Cross-linked polypropylene: features, specifications and reviews

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Cross-linked polypropylene is also called supermolecular and is the densest modification of the ethylene polymerization product. It has a network molecular structure and intermolecular bonds. The technical characteristics of polypropylene are unique, as they allow it to be used in areas inaccessible to non-crosslinked samples.

Some structural features

Normal non-crosslinked material is obtained by exposure to low pressure when catalysts are present. It has large polymer molecules with side branches. Most of them are in some kind of free "swimming" in the space between the molecules. Cross-linking allows to achieve side bonds that create an intermolecular network. As a result, it is possible to obtain a particularly strong structure, which has the form of a crystal lattice of solids.

When different crosslinking techniques are used, a substance with a certainthe number of bonds, which indicates a higher or less impressive strength. Some variants of crosslinked polypropylene are obtained in the presence of hydrogen peroxide and have the highest percentage of crosslinking, which can reach 85%. The most common and applicable in a wide range of products is the silane polymer, which has a 70% bonded structure.

The cross-linking will be 60% if the technology provides for the radiation method of manufacturing. In the presence of nitrogen, a material is created with rather complex reaction conditions. As a result, it is possible to achieve the same 70% cross-linking. Crosslinked polypropylene with a high percentage of crosslinking is more expensive and has the highest crack resistance, high melting point and impressive impact resistance. Such cross-linking makes it possible to achieve higher hardness and less plasticity of products, which does not mean high quality, but allows you to obtain various materials that will have their purpose.

Specifications

Cross-linked polypropylene performs as well as many solids, and some varieties outperform them in breaker resistance and durability. The density of the material is 940 kg/m3. Combustion occurs at a temperature of +400 ˚С, while the material decomposes into water and carbon dioxide. Melting temperature reaches +200 ˚С.

Additional Features

Elongation at break varies from 350 to 800%. This setting determinesmechanical strength. Cross-linked polypropylene is characterized by a high level of flexibility. It is impact-resistant when exposed to negative temperatures up to -50 ˚С. The service life of the material under standard conditions exceeds 50 years. The thermal conductivity of cross-linked polypropylene is 0.38 W/mK.

Main Features

The described material has many advantages, among which should be highlighted:

• high tensile strength;
• biological sustainability;
• ability to withstand high temperatures;
• excellent dielectric properties;
• crack resistance;
• resistance to alkalis, acids and organic solvents.

The material has good tensile strength and tensile strength. Even with temperature fluctuations, it is not covered with cracks. It is not biodegradable and can withstand even boiling water.

Pipes made of cross-linked polypropylene are durable and allow you to achieve high-quality pipe connections. This fact indicates the possibility of using products for communication in seismic areas.

Negative features and feedback about them

According to consumers, the described material has its drawbacks. For example, cross-linked polypropylene exhibits low resistance to solar radiation. If the ultraviolet is exposed to the pipes for a long time, the material will begin tobreak down, become brittle.

Buyers also emphasize that oxygen is destructive to polypropylene if it penetrates into the molecular structure. However, these problems can be eliminated by protecting products or by adding special substances at the stage of product development.

Polyethylene or polypropylene

Quite often, consumers are wondering what to choose - cross-linked polyethylene or polypropylene. In order to answer it, you need to familiarize yourself with the basic properties of materials and understand the areas of application of each. These materials are produced in a variety of ways. For example, polypropylene, which is also abbreviated as PP, is obtained by polymerization of propylene molecules. But cross-linked polyethylene, denoted by the letters PE-X, is made using the technology of physical or chemical cross-linking of ethylene molecules.

Both options have high wear resistance and the same tensile strength at break. But PP is more resistant to cracking, and under sharp loads it shows worse performance than PEX. In addition, cross-linked polyethylene has great flexibility, because the minimum bending of products from it is 5D. But for polypropylene, this figure is 8D.

Pipes made of these materials have memory properties, which allows them to restore their shape when heated up to +100 ˚С. You can also compare the melting point. For cross-linked polyethylene, it is 30 ˚С higher, but such pipes are used in lower temperaturemodes.

For both products, the maximum operating temperature is the same and is +90 ˚С. Here it will only be necessary to clarify what period of operation is relevant at different temperature conditions. As for the lower limit, it differs quite a lot. For example, for polypropylene, the critical temperature is -20 ˚С, while for cross-linked polyethylene, impact resistance will remain up to -50 ˚С.

Reviews on the use of material for domestic needs

Heated floor made of cross-linked polypropylene, according to home masters, will be a highly efficient system. Such pipes are considered today the most modern choice, since their characteristics fully meet the requirements. Among the shortcomings here, according to buyers, one can note only a small amount of flexibility, due to which the products do not hold their shape well during installation.

Cross-linked polypropylene for heating is also used quite often. However, here, as consumers emphasize, problems may arise due to the oxygen permeability of the material, which can cause activation of corrosion processes on structural elements. Therefore, for underfloor heating, for example, experts advise using pipes with diffusion protection.

In closing

If you still cannot decide for yourself which is better - polypropylene or cross-linked polypropylene, then you should know that the latter is good because it has a high melting point. Although this material is combustible, it requires a temperature of +400 ˚С.

If you use products made of cross-linked polypropylene at temperatures up to +75 ˚С, they will be ready to serve for about 50 years. But if the conditions are accompanied by high pressure and coolant temperature within +95 ˚С, then the service life can be reduced to 15 years. At the same time, the material will not be deformed, so it can be safely installed under a layer of plaster in those rooms where the aesthetic component of the interior is important.