Basic Knowledge of Plastics Chapter 1

Plastic production:

Plastic, also known as synthetic resin, is produced and extracted from petroleum and decomposed into raw materials such as ethylene, propylene... and other raw materials. After polymerization and purification, plasticizers, lubricants, dyes or fillers are added to obtain various plastic raw materials, which are usually in granular form for ease of use.

Key features:

①Good impact resistance;

②Has good transparency and abrasion resistance;

③Most plastics are lightweight, have good chemical stability and do not rust;

④Good insulation and low thermal conductivity;

⑤Good overall formability and paintability, low processing cost;

⑥Most plastics have poor heat resistance, high thermal expansion, and are flammable;

⑦Poor dimensional stability, easy to deform;

⑧Most plastics have poor low temperature resistance and become brittle at low temperatures;

⑨Aging easily;

⑩Some plastics dissolve easily in solvents

Coloring of plastic materials:

The plastic products we usually use are multi-colored, so how can plastic be dyed?

A. Pellet Transfer: The color of plastic is evenly distributed over each rubber compound. It is supplier of material who mixes colorant with rubber compound during production of material. granulator, its advantage is that color and color difference of material is well controlled, but relative cost of material is too high.

B. Toner Material: Mixes toner with raw material according to pre-calculated ratio. Before use, material and raw materials are evenly mixed with a mixer. . The benefits and costs are relatively low, there is no need to save a lot of raw materials. Disadvantages: uncomfortable, color is unstable, and difficult to control.

C. Dye concentrate: Dye concentrate is mixed with raw materials in proportion, mostly black, or products with low color requirements.

Fire resistance class of plastic materials:

The biggest disadvantage of plastic is that it is highly flammable because it is recycled from petroleum, but some compounds can be added to make it flame retardant. The addition of chlorine is commonly used to make plastic flame retardant. , V2, etc.

V0: When plastic is ignited by a fire, it immediately goes out when it leaves fire.

Option 2: When plastic is ignited by a fire, it will automatically go out within two seconds of leaving fire.

Advantages and disadvantages of plastic:

Advantages - light and strong, cheap, easy to produce in large quantities

In terms of synthesis, molding and transportation, plastic consumes less energy than any othermaterial, and its biggest advantage is that it is easy to shape and process.

Purpose of using plastic:

Reduce material costs - because resources are plentiful and cheap, but they need to be used in most appropriate place.

Reducing recycling costs - Plastics are suitable for mass production, and processing technology can be simplified or even automated. In addition, most plastics can be finished in a single process without painting or modification. , Therefore, investment in equipment. The amount can be reduced, and processing should take into account greatest possible reduction in labor costs.

Less Weight - The specific gravity is only one-eighth that of iron. The reduced part can be used to improve performance.

Avoid rust or corrosion - plastic will not have corrosion and rust problems because it does not need anti-corrosion treatment, it can avoid electroplating, painting and other processes, which reduces number of jobs . However, waste will not rot, so its disposal requires some effort.

Achieve perfect shape - can be turned into sheet metal, shapes or characteristics that cannot be obtained by stamping.

The shape and appearance of Shili Lixiang are bright colors, usually do not need to be painted. The shape is great, you can implement beautiful styles.

Good thermal insulation - can be used for keeping warm, keeping cold and other purposes.

Good electrical isolation - no need to worry about inductance or short circuits. Most of high frequency performance is good.

Plastic disadvantages and precautions:

◎The accuracy is slightly worse - expansion coefficient is large, usually one digit more than that of metals. In addition, some plastics warp or warp due to moisture or long-term deformation.

◎The heat resistance is generally not good - high temperature resistance is poor, usually not more than 100 degrees.

◎Flammability. Most of them are highly flammable. Some plastics release toxic gases when burned. When burned, they tend to give off black smoke or corrosive gases, or too much heat, which can easily damage incinerator.

◎Insufficient strength. Apart from commonly mentioned tensile strength, there are actually many problems caused by insufficient stiffness. Hardness is usually two numbers less than metal.

◎Solvent resistance, poor oil resistance - some dissolve or crack, especially when oil stained under load, some develop stress cracks

◎Wear (aging). Plastic deteriorates under influence of ultransviolet rays, heat, steam and chemicals.

◎No EMI protection - volume resistance is typically 1015, antistatic level is 107, conduction level is 100, and special EMI protection level is 10-2