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Polypropylene granules is what?

Date:2016-02-23
In 1954, Curie, natalia Giulio Natta polypropylene was synthesized. In different countries and regions of different polypropylene synthesis technology was "invented" many times. A large number of intellectual property rights lawsuit with the development of polypropylene volume. PP is in terms of metal organic rules made catalyst (Ziegler - Natta type), such as the delta - TiCl3 - (C2H5) 2 alcl or TiCl3 - (C2H5) 3 al efficiency (300 ~ 300 grams of TiCl3 polypropylene/g), make the acrylic monomers were synthesized under the condition of controlling the temperature and pressure. Obtained for the different catalysts and polymerization process, molecular structure of polymer chemical structure, there are three different types of 3 d number is different also. These three structure refers to the isotactic polymer, gauge between polymer and random polymer. The isotactic polypropylene (the most common form of commodity), methyl groups are on the same side of the polymer skeleton, the structure is easy to form amorphous. Isotactic forms of crystalline give it good solvent resistance and thermal performance. Used during the first decade of catalyst technology makes the isotactic isomer generation to a minimum, eliminated the worthless random the necessity of the separation of components, simplifying the production steps. Production of polypropylene process basically has two kinds: one kind is the gas phase method; Is a kind of liquid propylene slurry method. In addition, there are some old slurry process unit running, they used a liquid saturated hydrocarbon as the reaction medium. In comparison, high density and low density polyethylene has a high density, low melting point and low bending modulus of rigidity. These performance differences lead to the different end use. Stiffness and directional sex that polypropylene homopolymer is suitable for the production of fiber and extension, and their higher heat resistance can be used to make them hard molding pressure vessel and equipment and automobile parts. Affect the processing performance and physical properties of polypropylene homopolymer of the main factors include: the molecular weight (usually expressed in velocity); The molecular weight distributions (MWDS); There are rules set structure and additives. Polypropylene average molecular weight range from about 000 to 600 000 200. Molecular weight distribution is typically used were () and the number average molecular weight of polymer molecular weight () the ratio of the said, this type is also known as polydispersity index. A polymer molecular weight distribution on its processing and end-use performance have a significant impact. This is because the molten polypropylene is sensitive to shear, namely when the pressure increases, the apparent viscosity decreased. Narrow molecular weight distribution of a wide range of polypropylene than distribution is more sensitive to shear, and thus has a wide range of molecular weight distribution of material processing easier in injection molding process. Certain purposes, especially fiber, insist on a narrow range of molecular weight distribution. Molecular weight distribution and the catalyst system and polymerization process. Peroxide is commonly used in the reactor at the back of the extrusion process for chemical cracking, narrow the molecular weight distribution. A process known as control rheology (CR) process. Compared with polyethylene, isotactic polypropylene its unique molecular structure and spiral crystal led to its molecular chain more sensitive to light and heat and oxidation degradation. In the usual processing and end-use conditions, polypropylene subjected to random chain scission effect, results in the decrease of molecular weight and higher flow velocity. All commercial grade polypropylene contain stabilizers, in order to protect the material during processing, to provide satisfactory performance finally. For special purposes, in addition to add antioxidant and uv inhibitors, still must add other additives. For example: in the film lubricants and anti-sticking agents were added to the formula, in order to reduce the friction coefficient and to prevent adhesion film itself. In adding antistatic packaging materials to eliminate static charges. In order to improve the transparency or shorten model cycle, then need a nucleating agent. Homopolymer resin are usually classified by velocity and end use. Velocity depends on both the average molecular weight and molecular weight distribution. Some special purpose required flow rate is as high as 400 g/minutes, while ordinary commodity homopolymer velocity in within the range of 0.5-50 g/min. Velocity is usually determine the machining features of the main factors.
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