In 1868, Hyatt developed a plastic material he named celluloid. Celluloid had been invented by Alexander Parkes in 1851. Hyatt improved upon it, making it possible to process into finished shapes. Hyatt and his brother Isaiah patented the first plunger injection molding machine in 1872. This machine was relatively simple compared to those used in the 20th century. It operated essentially like a giant hypodermic needle. This giant needle (diffuser) injected plastic into a mold through a heated cylinder.
The Second World War in the 1940s created a huge demand for inexpensive, mass-produced products.
In 1946, American inventor James Watson Hendry built the first injection molding machine, which allowed for more precise control of injection speed and the quality of the produced articles. This machine also allowed for the thorough mixing of colored or recycled plastics with virgin material before injection. In 1951, the United States developed the first screw-type injection molding machine, which was not patented, and this device is still in use today.
In the 1970s, Hendry went on to develop the first gas-assisted injection molding process, allowing the production of complex, hollow products with rapid cooling. This greatly improved design flexibility and the strength and end-product manufacturing of parts, while reducing production time, cost, weight, and waste.