flower bulb storage
I have some white frost protection material (blanket) which is polypropylene in nature and about 1.5 mil thick. I was thinking of re-using this fabric to perhaps store flower bulbs this winter. The material is billed as breathable so I'm thinking it is ok. Please advise.
Cook County Illinois
I'm assuming that you are talking about digging up and overwinter tender perennial bulbs and tubers that won't overwinter in the garden. If you properly prepare the bulbs (curing, cleaning, etc.), then this row cover material may be usable for some of the plants. For example, gladiolus corms need to be stored in open paper sacks or mesh bags, so they would probably do well in this material.
Please download Purdue's publication on overwintering tender perennials for more advice: https://hort.purdue.edu/ext/HO-085.pdf .
Another quick ?....is there any advantage / disadvantage to using synthetic burlap vs natural burlap for Winter plant protection?
Since you are only temporarily wrapping the plants to protect them from wind or salt spray, I think using either natural or synthetic would work in this case. While normally I recommend against using plastic TARPS for winter protection (plastic usually has no insulation properties), there are enough holes to trap air that the synthetic burlap that it should still work.