There are many kinds of plastic packaging bags. The most commonly used plastics in plastic packaging are polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyurethane, and phenolic resin.
Honest Packaging summarizes and analyzes the advantages and disadvantages. You can contact us to learn more:
1. Polyethylene (PE)
Polyethylene is a high molecular polymer of ethylene and is a thermoplastic. According to its industrial production methods, there are high pressure, medium pressure and low pressure polymerization methods. Different production methods have different molecular structures, and product properties also vary with molecular structures. Polyethylene is a milky white waxy solid, lighter than water, softer, good in water resistance, low temperature resistance, odorless, non-toxic, poor in heat resistance, poor in air tightness of the film, and sensitive to ultraviolet rays. It is easy to be oxidized and aged, the thermal shrinkage changes greatly, and the printing performance is poor. by its density. It can be divided into high density, medium density, low density polyethylene, and linear low density polyethylene.
2. Polypropylene (PP)
Polypropylene is a by-product of petroleum refining, propylene. The refined propylene monomer is polymerized under the catalysis of a catalyst, and then separated from the polymer. The molecular weight is 100,000 to 500,000, and the density is very small, which is the smallest among the known plastics; non-toxic, tasteless, high transparency, mechanical properties, surface strength, friction resistance, chemical corrosion resistance, moisture resistance are all good; at room temperature In the above case, the impact resistance value is large, but the low temperature impact resistance value is small; it is easy to carry static electricity, and the printing performance is not good. Polypropylene has a wide range of raw material sources, low price and wide performance adaptability. Widely used in the food industry. It is mostly used to make films and composite films, with good transparency and surface gloss, and can withstand temperatures of 120 degrees; it can be made into packaging boxes, blow molded into plastic bottles, and some machine parts can be made by adding certain fillers.
3. Polystyrene (PS)
Polystyrene is obtained by the alkylation of ethylene and benzene under the catalysis of anhydrous trialumina to generate ethylbenzene, and then catalytic dehydrogenation to obtain styrene. Styrene monomer is heated and polymerized in an aqueous suspension of an appropriate amount of initiator (benzoyl peroxide) and dispersant (polyvinyl alcohol) to form polystyrene. Polystyrene is a colorless, transparent, non-ductile thermoplastic; non-toxic, odorless, odorless, good in coloring, more moisture-permeable than polyethylene, low in moisture absorption, dimensionally stable, and has good luster; processability Good, low cost; mechanical properties increase with the increase of molecular weight; low heat resistance, can not be used in boiling water; low temperature resistance, can withstand low temperature of -40 ℃; good indoor aging resistance; , Mineral oil has good tolerance, acid and alkali resistance is also very good. Due to its superior performance, low price and wide application, polystyrene can be made into films and containers, which are widely used in the food industry; the shrinkage rate can reach 60-70%, which is a good material for shrink packaging and has good insulation properties. It can make a variety of telecommunication parts; it can also make various machine parts, toys, daily necessities, etc.; adding foaming agent to polystyrene can make foam plastic, which is a good buffer packaging material.
4. Polyvinyl chloride (PVC)
Polyoxyethylene is polyvinyl chloride produced by suspension polymerization or emulsion polymerization through the action of an initiator. It is light brown, transparent, has good toughness, and has a density of 1.4g/cm3; it has good chemical stability and is not easily corroded by acids and alkalis; air tightness, water resistance, good heat sealing performance, good printability, and production energy consumption Less, cheaper; mechanical strength, wear resistance, pressure resistance are better than polyethylene and polypropylene. The main disadvantage is that the thermal stability is poor, it is easy to decompose when heated, and hydrogen chloride gas is released. Due to the different types and quantities of additives, such as plasticizers and stabilizers, polyvinyl chloride can be made into different products, and can produce rigid products, such as rigid pipes, building materials, etc.; can manufacture artificial leather, wire and cable insulation, plastic floor, etc. Its main function in packaging is to make film, which is divided into three types: soft film, hard film and shrink film. The soft film is soft and heat-sealing, suitable for high-frequency sealing; the tensile strength is small, the tear strength is high; the sliding property is poor, and the processing performance is also poor. The tensile strength and tear strength of the hard film are large, the texture is hard, and the elongation is small; the moisture permeability is small, the gas barrier property is good, and the sliding property is good; the printing adaptability is good, but an appropriate ink solvent must be selected; Poor temperature resistance, brittle at low temperature. The shrink film has good transparency, low air permeability, shrinkage when heated, wide shrinkage temperature range and large shrinkage rate, and is a good heat shrinkable packaging material. According to its different production processes, it can be divided into dry stretching. Tubular stretching and vertical and horizontal unidirectional stretching and other varieties.
5. Polyester (PET)
Polyester is the polycondensation product of terephthalic acid and ethylene glycol. Compared with other plastics, polyester has excellent barrier properties, such as good barrier to carbon dioxide, oxygen, water and fragrance; with excellent mechanical properties, it has 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; its structure has ester groups, so the printing performance is good. Polyester is a unique and versatile packaging material. It can be used to make films, make bottles, cans, cups and other packaging containers, and can also be used as a dual-purpose bakeable tray.
6. Phenolic plastic (PF)
Phenolic resin is formed by the polycondensation of phenols (mainly phenol) and aldehydes (mainly formaldehyde). The ratio of phenol to formaldehyde varies depending on whether the catalyst is acidic or basic. Thermoplastic resins or thermosetting resins are available. The two can be converted into each other under suitable conditions. Thermosetting resins are often used in practice. Phenolic resin has good mechanical strength and thermal strength; good moisture resistance and corrosion resistance; easy processing and low price. After adding different fillers and curing agents to phenolic resin, different phenolic plastics can be obtained. Various sheet fillers are added to thermosetting resin, and laminated boards with various properties can be obtained after lamination; phenolic foam plastics can be obtained by adding foaming agents; when phenolic plastics are used for packaging, phenolic resin is mixed with fillers and cured It is made into 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, wear resistance; not easy to deform, but poor elasticity; good electrical insulation; monotonous color, mostly dark red or black. Since its main raw materials are phenol and formaldehyde, both of which have certain toxicity, it is not suitable for food packaging materials.
7. Polyamide (PA)
Polyamide, commonly known as “nylon”, can be obtained by polycondensation of dibasic acid and dibasic acid. Polyamide is non-toxic, colorless and transparent; good abrasion resistance. Strong impact toughness, excellent mechanical properties; good light resistance, not easy to age in light; good oil resistance, good chemical stability, but not resistant to alcohol, formic acid and phenol; good air tightness; Use within the range of ~100 degrees; good printability and decoration; high hygroscopicity. Polyamide has a wide range of uses, and can be used to make bearings, gears, pump blades, auto parts, etc. Its application in packaging is mainly flexible packaging, and it can be made into film for food packaging and can also be used to make straps and ropes. Its firmness is better than that of polypropylene straps.
8. Urea-formaldehyde plastic (UF)
Urea-formaldehyde plastic, commonly known as “electric jade”, is made of urea and formaldehyde as raw materials, through polycondensation reaction to obtain urea-formaldehyde resin, and then processed into compression molding powder (electric jade powder) with fillers, colorants, lubricants, plasticizers, etc. The product is made by heating and molding. It has high surface hardness, certain mechanical strength, is not easy to deform, but is more brittle; odorless, tasteless, strong tinting strength, brightly colored, and looks like beautiful jade; good heat resistance, not easy to burn; acid and alkali resistance, water resistance is relatively high Poor, high water absorption, good electrical insulation. Urea-formaldehyde plastics can be made into a variety of products, such as daily necessities, electrical components, etc. On the bag, it can be made into beautiful packaging boxes, packaging trays, bottle caps, etc.; because formaldehyde has certain toxicity, it is not suitable for food packaging. Adding a foaming agent to the urea-formaldehyde resin, and foaming it by mechanical means, the urea-formaldehyde foamed plastic can be obtained. It is light in weight, cheap in price, good in heat preservation and corrosion resistance, and is a widely used buffer packaging material.
9. Melamine plastic (ME)
Melamine plastics and urea-formaldehyde plastics belong to amino plastics. It is mainly composed of resin obtained by the polycondensation reaction of melamine and formaldehyde, adding fillers, lubricants, colorants, hardeners, etc., and is made by hot pressing. It is also a thermosetting plastic. Melamine plastic is non-toxic, odorless, tasteless, and has good hygienic performance; high mechanical strength, good surface hardness, not easy to deform; smooth surface, feel like porcelain; strong impact resistance, anti-pollution ability; good chemical stability. Melamine plastics can be used to make packaging containers of various colors including food packaging.
10. Polyvinyl Alcohol (PVA)
Polyvinyl alcohol is a hydrolysis product of polyvinyl acetate. It is transparent, non-toxic and odorless; it has excellent gas barrier, water resistance and oil resistance; good chemical stability; good printability, no static electricity; good mechanical properties. Polyvinyl alcohol mostly uses its film in packaging, which can be used for food packaging, which has a significant effect on preventing food from oxidative discoloration, staleness and deterioration, and maintaining the freshness of food; it can also package other products, such as chemical products.
11. Polycarbonate (PC)
Polycarbonate is a general term for resins containing carbonate structures in the molecular chain, and generally refers to bisphenol A-type polycarbonates. It is colorless and transparent, with good gloss; excellent heat resistance and cold resistance, can be used for pressure sterilization; high mechanical strength. It can be juxtaposed with polyester and nylon; it has excellent impact toughness, and the product is not easy to break when impacted; water absorption, moisture absorption, and air permeability are small; chemical corrosion resistance is good, and it can prevent ultraviolet rays from passing through; it is non-toxic, odorless, and tasteless; It has good molding properties and can be used with general molding methods. The formed products have high precision. But the heat sealing performance is poor. Polycarbonate is an engineering plastic with excellent comprehensive properties, which can be used to make various gears, machine parts, etc.; it can be made into film to package food and other items. When sealing is required, it can be made into composite film to improve heat sealing performance. ; Can also be made into various packaging containers.
12. Polyvinylidene Chloride (PVDC)
Polyvinylidene chloride is a homopolymer of vinylidene oxide. It is non-toxic, odorless, transparent, and has high mechanical strength. Good toughness; oil and organic solvent resistance; good heat shrinkage and self-adhesion, easy adhesion between films; excellent air tightness and moisture resistance. However, it has poor machinability, poor thermal stability, is not easy to heat seal, and is easily decomposed by ultraviolet rays. The application of polyvinylidene chloride in packaging is mainly to make food packaging films, which can be used as sealed packaging and can effectively prevent food from absorbing moisture. Oxidation of oily food makes the food not bad for a long time; it can be used as sterilization food packaging because it can be heated and sterilized; it can also be used as a packaging material for household daily use.
13. Polyurethane (PVP)
Polyurethane, also known as polyurethane, is prepared 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 foamed plastics, and by changing the raw materials and proportions, different soft and hard foamed plastics can be obtained. Soft products have good toughness, good elasticity, and oil resistance. They are the main varieties of polyurethane foams and are widely used in packaging to make cushioning materials such as cushions. Hard products are heat-resistant, cold-resistant, heat-insulating, and have excellent shock resistance, and are widely used in the packaging of precision instruments and meters. The production of polyurethane foam is simple. The utility model has the advantages of convenient operation, low cost, good shockproof performance, and can be prepared at room temperature, especially through in-situ foaming, which brings great convenience to packaging.
