1. PE polyethylene
Polyethylene is a thermoplastic polymerized by ethylene. It is non-toxic, odorless, wax-like, and has excellent low temperature resistance and chemical stability.
Polyethylene is usually divided into low density polyethylene (LDPE), medium density polyethylene (MDPE) and high density polyethylene (HDPE), and their applications are different. LDPE is usually used to produce lightweight products such as films and fibers, and when it comes to the production of injection-molded pipes, HDPE or MDPE are usually used.
PE pipes are usually black and are generally used to transport cold water.
In the manufacture of pipes, due to the poor heat resistance of polyethylene, it needs to be modified in some high-demanding occasions (such as heating systems), so there are PE-RT and PE-X.
PE-RT refers to heat-resistant polyethylene. It adopts the method of copolymerization of ethylene and octene to improve the heat resistance of PE by controlling the number and distribution of side chains to obtain a unique molecular structure.
PE-X refers to cross-linked polyethylene. Cross-linking makes the linear macromolecular structure of polyethylene into a three-dimensional network structure, thereby improving its heat resistance and creep resistance. Cross-linked polyethylene is not thermoplastic and cannot be hot-melt bonded. Currently commercialized PE-X includes PE-Xa, PE-Xb, PE-Xc. It is worth noting that a and b here do not refer to product grades A or B, but they are in the cross-linking reaction. The methods used are different.
PE-RT and PE-X are often used as floor heating pipes.
2. PVC polyvinyl chloride
Polyvinyl chloride is one of the most widely used plastic products.
Polyvinyl chloride has poor stability to light and heat. It will decompose to produce hydrogen chloride at temperatures above 100°C or after long-term sunlight exposure, and further autocatalytic decomposition, resulting in discoloration and decreased mechanical properties. In practical applications, stabilizers must be added to improve the For thermal and light stability, the choice of stabilizer is the key to its quality and safety.
The difference between soft and hard PVC is the presence or absence of plasticizers. Soft PVC contains plasticizers. It is generally used for floors, ceilings and the surface of leather, and has poor physical and mechanical properties.
Rigid polyvinyl chloride (PVC-U) has no plasticizer added and is commonly used to make pipes. The most widely used ones are drainage pipes and electrical casings. The pipes of PVC-U are generally not connected by hot melt, but are connected by adhesive.
The above introduces some common plastics used to make pipes. In addition to the above materials, there are other materials, but they are not widely used, and the most important ones are the above materials.
