Which method is utilized to shape plastics into bottles using a heated parison?

The correct method for shaping plastics into bottles using a heated parison is blow moulding. In this process, a hollow tube of plastic, known as a parison, is heated until it becomes pliable. It is then placed in a mould, and air is blown into the parison. The air expands the heated plastic against the walls of the mould, shaping it into the final bottle form. This technique is highly efficient for creating hollow items like bottles, giving them uniform thickness and an integrated structure.

Other methods such as injection moulding are typically used for producing solid items by injecting molten plastic into a mould. Similarly, rotational moulding is more suited for creating large, hollow shapes by rotating a heated mould filled with plastic powder, which melts and coats the interior surface. Vacuum forming involves heating a thermoplastic sheet until it's soft and then using a vacuum to pull it over a mould, which is effective for shallow forms but not for making bottles from a parison. Each of these processes has its specific applications and advantages, but blow moulding is uniquely tailored for the production of hollow containers like bottles.