Don't leave those ikea bags out in the sun, they fall apart rather...quickly....
There's a "fix" though that should be good enough for a camping trip or two! Coat the bag with a powerful sunscreen. I'm not talking about those "SPF 50" spray bottles--those will wear off pretty fast. No, use Butt Paste:
Yes, it's diaper rash cream but it's 16% zinc oxide which is the primary ingredient in many sunscreen lotions/sprays. Even better, because it's a thick cream it will actually stick to that slippery blue Ikea polypropylene fabric and do a decent job at protecting it from the sun.