Which process involves heating a polymer and forcing it into a mold cavity?

The correct answer is injection molding, which is a widely used manufacturing process for creating objects from thermoplastic and thermosetting polymer materials. In this process, the polymer is first heated until it becomes fluid. Once it reaches the appropriate viscosity, the molten polymer is then injected under pressure into a mold cavity, which is in the shape of the final product. This method allows for high precision and the ability to produce complex shapes efficiently, making it suitable for both high-volume production and intricate designs.

The other processes mentioned do not specifically involve forcing heated polymer into a cavity in the same manner. For example, extrusion involves forcing the polymer through a die to create long shapes, such as pipes or sheets, rather than filling a mold. Blow molding typically incorporates air pressure to inflate molten polymer into a mold, often used for hollow objects like bottles. Thermoforming involves heating sheets of plastic until they are pliable and then shaping them over a mold, but it does not involve injecting the material under pressure. Each of these processes has distinct applications and methodologies that differentiate them from injection molding.