience, abrasion, melt index, yellowing resistance, high/low temperature resistance, hydrolysis, oil resistance.

A. Hardness test

Hardness is often test by GB/T531.1 test standard which is equivalent to ISO7619-1. The measuring instrument is a Shore A hardness tester or Shore D hardness tester. Shore hardness is a resistance value that uses the force of the spring to make the needle that at end of the durometer pierce the surface of the test piece. Shore A hardness tester can test the hardness that range from 1A-100A, For the hardness that over 100A must be test by Shore D hardness tester. TPU test coupons is usually be used to test hardness

Below main requirements for the hardness test for your reference:

1. The upper and lower surfaces of the test coupons must be flat

2. The thickness of the test piece is not less than 6mm

3. The thimble test position is not less than 12mm from any edge

4. The sample must be conditioned at room temperature for more than 1 hour before testing. For hardness testers of different manufacturers, the hardness will be within Shore1A deviation. The testing process has a greater impact on the results.

B. Tensile Strength and 100% modulus

Tensile strength, also known as breaking strength, tested according GB/T528 standard. Main test requirements is as below:

1.The TPU dog bone test piece be used to test tensile Strength and 100% modulus. Dog bone is with 2mm thickness and 6mm± 0.2mm width

2. The drawing speed of the tensile machine is selected as 500mm/min, and in some industries tensile strength is tested under 200mm/min drawing speed .

3. Tensile strength = maximum force value / cross-sectional area, Unit is MPa.

The test standard of 100% modulus is exactly the same as the method of tensile strength test. this physical property is the tensile strength when the test dog bone stretch 100% length. Generally the 100% modulus data is ignored by most companies that using TPU, but in some industries that the lifetime of the product required must not exceed 100% deformation,100% modulus is more important. This situation is also happen in the 5% modulus.

C. Tear strength

The physical properties are tested according to GB/T529. TPU tear strength is tested by the crescent part.

Tear strength=maximum force/thickness, unit is N/mm

The stretching speed is 500mm/min

D. Abrasion resistance

The commonly Abrasion resistance test instruments are Akron attrition machine and roller attrition machine. The former is gradually replaced by the latter due to the disadvantages of cumbersome, repetitive paths, and long time. The operation of the roller attrition machine adopts the GB/T9867 standard. The abrasion test particles is used to do TPU abrasion resistance test.

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