Overview of Phenolic Antioxidants
Phenolic antioxidants are among the most commonly used primary antioxidants in the rubber industry. They function primarily by capturing free radicals to terminate oxidative chain reactions. Compared with amine antioxidants, the core advantages of phenolic antioxidants are non-staining, non-discoloring, and low blooming, making them particularly suitable for light-colored, transparent, or appearance-sensitive rubber products.
Phenolic antioxidants are effective in the moderate temperature range. Studies have shown that hindered phenolic antioxidants provide good thermo-oxidative aging protection for NR/TBIR vulcanizates. However, many simple phenolic antioxidants gradually lose effectiveness at temperatures above 100°C. Therefore, for high-temperature applications, high molecular weight hindered phenolic antioxidants should be selected.
Phenolic Antioxidants Product List
The following are the most widely used phenolic antioxidants in rubber synthesis:
| Product Name | CAS No. | Chemical Name | Key Features | Suitable Systems |
|---|---|---|---|---|
| Antioxidant 1010 | 6683-19-8 | Tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane | High molecular weight, low volatility, strong extraction resistance, FDA approved | PE, PP, ABS, EPM, EPDM, IIR, SBS, SEBS, PU, synthetic rubber |
| Antioxidant 1076 | 2082-79-3 | Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate | Non-staining, good compatibility, resistant to hot water extraction | Polyolefins, ABS, synthetic rubber, elastomers, adhesives |
| Antioxidant 1098 | 23128-74-7 | N,N'-Hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide] | Strong extraction resistance, excellent color protection | Polyamide fibers, molded products, films |
| Antioxidant 3114 | 27676-62-6 | 1,3,5-Tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione | Extremely low volatility, excellent extraction resistance, odorless | EPDM, SBS, EPR, polyolefins, polyamides, adhesives |
| Antioxidant 1520 | 110553-27-0 | 2-Methyl-4,6-bis(octylthiomethyl)phenol | Liquid form, easy dispersion, environmentally friendly | BR, SBR, EPDM, NBR, SBS, SIS, adhesives |
| Antioxidant 2246 | 119-47-1 | 2,2'-Methylenebis(4-methyl-6-tert-butylphenol) | Non-staining, non-discoloring, FDA approved | Polybutadiene, SBR, butyl rubber, NBR, TPE, natural and synthetic latex |
| BHT (Antioxidant 264) | 128-37-0 | 2,6-Di-tert-butyl-4-methylphenol | General purpose, low cost | Various rubbers and plastics (general applications) |
| 4,4'-Butylidenebis(6-tert-butyl-3-methylphenol) | 85-60-9 | 4,4'-Butylidenebis(6-tert-butyl-3-methylphenol) | White sidewall grade, non-discoloring | NR, SBR, EPDM |
| MB | 583-39-1 | 2-Mercaptobenzimidazole | Secondary antioxidant, synergistic with amine antioxidants | NR, CR, SBR, NBR, EPR |
Natural Source Phenolic Antioxidants (Eco-friendly/R&D Grade)
In recent years, with increasing environmental awareness, natural phenolic antioxidants have gained attention as potential alternatives to traditional synthetic antioxidants. A study published in RSC Advances used a molecular simulation screening strategy to identify three candidates with good antioxidant performance in NR composites from 18 natural phenolic antioxidants:
| Product Name | CAS No. | Source | Features |
|---|---|---|---|
| Thymol | 89-83-8 | Natural phenol, extracted from thyme and other plants | Extends NR oxidation time, good biocompatibility |
| α-Tocopherol (Vitamin E) | 10191-41-0 | Natural phenol, main component of vitamin E | Excellent biocompatibility, eco-friendly antioxidant alternative |
| lsEGCG | — | Green tea extract derivative | Natural antioxidant, extends NR oxidation time |
Phenolic Antioxidants Selection Guide
1.Key Selection Factors
| Factor | Consideration |
|---|---|
| Color requirements | Light-colored/transparent products must use non-staining, non-discoloring phenolic antioxidants |
| Service temperature | Standard phenolics suitable for <100°C; high molecular weight hindered phenolics can withstand higher temperatures |
| Extraction/migration requirements | Products in contact with liquids or high-temperature environments require high molecular weight, extraction-resistant types (e.g., 1010, 3114) |
| Processing method | Liquid phenolics (e.g., 1520) offer easier dispersion; powders require dust control; Wingstay SP Powder uses inert silica carrier for easier handling |
| Synergistic effects | Phenolics are often combined with phosphites (secondary antioxidants) for better processing stability |
| Environmental requirements | Natural source phenolics (Thymol, α-Tocopherol) are suitable for green applications |
| Regulatory compliance | Check FDA, REACH certifications for food contact and medical applications |
2.Selection Decision Table
| Application Need | Recommended Product | Recommended Loading (phr) | Notes |
|---|---|---|---|
| General thermo-oxidative protection | Antioxidant 1076 | 0.1–0.5 | Non-staining, cost-effective, good compatibility |
| Long-term high-temperature aging protection | Antioxidant 1010 / 3114 | 0.1–0.5 | High molecular weight, low volatility, long-term stability |
| Light-colored/transparent products | Antioxidant 2246 / Wingstay SP Powder | 0.5–1.5 | Non-discoloring, non-staining |
| White sidewall compounds | 4,4'-Butylidenebis(6-tert-butyl-3-methylphenol) | 0.5–1.5 | Non-discoloring, specifically for white and light-colored rubber |
| Liquid, easy dispersion systems | Antioxidant 1520 | 0.5–1.5 | Liquid form, easy metering, suitable for continuous production |
| Adhesives/sealants | Antioxidant 3114 / 1520 | 0.1–0.5 | Good compatibility, non-staining |
| Polyamide fibers | Antioxidant 1098 | 0.1–0.5 | Strong extraction resistance, excellent color protection |
| Wire & cable insulation | Antioxidant 1010 / 3114 | 0.1–0.5 | Low volatility, good electrical properties |
| Natural latex products | Wingstay SP Powder | 0.5–1.5 | Powder form dispersion in latex, non-staining |
| Eco-friendly/biobased applications | Thymol / α-Tocopherol | R&D grade | Natural source, good biocompatibility |
| Secondary/synergistic protection | MB | 0.5–1.0 | Significant synergies with amine antioxidants |
Synergistic Combinations of Phenolic and Secondary Antioxidants
Phenolic antioxidants, as primary antioxidants (free radical scavengers), are often used in combination with secondary antioxidants to achieve better performance. Studies have shown that raw rubber containing a complex antioxidant system of hindered phenol, p-phenylenediamine, and phosphite exhibits the highest oxidation induction temperature and longest oxidation induction time, demonstrating the best thermo-oxidative aging resistance.
| Secondary Antioxidant Type | Representative Product | Synergistic Effect |
|---|---|---|
| Phosphites | Antioxidant 168 | Decomposes hydroperoxides, synergistic processing stability with phenolics |
| Thioesters | DLTDP, DSTDP | Provides long-term thermal aging protection, synergistic with hindered phenolics |
| p-Phenylenediamines | 6PPD, IPPD | Combined with phenolics provides comprehensive protection against thermo-oxidative aging and flex fatigue in NR/TBIR systems |
| Hydroxylamines | — | Efficient free radical scavenger, significantly improves stability at low addition levels |
Typical Addition Levels of Phenolic Antioxidants in Rubber
| Application | Recommended Loading (phr) | Recommended Product |
|---|---|---|
| Tire sidewalls (white/light-colored) | 0.5–1.5 | Antioxidant 2246, 4,4'-Butylidenebis(6-tert-butyl-3-methylphenol) |
| Conveyor belts | 0.1–0.5 | Antioxidant 1010, 3114 |
| Hoses, seals | 0.1–0.5 | Antioxidant 1076, 1520 |
| Adhesives | 0.1–0.5 | Antioxidant 3114, 1520 |
| Wire & cable insulation | 0.1–0.5 | Antioxidant 1010, 3114 |
| Natural latex products | 0.5–1.5 | Wingstay SP Powder |
| Footwear / consumer rubber goods | 0.1–0.5 | Antioxidant 1076 |
| Eco-friendly rubber products | R&D grade | Thymol, α-Tocopherol |
Comparison of Phenolic vs. Amine Antioxidants
Phenolic and amine antioxidants are the two most commonly used types of antioxidants in the rubber industry, each with their own advantages and disadvantages. Key comparison:
| Aspect | Phenolic Antioxidants | Amine Antioxidants |
|---|---|---|
| Staining | Non-staining | Staining |
| Suitable products | Light-colored, transparent, colored products | Dark-colored, black products |
| Heat aging protection | Moderate (effective below 100°C) | Strong (higher efficiency at elevated temperatures) |
| Flex fatigue protection | Weak, suitable for static or low-to-medium dynamic conditions | Excellent, high efficiency for dynamic protection |
| Synergistic combinations | Often used with phosphites, thioesters | Often used with phenolics to balance thermal and dynamic fatigue protection |
| Typical applications | White sidewalls, light-colored footwear, latex products | Tire sidewalls, conveyor belts, dynamic seals |
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