Q: is airport express needed for an airprinter

No, an AirPrint printer just needs a Wi-Fi network, that's all. No Airport required.

The concept is that you need a printer that is AirPrint compatible if you want to be able to print from an iPhone or iPad, etc without adding additional software.

Apple updates the AirPrint compatible list from time to time, but you can get a general picture of AirPrint compatible printers here:

About AirPrint - Apple Support