Melt spinning of polymers involves the forcing of polymer melt through spinnerates $($fine holes$)$ into an atmosphere kept at a temperature lower than the melting point of the polymer, which causes the fine diameter polymer melt to harden into filaments. Melt spinning is not used in case of the $\_\_\_\_\_\_\_\_\_$ fibres.

Acrylic

Polyester

Nylon $6$:$6$

Polypropylene