RIANOX 168
The most widely used organo-phosphite secondary antioxidant, offering excellent hydrolytic stability and low volatility. Effectively decomposes hydroperoxides formed during high-temperature processing of polymeric materials, preventing discoloration and degradation. Delivers outstanding synergistic performance when combined with hindered phenolic primary antioxidants such as RIANOX® 1010 and RIANOX® 1076.
| CAS No. | 31570-04-4 |
| Chemical Name | Tris(2,4-di-tert-butylphenyl) phosphite |
| Antioxidant Type | Secondary Antioxidant — Phosphite Ester |
| Molecular Weight | 647 |
| Melting Point (°C) | 181–185 |
| Appearance | White Crystalline Powder |
| Density @20°C (g/cm³) | 1.03 |
| Standard Packaging | 20 kg Bag |
| Solvent | Solubility |
|---|---|
| Toluene | 30 |
| n-Hexane | 11 |
| Cyclohexane | 10 |
| Ethyl Acetate | 4 |
| Acetone | 1 |
| Ethanol | 0.1 |
| Methanol | <0.01 |
| Water | <0.01 |
Polyolefin (PP / PE)
ABS
Polycarbonate (PC)
Polyester (PET / PBT)
Polyamide (PA)
PVC
PS / Engineering Plastics
Rubber & Elastomer
Petroleum Products
Automotive & Transportation
Packaging
Electronics & Appliances
Building & Construction
Agriculture
Textiles & Apparel
Renewable Energy
Healthcare & Medical
Where RIANOX 168 fits
RIANOX 168 is the most widely used phosphite secondary antioxidant (molecular weight 647, melting point 181–185 °C). It breaks down the hydroperoxides that form in the hot melt, so it protects melt flow and colour during compounding and molding, and it resists hydrolysis in storage. Typical uses:
- PP and PE compounding, film, fiber and molded parts
- ABS, styrenics and polyamide
- Elastomers and adhesives processed at high temperature
- Recycled polyolefins that need extra processing protection
Typical use levels
- Polyolefins: 0.05–0.2%, usually one to two times the phenolic level
- Engineering plastics and styrenics: 0.1–0.3%
These are starting points. Confirm the level with multiple-pass extrusion (melt flow retention and colour) and oven ageing on your own compound.
Choosing a secondary antioxidant
How RIANOX 168 compares with the other phosphites and thioesters we supply:
| Grade | Type | Mol. weight | Melting point | Main role |
|---|---|---|---|---|
| RIANOX 168 | Phosphite | 647 | 181–185 °C | Processing stability and colour; hydrolytically stable |
| RIANOX 626 | Diphosphite | 604 | 170–180 °C | High-activity processing stabilizer, colour control |
| RIANOX DSTP | Thioester | 683 | 63–69 °C | Long-term heat ageing synergist |
| RIANOX DLTP | Thioester | 515 | 39.5–42.5 °C | Long-term heat ageing; easier dispersion |
Pairing RIANOX 168 with a phenolic antioxidant
RIANOX 168 is a secondary antioxidant: it decomposes hydroperoxides but does not trap free radicals, so it is used together with a hindered phenol such as RIANOX 1010 or RIANOX 1076. A 1:1 or 2:1 blend of RIANOX 168 with RIANOX 1010 is the standard processing package for polyolefins. For long-term heat ageing, add a thioester such as RIANOX DSTP. For outdoor parts, add a HALS light stabilizer; our HALS UV stabilizer guide explains how the additives interact.
TDS, documents and samples
The full TDS, COA and SDS for RIANOX 168 are sent by email with the quotation, together with the producer’s REACH and food-contact declarations where applicable. Samples are available for qualification trials. Request the TDS and a quote, or compare the full antioxidants and HALS range.
