Polypropylene piping offers advantages such as thermal insulation, energy-saving, environmental friendliness, excellent heat stability, and superior hygiene properties. It is widely used in cold and hot water supply pipes, as well as for connecting high and low-temperature heating systems. Currently, polypropylene piping is also being utilized in the field of indoor drainage. The main types of plastic piping used domestically for the transmission of cold and hot water in buildings and for radiant floor heating are PPR and PPB. Abroad, in addition to the aforementioned two types of piping, a certain amount of PPH is also applied in indoor drainage. However, different types of PP piping have distinct characteristics, which can be clearly differentiated based on their structure, product mechanics, and physical properties. It is this distinction that determines their varied product characteristics, economic factors, and different application scenarios.
Here are several common methods for distinguishing and determining PPH, PPB, and PPR pipe materials:
PPB features a melting point of approximately 160°C with strong low-temperature impact resistance; PPR has a melting point around 140°C with lower low-temperature impact resistance; PPH falls between the two in melting point, yet exhibits poorer low-temperature impact resistance.
Materials can be differentiated by their structure, for instance, by means of nuclear magnetic resonance data.
PPH stands for polypropylene homopolymer, which is also known as Type I polypropylene. It is composed of a single polypropylene monomer and does not contain ethylene monomers in its molecular chain. The regularity of the PPH molecular chain is very high, leading to high crystallinity in the material and poor impact resistance.
PPB stands for block copolypropylene, which is what we refer to as Type II polypropylene. It has a higher ethylene content, typically around 715%. In the molecular sequence, there is a high probability of two ethylene monomers and three monomers being connected together, indicating that ethylene monomers only exist in the block phase. The ethylene chain segments existing in a block form greatly enhance the impact strength of the material. However, as the isotacticity of the PPH molecular chains cannot be reduced, the material's crystallinity, melting point, and thermal resistance cannot be fundamentally improved.
PPR, also known as random copolymer polypropylene or Type III polypropylene, is obtained by copolymerizing propylene monomers with a small amount of ethylene monomers under heat, pressure, and catalyst action. Ethylene monomers are randomly distributed within the propylene long chains, typically maintained between 35%. The random addition of ethylene monomers reduces the crystallinity and melting point of the polymer, enhancing its impact and heat resistance properties.
Distinguishing can be made from the performance of the piping materials.
From the performance requirements of the ISO15874 standard or the national standard GB/T18742 for the three types of pipes (PPH, PPB, PPR), it can be seen that PPH has a high modulus and strong pressure-bearing capacity, but does not have requirements for low-temperature impact resistance; PPB has poor high and low-temperature impact strength, but its pressure-bearing capacity in the high-temperature zone is slightly worse than that of PPR pipes. The differences among these three types of pipes greatly influence our choice of pipes. Pipe manufacturers and users can determine the type of PP material in a relatively simple manner by considering the characteristics introduced above.
Based on the aforementioned descriptions, the three materials exhibit different properties and should be applied in different scenarios. Each type of material can meet the design requirements; the key is for users to optimize their choices based on the actual engineering conditions. Different regions and countries have their preferences based on local circumstances and consumer habits, which is permissible under the standards.
Experts have categorized the usage of PPB and PPR based on the varying temperatures of the materials being transported through pipes. They suggest that 0℃ to 60℃ is the ideal application range for PPB, while 10℃ to 70℃ is suitable for PPR. The advantageous application area for PPB over PPR is from 0℃ to 10℃, and for PPR over PPB, it's from 60℃ to 70℃. This is also a straightforward method of selection.
Our country primarily applies PPH pipes in chemical pipeline systems and acidic alkaline wastewater treatment, where their advantages include high strength, excellent thermal resistance, and good corrosion resistance, enabling the transportation of highly corrosive media.
