Definition of resin and plastic

1、 Definition of resin: resin usually refers to the softened or melted range after heating When softened, it tends to flow under the action of external force It is a solid, semi-solid or sometimes liquid organic polymer at room temperature In a broad sense, any polymer that can be used as raw material for processing plastic products is called resin There are two kinds of resins: natural resin and synthetic resin Natural resin refers to the amorphous organic substances obtained from animal and plant secretions in nature, such as rosin, amber, shellac, etc Synthetic resin refers to the resin product obtained by chemical synthesis of simple organic matter or chemical reaction of some natural products 2 Definition of plastic: Plastic refers to the material that can flow and form in the process of processing, with resin (or monomer direct polymerization) as the main component, plasticizer, filler, lubricant, colorant and other additives as auxiliary components
The main characteristics of plastics are as follows: ① most of them are light in weight, good in chemical stability and corrosion resistance; ② good in impact resistance; ③ good in transparency and wear resistance; ④ good in insulation and low in thermal conductivity; ⑤ good in general molding, coloring and low in processing cost; ⑥ poor in heat resistance, high in thermal expansion rate and easy to burn; ⑦ poor in dimensional stability and easy to deform; ⑧ Most plastics have poor low temperature resistance and become brittle at low temperature; ⑨ they are easy to age; ⑩ some plastics are easy to dissolve in solvents Classification of resins and plastics I classification of resins there are many classification methods of resins Apart from the classification of natural resins and synthetic resins according to the source of resins, they can also be classified according to the synthesis reaction and main chain composition 1 According to the classification of resin synthesis reaction, the resin can be divided into addition polymer and condensation polymer according to this method Adduct is a kind of polymer produced by addition polymerization The chemical formula of its chain structure is the same as that of monomer, such as polyethylene, polystyrene, polytetrafluoroethylene, etc Polycondensation refers to the polymer produced by condensation polymerization The chemical formula of its structural unit is different from that of monomer, such as phenolic resin, polyester resin, polyamide resin, etc 2 According to the composition of resin molecular main chain, resin can be divided into carbon chain polymer, heterochain polymer and element organic polymer Carbon chain polymer refers to the polymer whose main chain is composed of carbon atoms, such as polyethylene, polystyrene, etc Heterochain polymer refers to the polymer whose main chain is composed of carbon, oxygen, nitrogen, sulfur and other two or more elements, such as polyformaldehyde, polyamide, polysulfone, polyether, etc Elemental organic polymers are mainly composed of silicon, oxygen, aluminum, titanium, boron, sulfur, phosphorus and other elements, such as organic silicon 2 Classification of plastics The classification system of plastics is relatively complex, and various classification methods are also intersected There are three kinds of classification according to the conventional classification: first, classification according to the use characteristics; second, classification according to the physical and chemical characteristics; third, classification according to the processing methods 1 Classification by use characteristics: according to the different use characteristics of named plastics, plastics are generally divided into three types: general plastics, engineering plastics and special plastics (1) general plastic generally refers to the plastic with large output, wide use, good formability and low price, such as polyethylene, polypropylene, phenolic, etc (2) engineering plastic general grease can bear certain external force, has good mechanical properties, high and low temperature resistance, good dimensional stability, and can be used as engineering structure plastics, such as polyamide, polysulfone, etc In engineering plastics, it is divided into general engineering plastics and special engineering plastics General engineering plastics include: polyamide, POM, polycarbonate, modified polyphenylene ether, thermoplastic polyester, ultra-high molecular weight polyethylene, methylpentene polymer, vinyl alcohol copolymer, etc Special engineering plastics can also be divided into crosslinking type and non crosslinking type The crosslinking types are: 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 that 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 ① reinforced plastic The shape of reinforced plastic materials can be divided into granular (such as calcium plastic reinforced plastic), fibrous (such as glass fiber or glass cloth reinforced plastic), sheet (such as mica reinforced plastic) According to the material, it can be divided into three types: cloth reinforced plastics (such as ragged reinforced plastics 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) (II) 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 After the stress is released, it can not be restored to its original state; soft foamed plastics are flexible, and the compression hardness is very small, so it is easy to deform After stress relieving, it can be restored to its original state and the residual deformation is smaller The flexibility and other properties of semi rigid foam plastics are between hard soft foam plastics Between 2 According to the classification of physical and chemical properties, plastics can be divided into two types: thermosetting plastics and thermoplastics (1) thermosetting plastic thermosetting plastic refers to the plastic that can be cured or has insoluble (melting) characteristics under heat or other conditions, such as phenolic plastic, epoxy plastic, etc Thermosetting plastics can be divided into formaldehyde crosslinking type and other crosslinking type 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, o-phthalic diallyl ester resin, etc (2) thermoplastics thermoplastics refer to plastics that can be repeatedly heated, softened and cooled and hardened in a specific temperature range, such as polyethylene, polytetrafluoroethylene, etc Thermoplastics can be divided into hydrocarbon, vinyl, engineering, cellulose and other types ① hydrocarbon plastics It is a kind of non-polar plastic, which can be divided into crystalline and non crystalline Crystalline hydrocarbon plastic includes polyethylene, polypropylene, etc., and non crystalline hydrocarbon plastic includes polyacetylene, etc ② vinyl plastic containing polarity gene In addition to fluoroplastics, most of them are amorphous transparent, including PVC, PTFE, polyvinyl acetate, etc Most vinyl monomers can be polymerized with free radical catalyst ③ thermoplastic engineering plastics It mainly includes POM, polyamide, polycarbonate, ABS, polyphenylene ether, polyethylene terephthalate, polysulfone, polyethersulfone, polyimide, polyphenylene sulfide, etc teflon Modified polypropylene is also included in this range ④ thermoplastic cellulose plastics It mainly includes cellulose acetate, cellulose acetate butyrate, celluloid, cellophane, etc 3 According to the classification of processing methods, according to different molding methods of various plastics, it can be divided into film pressing, laminating, injection, extrusion, blow molding, casting plastics and reaction injection plastics
Membrane plastics are mostly plastics with similar physical properties and processing properties to general solid plastics; laminated plastics refer to fiber fabrics impregnated with resin, which are combined into a whole material through lamination and hot pressing; injection, extrusion and blow molding are mostly plastics with similar physical properties and processing properties to general thermoplastic; cast plastics refer to plastics that can be poured into the mold without or with slight pressure A liquid resin mixture, such as MC nylon, which can harden into a certain shape of products; reaction injection plastic is a kind of plastic, such as polyurethane, which is injected into the membrane cavity with liquid raw materials under pressure to make it react and solidify into a certain shape of products