Viscose vs polyester thread

Can anyone tell me if viscose thread is strong enough to use in place of polyester? I picked some up because it would be perfect for some Christmas pillowcases Im making but I dont want to use it if it wont stand up to many washes and use. Thank you!

No it's not strong enough for construction.  Rayon thread is for decoration really only.  So if you're using it in an embroidery machine, you're good to go, but to seam something, you'll be disappointed.  On a bonus side, rayon thread is nice when you have to hand baste...the slipperiness of it makes those stitches pop right out.