Introduction of polypropylene random copolymer knowledge Polypropylene random copolymer The polypropylene random copolymer is also a kind of polypropylene, and the basic structure of the polymer chain is modified by adding different kinds of monomers. Ethylene is the most commonly used monomer which causes a change in the physical properties of polypropylene. Compared with PP homopolymer, random copolymer improves optical properties (increased transparency and reduces haze), improves impact resistance, increases flexibility, lowers melting temperature, and thus lowers heat fusion temperature At the same time, it is basically the same as the homopolymer in terms of chemical stability, water vapor barrier properties and organoleptic properties (low odor and taste). Developed PP random copolymers that combine improved transparency and impact strength for use in blow molding, injection molding, film and sheet extrusion processes for food packaging materials, pharmaceutical packaging materials and consumer products. Chemistry The PP random copolymer generally contains from 1 to 7% by weight of ethylene molecules and from 99 to 93% by weight of propylene molecules. On the polymer chain, ethylene molecules are randomly inserted in the middle of the propylene molecule. In this random or statistical copolymer, most (usually 75%) of the ethylene is incorporated by means of a single molecule insertion called the X3 group (three consecutive ethylene [CH2] are arranged in sequence in the main On the chain), this can also be seen as an ethylene molecule intercalated between two propylene molecules. Another 25% of ethylene is incorporated into the main chain by multi-molecule insertion, also known as the X5 group, because there are 5 consecutive methylene groups (two ethylene molecules intercalated between two propylene molecules). It is difficult to distinguish between X5 and higher groups such as X7, X9 and the like. In view of this, the ethylene content of XS and higher groups was counted together to be > X3%. The randomness ratio X3/X5 can be measured. When the percentage of groups above X3 is large, the crystallinity of the copolymer will be significantly lowered, which has a great influence on the final properties of the random copolymer. The effect of very high levels of ethylene in the copolymer on the crystallinity of the polymer is similar to that of high random polypropylene content. The random PP copolymer differs from the homopolymer because the ethylene molecules randomly inserted into the polymer backbone hinder the crystallographic arrangement of the polymer molecules. The decrease in crystallinity of the copolymer causes a change in physical properties: the random copolymer has lower rigidity, improved impact resistance, and better transparency than the PP homopolymer. Ethylene copolymers also have lower melting temperatures, which is an advantage in their application in certain aspects. Random copolymers contain more pliable and random PP, as well as polymer chains with much higher ethylene content. This higher level of extractable material, depending on the polymerization process, is present to varying degrees in all commercial copolymer materials and poses difficulties in meeting Federal Food Administration (FDA) regulations regarding food contact. Manufacturing method The ethylene/propylene random copolymer is obtained by simultaneously carrying out polymerization of an ethylene molecule and a propylene molecule, and the reactor used is the same as that for producing a PP homopolymer. The ethylene molecule is smaller than the propylene molecule and reacts faster than (about ten times the reactivity) propylene. This weakens the stereospecificity of the catalyst and increases the activity, resulting in an increase in the amount of random polypropylene produced. In order to reduce the formation of such a random substance, it is necessary to lower the reaction temperature, thereby reducing the activity of the catalyst, and reducing the content of the random isomer in the final product, resulting in a product having a more balanced property. Random copolymers with high ethylene content (>3%) are difficult to handle in the production process, and it is difficult to carry out the polymerization in hexane diluent because of the secondary by-products of the reaction (random polypropylene and ethylene content). Very high copolymer) soluble in hexane. This is the same in bulk polymerization of liquid propylene, albeit with lower solubility. The large amount of by-products produced by the hexane dilution process must be separated during the hexane recycle stage, which increases the overall production cost, but results in a cleaner polymer with a small amount of soluble components. In the bulk polymerization process, these impurities remain in the polymer and cause trouble in handling the flaky material. Moreover, the final copolymerized product contains more soluble impurities. Secondary cleaning with an organic solvent removes most of the impurities, but increases the overall production cost of the copolymer. Generally, when the content of by-products is high, the flaky random copolymer becomes more viscous, and this problem is more prominent when the ethylene content is more than 3.5% by weight. Increased handling problems and lower reactor temperatures result in lower production rates of random copolymers. Moreover, the production cycle of random copolymers is usually very short. These factors make the total production cost of the random copolymer higher than that of the homopolymer, especially for the random copolymer having a high ethylene content. The decrease in the melting point of the copolymer is directly related to the ethylene content. It has been reported that when the ethylene content is 7%, the melting point of the copolymer is as low as 152 °F. The effect of X3 content on the melting point of the copolymer is greater than that of the children and higher gene content. It also depends on the catalyst itself, and its ability to bind ethylene with an X5 group in place of the X3 group. performance Physical properties: Generally speaking, the random PP copolymer has better flexibility and lower rigidity than the PP homopolymer. They maintain moderate impact strength when the temperature drops to 32°F, and their usefulness is limited when the temperature drops to -4°F. The flexural modulus of the copolymer (the secant modulus at 1% strain) is in the range of 483 to 1034 MPa, and the homopolymer is in the range of 1034 to 1379 MPa. The molecular weight of the PP copolymer material has a lesser effect on the rigidity than the PP homopolymer. The notched Izod impact strength is typically in the range of 0.8 to 1.4 feet per pound per inch. Chemical resistance: random PP copolymer to acid. Alkali, alcohol, low-boiling hydrocarbon solvents and many organic chemicals are highly resistant. The PP copolymer is substantially insoluble in most organic solvents at room temperature. Also, when exposed to soap, soap and alkali. In aqueous reagents and alcohols, they do not suffer from environmental stress cracking damage like many other polymers. When in contact with certain chemicals, especially liquid hydrocarbons. Chlorinated organics and strong oxidants. Men Fitness T Shirt Polyester,Polyester Tshirts Plain,Polyester T Shirts For Women,Polyester T Shirts Custom Printing Shaoxing Yizhong Textile And Garment Co.,Ltd , https://www.yizhongsport.com
Introduction of polypropylene random copolymer