Developed photographic film is generally the better DIY choice. Floppy disk material is a poor IR filter, largely because of its metal content. For film, developed color film can work better: use unexposed if it’s reversal (slide) film, or exposed if it’s negative film. Undeveloped film and black-and-white film are not good choices because metal content reduces their usefulness as IR-pass filters.

That said, none of these DIY materials works as well as a proper IR-pass filter. If you want cleaner results, a cheap dedicated IR filter is the better option, with 720nm being a commonly recommended starting point. Other DIY methods people try include stacking colored gels, stacking ND filters, or using crossed polarizers/variable ND, but these are compromises rather than true replacements for a real IR filter.

If you plan to shoot infrared often with a digital camera, a full-spectrum camera conversion is a much better long-term solution.