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Differences in Plastic Water Pipes(Part 2)

Differences in Plastic Water Pipes(Part 2)

The above, Differences in Plastic Water Pipes (Part 1) introduced two kinds of plastics, polypropylene and polybutene, and their applications in pipes. Today, let’s take a look at the characteristics and applications of other materials.

3. PE Polyethylene

  • Polyethylene is a thermoplastic polymerize by ethylene. It is non-toxic, odorless, wax-like, and has excellent low-temperature resistance and chemical stability.
  • Polyethylene usually divide into low-density polyethylene (LDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), and their applications are different. LDPE is usually uses 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 uses.
  • PE pipes are usually black and are generally uses to transport cold water. In the manufacture of pipes, due to the poor heat resistance of polyethylene, it needs to modifie 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 not thermoplastic and cannot 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-Xoften used as floor heating pipes.

4. PVC Polyvinyl Chloride

Polyvinyl chloride is one of the most widely used plastic products.

Polyvinyl chloride has poor stability to light and heat. When it is above 100 ° C or exposed to sunlight for a long time, it will decompose to generate hydrogen chloride, and further autocatalytic decomposition, causing discoloration and mechanical properties. In practical applications, stabilizers must added to improve 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 uses 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 commonly uses to make pipes. The most widely used ones are drainage pipes and electrical casings. The pipes of PVC-U are generally not connect by hot melt but connect 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.

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