World War II is a dark period in history. But did you know that the great conflict that split the world into two opposing sides was also a time of opportunity, development, and progress for an emerging plastic industry? With aluminum, copper, steel, and other metals becoming precious commodity allocated solely for military use, plastics came into their own as a manufacturing material. At the same time, the fast-growing aviation and automotive industries fed the demand for inexpensive, mass-produced plastic parts and products.
Today, plastic is an essential part of our daily lives. The plastic items you come across just about anywhere are in all likelihood the product of a versatile manufacturing technique called plastic injection molding. Read on to know what the process is all about, its origin and the current state of the industry.
What is plastic injection molding?
Similar to die casting, plastic injection molding is the process of injecting molten plastic at high pressure into a custom-made metal mold. When the plastic cools and solidifies, the mold is opened, and the plastic parts is ejected. This manuacturing process is a fast and inexpensive way of mass-producing common-use plastic products.
What raw materials are used?
Thermoplastics and thermoset plastics are the two types of plastic raw material used.
Thermoplastics: Thermoplastics melt when heated and harden when cooled. They can be reheated, reshaped and, therefore, remolded multiple times. Thermoplastics are recyclable. Any waste during the manufacturing process can be reused. This makes them cost-effective. Additionally, they are flexible, have a superior finish and high impact resistance (which means they are not too hard and rigid). On the flip side, thermoplastics have a lower resistance to heat and can be more expensive than thermosets.
Popular thermoplastics and their applications: Acrylonitrile butadiene styrene or ABS (computer keyboard caps), polypropylene (car fenders), polyethylene (cable insulators, skincare product containers), polyvinyl chloride or PVC (raincoats), polystyrene (food packaging) and polycarbonate (phone cases).
Thermoset plastics: Thermoset plastics harden irreversibly when heated. Compared to thermoplastics, thermosets generally have higher heat and chemical resistance, mechanical strength, and dimensional stability. However, they cannot be recycled or recast, have lower impact resistance (are more brittle) and are harder to work with, particularly during the surface finish stage.
Popular thermosets and their applications: Fiberglass (bathtubs), silicone (gaskets and seals), bakelite (buttons) and melamine (tableware).
Plastic injection molding products can be found just about anywhereApplications
You’ll find products and components just about anywhere. Apart from the applications mentioned above, a few more examples of such common-use products are plastic grocery bags, drinking bottles, food containers, toilet seats, remote control and game console casings, toys such as Lego and medical equipment such as syringes. With this manufacturing process, you can make large objects such as trash cans and car dashboards as well as much smaller ones such as bottle caps and automotive parts.
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