Taken from rain x website...
Can it be used on transparent plastics
Generally no. The increasing variety of various coatings applied to plastics makes it impossible to pre-test for compatibility under all conditions, and users should satisfy themselves by treating an area outside the normal area of vision. Please note that constant, repetitive use should be avoided due to the possible formation of stress cracking, especially on clear, curved sections
We've witnessed this first hand on a takeover. On-site maintenance had reported hairline cracks on the PTZ dome covers. When questioned turns out they where using rain x several times a year.