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What are the raw materials for making plastic bags

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refer to Baidu Encyclopedia Ke/Item /plastic /573005? Fromtitle = @#protect@#
the raw materials and functions of plastic bags are as follows:
[synthetic resin]
synthetic resin is the main component of plastics, and its content in plastics is generally 40% ~ 100%. Because of the high content and the nature of resin often determines the nature of plastic, people often regard resin as a synonym of plastic. For example, PVC resin and PVC plastic, phenolic resin and phenolic plastic are confused. In fact, resin and plastic are two different concepts. Resin is an unprocessed original polymer. It is not only used in the manufacture of plastics, but also the raw material of coatings, adhesives and synthetic fibers. In addition to a small part of plastics containing 100% resin, the vast majority of plastics need to add other substances in addition to the main component resin
[filler]
filler is also called filler, which can improve the strength and heat resistance of plastics and reduce the cost. For example, adding wood powder to phenolic resin can greatly reduce the cost, make phenolic plastic one of the cheapest plastics, and significantly improve the mechanical strength. Fillers can be divided into organic fillers and inorganic fillers, the former such as wood powder, rags, paper and various fabric fibers, and the latter such as glass fiber, diatomite, asbestos, carbon black, etc
[plasticizer]
plasticizer can increase the plasticity and softness of plastics, reduce brittleness and make plastics easy to process and shape. Plasticizers are generally high boiling organic compounds that are miscible with resin, non-toxic, odorless and stable to light and heat. Phthalates are the most commonly used. For example, in the production of PVC plastics, if more plasticizers are added, soft PVC plastics can be obtained. If no or less plasticizers are added (dosage & lt; 10%), rigid PVC plastics can be obtained
[stabilizer]
in order to prevent the decomposition and damage of synthetic resin by light and heat during processing and use and prolong its service life, stabilizer should be added to plastics. Commonly used are stearate, epoxy resin, etc
[colorant]
colorant can make plastics have various bright and beautiful colors. Organic dyes and inorganic pigments are commonly used as colorants
[lubricant]
the function of lubricant is to prevent the plastic from sticking to the metal mold during molding, and make the plastic surface smooth and beautiful. Common lubricants include stearic acid and its calcium magnesium salts
in addition to the above additives, flame retardants, foaming agents and antistatic agents can also be added to plastics to meet different application requirements.

composition of plastic
the plastic we usually use is not a pure substance. It is made of many materials. Among them, high molecular polymer (or synthetic resin) is the main component of plastics. In addition, in order to improve the performance of plastics, various auxiliary materials, such as fillers, plasticizers, lubricants, stabilizers and colorants, should be added to the polymer in order to become plastics with good performance
1. Synthetic resin
synthetic resin is the main component of plastics, and its content in plastics is generally 40% ~ 100%. Because of the high content and the nature of resin often determines the nature of plastic, people often regard resin as a synonym of plastic. For example, PVC resin and PVC plastic, phenolic resin and phenolic plastic are confused. In fact, resin and plastic are two different concepts. Resin is an unprocessed original polymer. It is not only used in the manufacture of plastics, but also the raw material of coatings, adhesives and synthetic fibers. In addition to a small part of plastics containing 100% resin, the vast majority of plastics need to add other substances in addition to the main component resin
2. Filler
filler is also called filler, which can improve the strength and heat resistance of plastics and reduce the cost. For example, adding wood powder to phenolic resin can greatly reduce the cost, make phenolic plastic one of the cheapest plastics, and significantly improve the mechanical strength. Fillers can be divided into organic fillers and inorganic fillers, the former such as wood powder, rags, paper and various fabric fibers, and the latter such as glass fiber, diatomite, asbestos, carbon black, etc
3. Plasticizer
plasticizer can increase the plasticity and softness of plastics, reduce brittleness and make plastics easy to process and shape. Plasticizers are generally high boiling organic compounds that are miscible with resin, non-toxic, odorless and stable to light and heat. Phthalates are the most commonly used. For example, in the production of PVC plastics, if more plasticizers are added, soft PVC plastics can be obtained. If no or less plasticizers are added (dosage & lt; 10%), rigid PVC plastics can be obtained
4. Stabilizer
in order to prevent the decomposition and damage of synthetic resin by light and heat during processing and use and prolong its service life, stabilizer should be added to plastics. Commonly used are stearate, epoxy resin, etc
5. Colorant
colorant can make plastics have various bright and beautiful colors. Organic dyes and inorganic pigments are commonly used as colorants
6. Lubricant
the function of lubricant is to prevent the plastic from sticking to the metal mold during molding, and make the plastic surface smooth and beautiful. Common lubricants include stearic acid and its calcium magnesium salts
in addition to the above additives, flame retardants, foaming agents and antistatic agents can also be added to plastics to meet different application requirements
classification of plastics
I. classification by use characteristics
according to the different use characteristics of famous plastics, plastics are usually divided into three types: general plastics, engineering plastics and special plastics
① general purpose plastics
generally refer to plastics with large output, wide use, good formability and low price. There are five varieties of general plastics, namely polyethylene, polypropylene, polyvinyl chloride, polystyrene and ABS. They are all thermoplastics
② engineering plastics
generally refer to plastics that can bear certain external force, have good mechanical properties, high and low temperature resistance, and have good dimensional stability. They can be used as engineering structures, such as polyamide, polysulfone, etc
in engineering plastics, they are divided into general engineering plastics and special engineering plastics
general engineering plastics include polyamide, polyoxymethylene, polycarbonate, modified polyphenylene ether, thermoplastic polyester, ultra-high molecular weight polyethylene, methylpentene polymer, vinyl alcohol copolymer, etc
special engineering plastics can be divided into crosslinked and non crosslinked types. Crosslinking types include: polyamine bismaleamide, polytriazine, crosslinked polyimide, heat-resistant epoxy tree finger, etc. Non crosslinking types include: polysulfone, polyethersulfone, polyphenylene sulfide, polyimide, peek, etc.
③ special plastics
generally refer to plastics with special functions and can be used in special application fields such as aviation and aerospace. For example, fluoroplastics and organosilicon have outstanding special functions such as high temperature resistance, self lubrication and so on. Reinforced plastics and foam plastics have high strength, high cushioning and other special properties. These plastics belong to the category of special plastics. Br> A. strong plastics: the raw materials of reinforced plastics can be divided into granular (such as calcium plastic reinforced plastics), fibrous (such as glass fiber or glass cloth reinforced plastics) and flake (such as mica reinforced plastics). According to the material, it can be divided into cloth based reinforced plastics (such as rag reinforced or asbestos reinforced plastics), inorganic mineral filled plastics (such as quartz or mica filled plastics) and fiber-reinforced plastics (such as carbon fiber reinforced plastics)
B. foam plastics: foam plastics can be divided into three types: hard, semi hard and soft foam plastics. Rigid foam has no flexibility and high compression hardness. Only when it reaches a certain stress value can it produce deformation. Flexible foams are flexible and have very little compression hardness. They are easy to deform. They can be restored to original state after stress relieving, and the residual deformation is small. The flexibility and other properties of semi rigid foams are between hard rigid foam plastics. Br> 2. Classification by physical and chemical properties
according to the different physical and chemical properties of various plastics, plastics can be divided into thermosetting plastics and thermoplastics
⑴ thermosetting plastics
thermosetting plastics refer to plastics that can be cured or have insoluble (melting) characteristics under heating or other conditions, such as phenolic plastics, epoxy plastics, etc. Thermosetting plastics are divided into formaldehyde crosslinking type and other crosslinking types. It softens when heated and hardens when cooled. It can soften and harden repeatedly and maintain a certain shape. Soluble in certain solvents, with fusible and soluble properties. Thermoplastics have excellent electrical insulation, especially polytetrafluoroethylene (PTFE), polystyrene (PS), polyethylene (PE) and polypropylene (PP) have very low dielectric constant and dielectric loss, and are suitable for high frequency and high voltage insulation materials. Thermoplastics are easy to form and process, but they have low heat resistance and are easy to creep. Their creep degree changes with load, ambient temperature, solvent and humidity. In order to overcome these weaknesses of thermoplastics and meet the needs of applications in space technology, new energy development and other fields, countries are developing heat-resistant resins that can be melt molded, such as polyether ether ketone (PEEK), polyethersulfone (PES), polyarylene sulfone (pASU), polyphenylene sulfide (PPS), etc. The composites with them as matrix resin have high mechanical properties and chemical corrosion resistance, can be thermoformed and welded, and the interlaminar shear strength is better than that of epoxy resin. If peek is used as matrix resin and carbon fiber is made into composite, the fatigue resistance is better than that of epoxy /carbon fiber. It has good impact resistance, good creep resistance at room temperature and good processability. It can be used continuously at 240 ~ 270 ℃. It is a very ideal high temperature resistant insulating material. The composites made of polyethersulfone as matrix resin and carbon fiber have high strength and hardness at 200 ℃ and good impact resistance at – 100 ℃; It is non-toxic, non combustible, with the least smoke and good radiation resistance. It is expected to be used as a key component of spacecraft and molded into radar radome
formaldehyde crosslinked plastics include phenolic plastics and amino plastics (such as urea formaldehyde melamine formaldehyde, etc.)
other cross-linked plastics include unsaturated polyester, epoxy resin, phthalate diallyl resin, etc
⑵ thermoplastics
thermoplastics refer to plastics that can be repeatedly heated, softened, cooled and hardened within a specific temperature range, such as polyethylene, polytetrafluoroethylene, etc. Thermoplastics are divided into hydrocarbons, vinyl containing polar genes, engineering, cellulose and other types. After hot processing and molding, a solidified product with insoluble and insoluble is formed, and its resin molecules are crosslinked into a network structure by linear structure. Further heat will decompose and destroy. Typical thermosetting plastics include phenolic, epoxy, amino, unsaturated polyester, furan, polysilicate ether and other materials, as well as newer polyphenylene dicarboxylate plastics. They have the advantages of high heat resistance and not easy to deform when heated. The disadvantage is that the mechanical strength is generally not high, but its mechanical strength can be improved by adding fillers and making laminated materials or molding materials
 

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