Chitin's second life

Cellulose gets all the attention as nature's structural polymer, but its cousin chitin is nearly as abundant and, for our purposes, far more interesting. Chitin's molecular backbone forms long, stiff chains that pack into tight crystalline bundles held together by a dense hydrogen-bond network. In an insect, that's what makes an exoskeleton rigid at a fraction of a gram. In Chitospan, it's what carries tension.

From waste stream to feedstock

The world already produces millions of tons of chitin a year as shellfish-processing waste, most of it landfilled. That was our starting point — but harvesting a waste stream doesn't scale to structural volumes, and it varies batch to batch. So we grow it. Our bioreactor strains secrete chitin directly from CO₂-fed feedstock, giving a continuous supply at controlled molecular weight and purity that no waste stream can match.

Tension is about alignment. A tangle of strong chains is weak; a bundle of parallel ones is a cable.

Alignment is everything

A chitin chain is strong along its length and weak across it. Grown in bulk, the chains land in random orientations and the strength averages out to something unremarkable. The engineering in Chitospan is drawing — stretching the harvested polymer so the chains rotate into near-perfect parallel alignment before they're locked in. The more aligned the draw, the higher the grade:

• Z1 — moderate draw, 320 MPa, for everyday floor beams.
• Z3 — high draw, 460 MPa, for long-span roofs and footbridges.
• ZX — maximum draw, 540 MPa, the catalog's strongest compound.

Because the base polymer is so light, that strength comes at a density of 1.3–1.7 g/cm³ — under a quarter of steel's. The result is the highest specific strength we make: strength per unit weight that leaves structural steel far behind.

What that specific strength lets you actually build — clear spans steel can't reach without drowning in its own weight — is the subject of Designing 60-metre clear spans.