Since resistant to high and low temperatures, high density cross-linked polyethylene is used:
- in low (radiant panels) and high (radiators and floor heating) temperature networks
- in radiant cooling panel networks and antifreeze and anti-snow systems.
This thermoplastic macromolecular compound - derived from ethylene monomer polymerisation (CH2 = CH2) - has the following chemical formula:
- (CH2 - CH2) – n
in which n defines the length of the macromolecular chain (the average n value can also be 10,000 - 16,000).
The cohesion forces of the different macromolecular chains making up the polyethylene are not actual chemical bonds since they are of electrical nature ( “Van der Waals” forces). The low energy of these cohesion forces makes the thermoplastic material especially sensitive to temperature.
By entering intramolecular chemical bonds, called reticulation bonds, the thermal and resistance performance of the product can be considerably increased. In fact, reticulation changes the chemical material structure, creating connections between polymeric chains that compose a three-dimensional "network" structure. The new structure:
- increases dimensional stability properties, also at high temperatures
- improves resistance to pressure, to corrosion (from solvents, oils, water), to traction, to ultra-violet rays, to abrasion and to impacts
- reduces deformation under loads (creep deformation) and lengthening in proximity of the breaking point
- gives the material thermal memory characteristics (thermoelastic polymer).
PEX pipes ink jet marking
The PEX pipe is codified with an ink-jet marking which allows the manufacturer to identify the product in order to comply with the warranty conditions required by the standards.
To improve ink adhesion and especially to make it permanent in time, through the various uses and temperature change conditions which the PEX pipe will undergo, a superficial Atmospheric plasma treatment should be carried out.
By means of a torch on the pipe extrusion line - before the marking - the surface tension of the polyethylene is increased, and ink adhesion is optimised.
Based on the pipe diameter, which determines the printing surface, one or more torches can be applied, each of which guarantees a treatment of about 10 - 12 mm.
The atmospheric Plasma system does not produce ozone or other polluting gases and this is why it is easy to install on any pipe extrusion line. It only requires use of compressed air to properly channel the Plasma discharge towards the zone of the pipe to treat.