This kind of plastic is characterized by curing at a certain temperature after heating for a certain time or adding curing agent. The cured plastic is hard, insoluble in any solvent and cannot be softened again by heating. If the heating temperature is too high, it will decompose Common thermosetting plastics include bakelite, electric jade, decorative board and unsaturated polyester plastic.
2. Thermoplastics
This kind of plastic is characterized by softening by heating and hardening by cooling. Generally speaking, only physical changes occur during processing, and its chemical properties remain unchanged. The resin of this plastic is mostly formed by addition polymerization. Common thermoplastics are: nitrocellulose plastic, acetate fiber plastic, polyethylene plastic, polypropylene plastic, polystyrene plastic, polyvinyl chloride plastic and so on. For example, our common mineral water bottles, plastic bags and so on. Detailed ";
The meaning of plastic product identification and symbols China has formulated GB/T 16288-2008 "Plastic Product Identification" with reference to the material variety identification proposed and implemented by the American Plastics Association (SPE). The bottom of each plastic container has a digital sign to represent the plastic used in its manufacturing process. Therefore, the common plastic products on the market at present are generally divided into 1-7. In China, it is not mandatory to mark the plastic products with recycling marks. In order to facilitate the recycling of plastic products, some formal big brand enterprises have recently begun to mark recycling signs.
The signs of plastic products are generally triangular signs with arrows, marked with the number 1 ~ 7. First of all, the "triangle" is a symbol of plastic recycling. At present, China adopts the triangle symbol as the symbol of plastic recycling. Secondly, there are 1-7 numbers in the triangle, and each number represents a different material. However, the application scope and requirements of each plastic are very different. If it is less than "05", that is, "04" and below, or even without numbers, please do not reuse or heat it, because it will release harmful chemicals and cause cancer. Detailed ";
Safety grade of plastic products "1" polyester
Scope of application: common mineral water bottles, pure water buckets, carbonated beverage bottles, etc. Heat-resistant to 65℃ and cold-resistant to -20℃, only suitable for warm drinks or frozen drinks.
"No.2" HDPE high density polyethylene
Scope of application: common white medicine bottles, cleaning products, bath products, etc.
"No.3" PVC PVC
Scope of application: ordinary raincoats, building materials, plastic films, plastic boxes, etc. This material has excellent plasticity and low price, so it is widely used.
"No.4" low density polyethylene
Scope of application: Generally speaking, pe polyethylene, common plastic wrap, plastic film, etc.
"No.5" polypropylene
Scope of application: ordinary soybean milk bottles, sour milk bottles, fruit juice bottles, microwave lunch boxes.
"No.6" polystyrene
Scope of application: common bowls of instant noodles, fast food boxes, etc.
"No.7" PC other plastics
Scope of application: common kettles, water cups and milk bottles. Water cups made of this material are often used as gifts in department stores. Detailed ";
Advantages and disadvantages of plastic products 1, light weight.
Plastic is a light material with a relative density of 0.90-2.2. Obviously, can plastic float to the surface? In particular, foamed plastics are lighter because of their micropores, and their relative density is only 0.0 1. This feature enables plastics to be used to produce products that need to be reduced in weight.
2, excellent chemical stability
Most plastics have good corrosion resistance to chemicals such as acid and alkali. In particular, polytetrafluoroethylene (F4), often called the king of plastics, has even better chemical stability than gold, and will not deteriorate even if it is boiled in aqua regia for more than ten hours. F4 is an ideal corrosion-resistant material because it has good chemical stability.
3. Excellent electrical insulation performance
Ordinary plastic is a poor conductor of electricity, and its surface resistance and volume resistance are very large, which can reach 109- 10 18 ohm in digital terms. The breakdown voltage is large and the dielectric loss tangent is small. Therefore, plastics are widely used in electronic industry and mechanical industry. Such as plastic insulated control cables.
4, thermal poor conductor, with noise and shock absorption.
Generally speaking, the thermal conductivity of plastics is relatively low, which is equivalent to 1/75- 1/225 of steel. The micropores of foamed plastics contain gas, which has better heat insulation, sound insulation and impact resistance. For example, the thermal conductivity of PVC is only 1/357 for steel and11250 for aluminum. In terms of thermal insulation capacity, single-layer glass-plastic window is 40% higher than single-layer glass-aluminum window and double-layer glass is 50% higher.
5. The mechanical strength is widely distributed and the specific strength is high.
Some plastics are as hard as stone and steel, while others are as soft as paper and leather. From the mechanical properties of plastics, such as hardness, tensile strength, elongation and impact strength, it has a wide range of distribution and great use choices. Because of its low specific gravity and high strength, plastics have high specific strength.
Compared with other materials, plastics also have obvious disadvantages, such as easy combustion, lower rigidity than metals, poor aging resistance and heat resistance. Detailed ";
How to buy plastic products 1 and plastic bottles?
Common plastic bottles include mineral water bottles, carbonated beverage bottles and fruit juice bottles. No matter what raw materials you choose to make plastic bottles, you must first meet the requirements of non-toxic and tasteless, and these drinks mainly use polyester bottles made of PET plastic. If the bottle is not very bright and thorough, and the texture is particularly uneven, it is likely to be made of recycled waste.
2, plastic tableware purchase points
Melamine plastic is recommended for plastic tableware. It looks and feels like porcelain, which is acid and alkali resistant, high in hardness, impact resistant and long in service life. It can be cleaned and disinfected in a dishwasher below 120℃. You should buy melamine tableware produced by authentic factories in regular stores.
3. The main points of buying plastic bags
First of all, it depends on whether there is a "food use" sign on the appearance of plastic bags. Usually this sign should be placed on the front of the packaging bag, in a more eye-catching position; Second, look at the color. Generally speaking, the color of colored plastic bags is a colorant that is soluble in oil and harmful to human body. Finally, it depends on whether there are impurities in the plastic bag. Put the plastic bag in the sun or light to see if there are black spots and holes. The plastic bag with impurities must be made of waste plastic.
4, plastic wrap shopping points
See if it has a product description. If it is covered with pe plastic wrap or polyethylene plastic wrap, it can be used safely. If it says pvc or no material, try not to buy it. Polyethylene cling film is generally poor in viscosity and transparency, and it is easy to open after being rubbed by hand, while PVC cling film is good in transparency and viscosity, and it is not easy to spread and stick to hands after being rubbed by hand. Detailed ";
5. Key points of buying plastic toys
When buying toys, you must choose qualified products. Plastic toys made of inferior materials are harmful to the baby's health. High-quality plastic toys are usually made of PVC, PP, PE and other plastic raw materials, with bright colors; In addition, we should also be optimistic about 3C certification and toy label instructions. Manufacturer, place of origin, main material composition, warning slogan, product certificate and other labels. You should also check it. More precautions for purchasing ordinary plastic products ";
How to distinguish the advantages and disadvantages of plastic products 1, vision
Transparent and colorless goods look very transparent, and products without impurities are of good quality (mostly produced by original granular materials), such as fresh-keeping bags, cups, lunch boxes and fresh-keeping boxes.
Commodities with low transparency or many impurities are of poor quality (mostly made of raw flour) such as sorting boxes, pots, hangers and stools.
Opaque goods are mostly inferior goods (mostly produced by recycled materials, but recycled materials can be divided into many kinds, such as recycled materials produced by manufacturers and goods returned by dealers to manufacturers), such as trash cans, trash can liners and garbage bags.
Step 2 smell
It smells very light, but it has a faint plastic smell, mostly for better quality goods; The smell of plastic is very strong, and most of them are goods with slightly poor quality; The smell of plastic is very strong, and it has a pungent smell, mostly inferior goods.
Step 3 feel
Touch the edge of the goods, there is no feeling of pricking hands, the edge is cleaner, the mold is better, and the burr is better; It hurts hands to the touch, and the edge is rough, mainly because the mold is not good. Detailed ";
What are the hazards of plastic products? 1. Plastic products have low recycling value. In the process of use, plastic products are not only scattered in urban streets, tourist areas, water bodies, highways and railways, but also have potential hazards. Plastic has a stable structure, is not easily degraded by natural microorganisms, and does not separate in the natural environment for a long time. This means that if the waste plastic garbage is not recycled, it will become a pollutant in the environment, exist permanently and accumulate continuously, causing great harm to the environment.
It will affect the development of agriculture. Waste plastic products will accumulate in the soil, which will affect the absorption of nutrients and water by crops and lead to crop yield reduction.
3. Waste plastic products that pose a threat to the survival of animals and are abandoned on land or in water are swallowed by animals as food, resulting in the death of animals. Last year, 20 herdsmen killed nearly 1,000 sheep in Qinghai Lake, and the economic loss was about 300,000 yuan. Sheep like to eat oily residues wrapped in plastic products, but they often eat together. Because the plastic they eat is difficult to digest in their stomachs for a long time, their stomachs are so crowded that they can't eat any more, and finally they can only starve to death. Such things are common in zoos, pastoral areas, rural areas and oceans.
4. Waste plastics occupying land resources will not only occupy a lot of land for landfill, but also the occupied land will not be restored for a long time, which will affect the sustainable use of land. Waste plastic products entering domestic garbage will not degrade for 200 years if they are buried. It is very harmful to the land, changing its pH value will affect the absorption of nutrients and water by crops, resulting in reduced agricultural production. As for plastic products abandoned in water or land, it not only affects the environment, but also leads to death if swallowed passively. This destroys the ecological balance.
Toxic substances will decompose at high temperature. Plastic products are not toxic substances, but because of their imperfect recycling equipment, simple process and many manufacturers without legal business licenses, when the temperature reaches 65℃, toxic substances will precipitate and penetrate into food, causing harm to important parts of human body such as liver, kidney, reproductive system and central nervous system. Detailed ";
Plastic household goods brand 1, every holiday, is the time for online shoppers to show their talents, but they don't know how to start with a wide variety of goods and uneven prices.
Every holiday, it is the time for online shoppers to show their talents, but in the face of dazzling goods and uneven prices, they don't know how to start.
Industry recommended brand Lock &；; Lock Lock Lock Tupperware Camellia Flower Arrangement Clever Iris Alice Beauty Ya Maria Revitalization Li Taixi Tianlong Chenglong Recommended Reading 1. Every holiday is the time when online shoppers show their talents. However, faced with all kinds of goods and uneven prices, they don't know how to start.
Every holiday, it is the time for online shoppers to show their talents, but in the face of dazzling goods and uneven prices, they don't know how to start.
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