What happens to thermoplastics when heated in the FDM process?

When thermoplastics are heated in the Fused Deposition Modeling (FDM) process, they primarily undergo a physical change that allows them to become pliable and moldable. This is essential for FDM, as the primary goal is to extrude the material through a heated nozzle, enabling it to be deposited layer by layer to form the final object.

As the temperature increases, the polymer chains in the thermoplastic material gain mobility, allowing them to slide past each other more easily. This results in a softened state that facilitates the flow of the material, making it suitable for the additive manufacturing process. Once cooled, the thermoplastic solidifies again, retaining its shape and structural integrity.

The other options suggest processes that do not accurately describe what happens to thermoplastics during FDM. For example, becoming brittle typically refers to the properties of certain materials at low temperatures or after specific treatments, not heated thermoplastics in the context of FDM. Chemical reactions would imply a change in the material's composition, which is not a characteristic of thermoplastics when heated; they do not undergo a chemical transformation but rather a physical one. Lastly, the notion of evaporation into gases does not apply here, as thermoplastics tend to melt rather than