Certech is continually developing its range of services in the polymer sector. For product quality improvement, our R&D centre can now provide its customers with characterization following the ISO18488 standard method for determining the strain hardening modulus, which is used as a measure for the resistance to slow crack growth (ESCR – Environmental Stress Cracking Resistance) of polyethylene for pipe applications. The strain hardening modulus is obtained from stress-strain curves at 80°C on compression-moulded samples. The ISO18488 method is valid for all types of polyethylene, regardless of the manufacturing technology, comonomers or type of catalyst used in pipe and fitting applications. It should be noted that the method could also be developed for materials intended for other applications (rotational moulding, blow extrusion, etc.). This method has several advantages over conventional ESCR measurement: the test takes just a few hours, compared with possibly hundreds or thousands of hours for conventional ageing tests, and does not require the use of hazardous solvents. Moreover, only a limited amount of material (ca. 10 g) is needed for the test, making it a technique of choice for screening polyethylene materials synthesised at R&D level.
Accelerated tests for ESCR (Environmental Stress Cracking Resistance) properties
