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

What we usually call plastic is the plastic products in life, such as plastic cups, plastic toys, and plastic furniture. Scientific definition of plastics: Plastics are macromolecules, commonly known as plastics or resin, which are polymerized by addition polymerization or polycondensation reaction with monomer as raw material. They can freely change the composition and shape style, and are composed of synthetic resin and fillers, plasticizers, stabilizers, lubricants, pigments and other additives.

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

General purpose plastics are quite different from plastics in terms of definition, process and use.

Definition of general plastics: some kinds of plastics with large output, low price, wide use and wide influence are customarily called general plastics. Its connotation often changes with the times and the development of science and technology. Important general plastics include polyethylene, polypropylene, polyvinyl chloride, polystyrene and other varieties.

Engineering plastics can be used as engineering materials and plastics instead of metal to make machine parts. Engineering plastics have excellent comprehensive properties, such as high rigidity, low creep, high mechanical strength, good heat resistance, and good electrical insulation. They can be used for a long time in harsh chemical and physical environments, and can replace metal as engineering structural materials. However, they are expensive and have small output.

Engineering plastics can also be divided into general engineering plastics and special engineering plastics. The main varieties of the former include polyamide, polycarbonate, polyoxymethylene, modified polyphenylene ether and thermoplastic polyester; The latter mainly refers to engineering plastics with heat resistance above 150 ℃. The main varieties include polyimide, polyphenylene sulfide, polysulfone, aromatic polyamide, polyaryl ester, polyphenyl ester, polyaryl ether ketone, liquid crystal polymer and fluorine resin.

Plastics, general plastics, engineering plastics, their advantages and disadvantages, as well as the scope of application!

Features, advantages and disadvantages of plastics:

Material properties:

Chemical corrosion resistance

(2) Glossy, partially transparent or translucent

(3) Most of them are good insulators

Light and solid

Easy processing, mass production and low price

(6) Wide range of uses, multiple effects, easy coloring, and partial high temperature resistance

advantage:

1. Most plastics have strong corrosion resistance and do not react with acids and alkalis.

2. Low plastic manufacturing cost.

3. Durable, waterproof and light.

4. It is easy to be 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 the consumption of crude oil.

Disadvantages:

1. When recycling waste plastics, it is very difficult to classify, and it is not economical.

2. Plastic is easy to burn and produces toxic gas when burning. For example, toluene is produced when polystyrene is burned. A small amount of this substance can cause blindness, vomiting and other symptoms when inhaled. PVC combustion can also produce hydrogen chloride toxic gas. In addition to combustion, it is a high-temperature environment, which can cause the plastic to decompose into toxic components, such as benzene.

3. Plastics are made from petroleum refining products, and petroleum resources are limited.

4. Plastic will not decay after being buried underground for hundreds, thousands or even tens of thousands of years.

5. The heat resistance of plastics is poor and easy to age.

6. Due to the non natural degradability of plastic, it has become the No. 1 enemy of human di and has led to the tragedy of many animal deaths. For example, monkeys, pelicans, dolphins and other animals in the zoo will swallow the No. 1 plastic bottle thrown by tourists by mistake. Zui will die painfully after indigestion; Looking at the beautiful and pure sea surface, I came closer to see that there were various kinds of plastic garbage that could not be contained by the sea. In the intestines of several dead seabirds, I found various kinds of plastic that could not be digested.

Compared with wood, metal, cement, glass and other materials, general plastic has the following advantages and disadvantages.

advantage:

(1) Easy to shape, high design freedom;

(2) Easy to color;

(3) The specific strength is greater than that of metal;

(4) Light specific gravity;

(5) It is easy to modify and obtain the required performance;

(6) Good electrical insulation;

(7) Good water resistance, no rust;

(8) Good chemical resistance;

(9) The energy consumed in production is less than that of metal;

(10) As long as the waste plastics are treated well, the damage and pollution to the environment will be less than other materials.

Disadvantages:

(1) Poor weather resistance, especially poor UV light resistance, easy to age under UV light;

(2) It is easy to generate static electricity;

(3) Large thermal expansion coefficient, poor dimensional stability;

(4) Low surface hardness, easy to scratch;

(5) Poor durability and environmental stress cracking resistance.

However, with the continuous development and progress of blending technology, as well as the achievements made in the high-performance of general-purpose polymers, some of its shortcomings have been gradually improved, which has widened the application field of general-purpose plastics, making plastics more and more important in the national economy.

The performance characteristics of engineering plastics mainly include:

(1) Compared with general plastics, it has excellent heat resistance and cold resistance, excellent mechanical properties in a wide range of temperatures, and is suitable for use as structural materials;

(2) Good corrosion resistance, less affected by the environment, and good durability;

(3) Compared with metal materials, it is easy to process, has high production efficiency, and can simplify procedures and save costs;

(4) Good dimensional stability and electrical insulation;

(5) Light weight, high specific strength, and outstanding antifriction and wear resistance.