sterilizable and printable , wet - laid non - woven substrate exhibiting high - strength and temperature resistance above 140 ° c ., providing sufficient airflow to relieve pressure in a package formed from the substrate during sterilization , providing a significant barrier to penetration by bacteria and debris , and which is sealable to itself and to thermoplastic films , comprises blends of nanofibrillated lyocell fibers , microfibers , fibers having a flat , rectangular cross - section and binder fibers .