A roll-up curtain closure system having an impact resistant tension rod, wherein the system includes at least one flexible curtain having a first end fixedly attached adjacent a portal along a first end thereof and a second end folded back on itself to define a pocket opening towards the portal first end, an elongated tension rod captured within the pocket, and a curtain driving mechanism operably connected to the curtain second end for varying the height of the pocket. The elongated tension rod comprises an inner flexible fiberglass bar surrounded by an outer soft closed cell foam material, whereby the tension rod is flexible to bend in response to impact force and is resilient to return to its original position after the impact force is removed.