Melt flow rate
Polyethylene melt flow index (MFI polyethylene) characterized by its viscosity. This indicator determines how much polyethylene under a certain pressure and a given temperature for ten minutes pressed out through a small vessel – capillary. The higher the score, the polyethylene more fluid and less viscous. This parameter is important to select the method of processing of polyethylene. For example, for the production of the film must be extruded to the melt was sufficiently viscous so used polyethylene brands low MFR values.
Requirements for determining melt flow index of polyethylene
In various countries there are standards that are painted the temperature and the load level recommended for determination of the melt flow index of polyethylene. For different types of polyethylene apply their loads and temperature. Therefore, a comparison of MFI HDPE and LDPE MFI is incorrect, as the indicator for determining fluidity taken various load indicators. Compare MFI can only be one kind of materials of different brands.
To measure the MFR of polyethylene is usually used IIRT systems of various modifications, the principle of operation is based on the action of capillary viscometer.
The value of melt flow of various types and grades of polyethylene base
| Базовая марка | ПТР, г/10 мин. |
| Полиэтилен высокого давления плотностью 922-926 кг/м3 | |
| марки 2 | 0,24 – 0,36 |
| марки 6 | 0,56 – 0,84 |
| марки 13 | 3,4 – 4,6 |
| марки 69 | 3 – 5 |
| марки 84 | 16 – 24 |
| Полиэтилен высокого давления плотностью 917-921 кг/м3 | |
| марки 7 и 8 | 1,7 – 2,3 |
| марки 15 | 5,95 – 8,05 |
| марки 20 и 21 | 17 – 23 |
| марки 50 | 0,14 – 0,26 |
| марки 55 | 0,3 – 0,5 |
| марки 58, 62 и 64 | 1,5 – 2,5 |
| марки 66 | 0,825 – 1,375 |
| марки 68 | 5,25 – 8,75 |
| марки 74 и 84 | 16 – 24 |
| марки 75 и 76 | 0,45 – 0,75 |
| марки 77 | 0,8 – 1,2 |
| марки 78 | 1,125 – 1,875 |
| марки 80 | 2,1 – 3,9 |
| марки 81 | 2,45 – 4,55 |
| марки 82 | 4,125 – 6,875 |
| марки 83 | 9 – 15 |
| Полиэтилен высокого давления плотностью 927-930 кг/м3 | |
| марки 63 | 0,375 – 0,625 |
| марки 60 | 0,6 – 1 |
| Суспензионный полиэтилен низкого давления плотностью 0,948-0,959 г/см3 | |
| марки 1 | до 0,1 |
| марки 2 | 0,1 – 0,3 |
| марки 3 | 0,3 – 0,6 |
| марки 4 и 5 | 0,5 – 0,9 |
| марки 6 | 0,9 – 1,5 |
| марки 7 | 1,2 – 2 |
| марки 8 | 1,8 – 3 |
| марки 9 | 3 – 5 |
| марки 10 | 5 – 10 |
| Газофазный полиэтилен низкого давления | |
| марки 71 с термостабилизатором неокрашенный или слабоокрашенный | 0,45 – 0,65 |
| марки 73 с термо- и светостабилизаторами черного цвета | 0,3 – 0,55 |
| марки 73 с термостабилизатором первичной переработки неокрашенный | 0,4 – 0,65 |
| марки 73 с термо- и светостабилизаторами, черного цвета стойкий к фотоокислительному старению | 0,3 – 0,55 |
| марки 76 | 2,6 – 3,2 |
| марки 77 | 17 – 25 |
Thermal conductivity
Thermal conductivity is the ability of a material to transmit heat flow through itself, arising from the difference between the temperature readings on opposite surfaces. Different materials conduct heat in their own way: some do it faster (eg metals), the other is much slower (insulating materials).
The concept comes from thermal conduction of heat quantity (J), which is within 1 hour passes through the sample of material having a thickness of 1 m, the area of 1 sq. M., With the temperature difference on the opposite surfaces of plane K. Denoted at 1 letter A and the thermal conductivity is expressed in W / (m K). Materials having a thermal conductivity of not more than 0.175 W / (m • K), the average bed temperature 298 K and humidity, some guests or specifications related to thermal insulation.
Thermal conductivity depends on the density of the material (thermal conductivity increases with increasing density), its humidity, porosity, structure and temperature of the middle layer. With increasing porosity, the thermal conductivity decreases and increase the moisture content leads to a sharp increase of thermal conductivity, but reduces heat insulating properties. In this regard, heat insulating materials should be stored in the room and a heat-insulating structures provides protection from moisture in the form of a coating layer.
Polyethylene is a plastic material having good dielectric properties. Impact-resistant, does not break down, it has a small absorption capacity. It has a low gas and vapor permeability, is not soluble in organic solvents. Polyethylene is made of two types – high pressure and low pressure.
Polyethylene is easily recyclable and is subject to modification. As a result, it is possible to improve its thermal conductivity and chemical resistance. Despite the fact that the polyethylene has good insulating properties, thermal insulation properties of underground pipelines soil is sometimes more important than the same properties of the pipe itself.
polyethylene Thermal conductivity of 0,36-0,43 W / m0K.
The scientists carried out tests on the preparation of polymer material that has a higher thermal conductivity. Already achieved some results, allowing to use polyethylene fibers as a cheaper replacement metals.
Specific gravity
Specific Gravity (aka – density) polyethylene changed insignificantly – from 0.91 to 0.976 g / cm3.
At the same time, the properties of polyethylene with high specific gravity considerably different from the properties of the material with a low specific weight. This occurs due to the fact that there are two different polyethylene manufacturing technology. In fact, two different materials are synthesized with the same name and formula.
Measuring the weights of specific vesaSintezom at high pressure (100-280 MPa) is obtained by low-density polyethylene. In Russia it is abbreviated as LDPE (low density) and LDPE (high pressure), and in the English-speaking world – LD PE (Low Density Polyethylene).
In contrast, high density polyethylene is obtained by synthesis at low pressure (0.1-0.5 MPa). Abroad, this material is referred to as HD PE (High Density Polyethylene), and we have – HDPE and HDPE.
Properties LDPE (LD PE)
The weight of this polyethylene variety – about 0.92 g / cm3. The polymer chains have a relatively short length, but have a significant amount of crosslinking. Melting point not exceeding 110 ° C. Material obtained by plastic, it is easily stretches and is not afraid mechanical damage.
Properties HDPE (HD PE)
The proportion of higher – about 0.95 g / cm3. The difference is due to the properties of a long polymer chains: melting point above 130 ° C, this type of polyethylene less flexible, but it is able to withstand a higher load.
External differences between different grades of polyethylene
If we compare the film obtained from LDPE and HDPE, the former have a greater thickness, and easier to stretch to touch seems a bit greasy. In contrast, the film of the IPA is very thin, tougher and due to this issue when the characteristic rustling crumpled. These disadvantages include the so-called “zipper effect” – when pinholes film of such material may be little or no effort to burst into two halves.
Properties of mixed polyethylene (CAP)
To get rid of the disadvantages of these two varieties of polyethylene, technologists have invented a material called polyethylene blended. As the name implies, it is obtained by mixing LDPE granules and DED in the production of finished products. In addition, the composition is added to a small amount of auxiliary components that improve the appearance of the finished product. By varying the proportions of LDPE and DED, you can get the material with specified properties – more ductile or more rigid.
Polyethylene and its calorific value
Combustion polietilenaVazhneyshey characteristic heat of combustion is for a variety of fuels. The higher calorific value, the higher the fuel efficiency of the heating, for the engines, and the like.
For technical and production needs distinguish higher and lower heating value. The first includes the energy released by complete combustion of a certain volume of the substance, plus the energy released during cooling of the combustion products. The second energy that is released during cooling of the combustion products do not take into account.
Read more about PE
Polyethylene is a thermoplastic polymer, an ethylene product processing. The widespread use of polyethylene obviously, it can be found in the simplest of household products, and as a structural material for a very complex and demanding industrial applications.
Polyethylene, both high and low pressure, has a very high specific heat of combustion. There is nothing strange in this, since the polyethylene – a polymerized hydrocarbon.
The range of heat of combustion of polyethylene, depending on the grade – from 44,0 to 47.2 MJ / kg (megajoules per kilogram).
For comparison, the average combustion heat of gasoline – 42 MJ / kg. A wood burning heat of old, used as a fuel – 13.8 MJ / kg.
As an indication, polyethylene heat of combustion is used in the calculation of fire safety category. For such a case is taken as an estimated value for the polyethylene to 46.68 MJ / kg. Important indicators in this case are polyethylene ignition temperature (306 degrees) and the auto-ignition temperature (417 degrees). Category Fire has quite a lot, and the most negative scenario in case of fire into account the category “A” and “B”. If the room a lot of polyethylene, these are the categories of fire and it is mainly assigned.
Taken into account the heat of combustion of polyethylene and in the design of process equipment for its processing. Given the amount of energy released by an accidental fire polyethylene, such materials must withstand thermal stress and does not collapse. Or, at least, should prevent the spread of flame.
polyethylene waste can be recycled. Often they are used as secondary raw materials, but, when it is impossible or inappropriate reuse of this material in the manufacture of plastic products utilize it. The best way is to burn waste polyethylene, using as fuel. In this case, the heat of combustion is used to calculate the amount of thermal energy obtained.