Polypropylene is a thermoplastic polymer of propene. It is obtained by the technology of propylene polymerization using metal complex catalysts. The parameters for producing this material are similar to those for the production of low-density polyethylene.
Depending on which catalyst is used, any type of polymer or mixture thereof can be obtained. The melting point of polypropylene is one of the important characteristics of this material. It has the form of a white powder or granules, the bulk density of which varies up to 0.5 g/cm³. The described material can be dyed, stabilized or undyed.
Specifications: molecular structure
According to the molecular structure, polypropylene is divided into several main varieties, among them:
- isotactic;
- atactic;
- syndiotactic.
Stereoisomers of a material differ in physical,mechanical and chemical characteristics. For example, atactic polypropylene has the appearance of a rubber-like material, which is characterized by high fluidity. The melting temperature of polypropylene for extrusion in this case is approximately 80 ° C, while the density can reach 850 kg / m³.
This material dissolves very well in diethyl ether. The properties of isotactic polypropylene differ from those described above and have a high modulus of elasticity, its density reaches 910 kg/m³, while the melting point varies from 165 to 170 °C. In this variety, polypropylene is characterized by excellent resistance to chemicals.
Physical and mechanical properties
Today, the use of polypropylene is very common. The melting point of this material varies in individual varieties. Quite often it is compared with polyethylene, but polypropylene does not have such a high density, it is 0.91 g / cm³. In addition, polypropylene is harder, more abrasion resistant, and more temperature resistant.
The level of its softening starts at around 140 ° C, while the melting point reaches 175 ° C. The material is not subject to corrosion cracking. It is resistant to oxygen and light, but this sensitivity is reduced if stabilizers are added to the ingredients in the manufacture of polypropylene.
Many varieties of polypropylene are used in various industries today. Temperaturemelting of this material expands the scope. Elongation at break as a percentage can vary from 200 to 800%. The tensile yield strength is equal to the limit from 250 to 350 kgf / cm². The notched impact strength varies from 33 to 80 kgf cm/cm², while the Brinell hardness ranges from 6 to 6.5 kgf/mm².
Basic chemical properties
If you plan to purchase some products made of polypropylene, you should know the melting point of this material. It is discussed in the article. From it you can learn other chemical properties. For example, the material is chemically stable, and in organic solvents it swells only slightly. If the temperature rises to 100 °C, then the material will dissolve in aromatic hydrocarbons. In this case, we are talking about toluene and benzene.
Because polypropylene contains tertiary carbon atoms, it is resistant to oxygen, ultraviolet radiation and elevated temperatures. This causes a tendency to aging compared to polyethylene. Under the influence of aggressive environments, polypropylene is not as strong as polyethylene, it is subject to cracking. It is capable of undergoing cracking tests even under stress.
Melting point of polypropylene pipes
Quite often, the modern consumer is interested in the melting temperature of polypropylene. pipe itapplies if you plan to carry out the arrangement of the heating system. When exposed to a temperature of 140 ° C, the material becomes soft, while it loses its shape. Whereas if the temperature rises to 170 ° C, then the melting stage will begin. At the same time, it will cease to be hard and will lose the ability to maintain its technical characteristics and shape.
Heating systems are not designed for such a temperature level, therefore, polypropylene pipes are suitable for supplying water to the system. Manufacturers usually state that the maximum possible temperature for polypropylene pipes is 95 ° C. Products are able to withstand a higher level of temperature, but for a short time. If the pipes are used for a long time at a temperature of more than 100 ° C, then their service life will decrease.
When temperature changes, polypropylene will change in size. When heated, it will expand, and when cooled, it will shrink. Under the influence of high temperatures, the pipes may begin to sag between the fasteners, and you will notice swelling in the outer layer.
The nuances of using polypropylene pipes
You can also use polypropylene products. The melting temperature of such pipes can be different. This must be taken into account if you have products of the PN20 brand in front of you. In this case, we are talking about a pipe whose operating temperature reaches 60 ° C. But if we are talking about a PN25 product, then this indicates that it will be able to withstand temperatures up to 95 ° С.
Conclusion
Swe can say with certainty that the laying of polypropylene near the smoke shafts is allowed. The melting point of polypropylene, however, does not indicate that pipes should not be protected. Experts recommend purchasing reinforced products that are less susceptible to deformation when exposed to high temperatures. Therefore, the pipes must be additionally protected by insulation and have an internal fiberglass or aluminum layer. This will protect the pipes from expansion and prolong their service life.
