i would think it would be more difficult for it to work on a poly blend...pigma pens work great on cotton...but i write on the cotton- i don't know much about transfer labels--seems like you would need to use a transfer pencil with them- but i don't know what they are so----
but i use pigma pens for labels all the time...that's what they are made for....but i use cotton- not blends.
MICRON PIGMA PENS ARE PERMENENT- DO NOT FADE- DO NOT BLEED- ARE ARCHIVAL QUALITY ACID FREE- MADE TO WRITE ON TEXTILES.