In 1868, Hyatt developed a plastic material which he named celluloid. Celluloid had been invented in 1851 by Alexander Parkes. Hyatt improves it so that it can be processed into finished shapes. Hyatt and his brother Isaiah registered the patent for the first plunger injection machine in 1872. This machine is relatively simpler than those used in the 20th century. It operates basically like a giant hypodermic needle. This giant needle (diffusion barrel) injects plastic into the mold through a heated cylinder.
In the 1940s World War II created a huge demand for cheap, mass-produced products. , low-priced, 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 quality of produced items. This machine also enables material mixing before injection, so that colored or recycled plastics can be thoroughly mixed into the virgin material. In 1951, the United States developed the first screw injection machine. It did not apply for a patent, and this device is still in use.
In the 1970s, Hendry went on to develop the first gas-assisted injection molding process and allowed the production of complex, hollow products that were rapidly cooled. This greatly increases design flexibility as well as the strength and endpoints of manufactured parts while reducing production time, cost, weight and waste.