Brief introduction of plastics

Directory 1 Pinyin 2 English Reference 3 Overview 4 Invention of Plastics 5 Classification of Plastics 6 Application of Plastics 7 Effects of Plastics on Health 1 Pinyin Liao Si

2 English Reference Plastics [2 1 Century Bilingual Dictionary of Science and Technology]

Plastics [2 1 Century English-Chinese Dictionary]

Plastic materials [Xiangya Medical Dictionary]

Plastic body [Xiangya Medical Dictionary]

Overview Plastic is a synthetic polymer material that can be molded at a certain temperature and pressure, also known as polymer, which is a material generated by synthesis or polymerization of monomer raw materials. Synthetic polymers are thermoplastic and thermosetting, so plastics can be divided into thermoplastic and thermosetting plastics. Thermoplastics are mostly linear polymers and thermosetting plastics are bulk polymers.

4 the invention of plastics 1872, German chemist Adolf? Feng? Bayer found in the experiment that there was a stubborn residue at the bottom of the test tube after the reaction of phenol and formaldehyde. Because Bayer's research purpose at that time focused on synthetic dyes, he didn't realize that this viscous insoluble substance would open a new era of human synthetic materials. From 1904, American Belgian scientist Leo? Hendrick? Baekeland began to study this chemical reaction. Three years later, he got a paste, which was molded into translucent hard plastic phenolic plastic. On July 4th, 1907, Baekeland registered the invention patent of phenolic plastics.

5 Classification of plastics According to their uses, physical and chemical characteristics and processing methods, there are many kinds of plastics. If plastics are classified according to their properties and uses, they can be divided into general plastics, engineering plastics, special plastics and reinforced plastics. Generally speaking, the plastics we usually use are not a single substance, including basic components such as high molecular polymer or synthetic resin, and various additives to improve the properties of plastics, such as fillers, plasticizers, lubricants, stabilizers, colorants and so on.

6 Application of Plastics Because plastics have the advantages of corrosion resistance, good insulation, light and firm weight, low price, strong plasticity and easy coloring, they are widely used in people's daily work and life. Nowadays, plastic products have developed into a huge series of products, which are used in automobile, aerospace, construction, communication, packaging materials, agricultural films, pharmaceutical products, various pipes, plastic doors and windows, building plates, artificial leather, food and drinking water packaging, tableware and other fields. Plastic has become an indispensable basic material in people's daily work and life.

General plastics have large output, wide uses and low prices, among which polyethylene, polyvinyl chloride, polypropylene and polystyrene account for about 80% of all plastics output, especially polyethylene.

There are many kinds of plastics, and the main plastic varieties related to food involve:

Polyethylene plastic (PE) is used to produce food bags and plastic packaging.

Polypropylene plastic (PP) is used to produce microwave lunch boxes;

Polyethylene terephthalate (PET) is used to produce mineral water bottles and beverage bottles.

Polycarbonate resin (PC) is used to produce kettles, cups and bottles.

Polystyrene plastic (PS) is used to produce fast food boxes and barreled instant noodle boxes.

With the improvement of modern science and technology and people's demand for their own health, people gradually realize that plastics in close contact with people bring convenience to life, while the migration of harmful monomers and various molecular substances in plastic components and additives may also bring potential harm. Especially in the field of food hygiene, problems such as cancer-causing plastic wrap, cancer-causing lunch boxes, recycled polycarbonate plastic processing drinking water barrels, heavy metal migration in tableware, and excessive microorganisms, especially the social hot issues such as bisphenol A in children's bottles, plasticizer for sports drinks in Taiwan Province Province, and "excessive plasticizer" in alcoholic liquor, make people question the safety of plastic materials, which leads to the sigh of what to eat and use! But in terms of the application scope and scale of plastics around us today, it plays an indispensable and important role.

Will plastics bring disaster to mankind? Plastic was invented by human beings. Can't the safe application of plastics be controlled by humans? At present, the development of social economy is always faced with the confusion of economic growth and environmental pollution. Plastic was invented by human beings. By effectively controlling its basic ingredients and additives, human beings may obtain the protection of basic health rights and interests.

On1October 26th, the Ministry of Health promulgated China's Administrative Measures on Plastic Products and Raw Materials for Food, 1990, 165438, covering all kinds of plastic tableware, containers, production pipelines, conveyor belts and packaging materials. And all additives used. The management measures require that synthetic resin and processed plastic products should meet their own hygiene standards and can only leave the factory after passing the inspection; Plastic products for food must be printed with the words "for food" in a conspicuous position.

The migration of monomer, the basic component of plastics, is related to human health. The molecular chains of some thermosetting plastics are crosslinked when heated, but they will not soften when heated after molding, and monomer migration will not occur under normal use conditions, so they can be used in food containers and food packaging materials.

Polyethylene terephthalate plastic is used as the material of mineral water bottles and carbonated beverage bottles, with heat resistance of 65℃ and cold resistance of 20℃. Suitable for filling warm drinks or normal temperature drinks, which are easy to deform when heated. It has been reported that the beverage bottle may release plasticizer after continuous use for 65,438+00 months, so it is not suitable for use as a water container. There are reports on the Internet that bottled water exposed in the car will produce harmful substances such as plasticizers. However, in recent years, domestic related studies have confirmed that there is no plasticizer precipitation after the bottled water with complete packaging is exposed to the car for 7 days.

The total number of colonies did not change significantly. However, if it is bottled water that has been opened for drinking, it will easily lead to the growth of bacteria at high temperature due to the entry of external bacteria.

Polyethylene and polypropylene have low boiling points and are volatile, so there is generally no problem of residue. Food-grade low-density polyethylene is safe for food packaging such as plastic wrap at room temperature, but if the temperature exceeds 1 10℃, it will melt and may precipitate harmful substances. Moreover, food is wrapped and heated with plastic wrap, and the grease in food is easy to dissolve harmful substances in plastic wrap; So to heat food in a microwave oven, you need to take off the plastic wrap first. Polypropylene microwave lunch box is the only plastic box that can be heated by microwave oven. It is necessary to pay attention to some microwave lunch boxes. The box body is made of polypropylene, but the cover is made of polyethylene terephthalate (PET). Because PET can't withstand high temperature, it can't be heated in the microwave oven with the box.

The softening or melting range of PVC is only 7590 degrees Celsius. In contact with the fat in food or at high temperature, vinyl chloride monomer may be precipitated, which will have adverse effects on human nervous system, liver and vascular system at a certain dose, and vinyl chloride has a clear carcinogenic effect. Therefore, PVC plastics can't usually be used for food packaging. Codex Alimentarius Commission (CAC) stipulates that vinyl chloride monomer in food packaging materials should be ≤ 1.0mg/kg.

At present, the world produces 27 million tons of plastics containing bisphenol A every year. 65438-0992, foreign researchers found that bisphenol A has a weak estrogen-like effect on mammals, and the environmental and health effects of related products have attracted widespread attention.

Bisphenol A(BPA), also known as 2,2 bis (p-hydroxyphenyl) propane, is the raw material for making polycarbonate, epoxy resin and other materials. BPA can make plastic products colorless, transparent, light and durable, so it is widely used in the production of food packaging materials, tableware, baby products and other products.

Due to the wide application of bisphenol A, a large number of products containing bisphenol A enter people's living space, and the residual bisphenol A in the products can migrate to food, water or air and enter the human body through various channels.

Domestic researchers found that after 7 weeks of subcutaneous injection of bisphenol A2040ug/kg, it caused irreversible damage to the testis of mice, affected the diameter of testicular convoluted tubule and spermatogenesis of mice, and led to a decrease in the number of mice. Related animal experiments have found that bisphenol A can imitate estrogen, and low-dose exposure can also make female animals precocious. Foreign researchers surveyed people over 6 years old and found that 93% of the subjects contained BPA in their urine, as well as BPA in breast milk, pregnant women's blood and umbilical cord blood.

Although medical research is controversial about whether dietary exposure of bisphenol A causes health hazards, some countries have begun to restrict the use of plastic products containing bisphenol A, considering the risk discovery of animal experiments and the uncertainty of low-dose exposure effect. According to the regulations of the relevant departments of the European Union, from March of 1 1, the use of bisphenol A in polycarbonate bottles for infants under 1 is prohibited; The migration limit of other food-related materials bisphenol A is 0.6mg/kg. At present, Japan's Food Hygiene Law stipulates that the migration limit of bisphenol A in polycarbonate food containers is 2.5mg/kg. China's GB 14942 1994 "Hygienic Standard for Polycarbonate Molded Products for Food Container Packaging Materials" stipulates that phenol in resin materials and molded products is 0.05 mg/L. Six departments, including the Ministry of Health, issued an announcement on April 20, 201year, requiring that it be released from 20/KLOC.

Plasticizer usually refers to phthalate esters, which is the general name of about 30 esters formed by phthalic acid. It is a colorless and transparent oily liquid at room temperature, insoluble in water, soluble in various organic solvents such as methanol, ethanol and ether. Phthalates can be absorbed by human body through respiratory tract, digestive tract and skin.

Since the 1930s, phthalates have been widely used as plasticizers for plastics, as well as as as raw materials for pesticide carriers, insect repellents, cosmetics, lubricants and detergents. In the past, it was always considered that the production and use of phthalate esters were low in toxicity and unrestricted. In developed countries such as Europe, America and Japan,

Each person consumes as much as 5060 kilograms of plastic every year. In all kinds of plastic products, especially PVC plastic products, in order to increase the plasticity and strength of plastics, it is necessary to add phthalate esters, the content of which can sometimes reach 50% of the products.

The compatibility between phthalate esters and plastic molecules is very good, but there is no tight chemical bond between them, and they maintain an independent chemical structure. Therefore, when plastic products come into contact with water and fat in food, the phthalates in them will be dissolved.

The acute toxicity of phthalates is very low, and there are differences among animal species, among which the oral lethal dose of DEHP rats is as high as 30 ~ 34 g/kg. Chinese scholars ingested DEHP with concentrations of 250 mg/L, 500 mg/L, 1000 mg/L and 2000 mg/L for 60 days, and the organ coefficients of male and female mice were abnormal to varying degrees. Since 198 1 first reported that DEHP may induce rodent tumors, there have been more and more literatures about its genotoxicity. Mammalian experiments show that high dose DEHP (1000mg/kg, 2000mg/kg) can cause micronucleus formation and chromosome aberration of polychromatic erythrocytes in mouse bone marrow.

Although phthalates are widely distributed in the environment, the actual exposure of people is much lower than that of experimental animals. Up to now, people still lack a thorough understanding of the mechanism of various biotoxicity caused by phthalates, but with people's increasing concern about health and environmental problems, it is an inevitable trend for plastic products to develop in the direction of non-toxicity and environmental protection. In June 5438+February 65438+April 2005, the European Parliament and the Council of the European Union issued the directive 2005/84/EC, stipulating that the contents of 2- ethylhexyl phthalate (DEHP), dibutyl phthalate (DBP) and butyl benzyl phthalate (BBP) in children's toys and child care products should not exceed 0. In China's national standard "Hygienic Standard for the Use of Additives for Food Containers and Packaging Materials" GB96852008, eight kinds of phthalate plasticizers are allowed to be used, and restrictions such as the variety, maximum dosage and specific migration of food containers and packaging materials are stipulated.

It is reported that nearly 15% couples of childbearing age in the world suffer from infertility, and about 70% of them are from men. In the past 50 years, the number of human beings has dropped by almost 50%.

The word "environmental hormone" is 1996, which was written by a reporter from Boston Environment. Da Manovski's book The Stolen Future was first proposed. Since the 1930s, estrogen has been produced by synthetic methods and used as medicine, detergent and printing and dyeing agent. Over the years, when the progress of science and technology has brought material civilization to mankind, people have discovered some hormones that exist in vitro and are widely used in agricultural production and people's daily life. While gaining temporary benefits, they also bear great risks.