[Weekly Topic] Special lecture on polymer materials: “Plastics” – Learn a little every day (2) Polyethylene “Improve yourself””

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This post was last edited by tclz007 on 2013-12-9 at 19:04. Starting this month, learning activities will be carried out in the field of polymer materials; we hope that fellow enthusiasts will come to learn, offer good suggestions, engage actively in learning, and those who participate in in-depth discussions will receive substantial rewards in terms of wealth and charms~~! To encourage everyone to come and participate in discussions more actively, as well as to study more diligently, the top ten participants each time will receive a “Motivation Reward for Active Learning.” Some people might think that it’s terrifying to spend their working days doing nothing, performing menial tasks without knowing what to do or what to learn, day after day, year after year, with no vision for their future We must start working hard from now on; even if we learn a little knowledge every day, it will add up over time and help us enrich ourselves. We need to set clear goals – only by filling our minds first can we enrich other aspects of our lives as well. . . . . . It only takes a mere ten-odd minutes each day, and you’ll get to see the future! ! ! (Anyway, I have learned it; whether you learn it or not is up to you. Apart from those experts like Hai Chuan, there are still others who know it.) . . ) Enough talk – let’s start with the basics today!! Polyethylene – abbreviated as PE; its English name is Polyethylene. Polyethylene (PE) is one of the five major synthetic resins, and it is the type with the largest production capacity and the highest import volume among synthetic resins in China. Polyethylene is mainly divided into three categories: linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), and high-density polyethylene (HDPE). Applications of polyethylene (PE) include plastic wrap, vest-style plastic bags, plastic food bags, baby bottles, buckets, water bottles, and more. Characteristics: PE is relatively soft to the touch and has a waxy feel. Compared to other plastics of the same type, it is quite lightweight. It also exhibits a certain degree of transparency. When burned, it produces a blue flame. Toxicity: Non-toxic and harmless to humans. Main uses: Ethylene is an important chemical raw material that can be used to produce a range of chemical products, such as polyethylene. Ethylene is an important chemical raw material that can be used to produce a range of chemical products such as polyethylene. Ethylene was initially produced by the dehydration of ethanol. At that time, since ethanol was produced from grain, the production process was unreasonable and the output of the product was limited, which hindered the development of production. Since the industrialization of the technology for producing ethylene through oil cracking, the petrochemical industry has developed rapidly. So-called petroleum hydrocarbon cracking is the process of using petroleum hydrocarbons as raw materials and undergoing pyrolytic chemical reactions at high temperatures for a short residence time to obtain pyrolysis gas. Then, the pyrolysis gas is processed through cooling, washing, compression, purification, and separation to yield ethylene, while important by-products such as propylene, butadiene, benzene, toluene, xylene, and acetylene are also obtained. Ethylene is the most important basic raw material in the petrochemical industry. Ethylene can be used to produce polyethylene. Through different processing techniques, high-density polyethylene, low-density polyethylene, and linear low-density polyethylene can be obtained, which can then be processed into various polyethylene plastic products. Ethylene can also be used to produce vinyl chloride, which is polymerized to make polyvinyl chloride; this is then processed into PVC products. Ethylene is directly oxidized to ethylene oxide in the presence of silver. Ethylene oxide hydrates to form ethylene glycol, with diethylene glycol, polyethylene glycol, and other substances being produced as by-products. Ethylene glycol is one of the monomers used in polymerization, and it can also be used to make antifreeze. Ethylene oxide is an important raw material for polyethers, as well as a key ingredient in the fine chemical industry, surfactants, and pesticides. By-product diethylene glycol and polyethylene glycol are very useful additives and raw materials for surfactants. Ethylene is directly oxidized to acetaldehyde under the action of palladium chloride and copper chloride catalysts. Acetaldehyde can be further oxidized to acetic acid under the action of a manganese acetate catalyst. Acetaldehyde and acetic acid are important organic chemical raw materials. Acetic acid can be used to produce vinyl acetate and polyvinyl alcohol, which are then used to manufacture vinylon fibers. Ethylene is directly hydrated to produce ethanol in one step under the action of a phosphoric acid catalyst. Ethanol is an important raw material in the organic chemical industry, and can be used in solvents, beverages, pesticides, pharmaceuticals, dyes, detergents, and other applications. Ethanol can further react to form diethyl ether, which is used as a **reagent and solvent, among other things. Ethylene can undergo a hydrocarbonation reaction with benzene to produce ethylbenzene, which is then dehydrogenated to yield styrene. Styrene is a key raw material for producing synthetic materials such as polystyrene, styrene-butadiene rubber, ABS, SBS, and AS, and it is widely used in the manufacture of coatings, ion exchange resins, and other products. Ethylene can also react with propylene, or a third monomer can be added to produce ethylene-propylene-diene rubber or ethylene-propylene-triene rubber. Low-molecular-weight EPDM is used for coating materials and viscosity adjustment of lubricants, while high-molecular-weight EPDM is used in the production of rubber products. The main use of ethylene is in the production of polyethylene, accounting for about half of the total consumption. Typically, polyethylene plants and ethylene plants are built together within the same petrochemical complex. Ethylene can now be transported in liquid form using specialized ships or tanks. High Density Polyethylene is known in English as “High Density Polyethylene”, abbreviated as “HDPE”. HDPE is a thermoplastic resin with high crystallinity and non-polarity. Native HDPE has a milky white appearance, and its thin cross-section is somewhat translucent. PE has excellent resistance to most household and industrial chemicals. Certain types of chemicals can cause chemical corrosion, such as corrosive oxidizers (concentrated nitric acid), aromatic hydrocarbons (xylene), and halogenated hydrocarbons (carbon tetrachloride). This polymer is non-hygroscopic and has good vapor resistance, making it suitable for packaging applications. HDPE has excellent electrical properties, particularly a high insulating dielectric strength, which makes it very suitable for use in wires and cables. The medium to high molecular weight grades possess excellent impact resistance, both at room temperature and even at low temperatures of -40F. 　　HDPE is a thermoplastic polyolefin produced by the copolymerization of ethylene. Although HDPE was introduced in 1956, this plastic had not yet reached a mature stage. This versatile material continues to develop new applications and markets. Low density polyethylene – The English name is Low Density Polyethylene (LDPE). It is a plastic material that is suitable for various thermoplastic molding processes. It has good processability, enabling applications such as injection molding, extrusion, blow molding, rotational molding, coating, foaming, thermoforming, hot air welding, and thermal welding. Primary uses: LDPE is used for film products; it is suitable for making films, heavy-duty packaging films, cable insulation materials, as well as blown and injection-molded foam products. 　　Such as agricultural films, ground cover films, farming films, and films for large vegetable greenhouses, etc ； Packaging films for packaging candies, vegetables, frozen foods, etc ； Blow-molded films for liquid packaging (milk, soy sauce, fruit juice. Tofu, soy milk) ； Repackaging bags, shrink wrap films, elastic films, lining films ； Film for construction, general industrial packaging film, and food bags, etc. LDPE is also used in injection-molded products, such as small containers, lids, household items, plastic flowers, and injection-molding-stretching-blow-molding containers. Medical devices, pharmaceuticals and food packaging materials, extruded pipes and sheets, wire and cable coatings, profiles, thermformed products, and other such items ； Blown-molded hollow products, such as food containers for dairy products and jams, as well as containers for medicines, cosmetics, chemical products, and tanks. Application areas of LLDPE The main application areas of LLDPE include agricultural films, packaging films, wires and cables, pipes, and coated products. 　　Linear low-density polyethylene is mainly used for manufacturing films due to its high tensile strength and good resistance to puncture and tearing. In 2005, global LLDPE consumption was 16.17 million tons, representing a year-on-year increase of 6.4%. In the consumption structure, film products still account for the largest share, with a consumption volume of 11.9 million tons, representing 73.6% of the total consumption. Injection molding comes next, with a consumption volume of 1.148 million tons, accounting for approximately 7.1% of the total LLDPE consumption. Current situation: At present, since there is no large-scale domestic production of hexene and octene, and their import prices are relatively high, butene is primarily used as a copolymerization monomer in domestically produced LLDPE resin. Some domestic companies, when introducing LLDPE production plants, used hexene as a copolymerizing monomer in certain grades; however, they were forced to give up on this approach due to the lack of hexene production in the country, and only imported small amounts of hexene for startup testing. Most of the high-quality LLDPE imported into our country is of this type. It is expected that demand for LLDPE using 1-hexene as a monomer will experience significant growth in the future. Special Lecture Series: Lectures on Polymer Materials – “Plastics”. Learn a little every day (6): Polystyrene. “Improve yourself” – http://bbs.hcbbs.com/thread-1257966-1-1.html Lectures on Polymer Materials – “Plastics”. Learn a little every day (5): Polystyrene. “Improve yourself” – http://bbs.hcbbs.com/thread-1257435-1-1.html Lectures on Polymer Materials – “Plastics”. Learn a little every day (4): ABS plastic. “Improve yourself” – http://bbs.hcbbs.com/thread-1257228-1-1.html Lectures on Polymer Materials – “Plastics”. Learn a little every day (3): Polyvinyl chloride. “Improve yourself” – http://bbs.hcbbs.com/thread-1256914-1-1.html Lectures on Polymer Materials – “Plastics”. Learn a little every day (2): Polyethylene. “Improve yourself” – http://bbs.hcbbs.com/thread-1256622-1-1.html Lectures on Polymer Materials – “Plastics”. Learn a little every day (1): Engineering plastics. “Improve yourself” – http://bbs.hcbbs.com/thread-1256345-1-1.html Everyone is welcome to listen. I’m already broadcasting; I hope those who, like me, want to gain knowledge every day will listen. Let’s learn together every day and discuss!! [Special Lecture] Special lecture on polymer materials: “Plastics”. Continuously being updated. http://bbs.hcbbs.com/thread-1256917-1-1.html