Tarp falling apart after only two months

I had a tarp on my RV for four years. It started getting brittle, ripped easily, and formed this annoying dust-like powder, shedding like dandruff all over.

I bought a new tarp in June of this year.

It's barely September, and the new tarp is doing the same thing. But it's barely three MONTHS old.

Is there a good tarp that can stand the Sacramento sun plus our occasional rain showers without falling apart after three months?

I believe the tarp is plastic. I threw away the package, but it's the typical tarp from ACE/Lowe's/Home Depot.

Thanks!