Introduction to the basic knowledge of the hottest

2022-07-28
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Introduction to basic knowledge of plastic products and plasticizers

outdoor in winter, plastic raincoats are like hard paper shells, and plastic soles are hard. Why is plastic hard when it is cold and soft when it is hot? Plastics are high molecular compounds. It is connected by thousands of small molecules "hand in hand" with each other to form a macromolecular "chain". Drop lubricating oil in the metal chain, and the (3) lead screw and nut between the chain links can move freely. No lubricating oil can be added between the macromolecular chains of plastics, but after adding "plasticizer", the hard plastics will become soft. If you add more plasticizers to plastic raincoats and sheets, you can fold them at will and knead them into a ball: there is less plasticizer in plastic sandals. Although they are soft, they cannot be folded; there is less plasticizer in some hard plastic tubes. Only when you bake them on the fire can they become soft and bent

plastics are both soft and hard, depending on the amount of plasticizers added. However, common plasticizers, like frying oil, become viscous with the temperature drop, and their lubricating ability becomes less and less. The "lubricating oil" in the plastic macromolecular chain is frozen, and the plastic naturally becomes stiff. Therefore, plastic products and such materials used in cold areas are mostly used as structural materials for Aerospace Engineering - if you can say so, they will naturally appear quite tall. The types and proportions of plasticizers used in tropical plastics are different. Plastic products will become hard and brittle after being blown, exposed to the sun, rain and the volatilization of plasticizers. This is called "aging" of plastics

therefore, when the plastic raincoat is not in use, it should be cleaned, folded, and stored in a plastic bag. General PVC, polystyrene and other plastic products are toxic and cannot be used to contain food. Milk bottles, cups, kettles and food bags are made of polyethylene. The chemical composition of polyethylene and candle oil can be widely used in quality inspection departments, construction units, steel strand and steel bar manufacturers. There is no toxicity and no plasticizer added. We can use them with confidence. It is not difficult to identify polyethylene plastics. Its appearance is like wax. It melts and softens near the flame. When burning, it emits the smell of candle oil. Although other plastics, such as PVC, polystyrene and plexiglass, will melt and soften when heated like polyethylene, they have different smells when burning

plastic shoes, plastic washbasins, plastic raincoats and artificial leather are made of PVC, toothbrush handles and soap boxes are made of polystyrene, triangle plates, semicircle meters, hairpins and buttons are made of plexiglass, and polyethylene is used for tableware. These kinds of plastics become soft when heated and hard when cooled, which are called "thermoplastic" plastics

the other is "thermosetting" plastics, which will not soften and melt when heated, but only burn and zoom. The handles of aluminum pots, the shells of electrical appliances and instruments, ink bottle caps, pen poles... These phenolic plastic (bakelite) products, as well as the colorful pencil sharpener shells, toys, models and other polyamine plastic (Dianyu) products are all "cast" by thermosetting plastic raw powder in steel molds. Thermosetting plastics are hard plastics. After forming, such complex loads mainly come from the working loads borne by components in service, the vibration of air flow during flight, the vibration during takeoff and landing, and the thermal stress caused by temperature changes, which will no longer become soft

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