The bottom of general plastic products will be marked as above. They define the scope of use. Vessels marked with these numbers are qualified products, but if used improperly, they will become poisons.
1. PET: Polyethylene Terephthalate
It is often used to make mineral water bottles, cola beverage bottles, juice bottles, screen protection films and other transparent protection films, etc., usually colorless and transparent. Because it can only heat up to 70°C, this beverage bottle is only suitable for cold and warm drinks. It is easy to deform when it is filled with high-temperature liquids (such as hot water) or heated, and substances harmful to the human body can be dissolved; and the plastic products After 10 months of use, it may release carcinogens, which are toxic to humans.
PET can also be spun, which is what we often call polyester, so during the Olympics there is a saying that beverage bottles will be recycled to make clothes. Many sportswear pursuing breathability and lightness are made of polyester. The popular clothing material "Queenliang" was also this thing a long time ago. However, due to the backward spinning methods at that time, the clothing of Zhenliang was not as comfortable to wear as it is now. In addition, PET also has many engineering applications.
Commonly Used:
Filling mineral water, carbonated drinks, fruit juices, etc.
Advantages:
High transparency, the contents of the bottle can be seen clearly; acid and alkali resistance, can be filled with carbonated drinks; high water resistance, not easy to seep.
Note:
Non-toxic, but monomers, low-molecular-weight oligomers and side reaction products such as diethylene glycol may remain in the synthesis process. These are all toxic. The PET raw materials used in beverage bottles have strict national standards.
Plastic bottles made of PET can not be placed in the car in the sun; do not contain alcohol, oil and other substances, as harmful substances are easy to dissolve. Do not install liquids above 70°C. Excessive temperature will cause the material to decompose and release harmful chemicals.
2. HDPE: High Density Polyethylene
Suitable for loading food and medicine, cleaning supplies and bath products, shopping bags, trash cans, etc. At present, most of the plastic bags used in supermarkets and shopping malls are made of this material, which can withstand a high temperature of 110 ℃, and the plastic bags marked for food can be used to hold food. HDPE is widely used in various translucent and opaque plastic containers, and it has a thicker hand feeling.
Commonly Used:
White medicine bottles, opaque shampoo bottles, yogurt bottles, chewing gum bottles, etc.
Advantages:
It is more resistant to various corrosive solutions, and is mostly used in cleaning products, bath products, etc.
Note:
The bottles containing cleaning supplies and bath products can be reused after cleaning, but these containers are usually not cleaned, and the residual substances will become a breeding ground for bacteria. Do not recycle, especially not recommended as a container for circulating food and medicine. use.
3. PVC: Polyvinyl Chloride
PVC is now mostly used to make some cheap artificial leather, foot pads, sewer pipes, etc.; due to its good electrical properties and certain flame retardant properties, it is widely used in the manufacture of wire and cable sheaths. In addition, PVC is widely used in industrial fields, especially in places with high requirements for acid and alkali corrosion.
Commonly Used In:
Raincoat, PVC plastic line pipe, water pipe, plastic switch, socket.
Advantages:
High strength, weather resistance and good corrosion resistance.
Note:
This material can only heat up to 81°C, so it cannot be used in places with higher temperatures. A large number of plasticizers (plasticizers, such as DOP) and heat stabilizers containing heavy metals are used in the production of PVC, and it is difficult to eliminate the existence of free monomers during the synthesis process. When encountering high temperatures and grease, it is easy to precipitate toxic substances, which is easy to cause cancer. Therefore, PVC is basically replaced by PP and PE when it comes into contact with the human body, especially in medical and food applications.
4. Low-density polyethylene (LDPE)
Plastic film and cling film, paper milk cartons, beverage cartons and other packaging boxes all use it as the inner film. It is mostly used on plastic film and other utensils, not suitable for beverage containers.
Commonly Used:
Plastic wrap, plastic film, toothpaste or facial cleanser tube packaging.
Advantages:
Good ductility, widely used in life.
Note:
LDPE products will soften or even melt at higher temperatures, so please try to avoid using them at 100°C higher than the boiling water temperature. The plastic wrap will melt when the temperature exceeds 110°C. Therefore, the wrapped plastic wrap must be removed before the food is placed in the microwave.
5. Polypropylene (PP)
The microwave lunch box is made of this material, which can withstand high temperatures of 130°C and has poor transparency. This is a plastic box that can be placed in a microwave oven and can be reused after careful cleaning. PP has high hardness and shiny surface.
The scope of application of PP is also very wide, daily necessities such as packaging, toys, washbasins, buckets, hangers, water cups, bottles, etc.; engineering applications such as car bumpers. PP spun into silk is called polypropylene and is very common in textiles, non-woven fabrics, ropes, fishing nets and other products.
Commonly Used:
Disposable juices, beverage cups, plastic dinner plates, LOCK&LOCK fresh-keeping boxes, etc.
Advantages:
Good air permeability, heat-resistant temperature up to 167℃, it is a light plastic container.
Note:
If the temperature is too high, gases that are not good for the human body will still diffuse out. In addition, some microwave oven lunch boxes are made of PP, but the lid is made of No. 6 PS. Check carefully before use. If this is the case, remove the lid and heat it.
Compared with PE products, PP products have slightly better heat resistance. Typical LOCK&LOCK water cups can be used at a temperature of 110°C, but no matter how high the temperature is, there is a danger of softening and melting, and should be avoided as much as possible.
6. Polystyrene (PS)
Too high a temperature will release harmful substances. It cannot be heated in a microwave oven. Do not use it to hold hot food. It also cannot contain strong acid (if juice) and strong alkaline substances.
There are two types of foaming and unfoaming: foaming is a common foam plastic lunch box; unfoaming such as yogurt bottles; unfoaming light folds have white marks, which can usually be torn by hand.
Commonly Used:
Ice container, fast food box, cheap transparent products, foam plastic, CD box, water cup, fast food box, thermal insulation material layer, etc.
Advantages:
good transparency and heat resistance. It is often used to store high-temperature foods, such as bowls of instant noodles (now more often in paper containers). It has good cold resistance, and all kinds of shaved ice also love this container.
Note:
If PS encounters strong acid or alkaline substances, harmful substances will be produced. Be careful when using PS appliances and do not store acidic or alkaline foods. Do not use fast food boxes to pack hot food, and do not use microwave ovens to heat bowls of instant noodles.
In addition, polystyrene is flammable, especially PS after foaming. Burning will produce a lot of toxic gas. In some high-rise fire house accidents, because the widely used PS foam board is used as the insulation material, a large amount of smoke and toxic gas generated after the fire have become the main cause of a large number of casualties.
7. Polycarbonate Phenol (PC Or OTHER)
It is synthesized using bisphenol A and diphenyl carbonate as raw materials, and is often used to make kettles, drinking cups, and milk bottles. In the process of making PC, the raw material bisphenol A should completely become a structural component of the plastic and should not be released during use. However, unqualified products cannot do it. A small part of the bisphenol A cannot be completely converted into the plastic. It is released into food and is harmful to children and fetuses. (The PC baby bottle incident in 2011 started because of this.) At present, many department stores and automobile manufacturers use water cups made of this material as gifts.
Commonly Used:
It is often used for transparent water cups, baby bottles, drinking buckets, CD substrates, lenses and lampshades in daily life.
Advantages:
Good light transmission, good heat resistance and impact resistance, resistance to weak acids, weak bases, and neutral oils.
Note:
UV resistance and weather resistance are poor; the surface is not abrasion-resistant and easy to scratch; it is not resistant to strong alkalis.
8. Polyamide (PA or OTHER)
Mention another name for polyamide: nylon-everyone must be familiar with it. The polyamide family is very powerful, with many varieties, all with excellent physical and chemical properties. This is also the reason why PA is widely used in the electronics and automotive industries. In daily life, nylon ropes and nylon stockings are also common items. The spun PA fiber is called nylon and is used for fishing lines, fishing nets, ropes and conveyor belts.
Commonly Used:
Nylon rope, nylon socks; fishing line, fishing net, rope and conveyor belt, etc.
Advantages:
Nylon is non-toxic and has good heat resistance, especially heat resistance and not easy to deform, so it can even be used for the manufacture of engine parts.
Note:
Nylon has poor ventilation and is easy to generate static electricity.
9. ABS resin (acrylonitrile-butadiene-styrene copolymer) (ABS or OTHER)
There are many types of ABS, which are widely used in various electrical appliance casings, office supplies components, safety helmets, door and window pipes, etc. In the industry, ABS is often used in the blending and modification of other plastics.
Use Note:
ABS is non-toxic, but it is mostly used in structural materials, and it is rarely used in the packaging of daily utensils.
ABS has many advantages, but it still has the common characteristics of plastics: not heat resistant.
10. Blend (XX-XX alloy) (OTHER)
Because it is difficult for a single plastic to meet complex use requirements, different plastics are often mixed together in the plastics industry to make plastic alloys, which can not only take advantage of the advantages of different materials, but also save the cost of developing new materials.
Main Application:
Plastic alloys are widely used in various structural materials. For example, mobile phone shells are mostly PC-ABS alloy; some sewer pipes are made of two kinds of PE alloys in order to meet the performance and processing needs, called bimodal polyethylene.
Use Note:
Although combining the advantages of multiple plastics, the material is still plastic after all, and heat resistance is still a major disadvantage. However, in practical applications, most products will not be exposed to high temperatures. As long as you pay attention to the application environment, plastic is a good material that is cheap and suitable.