Hello,
Hydroxypropyl xylan, known as "HPX", is a bio-polymer produced from the sugar xylose. It is a biodegradable, film-forming thermoplastic. In its normal form it is water-soluble, although a version called "acetylated HPX" is similar but non-water soluble.
So far I have not been able to find any commercial sources of HPX, although it is discussed heavily in the literature. If it ever becomes cheaply available, I think it would be worth investigating as a support material.
Jacob
