Do you know the difference of PP PE PS PA ABS PVC?
In daily life, more than 70% of daily necessities are plastic products. Among them, the main plastic materials are PP, PS, PA, PC, PE, ABS, and PVC. If you want to distinguish them, you must know them. Characteristics and differences, before understanding them, we must first understand what thermosets and thermoplastics are.
Thermosetting plastics are plastics that need to be heated to be cured during processing and forming. Two different plastics are mixed and injected into the mold at the same time. After the heating causes a reaction, a single molecule becomes a three-dimensional network structure, that is, it will be heated after heating. Hardened plastic has the advantage of high heat resistance, but the disadvantage is that it is not easy to recycle and reuse. Thermosetting plastics include FRP bathtubs and tableware.
Thermoplastics are plastics that will melt after heating. The solid plastic particles are heated and injected into the mold after the plastic is melted. After the finished product is cooled and solidified, the product is completed. The advantage is that the product can be recycled, but the disadvantage is that it is not. Heat-resistant, thermoplastic plastics include PE, PP, PS, PVC, ABS, PA, PC, etc.
Each of us has our own ID card, which can distinguish everyone's identity. Can plastic also be distinguished? After purchasing a plastic product, if you observe carefully, you will see a serial number on the outer shell of the product. This is to distinguish the types of plastics and develop a plastic identification code. This identification code is universal in the world. The triangle composed of three clockwise rotating arrows is marked with a number representing each material in the middle. There are currently 7 types of identification codes. In addition to allowing us to recognize plastic materials through coding, these identification codes also assist in recycling, which can subdivide types and Reuse.
PET (polyester) is code number 1, also called polyester resin. The raw material is milky white or light yellow, with good transparency, non-toxic, high density, high hardness, abrasion resistance, but it is not resistant to heat and water intrusion and alkali. Features: The operating temperature is 65°C~-20°C. It is easy to release harmful substances above this temperature and cannot be used repeatedly for a long time. It is mainly used for beverage bottles, mineral water bottles in packaging materials, housings and accessories in electronic appliances.
HDPE (high-density polyethylene) code 2, also called low-pressure ethylene, the raw material is white, non-toxic and odorless, has the characteristics of low density, good toughness, acid and alkali resistance, but poor anti-aging performance. It is difficult to clean and do not recycle. Used for detergent packaging bottles, wire and cable sheaths, etc.
PVC (polyvinyl chloride) code number 3, also called attached film, the raw material is yellow and translucent, good transparency, high strength, good flexibility, not easy to be brittle, etc. PVC is soft and hard, and the difference between them depends on the difference. Whether softening agent is added, PVC itself is not toxic, if plasticizer, antioxidant, etc. are added, it will become toxic, so soft PVC is not toxic, rigid PVC is toxic, mainly used in packaging materials, pipelines in the building materials industry , Doors and windows, etc.
LDPE (low-density polyethylene) code 4, also known as high-pressure polyethylene, the raw material is milky white, odorless, non-toxic, with good transparency, good flexibility, alkali resistance, but not good heat resistance. The density is all poly The lowest of ethylene, it will melt to release toxic substances when it exceeds 110℃, and it is mainly used for cling film and plastic film.
PP (polypropylene) code number 5, also called Baizhe glue, with low density, transparent and light appearance of raw materials, non-toxic and tasteless, high strength and flexibility, chemical resistance, impact resistance, high temperature resistance of 100 to 120 degrees Celsius, and can be put Heat in a microwave oven, but it is prohibited to use recycled products to hold food. Commonly used in plastic lunch boxes, water cups, food packaging boxes and other products are made of PP material. Because of these characteristics of PP, Australian currency is made of this plastic .
PS (polystyrene) code number 6, also called hard rubber, the hardness will be higher than PP, the raw material has high transmittance, colorless and tasteless, easy to dye, but the toughness is poor, easy to be brittle, the temperature exceeds 70 ℃ will release harmful Substances are commonly used in disposable foam lunch boxes, packaging linings, and decoration materials. Because they are not easy to recycle, they are now gradually replaced with paper materials.
PA (polyamide) is also called nylon. It has no code. The raw material is non-toxic and odorless. It has good toughness, abrasion resistance, heat resistance, and chemical resistance. There are many varieties of PA plastics. Especially now by mixing various fiber materials, PA The various properties of plastics have been significantly improved, and they have replaced some metals, and are widely used in the fields of auto parts, housings of household appliances, and protective equipment.
ABS plastic does not have a code. It is a composite of acrylonitrile (A), butadiene (B), and styrene (C), which is also called ABS resin. Therefore, ABS also has the common properties of these three substances. Impact resistance, heat resistance, low temperature resistance, good overall performance, low price, wide range of uses, ABS plastic is non-toxic, odorless, and translucent or transparent in appearance. Many parts in automobiles are made of ABS plastic. In household appliances , The parts on the office machine are also made of ABS.
Other types, code number 7, including acrylic, polycarbonate, polylactic acid, etc. The characteristics of these plastics are that they cannot be heated in a microwave oven, cannot be sterilized by high temperature, and cannot be directly exposed to the sun, because this may release bisphenol A and cause harm to the human body. Wait.
In fact, the development of plastics to the present is far more than the above. Various synthetic plastics make people feel confused in an instant. You may have heard that PBT (collectively called thermoplastic polyester together with PET), HIPS (impact resistant polystyrene) Ethylene, which is often referred to as engineering plastics), POM (polyoxymethylene thermoplastic crystalline polymer), EVA (copolymerization of ethylene and acetic acid), etc., etc., there are too many, so I won’t give an example here.
You will find that there are still many plastic products that do not have an identification code. How can we know what plastic material they are? In addition to the use of professional instruments for analysis, there are also relatively simple identification methods. Of course, this method is only a reference and cannot completely determine the type of plastic.
Buoyancy test is to distinguish the material according to the density of the plastic. At present, the common plastics on the market will have a density of 0.9~2.0g/cm without adding other ingredients, and the density of water will be exactly 1g/cm. Among the common plastics, only the density of PP and PE is less than 1.0, so the ones that can float on the water surface are PP and PE. Other plastic materials will sink to the bottom because the density is greater than water.
Combustion test, if you want to distinguish various plastic materials more clearly, you can distinguish by burning. The burning test is to burn various plastics and observe the characteristics and changes in the process to judge the plastics. The materials, the observed states are the state away from the fire source, the burning smell, the color of the flame, the state after burning, the degree of flammability, and the burning test is based on the conclusions of the special effects of plastics, and cannot be used as a science to distinguish plastics. in accordance with.
PET burns and emits black smoke, with a sour taste
PP can burn all the time, the flame is yellow up and blue down, with the smell of candles
PS can also burn all the time, the flame is yellow and black smoke, there is carbon dust after burning, there is pine oil smell
After being ignited, ABS can continue to burn quickly, and the flame is yellow and black smoke, which softens without dripping after burning, and has a strong rubber smell
PC is more difficult to burn, and the fire will be extinguished when taken away. The flame is a small amount of black smoke, which softens and foams after burning, and has no special smell;
The flame of PE is yellow up and down blue. After burning, it softens and drips, and there is a burning smell of paraffin; (Have you burned plastic bags when you were a child? Didn't you forget the feeling of dripping? Do you remember the pain when dripping on your hands? ?)
PA is not easy to burn, it will be extinguished when it leaves the fire source. The flame is yellowish grayish white smoke, blistering and dripping after burning, with the smell of sheepskin and nails;
PVC is not easy to burn, it will go out when you leave the fire source. The flame is blue and green and smokey. It is difficult to soften after burning and has a pungent sour taste; (the shrink film on the packaging, the harder one is PCV)