Abstract
As the external coatings of steel line pipes, polyolefine resins which have exellent anti-corrosive properties are applied commonly. However, against the background of the worldwide energy crisis in recent years, the situations and the conditions associated with pipeline construction and operation tend to be increasingly severe.
So, we have researched the thermal characteristics and the long term durability of poly-olefine resins and referred to the influences of these characteristics on the coating properties. Moreover, in order to estimate the high temperature life of polypropyrene coating, a new accelerated test method of heat deterioration which is different from the extrapolation of the oxidative induction time is tried to be established.
The following results were obtained :
As for the polyethylene coating, a medium density polyethylene shows the best characteristics at the temperature between -45°C and 80°C.
As for the polypropyrene coating, a new type of the block-copolymerized polypropylene shows the exellent mechanical strength at the temperature between -30°C and 110°C.
The long term durability at high temperature is enable to be solved by the addition (>2.4%) of specific anti-oxidants, which are sulfide and phenol compounds.
