What is a primary use of polypropylene line?

Polypropylene line is primarily known for its use in applications where lightweight and buoyant characteristics are important. Among the options given, painting on safety gear stands out as it relates to the versatility of polypropylene in various materials.

Polypropylene is often used to create lightweight ropes or lines that float on water, making them ideal for certain marine applications, but it is not typically painted on safety gear for visibility or identification. Instead, other materials would be more suited for that function due to their durability and visibility.

The buoyancy and resistance to moisture of polypropylene make it an excellent choice for uses like anchoring or mooring lines, where the line needs to be handled on the water. Its resistance to chemicals and mildew also adds to its appeal in marine settings. Hence, while painting on safety gear may be a possible use, it is not the primary use of polypropylene line when compared to its performance in marine and construction applications.