The plastics industry consists of three main processes: resin production, plastic preparation, and plastic product manufacturing.
The manufacturing process of resin involves linking many small molecular raw materials (monomers) together through polymerization reactions to form high molecular compounds. Polymerization reactions can be classified into addition polymerization and condensation polymerization based on the composition and structural changes of the monomers.
Addition polymerization involves the reaction of monomers joining together, such as in the case of polyethylene, where the double chains of ethylene monomers are opened, allowing each ethylene molecule to “hold hands” and form polyethylene. Condensation reactions, on the other hand, not only form high polymers but also produce low molecular by-products like water, alcohol, and ammonia during the reaction.
How does resin transform into plastic? In today’s society, there is an increasing demand for plastic products that simultaneously fulfill diverse and high-quality requirements using a single synthetic resin. Therefore, a common approach is to use a “modification” method, where various additives are incorporated into the synthetic resin to alter its properties, transforming a limited range of single resins into a variety of high-performance new materials.
The final step in the plastics industry is plastic molding, where plastic is shaped into specific objects or formed materials. The plastic molding process generally involves transforming polymer granules or powders into a pliable, flowable state through heating and melting, or by creating solutions, emulsions, or pastes. The flowable plastic is then filled into mold cavities, extruded into films, or sprayed through nozzles, and then cooled and solidified after shaping. For fibers and films, additional processing steps such as stretching, annealing, and quenching are required to achieve stable product shapes and the desired performance. It’s worth noting that resins can be used to produce both plastic products and fibers.
