Crosslinked polypropylene is also called supermolecular and represents the most dense 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 its use in areas inaccessible to non-crosslinked samples.
Some structural features
Conventional uncrosslinked material is obtained by 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. Stitching allows you to achieve lateral bonds that create an intermolecular network. As a result, it is possible to obtain a particularly strong structure, which has the form of a crystalline lattice of solids.
When different crosslinking techniques are used, a substance with a certain number of bonds is obtained, 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 a silane polymer, which has a 70 percent bound structure.
Crosslinking will be 60% if the technology provides a radiation manufacturing method. In the presence of nitrogen, a material is created with rather complicated reaction conditions. As a result, it is possible to achieve the same 70% crosslinking. 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 stitching allows to achieve higher hardness and less ductility of products, which does not mean high quality, but allows you to get various materials that will have their purpose.
Specifications
Crosslinked polypropylene in its characteristics is not inferior to many solids, and some varieties surpass them in resistance to destroyers and in the long term of operation. The density of the material is 940 kg / m 3 . Combustion occurs at a temperature of +400 ˚, while the material decomposes into water and carbon dioxide. Melting point reaches +200 ˚.
additional characteristics
Tensile strength varies from 350 to 800%. This parameter determines the mechanical strength. Crosslinked polypropylene is highly flexible. It is shockproof when exposed to negative temperatures up to -50 ˚. The life of the material under standard conditions exceeds 50 years. The thermal conductivity of crosslinked polypropylene is 0.38 W / mK.
Key Features
The described material has many advantages, among which are:
- high tensile strength;
- biological stability;
- ability to withstand high temperatures;
- excellent dielectric properties;
- resistance to cracking;
- resistance to alkalis, acids and organic solvents.
The material undergoes good tensile strength and is characterized by tensile strength. Even with temperature fluctuations it is not covered by cracks. It is not biodegradable and can withstand even boiling water.
Pipes made of cross-linked polypropylene are durable and allow to achieve high-quality annular joints. This fact indicates the possibility of using products for communication in seismic zones.
Negative features and reviews about them
According to consumers, the described material has its drawbacks. For example, crosslinked polypropylene exhibits low resistance to sunlight. If ultraviolet light acts on the pipes for a long time, the material will begin to break down and become brittle.
Buyers also emphasize that oxygen is damaging to polypropylene if it penetrates 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 made in many ways. For example, polypropylene, which is also referred to as PP, is obtained by the polymerization of propylene molecules. But cross-linked polyethylene, denoted by the letters PE-X, is made by the technology of physical or chemical crosslinking of ethylene molecules.
Both options have high wear resistance and the same tensile strength. 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 bend of products made from it is 5D. But for polypropylene this figure is 8D.
Pipes from these materials have memory properties, which allows you to restore shape when heated to +100 ˚. You can also compare the melting point. For cross-linked polyethylene, it is 30 ° C higher, but such pipes are used in lower temperature conditions.
For both products, the maximum operating temperature is the same and is +90 ˚. 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 ° C, and for cross-linked polyethylene, impact resistance will remain up to -50 ° C.
Reviews on the use of material for domestic use
Cross-linked polypropylene underfloor heating, according to home craftsmen, will be a highly efficient system. Such pipes are today considered the most modern choice, since their characteristics fully comply with the requirements. Among the shortcomings here, according to customers, only a small flexibility can be noted, because of which the products do not hold their shape well during installation.
Crosslinked 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 a warm floor, for example, experts advise using pipes with diffusion protection.
Finally
If you still cannot decide for yourself which is better - polypropylene or crosslinked polypropylene, then you should know that the latter is good because it has a high melting point. Although this material is combustible, a temperature of +400 400 is required for this.
If you operate products made of cross-linked polypropylene at temperatures up to +75 ˚, they will be ready to last about 50 years. But if the conditions are accompanied by high pressure and coolant temperature within +95 ˚, then the service life can be reduced to 15 years. At the same time, the material will not undergo deformation, therefore it can be safely mounted under the plaster layer in those rooms where the aesthetic component of the interior is important.