Dry cleaning hangers, Plastic clothes hanger
Blue Bins & Chutes
While these hangers are officially accepted in the recycling bins in Singapore, most plastic hangers are made from non-recyclable plastic (#6 polystyrene and #7 polycarbonate) so they will get removed during the recycling sorting process and eventually end up incinerated.
Do the system a favor and just put it directly in the trash yourself.
Freecycle / Give Away
Offer them online
Online Freecycle Groups
Tips & Suggestions
Some dry cleaners are happy to take them back and may even offer a small (very small $0.05) credit for doing so.
The biggest source of surplus plastic hangers is from dry cleaners (most clothes stores keep their hangers after a sale).