Polyethylene is a polymer of ethylene and thermoplastics. According to its industrial production methods, there are high pressure, medium pressure and low pressure polymerization methods. Different production methods have great differences in molecular structure, and the properties of products are also different with different molecular structures.
Polyethylene is a milky wax-like solid, lighter than water, softer, better water resistance, low temperature resistance, tasteless and nontoxic, poor heat resistance, poor membrane air tightness and sensitive to ultraviolet rays. It is easy to be oxidized and aged, with large thermal shrinkage change and poor printing performance. According to its density. It can be divided into high density, medium density, low density polyethylene and linear low density polyethylene.
2. Polypropylene
Polypropylene is a by-product of petroleum refining. The refined propylene monomer is polymerized under the catalysis of catalyst and then separated from polymer. The molecular weight is10 ~ 500 thousand, and the density is very small, which is the smallest among the known plastics; Non-toxic, odorless, high transparency, good mechanical properties, surface strength, friction resistance, chemical corrosion resistance and moisture resistance; High impact resistance above room temperature, but low impact resistance at low temperature; Easy to carry static electricity, poor printing performance. Polypropylene has a wide range of raw materials, low price and wide performance adaptability. Widely used in food industry. It is mostly used to make films and composite films, with good transparency and surface gloss, and can withstand the temperature of 120 degrees; It can be made into packaging boxes, blow-molded into plastic bottles, and some machine parts can be made by adding some fillers.
3. Polystyrene
Ethylene and benzene are alkylated under the catalysis of anhydrous alumina to produce ethylbenzene, and then styrene is obtained by catalytic dehydrogenation to produce polystyrene. Styrene monomer is polymerized by heating in an aqueous suspension of initiator (benzoyl peroxide) and dispersant (polyvinyl alcohol) to form polystyrene. Polystyrene is a colorless, transparent and inextensible thermoplastic. Non-toxic, tasteless, odorless, good coloring, higher moisture permeability than polyethylene, low hygroscopicity, stable size and good luster; Good processing performance and low cost; The mechanical properties increase with the increase of molecular weight; Low heat resistance, can not be used in boiling water; Low temperature resistance, can withstand the low temperature of -40℃; Good indoor aging resistance; It has good tolerance to alcohol organic solvents and mineral oil, and also has good acid and alkali resistance.
Polystyrene has excellent performance, low price and wide application. It can be made into films and containers and is widely used in food industry. The shrinkage rate can reach 60 ~ 70%, which is a good material for making shrink packaging. It has good insulation performance and can be used to manufacture various telecommunication components. Can also make all kinds of machine parts, toys, daily necessities and so on; Foam plastics can be made by adding foaming agent to polystyrene, which is a good cushioning packaging material.
4. PVC
Polyoxyethylene is polyvinyl chloride produced by suspension polymerization or emulsion polymerization of vinyl chloride under the action of initiator. Light brown, transparent, good toughness, density 1.4g/cm. Good chemical stability, not easy to be corroded by acid and alkali; Good air tightness, water resistance, heat sealing performance, good printability, low production energy consumption and low price; Mechanical strength, wear resistance and pressure resistance are better than those of polyethylene and polypropylene. The main disadvantages are poor thermal stability, easy decomposition when heated, and release of hydrogen chloride gas. Due to the types and quantities of additives, such as plasticizers and stabilizers, PVC can be made into different products and hard products, such as hard pipes and building materials. Can make artificial leather, wire and cable insulation layer, plastic floor, etc. Its main function in packaging is to make films, which can be divided into three types: soft film, hard film and shrink film. Soft film is soft in texture and good in heat sealing, which is suitable for high frequency sealing; The tensile strength is very small and the tear strength is very high; Poor smoothness and poor processability. The dura mater has high tensile strength and tear strength, hard texture and low elongation; Small moisture permeability, good gas barrier and good sliding property; The printing adaptability is good, but the appropriate ink solvent should be selected; Poor temperature resistance, fragile at low temperature. Shrinkage film has good transparency, low air permeability, heat shrinkage, wide shrinkage temperature range and large shrinkage rate, and is a good heat shrinkable packaging material. According to different production processes, it can be divided into dry stretching. Tubular stretching and longitudinal and transverse unidirectional stretching.
5. Polyester fiber (PET)
Polyester is the polycondensation product of terephthalic acid and ethylene glycol. Compared with other plastics, polyester has excellent barrier properties, such as carbon dioxide, oxygen, water and fragrance. It has excellent mechanical properties, high strength, compression resistance and impact resistance; Good chemical stability, acid and alkali corrosion resistance; High transparency, good gloss and optical properties; Non-toxic, tasteless, in line with food hygiene standards; There are ester groups in its structure, so it has good printing performance. Polyester is a unique and widely used packaging material. It can be made into packaging containers such as films, bottles, cans and cups, and can also be used as a dual-purpose baking tray.
6. Phenolic plastics
Phenolic resin is formed by polycondensation of phenols (mainly phenol) and aldehydes (mainly formaldehyde). The ratio of phenol to formaldehyde varies according to whether the catalyst is acidic or alkaline. Thermoplastic resin or thermosetting resin can be obtained. Under appropriate conditions, the two can be transformed into each other. Thermosetting resin is often used in practice. Phenolic resin has good mechanical strength and thermal strength; Good moisture resistance and corrosion resistance; Easy to process and low in price.
Adding different fillers and curing agents to phenolic resin can make different phenolic plastics. By adding various flaky fillers into thermosetting resin, laminates with various properties can be obtained after lamination; Phenolic foam can be made by adding foaming agent; When phenolic plastics are used in packaging, phenolic resin is mixed with fillers, curing agents and colorants to make molding powder, and then molded into bottle caps, machine parts, daily necessities and some packaging containers.
Phenolic plastic products have good chemical stability; Excellent heat resistance; High mechanical strength and wear resistance; Not easy to deform, but the elasticity is poor; Good electrical insulation; The color is monotonous, mostly dark red or black. Because its main raw materials are phenol and formaldehyde, both of which have certain toxicity, it is not suitable for food packaging materials.
7.polyamide
Polyamide, commonly known as "nylon", can be formed by polycondensation of dibasic acids and dibasic acids. Polyamide is nontoxic, colorless and transparent; Good wear resistance. Strong impact toughness and excellent mechanical properties; Good light resistance, light is not easy to age; Good oil resistance and chemical stability, but not resistant to alcohols, formic acid and phenol; Good air tightness; Strong adaptability to temperature, which can be used in the range of -40 ~ 100 degrees; Good printability and decoration; High hygroscopicity.
Polyamide is widely used in manufacturing bearings, gears, pump blades, automobile parts and so on. Its application in packaging is mainly soft packaging. When it is made into film for food packaging, it can also be used as packaging tape and packaging rope, which is stronger than polypropylene packaging tape.
8. Urea-formaldehyde plastic (UF)
Urea-formaldehyde plastic, commonly known as "electric jade", is a product made of urea and formaldehyde by polycondensation, adding fillers, colorants, lubricants, plasticizers, etc. into compression molding powder (electric jade powder), and then heating molding. High surface hardness, certain mechanical strength, not easy to deform, but fragile. Odorless and tasteless, strong coloring, bright colors, such as beautiful jade; Good heat resistance, not easy to burn; Acid and alkali resistance, poor water resistance, high water absorption and good electrical insulation. Urea-formaldehyde plastics can be made into many products, such as daily necessities and electrical components. Beautiful packaging box, packaging tray, bottle cap, etc. Can be made on the bag; Formaldehyde is not suitable for food packaging because of its toxicity. Urea-formaldehyde foam can be obtained by adding foaming agent to urea-formaldehyde resin and foaming by mechanical method. It is light in weight, cheap in price, good in heat preservation and corrosion resistance, and it is a widely used cushioning packaging material.
9. melamine plastic
Melamine plastics and urea-formaldehyde plastics belong to amino plastics. It is made of resin condensed from melamine and formaldehyde as the main component, with fillers, lubricants, colorants, hardeners and so on. It is also a thermosetting plastic.
Melamine plastic is non-toxic, odorless and tasteless, and has good sanitary performance; High mechanical strength, good surface hardness and difficult deformation; Smooth surface, feel like porcelain; Strong impact resistance and pollution resistance; Good chemical stability. Melamine plastic can be used to make packaging containers of various colors, including food packaging.
10, polyvinyl alcohol
Polyvinyl alcohol is the hydrolysis product of polyvinyl acetate. It is transparent, non-toxic and tasteless; Excellent gas barrier, water resistance and oil resistance; Good chemical stability; Good printability and no static electricity; Good mechanical properties.
Polyvinyl alcohol can be used in food packaging, which has a significant effect on preventing food from oxidation, discoloration, taste and deterioration and maintaining food freshness. It can also package other products, such as chemical products.
1 1, polycarbonate (Pc)
Polycarbonate is the general name of resin with carbonate structure in its molecular chain, which usually refers to bisphenol A polycarbonate. Colorless and transparent, with good luster; Excellent heat resistance and cold resistance, can be used for pressure sterilization; High mechanical strength. Can be juxtaposed with polyester and nylon; Excellent impact toughness, the product is not easy to break when it is impacted; Low water absorption, hygroscopicity and air permeability; Good chemical resistance, non-toxic, odorless and tasteless, which can prevent ultraviolet rays from penetrating; The molding performance is good, and general molding methods can be used. The molded product has high precision. But the heat sealing performance is poor. [Page]
Polycarbonate is an engineering plastic with excellent comprehensive properties, which can be used to manufacture various gears and mechanical parts. Can be made into film-packed food and other articles, and can be made into composite film to improve heat sealing performance when sealing is needed; It can also be made into various packaging containers.
12, polyvinylidene chloride (PVDC)
Polyvinylidene chloride is a homopolymer of vinylidene oxide. It is non-toxic, tasteless and transparent; High mechanical strength. Good toughness; Oil resistance and organic solubility; Good thermal shrinkage and self-adhesion, and easy adhesion between films; Excellent air tightness and moisture resistance. However, it has poor processability, poor thermal stability, difficult heat sealing and easy decomposition under the action of ultraviolet rays.
The application of polyvinylidene chloride in packaging is mainly to make food packaging film, which can be used as sealed packaging and can effectively prevent food from absorbing moisture. The oxidation of oil makes food keep good quality for a long time; Can be used as sterilization food packaging, because it can be heated for sterilization; It can also be used as a packaging material for home use.
13, polyurethane (PVP)
Polyurethane, also known as polyurethane, is formed by the reaction of isocyanate and hydroxyl compounds. The main characteristics of polyurethane are good wear resistance, excellent low temperature resistance, outstanding oil resistance and chemical corrosion resistance. Polyurethane is mainly processed into foam, and different soft and hard foams can be obtained by changing raw materials and ratio. Soft products have good toughness, elasticity and oil resistance, and are the main varieties of polyurethane foam, which are widely used to make cushioning materials such as cushioning pads in packaging. Hard products have excellent heat resistance, cold resistance, heat insulation and impact resistance, and are widely used in the packaging of precision instruments. The production of polyurethane foam is very simple. Convenient operation, low cost, good shock-proof performance, can be made at room temperature, especially on-site foaming, which brings great convenience to packaging. 1, polyethylene
Polyethylene is a polymer of ethylene and thermoplastics. According to its industrial production methods, there are high pressure, medium pressure and low pressure polymerization methods. Different production methods have great differences in molecular structure, and the properties of products are also different with different molecular structures.
Polyethylene is a milky wax-like solid, lighter than water, softer, better water resistance, low temperature resistance, tasteless and nontoxic, poor heat resistance, poor membrane air tightness and sensitive to ultraviolet rays. It is easy to be oxidized and aged, with large thermal shrinkage change and poor printing performance. According to its density. It can be divided into high density, medium density, low density polyethylene and linear low density polyethylene.
2. Polypropylene
Polypropylene is a by-product of petroleum refining. The refined propylene monomer is polymerized under the catalysis of catalyst and then separated from polymer. The molecular weight is10 ~ 500 thousand, and the density is very small, which is the smallest among the known plastics; Non-toxic, odorless, high transparency, good mechanical properties, surface strength, friction resistance, chemical corrosion resistance and moisture resistance; High impact resistance above room temperature, but low impact resistance at low temperature; Easy to carry static electricity, poor printing performance. Polypropylene has a wide range of raw materials, low price and wide performance adaptability. Widely used in food industry. It is mostly used to make films and composite films, with good transparency and surface gloss, and can withstand the temperature of 120 degrees; It can be made into packaging boxes, blow-molded into plastic bottles, and some machine parts can be made by adding some fillers.
3. Polystyrene
Ethylene and benzene are alkylated under the catalysis of anhydrous alumina to produce ethylbenzene, and then styrene is obtained by catalytic dehydrogenation to produce polystyrene. Styrene monomer is polymerized by heating in an aqueous suspension of initiator (benzoyl peroxide) and dispersant (polyvinyl alcohol) to form polystyrene. Polystyrene is a colorless, transparent and inextensible thermoplastic. Non-toxic, tasteless, odorless, good coloring, higher moisture permeability than polyethylene, low hygroscopicity, stable size and good luster; Good processing performance and low cost; The mechanical properties increase with the increase of molecular weight; Low heat resistance, can not be used in boiling water; Low temperature resistance, can withstand the low temperature of -40℃; Good indoor aging resistance; It has good tolerance to alcohol organic solvents and mineral oil, and also has good acid and alkali resistance.
Polystyrene has excellent performance, low price and wide application. It can be made into films and containers and is widely used in food industry. The shrinkage rate can reach 60 ~ 70%, which is a good material for making shrink packaging. It has good insulation performance and can be used to manufacture various telecommunication components. Can also make all kinds of machine parts, toys, daily necessities and so on; Foam plastics can be made by adding foaming agent to polystyrene, which is a good cushioning packaging material.
4. PVC
Polyoxyethylene is polyvinyl chloride produced by suspension polymerization or emulsion polymerization of vinyl chloride under the action of initiator. Light brown, transparent, good toughness, density 1.4g/cm. Good chemical stability, not easy to be corroded by acid and alkali; Good air tightness, water resistance, heat sealing performance, good printability, low production energy consumption and low price; Mechanical strength, wear resistance and pressure resistance are better than those of polyethylene and polypropylene. The main disadvantages are poor thermal stability, easy decomposition when heated, and release of hydrogen chloride gas. Due to the types and quantities of additives, such as plasticizers and stabilizers, PVC can be made into different products and hard products, such as hard pipes and building materials. Can make artificial leather, wire and cable insulation layer, plastic floor, etc. Its main function in packaging is to make films, which can be divided into three types: soft film, hard film and shrink film. Soft film is soft in texture and good in heat sealing, which is suitable for high frequency sealing; The tensile strength is very small and the tear strength is very high; Poor smoothness and poor processability. The dura mater has high tensile strength and tear strength, hard texture and low elongation; Small moisture permeability, good gas barrier and good sliding property; The printing adaptability is good, but the appropriate ink solvent should be selected; Poor temperature resistance, fragile at low temperature. Shrinkage film has good transparency, low air permeability, heat shrinkage, wide shrinkage temperature range and large shrinkage rate, and is a good heat shrinkable packaging material. According to different production processes, it can be divided into dry stretching. Tubular stretching and longitudinal and transverse unidirectional stretching.
5. Polyester fiber (PET)
Polyester is the polycondensation product of terephthalic acid and ethylene glycol. Compared with other plastics, polyester has excellent barrier properties, such as carbon dioxide, oxygen, water and fragrance. It has excellent mechanical properties, high strength, compression resistance and impact resistance; Good chemical stability, acid and alkali corrosion resistance; High transparency, good gloss and optical properties; Non-toxic, tasteless, in line with food hygiene standards; There are ester groups in its structure, so it has good printing performance. Polyester is a unique and widely used packaging material. It can be made into packaging containers such as films, bottles, cans and cups, and can also be used as a dual-purpose baking tray.
6. Phenolic plastics
Phenolic resin is formed by polycondensation of phenols (mainly phenol) and aldehydes (mainly formaldehyde). The ratio of phenol to formaldehyde varies according to whether the catalyst is acidic or alkaline. Thermoplastic resin or thermosetting resin can be obtained. Under appropriate conditions, the two can be transformed into each other. Thermosetting resin is often used in practice. Phenolic resin has good mechanical strength and thermal strength; Good moisture resistance and corrosion resistance; Easy to process and low in price.
Adding different fillers and curing agents to phenolic resin can make different phenolic plastics. By adding various flaky fillers into thermosetting resin, laminates with various properties can be obtained after lamination; Phenolic foam can be made by adding foaming agent; When phenolic plastics are used in packaging, phenolic resin is mixed with fillers, curing agents and colorants to make molding powder, and then molded into bottle caps, machine parts, daily necessities and some packaging containers.
Phenolic plastic products have good chemical stability; Excellent heat resistance; High mechanical strength and wear resistance; Not easy to deform, but the elasticity is poor; Good electrical insulation; The color is monotonous, mostly dark red or black. Because its main raw materials are phenol and formaldehyde, both of which have certain toxicity, it is not suitable for food packaging materials.
7.polyamide
Polyamide, commonly known as "nylon", can be formed by polycondensation of dibasic acids and dibasic acids. Polyamide is nontoxic, colorless and transparent; Good wear resistance. Strong impact toughness and excellent mechanical properties; Good light resistance, light is not easy to age; Good oil resistance and chemical stability, but not resistant to alcohols, formic acid and phenol; Good air tightness; Strong adaptability to temperature, which can be used in the range of -40 ~ 100 degrees; Good printability and decoration; High hygroscopicity.
Polyamide is widely used in manufacturing bearings, gears, pump blades, automobile parts and so on. Its application in packaging is mainly soft packaging. When it is made into film for food packaging, it can also be used as packaging tape and packaging rope, which is stronger than polypropylene packaging tape.
8. Urea-formaldehyde plastic (UF)
Urea-formaldehyde plastic, commonly known as "electric jade", is a product made of urea and formaldehyde by polycondensation, adding fillers, colorants, lubricants, plasticizers, etc. into compression molding powder (electric jade powder), and then heating molding. High surface hardness, certain mechanical strength, not easy to deform, but fragile. Odorless and tasteless, strong coloring, bright colors, such as beautiful jade; Good heat resistance, not easy to burn; Acid and alkali resistance, poor water resistance, high water absorption and good electrical insulation. Urea-formaldehyde plastics can be made into many products, such as daily necessities and electrical components. Beautiful packaging box, packaging tray, bottle cap, etc. Can be made on the bag; Formaldehyde is not suitable for food packaging because of its toxicity. Urea-formaldehyde foam can be obtained by adding foaming agent to urea-formaldehyde resin and foaming by mechanical method. It is light in weight, cheap in price, good in heat preservation and corrosion resistance, and it is a widely used cushioning packaging material.
9. melamine plastic
Melamine plastics and urea-formaldehyde plastics belong to amino plastics. It is made of resin condensed from melamine and formaldehyde as the main component, with fillers, lubricants, colorants, hardeners and so on. It is also a thermosetting plastic.
Melamine plastic is non-toxic, odorless and tasteless, and has good sanitary performance; High mechanical strength, good surface hardness and difficult deformation; Smooth surface, feel like porcelain; Strong impact resistance and pollution resistance; Good chemical stability. Melamine plastic can be used to make packaging containers of various colors, including food packaging.
10, polyvinyl alcohol
Polyvinyl alcohol is the hydrolysis product of polyvinyl acetate. It is transparent, non-toxic and tasteless; Excellent gas barrier, water resistance and oil resistance; Good chemical stability; Good printability and no static electricity; Good mechanical properties.
Polyvinyl alcohol can be used in food packaging, which has a significant effect on preventing food from oxidation, discoloration, taste and deterioration and maintaining food freshness. It can also package other products, such as chemical products.
1 1, polycarbonate (Pc)
Polycarbonate is the general name of resin with carbonate structure in its molecular chain, which usually refers to bisphenol A polycarbonate. Colorless and transparent, with good luster; Excellent heat resistance and cold resistance, can be used for pressure sterilization; High mechanical strength. Can be juxtaposed with polyester and nylon; Excellent impact toughness, the product is not easy to break when it is impacted; Low water absorption, hygroscopicity and air permeability; Good chemical resistance, non-toxic, odorless and tasteless, which can prevent ultraviolet rays from penetrating; The molding performance is good, and general molding methods can be used. The molded product has high precision. But the heat sealing performance is poor. [Page]
Polycarbonate is an engineering plastic with excellent comprehensive properties, which can be used to manufacture various gears and mechanical parts. Can be made into film-packed food and other articles, and can be made into composite film to improve heat sealing performance when sealing is needed; It can also be made into various packaging containers.
12, polyvinylidene chloride (PVDC)
Polyvinylidene chloride is a homopolymer of vinylidene oxide. It is non-toxic, tasteless and transparent; High mechanical strength. Good toughness; Oil resistance and organic solubility; Good thermal shrinkage and self-adhesion, and easy adhesion between films; Excellent air tightness and moisture resistance. However, it has poor processability, poor thermal stability, difficult heat sealing and easy decomposition under the action of ultraviolet rays.
The application of polyvinylidene chloride in packaging is mainly to make food packaging film, which can be used as sealed packaging and can effectively prevent food from absorbing moisture. The oxidation of oil makes food keep good quality for a long time; Can be used as sterilization food packaging, because it can be heated for sterilization; It can also be used as a packaging material for home use.
13, polyurethane (PVP)
Polyurethane, also known as polyurethane, is formed by the reaction of isocyanate and hydroxyl compounds. The main characteristics of polyurethane are good wear resistance, excellent low temperature resistance, outstanding oil resistance and chemical corrosion resistance. Polyurethane is mainly processed into foam, and different soft and hard foams can be obtained by changing raw materials and ratio. Soft products have good toughness, elasticity and oil resistance, and are the main varieties of polyurethane foam, which are widely used to make cushioning materials such as cushioning pads in packaging. Hard products have excellent heat resistance, cold resistance, heat insulation and impact resistance, and are widely used in the packaging of precision instruments. The production of polyurethane foam is very simple. Convenient operation, low cost, good shock-proof performance, can be made at room temperature, especially on-site foaming, which brings great convenience to packaging.