The American inventor John Wesley Hyatt patented the first injection molding machine in 1872. This machine was relatively simple compared to the machines in use today: it worked like a large hypodermic needle, using a plunger to inject plastic into a mold through a heated cylinder. At the time, they produced principally necklaces, buttons, and combs.

To begin the injection molding process, the polystyrene is heated into a liquid form. It is then added to a two-sided mold to create the desired shape. Once the item has cooled, it is released into a bin and then moved into post–processing for finishing touches. The advantage of using injection molding for your polystyrene part is that once the tool has been made, it can be used over and over again, producing a large volume of high-quality polystyrene products.

However, this method has a cost because it requires the design of a steel mold, which allows the duplication of many series parts. This is why it is not recommended for designs for small series. For this, silicone molding is preferred, for example. (See our section on silicone molding.)

Polystyrene is also available as a thermoset plastic. Thermoset plastics can only be heated once as attempting to heat them a second time would cause the material to burn. Polystyrene in thermoset form is not recyclable.

ICOMold has been producing custom polystyrene and other thermoplastic injection molded parts for many years. Our team of experts will work with you to find the best material for your unique project. The custom plastic injection mold created for your product will last over 100,000 cycles, increasing your efficiency and uniformity while passing on cost-savings to the customer.

Thermoplastic injection, or injection molding, use the thermoplastic properties of certain materials to inject a softened plastic into a mold to create an impression from it. This technique provides the best quality for your productions of large and very large series.

Polystyrene is popular in both foam or plastic form. Polystyrene foam is easy to cut, paint, sand, glue and is widely available. Polystyrene in plastic form is most commonly used for disposable items, such as food packaging. Some common uses of polystyrene in injection molding include:

Polystyrene is a popular material for injection molding because it is cost-effective and versatile. Some of these primary benefits of using polystyrene for injection molding projects include:

Polystyrene is a homopolymer made only of a combination of monomer styrene available as foam or solid. It is clear, hard and brittle. As a thermoplastic, it will become liquid at a melting point of 410-480◦F. Once polystyrene has been liquified, it can be cooled into a solid, then reheated again without degradation. Its ability to liquefy instead of burn is what makes it a good material for injection molding. It is not biodegradable. Properties of polystyrene:

Polystyrene (PS) is a transparent thermoplastic most often used to create single-use products. It is odorless and non-toxic. Polystyrene is available in either solid or foamed. As a solid, it is used to make plastic cutlery, electronics, toys and auto parts. As a foam (Styrofoam), it can be extruded to make packing peanuts, disposable drinking cups and more. Injection molding polystyrene has many advantages and applications.

The industry developed rapidly in the 1940s, following huge demand for inexpensive, mass-produced products. In 1946, the American inventor James Watson Hendry built the first machine with injection screws, allowing much more precise control of the injection speed and the quality of the products produced. This machine made it possible to add colored or recycled plastic to the virgin material prior to injection. Today, machines with injection screws represent the vast majority of all injection machines.

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The thermoplastic injection molding industry has evolved over the years: initially focused on the production of combs and buttons, it has evolved to the production of a wide range of products for many industries including automotive, medical, aerospace, consumer products, toys, plumbing, packaging, and construction.

In 1919, Arthur Eichengrün developed the first injection molding press, which can be considered the first modern injection molding machine. A few years later, in 1926, Eckert and Ziegler patented the first injection molding machine with commercial characteristics. The 1930s saw the emergence of the first injection molding machines in France. This marked the start of plastic household items and toys on the consumer market.

The advantage of this method is that it allows the duplication of many identical objects of high quality, thanks to the re-use of the mold, and in the right material. This is why this method is particularly suited to large or very large series production. A final advantage is that the parts thus designed require little or no subsequent machining.

The principle of plastic injection is the use of heat to soften a thermoplastic (TP) material in the form of pellets. The softened material is kneaded and injected into an endless screw. The rotation of the screw and the pressure added inserts the material into a mold. The material then takes on the impression of the mold. After cooling, the object takes on solid form and can be removed from the mold. The mold can then be reused for another injection.