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| Polyether Block Amides | |
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| Polyether Block Amides | |
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| Mechanical Properties |
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1. A large range of mechanical properties 5. Outstanding properties at low temperature 6. Dynamic Mechanical Analysis (DMA)
1. A large range of mechanical properties
Hardness can be defined as the resistance of a material to an indentation deformation. The higher the hardness, the better the material’s resistance to the indenting deformation will be. For thermoplastic materials, the hardness is characterized with the Shore D reference, whereas the Shore A reference is used for elastomers and low modulus materials.
Shore D Hardness:
This test enables the determination of the penetration depth in the sample under a given load and during a fixed time lap. The indentation device is not supposed to be deformable.
The flexural resistance can be measured thanks to the three point method: a sample is positioned on two supports. A force is applied in the middle, leading to the so-called three point loading (see figure). This test combines compression, tensile and shear solicitations in the material. Two essential material characteristics are measured thanks to this test: the flexural elasticity modulus and the flexural stress at break.
The flexural stress versus strain curve is then plotted to determine the flexural modulus.
The flexural modulus corresponds to the tangent of the stress versus strain curve measured in the initial linear portion where the material is only slightly deformed.
The flexural modulus value is expressed in MPa. These tests are generally performed using the ISO 178 standard or the ASTM D 790 standard. When using the ISO 178 standard, the sample geometries are 80 x 10 x 4 mm3 bars.
This graph illustrates the flexural modulus range offered by the pebax® 33 series, going from approximately 10 to 500 MPa.
The tensile stress-strain curves shown in the graphs below have been obtained using ASTM D638, after a standard conditioning of 14 days at 23°C and under 50% relative humidity.
Tensile tests give access to:
The stress and strain at break values can be obtained from tensile tests at 23°C using two possible standards: the ISO 527 1 BA standard (using a strain rate of 200 mm/min and ISO 527-1BA type samples) or the ASTM D 638 standard (using a strain rate of 500 mm/min and ASTM D638 type IV samples).
It is often useful to determine the stress and strain values of pebax® for a given elongation, as the modulus and strain at break values are not always a reflection of the solicitation of the material in a given application.
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