Tuesday, May 21, 2024
Home xin What is PE plastic bag?

What is PE plastic bag?

by admin
0 comment

PE is explained as follows:

1= Prince Edward Island
2= Price earning ratio
3= Physical ecation
4= Polyethylene

but in your question, it means “polyethylene”

sanitation of plastics and their products


plastics are a kind of high molecular compounds. Plastic products are made from synthetic resin as the main raw material, adding an appropriate amount of plasticizers, stabilizers, antioxidants and other additives under certain plasticizing conditions. At present, polyethylene, polypropylene, polyvinyl chloride, vinylidene chloride, polycarbonate, polyethylene terephthalate, nylon, unsaturated polyester resin, acrylonitrile styrene copolymer resin, reynitrile styrene copolymer resin, acrylonitrile butadiene styrene copolymer resin, etc. are allowed to be used as food containers, packaging materials and thermoplastics used for manufacturing food tools and equipment in China; Thermosetting plastics include melamine formaldehyde resin, etc. ?
(I) polyethylene (, PE) and polypropylene (, PP)?
1. Physical and chemical properties: polyethylene and polypropylene plastics are polymer compounds formed by polymerization with ethylene and propylene as monomers respectively
molecular formula of polyethylene:
molecular weight:
molecular formula of polypropylene:
molecular weight: about 100000 ~ 500000
according to the pressure during polymerization, polyethylene plastics are divided into high-pressure polyethylene or low-density polyethylene (LDPE) and low-pressure polyethylene or high-density polyethylene (HDPE). High pressure polyethylene is mainly used to make food plastic bags, fresh-keeping films, etc; Low pressure polyethylene is mainly used to manufacture plastic containers, tubes, cutting boards, etc. for food. Polypropylene plastic film can be stretched longitudinally and transversely to change its mechanical properties and increase its strength and transparency. According to the stretching direction, polypropylene plastic film is mainly used to manufacture food plastic bags, especially composite plastic bags; Polypropylene can also be processed into both low temperature and high temperature resistant food containers, such as fresh-keeping boxes and containers for microwave ovens. ?
2. Main health problems: polyethylene and polypropylene resins have very low toxicity, and kd50 is greater than the maximum possible intragastric dose. Due to its super long saturated linear alkanes, it has high chemical stability and low biological activity. No obvious toxic effect has been found in oral subacute and chronic tests, teratogenic and carcinogenic tests. The content of ethylene and propylene monomers in polyethylene and polypropylene resins is very low, and the toxicity of ethylene and propylene itself is also low. Agents are rarely used in the production of polyethylene and polypropylene resins and molded products. Therefore, polyethylene and polypropylene plastics are relatively safe plastics, which can be widely used as food containers and packaging materials. However, low molecular weight polyethylene is easily soluble in oil, so polyethylene tableware should not always contain edible oil, so as to avoid the taste of oil. According to GB 9691-88 hygienic standard for polyethylene resin for food packaging, GB9687-88 hygienic standard for polyethylene molded products for food packaging, gb9693-88 hygienic standard for polypropylene resin for food packaging and gb9688-88 hygienic standard for polypropylene molded products for food packaging, free monomers shall be controlled for both resin and molded products. (II) polyvinyl chloride (PVC)
1. Physical and chemical properties: polyvinyl chloride is polymerized with vinyl chloride as monomer. Molecular formula:
molecular weight: about 50000 ~ 120000
according to the amount of plasticizer added to PVC, it can be divided into hard, semi-hard and soft PVC. Plasticizers added to rigid PVC are generally < 10%, 10 ~ 30% for semi-rigid and 30 ~ 50% for soft. Its physical and mechanical properties also vary with its components. Generally speaking, PVC has the characteristics of good chemical resistance, high mechanical strength, good insulation and low price. PVC semi-rigid sheet can be processed into plastic box by plastic absorption; Soft PVC can be used as the gasket of beverage cap and four screw bottle cap (commonly known as drop plastic); UPVC can be processed into plastic pipes and plates. ?
2. Main health problems: PVC itself is non-toxic, but its monomer and degradation products are highly toxic, and the content of plasticizer in PVC is high. ?
(1) toxicity of vinyl chloride monomer and degradation products: polyvinyl chloride resin and molded products often contain a certain amount of vinyl chloride monomer, which can migrate to food when in contact with food. After the absorption of vinyl chloride through the gastrointestinal tract, part of it is discharged through the respiratory tract, and the other part is decomposed into chloroethanol and monochloroacetic acid. It can also bind to deoxyribonucleic acid (DNA) in vivo. It mainly produces toxic effects on nervous system, bone and liver. The results show that vinyl chloride monomer and its decomposition products have carcinogenic effect. There are epidemiological investigation reports of angiosarcoma in human body. Therefore, various countries have stipulated the residual amount of vinyl chloride monomer in PVC resin, such as Japan, the United States, Britain, France, the Netherlands, Italy, Switzerland and other countries, which should be less than 1mg/kg; France, Italy and Switzerland also stipulate that the migration amount in food shall not be greater than 0.05mg/kg. China’s gb4803-94 hygienic standard for polyvinyl chloride resin for food containers and packaging materials and gb9681-88 hygienic standard for polyvinyl chloride molded products for food packaging stipulate that the content of vinyl chloride monomer in polyvinyl chloride resin and molded products for food packaging shall be controlled below 5mg/kg and 1mg /1 respectively. –
(2) toxicity of halogenated hydrocarbons: according to the preparation method of vinyl chloride monomer, polyvinyl chloride is divided into acetylene polyvinyl chloride and ethylene polyvinyl chloride. Due to different synthetic processes, the halogenated hydrocarbons contained in PVC are also different. Acetylene PVC contains 1,1-dichloroethane, while ethylene PVC contains 1,2-dichloroethane. The toxicity of the latter is 10 times that of the former. Therefore, gb4803-94 hygienic standard for vinyl chloride resin used for food containers and packaging materials stipulates that the residue of 1,1-dichloroethane in polyvinyl chloride resin by acetylene method shall be less than 150mg/kg; The residual amount of 1,2-dichloroethane in vinyl chloride resin shall be less than 2mg/kg. –
(3) migration of plasticizers: a large number of plasticizers are used in PVC molded products, especially semi-rigid and soft PVC, some of which are highly toxic (see table 5.1). In addition to plasticizers, additives such as stabilizers and UV absorbers are also added to the production of PVC molded products, which will also migrate to food. Therefore, great attention must be paid to the toxicity of additives. It shall comply with gb9685-94 hygienic standard for the use of additives for food containers and packaging materials. ?
(III) polystyrene (, PS)
1. Rational properties: polystyrene is polymerized from styrene monomer. Molecular formula:
molecular weight: about 200000
universal polystyrene is colorless and transparent, resistant to oil, acid, alkali and alcohol, but brittle and poor impact resistance; High impact polystyrene (HIPS) with high impact strength can be prepared after modification, which can be used to make fruit and vegetable boxes in refrigerators and household food processing machinery; EPS can also be prepared by adding a certain amount of foaming agent (i.e. pentane, hexane, freon and other foaming agents) to the suspension p
olymerized polystyrene, and then the fast-food lunch box can be prepared through secondary processing. ?
2. Main health problems: Polystyrene itself is non-toxic. It is mixed with feed to feed animals, and no toxicity is found. However, polystyrene contains free styrene monomer, toluene, ethylbenzene, cumene and other volatile substances. These volatile substances have great toxicity. The LD50 (oral) of styrene monomer to rats is 1 ~ 1.2g/kg body weight. Chronic toxicity test shows that growth retardation, liver and kidney weight reduction; Benzene series compounds such as toluene, ethylbenzene and propylbenzene have toxic effects on the nervous system (see table 5.2). Therefore, the residues of styrene and ethylbenzene in GB9692-88 alkene resin should be controlled below 0.5% and 0.3% respectively. The foaming agent freon in EPS is highly toxic, and the residual amount in EPS can be as high as tens to hundreds of mg/kg. However, pentane and butane have little toxicity and have been listed in the hygienic standard for the use of additives for food containers and packaging materials. Degradable EPS includes biodegradation, photodegradation and mixed degradation. Generally, 10-30% starch and /or cellulose are added to EPS for biodegradation; Generally, photosensitive catalyst must be added to EPS for photodegradation. The hygienic standard for the use of additives for food containers and packaging materials stipulates that ferrocene derivatives can be used as photosensitive catalysts: photosensitive catalysts must be added to EPS for mixed degradation. At present, China has not formulated the hygienic standard of EPS for food containers and packaging materials. ?
(IV) melamine formaldehyde resin (melamine formalin: MF)
1. Physical and chemical properties: melamine formaldehyde resin is formed by condensation polymerization of melamine and formaldehyde. Δ br> molecular formula: Δmolecular weight: > 300
melamine formaldehyde resin is a thermosetting plastic (known as melamine). It is heat resistant (120 ℃), oil resistant, alcohol resistant and pollution resistant. It can be made into tableware and tableware of various colors and imitated porcelain. Δ br> 2. Main health problems: melamine formaldehyde resin is non-toxic. However, melamine formaldehyde resin contains a certain amount of free formaldehyde, especially the phenolic resin (commonly known as bakelite) condensed from phenol and formaldehyde and the urea formaldehyde resin (commonly known as Dianyu) condensed from urea and formaldehyde. Formaldehyde is a kind of protoplasm poison of cells. When animals ingest formaldehyde orally, hepatocyte necrosis and lymphocyte infiltration can occur. Therefore, phenolic resin and urea formaldehyde resin shall not be used in food containers and packaging materials. The migration amount of formaldehyde in melamine formaldehyde resin decreased with the increase of thermosetting pressing time, thermosetting molding time and thermosetting pressing temperature. According to gb9690-88 hygienic standard for melamine molded products for food packaging, the content of free formaldehyde in the finished products of melamine formaldehyde resin for food packaging shall be controlled below 10mg/l. ?
(V) polycarbonate resin (, PC)?
1. Physical and chemical properties: polycarbonate resin is a general term for a class of high molecular compounds containing carbonate in the molecular chain. Polycarbonates can be divided into aliphatic, alicyclic, aromatic and aliphatic aromatic polycarbonates according to the types of R-groups. At present, there is only aromatic polycarbonate resin of bisphenol a type, which is made from bisphenol A and diphenyl carbonate through transesterification and polycondensation. Its molecular formula is: polycarbonate resin is a kind of thermoplastic engineering plastic with heat resistance, cold resistance and good mechanical properties. Due to the characteristics of tasteless, oil resistant and not easy to pollute, polycarbonate resin is mainly used to manufacture and process horizontal tools for food (such as biscuits, Kongli molds, etc.), baby bottles, food processing machinery and other food containers and food processing equipment with impact resistance and certain transparency requirements. Δ br> 2. Main health problems: polycarbonate resin is non-toxic, and its oral LD50 is > 10g/kg body weight, negative mutagenicity test (a, ES test, micronucleus test and sperm abnormality test). However, when bisphenol A is exchanged with diphenyl carbonate, phenol, an intermediate, is produced. Phenol not only has certain toxicity, but also

You may also like

Leave a Comment

Soledad is the Best Newspaper and Magazine WordPress Theme with tons of options and demos ready to import. This theme is perfect for blogs and excellent for online stores, news, magazine or review sites.

Buy Soledad now!

Edtior's Picks

Latest Articles

u00a92022u00a0Soledad.u00a0All Right Reserved. Designed and Developed byu00a0Penci Design.