The UV stabilized RNC is pretty tough but it is still not supposed to be installed where it is subject to physical damage.
Schedule 80 is a bit tougher but still no match for vehicular traffic or aggressive power tools. I doubt a string trimmer would hurt it right away but I have seen 4x4 mail box posts rounded off over time. The landscape guys seem to be ambivalent to what their trimmer is "trimming". Eventually they will eat a hole in it.
