What is engineering plastic?

                                                What is engineering plastic?

      To define engineering plastics, you must first understand plastics and general plastics.

     Because the production of plastic is very simple, it has its unique performance, advantages and disadvantages.

    Compared with plastics, general-purpose plastics are quite different in definition, process and use.

    Definition of general-purpose plastics: People generally refer to some plastic varieties with large output, low price, wide application and wide influence as general-purpose plastics. Its connotation often changes with the development of time and technology. Important general-purpose plastics include polyethylene, polypropylene, polyvinyl chloride, polystyrene and other varieties.
    Engineering plastics can be used as engineering materials and plastics instead of metal for machine parts. Engineering plastics have excellent comprehensive properties, high rigidity, small creep, high mechanical strength, good heat resistance, good electrical insulation, can be used for a long time in harsh chemical and physical environments, and can replace metals as engineering structural materials , But the price is more expensive and the output is smaller.
    Engineering plastics can be divided into general engineering plastics and special engineering plastics. The former main varieties include polyamide, polycarbonate, polyoxymethylene, modified polyphenylene ether and thermoplastic polyester five general engineering plastics; the latter mainly refers to engineering plastics with heat resistance above 150 ℃, the main varieties are polyimide , Polyphenylene sulfide, polysulfones, aromatic polyamides, polyarylate, polyphenylester, polyaryl ether ketone, liquid crystal polymer and fluororesin, etc.
Plastics, general plastics, engineering plastics, their respective advantages and disadvantages, and scope of application!


The characteristics, advantages and disadvantages of plastics:
Material properties:
〈1〉 Chemical resistance
〈2〉 Glossy, partially transparent or translucent
〈3〉 Most of them are good insulators
〈4〉 Light weight and strong
〈5〉 Easy processing, mass production and cheap price
〈6〉 Widely used, multi-purpose, easy to color, and partly resistant to high temperature
advantage:
1. Most plastics have strong corrosion resistance and do not react with acids and alkalis.
2. Plastic manufacturing costs are low.
3. Durable, waterproof and lightweight.
4. It can be easily molded into different shapes.
5. It is a good insulator.
6. Plastics can be used to prepare fuel oil and fuel gas, which can reduce crude oil consumption.
Disadvantages:
1. When recycling waste plastics, sorting is very difficult and economically uneconomical.
2. Plastic is easy to burn and produces toxic gas when burning. For example, polystyrene produces toluene when it is burned. A small amount of this substance can cause blindness, vomiting and other symptoms. PVC burning can also produce hydrogen chloride toxic gases. In addition to burning, it is a high temperature environment that can cause plastics to decompose toxic components, such as benzene. .
3. Plastics are made from petroleum-refined products, and petroleum resources are limited.
4. Plastics will not rot for hundreds of years, thousands of years or even tens of thousands of years.
5. The heat resistance of plastics is poor and easy to age.
6. Due to its inability to degrade naturally, plastic has become the number one enemy of human beings, and has also led to the tragedy of many animal deaths. For example, monkeys, pelicans, dolphins and other animals in the zoo will accidentally swallow the No. 1 plastic bottle thrown away by tourists, and finally die painfully due to indigestion; looking at the beautiful and pure sea, walking closer, it is actually full Various kinds of plastic garbage that cannot be contained in the ocean have been found in the intestines of many dead seabird samples.

      Compared with wood, metal, cement, glass and other materials, general-purpose plastics have the following advantages and disadvantages.
advantage:

(1) It is easy to form and has high design freedom;
(2) Easy to color;
(3) The specific strength is greater than that of metal;
(4) Light weight;
(5) It is easy to modify and obtain the required performance;
(6) Good electrical insulation;
(7) Good water resistance, no corrosion;
(8) Good chemical resistance;
(9) Less energy is consumed in production than metal;
(10) As long as the waste plastics are handled properly, there will be less damage and pollution to the environment than other materials.

Disadvantages:

(1) Poor weather resistance, especially ultraviolet light resistance, easy to aging under ultraviolet light;
(2) Easily produce static electricity;
(3) Large thermal expansion coefficient and poor dimensional stability;
(4) The surface hardness is low, easy to produce scratches;
(5) Poor durability and poor resistance to environmental stress cracking.
However, with the continuous development and progress of blending technology and the achievements of high-performance general-purpose polymers, some of its shortcomings have gradually improved, broadening the application field of general-purpose plastics, making plastics more and more important in the national economy. important.