Strain at yield

This is an indication of the degree of strain that a material can accept without yielding. The values given are typical room temperature values. If a material is brittle and does not exhibit a yield point, then the value given in Table 2.1 is termed N/A (i.e., not applicable). 

If the material is ductile and does not exhibit a yield point, then the polymer is classified as N/Y (i.e., no yield point). 

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Physical characterization of polymers is a common activity that research and development technologists at the Dow Chemical Company perform. A material property evaluation that is critical for most polymer systems is a tensile test. Many instruments such as an Instron test frame can perform a tensile test and, by using specialized software, can acquire and process data. Use of an extensometer eliminates calibration errors and allows the console to display strain and deformation in engineering units. Some common results from a tensile test are modulus, percent elongation, stress at break, and strain at yield. These data are then used to better understand the capabilities of the polymer system and in what end-use applications it may be used. 

Stress and strain at yield are the values of the stress and strain corresponding to the yield point. 

The mechanical properties are generally fair with high elongations at break but much more limited strains at yield. Moduli and hardnesses are higher than those of polyethylene but... 

The mechanical properties are generally good with high moduli but limited strains at yield... 

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