Temperature Influences. The physical properties of Vinidex PE pipes are related to a standard reference temperature of 20°C. Where physical property values are quoted to ISO and DIN Standard test methods, these are for the 20°C condition, unless otherwise quoted. PE pipes may be used at operating temperatures between -40°C and +80°C. For temperatures less than 20°C it is convention to use the 20°C hydrostatic design stress. Below freezing, additional care may be required as the impact strength of PE is reduced.