An innovative way of ranking the long-term behavioural properties of plastics has become ISO 18488 standard.
The method, which was developed by petrochemicals company, SABIC, significantly reduces the time taken to test the slow crack growth (SCG) resistance of high density polyethylene (HDPE) with particular relevance for pressure pipes.
The strain hardening test method, which reduces the time and cost associated with getting material for plastic pressure pipes to market, was first launched in 2010.
While traditional methods to evaluate environmental stress crack resistance (ESCR) in pressure pipe materials, such as the Full Notch Creep test, can take months, if not years, to complete, SABIC’s development reduces this test time significantly, to just a few days.
The Strain Hardening Test Method also does not require either notched specimen or detergents, further reducing the costs associated with the assessment of long-term behaviour in HDPE.
Hans Pierik, SABIC’s Senior Manager for HDPE, said: “SABIC is delighted that the strain hardening test method has been laid down in ISO 18488. For suppliers of pressure pipes this brings significant positive benefits. Obtaining reliable data on the long-term behaviour of plastics has always been difficult, and this innovation is an important development for the market.”
The test was developed, in part, to help suppliers meet increasingly demanding requirements as set out by the Publicly Accessible Standard 1075, which necessitates higher resistance to slow crack growth than expected in the PE100 specification.
The method requires a tensile test at 80°C, and is based on fundamental postulates of crack propagation. ISO 18488 analyses the basic polymer properties that cause stress crack resistance – a different way of obtaining information on the behavioural properties of plastics than traditional testing methods.