10 is, with certainty, the thermoplastic with which we are more familiarized in our day-to-day. The HDPE, or high density polyethylene, is present in objects so common as bottles, containers, toys, helmets, cosmetic and food containers and all kind of domestic objects. In fact, it is synthetic polymer with a higher volume of production in all over the world. It is odourless, insipid and non-toxic.
Besides its countless uses in the home, the use of the pipes of this material is habitual also for the conduction of liquids in sewage or in the agriculture. Their advantages make them to be used besides in construction, industry and chemical products or in fishing.
The High Density Polyethylene (HDPE) among its characteristics we can find its lightness and flexibility, even with low temperatures and its high resistance to the impacts. The products and chemical agents, as well as the acids don’t produce any harm to it and it also supports temperatures of the water above 100°C.
The HDPE suffers oxidation at 50 ºC together with the degradation of the molecules of polymer. Even at ordinary temperatures, in the presence of the light, suffers degradation. Before a thermal oxidation, the incorporation of antioxidants can reduce it and even eliminate it. Regarding to the electrical conductivity, in the case of this thermoplastic is low. Besides, it has high dielectrical resistance and a low power factor (9.15). In addition, it is recyclable and respectful with the environment.
With these characteristics, the pipes which use it as the main component have great advantages regarding to others.
- Quick Installation. Due to its lightness, the transportation, handling and installation process is shortened. Besides, it doesn’t need heavy machine to move it.
- Flexibility. They are adapted to changes of direction and bends, so they don’t do fittings or additional tools. In comparison, it is more flexible than the polyethylene.
- Resistance. They support vertical loads due to they transfer the higher part of the load to the soil which is around the pipe. This is due to its corrugated external wall.
- Useful life. They are resistant to the effects of the abrasive liquids, to impacts and to other chemical agents; the useful life of the HDPE pipes is estimated of 50 years.
- Safety. They are not used together as the welding is done by thermofusion welding, with which the safety of the installation is complete.
- Efficiency. Due to its flat inside part, they facilitate a flow of liquids to the pipes of other materials. Besides, they don’t accumulate sediments or incrustations inside them.
The HDPE is different from the conventional density polyethylene because it has higher molecular weight, and its fabrication can be done by three methods; the Ziegler, Phillips method or ‘gas phase’. Unlike the low density polyethylene, is harder, stronger and heavier, besides of being less ductile.
Within the family of the polyethylene, the HDPE coexists with the UHMWPE (Ultra High Molecular Weight Polyethylene), which is used to manufacture very resistant fibres, like the ones which are used in the bulletproof jackets, and it is up to 15 times more resistant than the carbon steel before the abrasion.