# Rubber chemicals and Sulfur Sulphur and rubber chemicals are the two halves of the cure that turns raw rubber into a tyre: sulphur forms the cross-links and accelerators, themselves partly made with sulphur, control how fast and how well they form. Rubber is a small outlet for sulphur next to fertiliser, so rubber chemical makers take sulphur prices set by the phosphate market. Source page: https://www.materialinsights.org/links/rubber-chemicals-and-sulfur/ [Rubber chemicals](https://www.materialinsights.org/chemicals/rubber_chemicals/) (chemical) and [Sulfur](https://www.materialinsights.org/commodities/sulfur/) (commodity): 4 relationships. ## How they are linked ### 1. Sulphur in accelerator synthesis *Physical flow · Medium · Sulphur to rubber chemicals* MBT, a widely used vulcanisation accelerator, is made industrially by reacting aniline, carbon disulphide and sulphur at high temperature and pressure, so sulphur enters accelerators as a raw material as well as in the cure. Indian accelerator makers report that aniline, benzene and other crude-linked raw materials make up a high share of their inputs, so accelerator costs track crude oil more than sulphur. The MBT reaction also gives off hydrogen sulphide, which plants must capture and handle. Sources: [International Agency for Research on Cancer (WHO)](https://publications.Iarc.Fr/_publications/media/download/5402/625abf3783052317affafe28e7497a31e92109f8.pdf); [CRISIL Ratings](https://www.crisil.com/mnt/winshare/Ratings/RatingList/RatingDocs/NOCILLimited_January 16_ 2025_RR_360327.html) ### 2. Accelerator to sulphur balance *Substitution · Medium · More accelerator allows less sulphur* Compounders choose the ratio of accelerator to sulphur: more accelerator and less sulphur gives shorter, heat-stable cross-links, so the two partly trade off against each other in a recipe. - **2.0 to 3.5 phr** sulphur in a conventional cure, with 0.4 to 1.2 phr accelerator - **0.4 to 0.8 phr** sulphur in an efficient cure, with 2.0 to 5.0 phr accelerator Efficient cures resist heat ageing better, which suits demanding tyre parts, while conventional cures use more cheap sulphur and less costly accelerator. The choice is made compound by compound, so the trade-off shifts sulphur and accelerator use within a recipe rather than between suppliers. Sources: [Chulalongkorn University](https://cuir.car.chula.ac.th/bitstream/123456789/77828/3/Wisullaya_ph_ch2_p.pdf) ### 3. Same tyre makers *Shared risk · Strong · Both sold into tyre compounding* Every sulphur-cured tyre needs both, so demand for accelerators and for rubber-grade sulphur rises and falls with tyre output. - **about two thirds** of NOCIL revenue from the tyre industry - **about 40%** NOCIL share of India's rubber chemicals market For rubber chemical makers, tyre volumes are the main driver; for sulphur producers, rubber is a small niche next to fertiliser. That asymmetry means a tyre slump hurts accelerator makers but barely touches sulphur prices. Sources: [CRISIL Ratings](https://www.crisil.com/mnt/winshare/Ratings/RatingList/RatingDocs/NOCILLimited_January 16_ 2025_RR_360327.html); [Kelewell](https://www.kelewell.de/en/post/surging-sulfur-prices-who-is-choking-the-global-phosphate-fertilizer-industry) ### 4. Price link: vulcanising agent *Cost and price · Strong · Both ways* The two are always used together in curing, and both sit on industrial chemical cycles, so their prices drift together over a year. - **0.16** monthly change correlation - **0.71** 12-month change correlation - **0.31** fitted elasticity The site's sulphur proxy is a sulphuric acid index, so the strong yearly link partly reflects a shared industrial cycle rather than direct cost pass-through. Sulphur prices are set by phosphate fertiliser demand, which takes more than half of world supply, as in 2025 when the US average unit value rose from about USD 46 to USD 180 a tonne. Sources: [Material Insights (World Bank, FRED, IMF data)](https://www.materialinsights.org/chemicals/rubber_chemicals/correlation/); [USGS](https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-sulfur.pdf); [Kelewell](https://www.kelewell.de/en/post/surging-sulfur-prices-who-is-choking-the-global-phosphate-fertilizer-industry) ## For investors ### Key learnings 1. Rubber chemical makers' margins depend far more on aniline and benzene costs and tyre volumes than on sulphur, which is a small input bought at prices set by fertiliser demand. 2. Where compounders move to efficient cures for heat resistance, accelerator use per tyre rises and sulphur use falls, which favours accelerator makers. 3. Imports from China and Korea compete closely with Indian accelerator makers, so trade remedies matter for domestic producers' margins. ### What to track - **Tyre production and replacement demand**: Drives volumes for accelerators and rubber-grade sulphur (Monthly · ATMA, company results) - **Aniline and benzene prices**: Main cost driver for accelerators (Weekly · industry price reports) - **Middle East sulphur price**: Sets the sulphur cost for curing and for MBT synthesis (Monthly · USGS, industry reports) ## For policymakers ### Key learnings 1. India has a domestic rubber chemicals producer with a large share of its market, which reduces import reliance for a critical tyre input. 2. Competition from Chinese and Korean imports makes trade policy the main lever on domestic rubber chemical capacity. 3. Sulphur for curing is available from Indian refineries, so the supply risk in this pair lies in aniline and accelerator imports rather than sulphur. ### What to track - **Imports of rubber accelerators by origin**: Rising Chinese share signals pressure on domestic producers (Monthly · DGCIS) - **Trade remedy cases on rubber chemicals**: Duties change the competitiveness of domestic supply (As notified · DGTR) ## India NOCIL holds about 40% of India's rubber chemicals market and earns about two thirds of its revenue from tyre makers, competing with imports from China and Korea. India produced about 3.7 Mt of sulphur in 2025, so curing sulphur is not an import constraint. ## Sources 1. [Price correlation, Material Insights](https://www.materialinsights.org/chemicals/rubber_chemicals/correlation/), Material Insights (World Bank, FRED, IMF data) 2. [IARC Monographs Volume 115: 2-Mercaptobenzothiazole](https://publications.Iarc.Fr/_publications/media/download/5402/625abf3783052317affafe28e7497a31e92109f8.pdf), International Agency for Research on Cancer (WHO) (2018) 3. [Theory and literature review: sulphur vulcanisation systems (thesis chapter 2)](https://cuir.car.chula.ac.th/bitstream/123456789/77828/3/Wisullaya_ph_ch2_p.pdf), Chulalongkorn University 4. [Rating rationale: NOCIL Limited](https://www.crisil.com/mnt/winshare/Ratings/RatingList/RatingDocs/NOCILLimited_January 16_ 2025_RR_360327.html), CRISIL Ratings (2025) 5. [Mineral Commodity Summaries 2026: Sulfur](https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-sulfur.pdf), USGS (2026) 6. [Surging sulfur prices: who is choking the global phosphate fertilizer industry?](https://www.kelewell.de/en/post/surging-sulfur-prices-who-is-choking-the-global-phosphate-fertilizer-industry), Kelewell (2025)