1. What is plastic
Plastic consists of polymer synthetic resin as main raw material and a certain amount of additives.
Synthetic resins are among them, as opposed to natural resins. (eg sticky resin of pine bark, tree fat) Synthetic resin is a high molecular weight compound resulting from polymerization of monomers.
For example, polyethylene: from ethylene at 100 MPa and 200 °C, double bonds of molecule open and recombine, forming long carbon single bonds to form polyethylene, as shown in figure below.
2. Plastic composition
Fillers: reduce resin content, change properties. For example, calcium, toner, fiberglass, carbon fiber, etc.
Plasticizer: Increases fluidity, ductility and other molding properties, but reduces strength.
Dyes: color change
Lubrication: improves formability.
Stabilizer: Increases stability, such as heat resistance, for longer life.
3. Plastic classification
1. By molecular structure
Thermoplastics: molecular structure is linear and can be recycled.
Thermosetting plastics: molecular structure consists of a network and a body. Can only be used once after molding.
4. Common plastic
PE polyethylene, such as mineral water bottles, is used at a temperature of 80°C, and if temperature exceeds 80°C, deformation will occur.
PVC, e.g. electrical wire insulation
PF Phenolic Resin, which is a thermosetting plastic such as a shovel handle
5. Engineering plastics
Polyamide PA, commonly known as nylon
PTFE, good corrosion resistance
6. Characteristics of plastic
-Low density 0.83kg/dm3～2.2kg/dm3
-High specific strength (δb/ρ), high specific stiffness (E/ρ)
-Good chemical stability
-Good electrical insulation, heat insulation and sound insulation
-Good wear resistance and self-lubrication
-Good molding characteristics, good coloring characteristics
-Good vibration absorption, good anti-static