Why is this code in the script not stopping the rotation of the Gameobject?

 if (Input.GetKey(KeyCode.A) && (this.transform.rotation.x<=18f))
         {
             transform.Rotate(Time.deltaTime*15, 0, 0);
 
         }
         else
         if (Input.GetKey(KeyCode.Q) && (this.transform.rotation.x >= -18f))
         {
             transform.Rotate(-Time.deltaTime*15,0,0);
 
         }

both cases don't work.