Thermoplasticity refers to the property that a substance can flow and deform when heated and maintain a certain shape after cooling. Most linear polymers exhibit thermoplastic properties and are easily processed by extrusion, injection or blow molding. Thermoset refers to the property that it cannot be softened and molded repeatedly when heated, nor is it dissolved in solvents. Body-shaped polymers have this property.

Thermosetting is a chemical change. After being heated, the structure has changed and turned into another substance. For example, if an egg is cooked, it cannot be restored. Thermoplasticity is a physical change. It only changes the state of the substance when heated, but the structure remains unchanged. For example, if a candle melts when heated, it can be restored to the original candle, but the burning of the candle is a chemical change.

Thermosetting resin
Common resins: epoxy resin, phenolic resin and other pastes
High density, low strength, easy to crack and powder
It has a strong smell and produces irritating odor during production and use. It cannot be reused and is difficult to degrade.
The curing process is a chemical change and is irreversible

Thermoplastic resin

Common resins: PP, PA, PE, etc. granular
Low density, high toughness, good weather resistance
It has no smell, can be reused, and the molded product can even be implanted into the human body.
The curing and softening processes are physical changes and are reversible.

1. Thermoplastics
It becomes soft and even flows when heated, and hardens when cooled. This process is reversible and can be repeated. Polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyoxymethylene, polycarbonate, polyamide, acrylic plastics, other polyethylene and its copolymers, polyethylene, polyphenylene ether, chlorinated polyether, etc. It's a thermoplastic. The resin molecular chains in thermoplastics are all linear or branched structures. There are no chemical bonds between the molecular chains and they soften and flow when heated. The process of cooling and hardening is a physical change.

2. Thermosetting plastics
It can soften and flow when heated for the first time. When heated to a certain temperature, a chemical reaction occurs and cross-linking solidifies and hardens. This change is irreversible. After that, when heated again, it can no longer soften and flow. It is with the help of this characteristic that the molding process is carried out, using the plasticizing flow during the first heating to fill the cavity under pressure, and then solidify into products of a certain shape and size. This material is called a thermoset.

The resin of thermosetting plastics is linear or branched before curing. After curing, chemical bonds are formed between the molecular chains and become a three-dimensional network structure. Not only can they no longer be melted, they cannot be dissolved in solvents. Plastics such as phenolic, formaldehyde, melamine formaldehyde, epoxy, unsaturated polyester, and silicone are all thermosetting plastics.