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Technical Data Sheet
Crystex™ OT 33

  • Tires

Product Description

Chemical name: Polymeric sulfur

Crystex™ OT 33 is a non-blooming vulcanizing agent for unsaturated elastomers.


  • Crystex OT 33 is polymeric sulfur and is insoluble in elastomers. Consequently it will retard bin scorch, prevent migration of sulfur and preserve surface tack. This is important in the manufacture of tires and other plied-up rubber goods.
  • At vulcanization temperatures Crystex OT 33 will de-polymerize to soluble sulfur and will behave similar to "Rubber Maker's" sulfur.
  • Crystex OT 33 is a metastable product which can revert to soluble sulfur if not stored under proper conditions.
  • Reversion of Crystex OT 33 to soluble sulfur is also catalyzed by alkaline products. The presence of alkaline accelerators can be critical.
  • Crystex OT 33 is used in compounds containing a relatively large sulfur loading above the solubility of sulfur in the elastomer.
  • Crystex OT 33 is non-staining and non-discoloring.

Typical Properties

PropertyTypical Value, Units
FormInsoluble sulfur, 33% oil treated powder
Specific Gravity 
     @ 20°C1.43 approximate
Bulk Density 
     Packed600-800 kg/m3
     Unpacked400-600 kg/m3
Mean particle size<30 µm

Compounding Information

Because insoluble sulfur is a metastable product temperatures should be kept as low as possible during mixing. Between 100°C and 130°C significant reversion can take place to soluble sulfur.

Dispersion of Crystex™ OT 33 in rubber is critical. Due to its small particle size and its tendency for electrostatic charge build-up agglomerates can be formed which can result in inhomogeneous vulcanizates. Sufficiently long mixing times should be applied preferably in a separate mixing step under well controlled conditions.

If dry pre-mixes are produced of Crystex OT 33 and other vulcanization chemicals, reversion can take place if Crystex OT 33 is in direct contact with alkaline components.

Handling Precautions
For detailed information on toxicological properties and handling precautions please refer to the current Safety Data Sheet. This information sheet can be downloaded from our web site or requested from the nearest Eastman office and should be consulted before handling this product.

Store Crystex™ OT 33 in a well ventilated area below 30°C, avoiding exposure of the packaged product to direct sunlight. Do not store near products that can emit free amines such as sulfenamides and DTDM. Amines and other alkaline vapors can cause Crystex OT 33 to revert to "Rubber Maker''''s" sulfur at any temperature. High­ temperatures will also cause Crystex OT 33 to revert to "Rubber Maker''''s" sulfur. When stored in closed containers below 20°C the reversion rate is less than 1%/year. Reversion of Crystex OT 33 could result in sulfur bloom of uncured rubber.

Properties reported here are typical of average lots. Eastman makes no representation that the material in any particular shipment will conform exactly to the values given.

Eastman and its marketing affiliates shall not be responsible for the use of this information, or of any product, method, or apparatus mentioned, and you must make your own determination of its suitability and completeness for your own use, for the protection of the environment, and for the health and safety of your employees and purchasers of your products. No warranty is made of the merchantability of fitness of any product, and nothing herein waives any of the Seller's conditions of sale.

10/19/2021 8:24:06 AM