In applications where plastic components are designed to withstand stress, the mechanical properties of polymers play a particularly important role. The fundamental mechanical material characteristics include:
Such properties can be investigated and compared between different products using standardised test methods. For example, tensile properties of plastics such as plastic tensile strength and rigidity can be determined according to DIN EN ISO 527 by briefly applying load in one direction with a tensile test. The possible results and typical values observed during such tests, depending on material behaviour, are summarised in the graph.
Flexural strength and tensile strength of plastic are two of the most commonly used values to compare materials. The addition of carbon fibre and glass fibre reinforcement in extruded materials generally improves tensile and flexural strength, but the effect is more limited than in injection molded samples.
Testet on specimen machined from semifinished products.
The rigidity of unfilled materials is expressed by the tensile modulus. Ensinger products with the best stiffness values include TECASINT 4111 (PI), TECAPEEK (PEEK), TECAST (PA 6 C), TECAFORM AD (POM-H) and TECAPET (PET) .
For maximum E-modulus values, carbon fibre and glass fibre filled materials are available.
Testet on specimen machined from semifinished products.
Compressive strength gives a good indication of the short term loading capabilities of different plastic materials. It is measured by applying an increasing force on cylindrical or cubical specimens held between two plates, while measuring both pressure and elongation.
With thermoplastics, the property of compressive strength at break is not always the relevant measurement, because for many ductile materials the specimen deforms without clear breakage. Excessive deformation under load would thus not be a good indication for success in any real industrial application. For these reasons, the compressive load is not normally given at break, but is instead given at a defined deformation point (commonly 1 %, 2 % or 10 %). It is very important to check the test conditions before comparing compressive values from different sources!
It should also be noted that the addition of carbon fibre or glass fibre reinforcement generally improves the compressive strength of the polymer, but the macroscopic effect is more visible in the long term rather than in short term load performance, due to the improvement of creep properties.
Testet on specimen machined from semifinished products.
While surface hardness can be measured in many different ways, one of the most common methods used to test thermoplastics is called “ball indentation hardness”.A metallic sphere of standard dimensions is pressed into the material with a defined force and for a defined time, the residual mark in the material defines the hardness value. Another common method of hardness testing is referred to as Rockwell Hardness testing.
Glass fibre and carbon fibre filled materials exhibit the highest surface hardness.
The impact strength of thermoplastics is measured either by Charpy or Izod impact tests. A small rectangular rod is struck by a pendulum at high speed and the energy absorbed while breaking the specimen is measured; the higher the value, the better the impact resistance. In the case of high impact resistant plastics, where such samples do not break, resulting in no usable value, the test is repeated with a notch made on the specimen to obtain information under this more severe condition.
Testet on specimen machined from semifinished products.
Glass fibre and carbon fibre filled materials exhibit the best mechanical properties, but there are also many unfilled materials which meet these requirements.
To complement our products, we offer a comprehensive range of processing methods as well as customised profiles and tubes to meet your individual requirements for your finished part.
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