Three, PE polyethylene
Polyethylene is a kind of thermoplastic plastic polymerized by ethylene, it is non-toxic, odorless, feel like wax, low temperature resistance, chemical stability is very excellent.
Polyethylene usually has low density polyethylene (LDPE), medium density polyethylene (MDPE) and high density polyethylene (HDPE), their application is not the same. LDPE is usually used to produce lightweight products such as films and fibers, while HDPE or MDPE is usually used in pipe production involving injection molding.
PE tubes are usually black and are generally used to transport cold water.
In the manufacturing of pipelines, because of the poor heat resistance of polyethylene, so in some demanding occasions (such as heating systems), it needs to be modified, so there are PE-RT and PE-X.
Pe-rt refers to heat-resistant polyethylene, which uses ethylene and octene copolymerization method, by controlling the number and distribution of side chains to get a unique molecular structure, to improve the heat resistance of PE.
Pe-x refers to cross-linked polyethylene. Cross-linking makes the linear macromolecular structure of polyethylene become a three-dimensional network structure, thus improving its heat resistance and creep resistance. Crosslinked polyethylene is not thermoplastic and cannot be hot-fused. At present, the commercial PE-X includes PE-XA, PE-XB and PE-XC. It is worth noting that A and B here do not refer to the product grade of A or B, but they adopt different process methods in the cross-linking reaction.
Pe-rt and PE-X are commonly used as floor heating pipes.
Four, PVC PVC
Polyvinyl chloride is one of the most widely used plastic products, which is made by polymerization of vinyl chloride monomer.
Polyvinyl chloride (PVC) heat and light stability, in more than 100 ℃ or the sun for a long time, can produce hydrochloric acid decomposition, and further automatic catalytic decomposition, cause discoloration and mechanical performance degradation, stabilizer must be added in the practical application in order to improve the stability of heat and light, the choice of stabilizer is the key to its quality and safety.
The difference between the soft and hard polyvinyl chloride is that there is no plasticizer added. Soft PVC contains plasticizer, which is generally used for the floor, ceiling and leather surface, with poor physical and mechanical properties.
Hard polyvinyl chloride (PVC-U) without added plasticizer is commonly used to make pipes. At present, the most widely used are drainage pipes and electrical casing. The pipes of PVC-U are not usually connected by hot melt, but are connected by adhesive.
The above describes some common plastics used in the manufacture of pipes. In addition to these materials, there are other materials, but they are not widely used, the most important is the above materials.
