What is a typical velocity factor for coaxial cable with polyethylene dielectric?

Coaxial cables use different types of insulating materials (dielectrics) which dictate how fast the signal travels. For a standard coaxial cable using a solid polyethylene dielectric, the typical velocity factor is 0.66. This means that an RF signal travels through this specific type of cable at exactly 66% of the speed of light in a vacuum. Other materials will yield different values; for example, foam dielectrics have velocity factors closer to 0.80 or higher. However, 0.66 is the fundamental textbook benchmark for solid polyethylene. An option like 2.7 is impossible because a signal cannot exceed the speed of light (which would be a VF greater than 1.0).