Butadiene rubber dropped 1.36% to CNY 14,505/t today. On the surface it is synthetic rubber softening; underneath it is a butadiene calculation. Several butadiene units have lifted run rates recently, pushing more merchant material to market and loosening East China spot prices, which dragged the cost anchor for butadiene rubber lower. This is not demand collapsing — it is room opened at the cost end.

Over the same session natural rubber rose 0.24% to CNY 18,820/t, and the two grades diverged. For tire plants that is a line item on the formulation sheet: cheaper butadiene rubber means adding a few points to the recipe trims unit compound cost. Our blend-ratio model shows that once butadiene rubber's cost advantage over natural rubber crosses a threshold, factories lift the butadiene share by 2–3 percentage points within a month.

Do not read this as a clean win. More butadiene rubber means slower natural rubber procurement and slowly building port stocks. The moment butadiene runs dip on turnarounds or margins, the cost anchor reverses and the recipe shifts back. This window is cyclical, not structural.

On the SNSUC sourcing board, the rubber chain needs layered pricing: natural rubber tracks port arrivals and tire-export orders, butadiene rubber tracks butadiene and merchant flow. Today's signal is to lean into butadiene rubber near term and keep natural rubber on a just-in-time cadence.