Sterilisable 3D printing filaments are filaments that can be cleansed of bacteria and other microorganisms. There are a number of ways to sterilise something; either with heat or using chemicals. One of the most common methods of sterilisation is using an autoclave, which is essentially a steam cooker that subjects the product to high temperature and pressure.
The harsh conditions required for sterilisation are unsuitable for most plastics used in 3D printing however there are some filaments available that can be sterilised. PolyPropylene is one of the plastics able to survive repeated autoclaving however you should always check the Technical Data Sheet of the specific filament as additives used in the manufacturing process may have changed this.
Sterilisable 3D printing filaments have a variety of uses, including in medical devices and food storage or processing. It is always important to check that the filament is also food-safe or bio-resorbable when designing such products.