Rubber Aging Pathways and Antidegradant Selection: From Thermo-Oxidative Aging and Ozone Cracking to Migration and Extraction Control

1. What are rubber antidegradants?

Rubber antidegradants are additives incorporated into rubber formulations, latex systems, or rubber surface-protection systems to delay performance deterioration caused by heat, oxygen, ozone, light exposure, mechanical deformation, metal ions, and chemical media. Their role is not to make rubber permanently resistant to aging, but to slow down the aging rate so that rubber products can better retain elasticity, strength, elongation, crack resistance, and appearance stability during storage, processing, and service.

The scope of rubber antidegradants is broader than that of ordinary antioxidants. Antioxidants mainly target oxidative aging, while rubber antidegradants also include antiozonants, anti-flex-cracking agents, metal-deactivating antidegradants, and protective waxes. In general, rubber antidegradants are substances that inhibit aging factors such as oxidation, heat, or light radiation, thereby delaying polymer degradation and extending the service life of rubber products.

2. Why does rubber age?

The direct signs of rubber aging include hardening, embrittlement, tackiness, cracking, reduced strength, lower elongation, surface chalking, or loss of elasticity. Behind these changes are alterations in rubber molecular chains, the crosslinking network, filler interfaces, and formulation additives under service conditions. The common aging pathways of rubber products can be divided into six major types.

Aging pathway	Main conditions	Typical manifestations	Protection focus
Thermo-oxidative aging	High temperature, air, long-term storage, or long-term service	Hardening, embrittlement, decreased tensile strength, decreased elongation at break	Inhibit free-radical chain oxidation and reduce further peroxide decomposition
Ozone aging	Atmospheric ozone, tensile strain, outdoor exposure	Fine cracks roughly perpendicular to the direction of tensile strain	Combine antiozonants with protective waxes
Flex-fatigue aging	Repeated deformation in tires, belts, hoses, vibration-damping parts, etc.	Crack initiation and propagation, shortened dynamic service life	Coordinate anti-flex-cracking antidegradants, rubber type, carbon black, and curing system
Metal-catalyzed aging	Residual or contacted metal ions such as copper, manganese, and iron	Accelerated local oxidation and abnormal performance loss	Use metal-deactivating or heterocyclic antidegradants
Photo-oxidative aging	Outdoor light exposure, ultraviolet radiation, and oxygen	Surface discoloration, chalking, cracking	Use antioxidant systems, light shielding, and surface protection
Extraction-induced aging by media	Long-term contact with oil, water, solvents, or cleaning agents	Loss of antidegradants, plasticizers, or soluble components	Verify low-extraction antidegradants and resistance to service media

Different rubbers have different aging sensitivities. Natural rubber, styrene-butadiene rubber, butadiene rubber, and nitrile rubber contain relatively high levels of unsaturated structures and are therefore susceptible to ozone, oxygen, and heat. Ethylene-propylene-diene rubber has a highly saturated main chain and generally offers good ozone resistance, but it still requires antioxidant and weathering protection under high temperature, light exposure, and long-term outdoor service.

3. Development of rubber antidegradants

The development of rubber antidegradants is not simply a matter of product replacement. It has been driven by the service requirements of rubber products.

3.1 From storage protection to processing protection

Early rubber products first faced problems such as tackiness during storage, cracking, and thermo-oxidative damage during processing. At this stage, antidegradants were mainly used to inhibit oxidation and reduce performance loss during processing, storage, and early service.

3.2 From static protection to dynamic protection

With the widespread use of tires, hoses, belts, conveyor belts, and vibration-damping products, rubber was required not only to resist thermo-oxidative aging, but also to withstand ozone and repeated flexing. As a result, p-phenylenediamine and quinoline antidegradants became important categories in dark-colored dynamic rubber products.

Antidegradant 4020, namely N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, is commonly referred to as 6PPD in environmental studies. Antidegradant RD, namely polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, is another common representative. Research data show that p-phenylenediamine and aromatic amine antidegradants have prominent effects in antioxidation, antiozonation, heat resistance, and flex-fatigue resistance. Copper-induced degradation or metal-catalyzed aging usually requires benzimidazole antidegradants, metal-deactivating antidegradants, or a combined protection system. Amine antidegradants tend to discolor white or light-colored rubber, so they are not suitable for products sensitive to color change or contact staining.

3.3 From high-efficiency protection to low-staining protection

White rubber, light-colored rubber, transparent latex, medical rubber, food-contact rubber, and precision electronic rubber have higher requirements for color, odor, migration, contact staining, and safety. For this reason, hindered phenols, heterocyclic antidegradants, phosphites, and low-staining combined systems have received increasing attention.

Phenolic antidegradants have less impact on color and are often used in light-colored rubber. Heterocyclic antidegradants can be used for thermo-oxidative aging and copper-induced degradation protection. Phosphites are usually used as secondary antioxidants and are combined with phenolic or amine antidegradants to improve the completeness of thermo-oxidative protection.

3.4 From formulation performance to environmental transformation risk

Modern antidegradant research no longer focuses only on whether an antidegradant has strong anti-aging performance. It also considers migration, blooming, extraction, environmental release, and transformation products.

Antidegradant 4020 remains an important material for preventing ozone cracking in tires, but its ozonation product, 6PPD-quinone, has been identified in studies as an important toxicant associated with acute mortality of coho salmon in stormwater runoff. This finding has moved rubber antidegradant research into a new stage: it is necessary not only to ensure the safety and durability of tires and rubber products, but also to evaluate the environmental release, exposure levels, and ecological risks of antidegradants and their transformation products.

4. How do antidegradants delay rubber aging?

The action of antidegradants can be divided into two categories. One is chemical protection, in which the antidegradant directly participates in reactions related to oxidation, ozone, or metal-catalyzed degradation. The other is physical protection, in which surface isolation reduces the contact between rubber and ozone or oxygen.

Protection mode	Main function	Representative types	Corresponding aging problems
Free-radical scavenging	Interrupts chain reactions in thermo-oxidative aging	Amine and phenolic antidegradants	Thermo-oxidative aging, oxidation during processing
Hydroperoxide decomposition	Reduces further free-radical formation from oxidative intermediates	Phosphite and thioester secondary antioxidants	High-temperature oxidation, long-term heat aging
Preferential reaction with ozone	Allows the antiozonant to be consumed by ozone before the rubber main chain is attacked	p-Phenylenediamine antidegradants	Ozone cracking, dynamic cracks
Formation of a surface barrier layer	Reduces contact between ozone/oxygen and the rubber surface	Protective waxes such as paraffin wax and microcrystalline wax	Static ozone aging, storage aging
Metal ion deactivation	Reduces oxidation catalyzed by metal ions	Benzimidazole and metal-deactivating antidegradants	Copper-induced degradation, aging caused by metal contact

Whether an antidegradant is effective depends on three conditions.

① The antidegradant must be able to reach the site where aging occurs. For example, antiozonants need to function continuously at the rubber surface, and protective waxes also need to migrate to the surface to form a wax film.

② The antidegradant must be compatible with the rubber system. Poor compatibility can cause blooming, whitening, staining, poor adhesion, or failure in subsequent coating processes.

③ The antidegradant must withstand the service environment. Oil, water, solvents, cleaning agents, and high temperature may all cause the antidegradant to leach out or lose effectiveness.

5. What are the main categories of rubber antidegradants?

Rubber antidegradants can be classified by chemical structure or by function. By chemical structure, common chemical antidegradants include amines, phenolics, heterocyclic compounds, phosphites, and nickel salts. In actual production, combined systems are often used to obtain comprehensive protection.

5.1 Amine antidegradants

Amine antidegradants include p-phenylenediamines, diaryl secondary amines, ketone-amine condensates, and aldehyde-amine condensates. They generally provide strong protection against thermo-oxidative aging, ozone aging, and flex-fatigue aging, and are widely used in dark-colored rubber products.

Representative type	Main function	Application scenarios	Notes
p-Phenylenediamines	Antiozonation, flex-fatigue resistance, thermo-oxidative protection	Tires, hoses, belts, conveyor belts	Prone to discoloration and staining; environmental transformation products need attention
Quinoline antidegradants	Thermo-oxidative protection and improved long-term heat resistance	Dark-colored rubber, tires, industrial rubber parts	Mainly used for thermo-oxidative aging and long-term heat protection; ozone-cracking resistance is usually weaker than that of p-phenylenediamines; in dynamic rubber products, they are often used as thermo-oxidative protection components in combined systems

5.2 Phenolic antidegradants

Phenolic antidegradants include hindered phenols, bisphenols, polyphenols, and thiobisphenols. They mainly delay thermo-oxidative aging by terminating free-radical chain reactions. Compared with amine antidegradants, phenolic antidegradants have less impact on color and are often used in light-colored rubber products.

Main features	Application scenarios	Notes
Low staining and low discoloration; suitable for light-colored systems	White rubber, light-colored rubber, transparent products, low-staining products	Protection against ozone and dynamic fatigue is usually limited; combined systems should be selected according to service conditions

5.3 Heterocyclic antidegradants

Common heterocyclic antidegradants include 2-mercaptobenzimidazole and its zinc salt. They are mainly used for thermo-oxidative aging and copper-induced degradation protection, and may also be used in light-colored, transparent, or latex products.

Main features	Application scenarios	Notes
Helpful for thermo-oxidative aging and metal-catalyzed aging	Wire and cable, latex products, light-colored rubber, metal-contact rubber parts	Food-contact, medical, and long-term skin-contact applications require separate review of regulatory status and migration data

5.4 Phosphite and thioester secondary antidegradants

Phosphites and thioesters are usually used as secondary antioxidants. Phosphites can decompose hydroperoxides and improve processing and thermo-oxidative stability. Thioesters are commonly used in synergy with hindered phenolic antioxidants for long-term thermo-oxidative aging protection. They usually do not serve as the sole core protection component in rubber, but are combined with phenolic or amine antidegradants to improve the completeness of thermo-oxidative protection.

Main features	Application scenarios	Notes
Secondary antioxidant function, improved heat stability, relatively low impact on color	High-temperature processing, light-colored systems, combined antioxidant systems	Limited protection against ozone cracking and dynamic fatigue when used alone

5.5 Protective waxes

Protective waxes are physical protection materials, commonly including paraffin wax and microcrystalline wax. They can migrate to the rubber surface and form a thin film, reducing direct contact between the rubber and ozone or oxygen. In the literature, this barrier-film formation is also classified as a physical anti-aging approach.

Main features	Application scenarios	Notes
Provides static ozone protection through a surface wax film	Tire sidewalls, outdoor hoses, seals, storage protection	The wax film may rupture under dynamic flexing; excessive use may affect appearance, adhesion, and coating

Protective waxes usually do not provide full protection on their own. Instead, they complement p-phenylenediamine antiozonants.

5.6 Nickel salts and other protective agents

Nickel salt antidegradants provide a certain degree of antiozonant and weathering protection. However, due to color, metal residues, regulatory requirements, and environmental concerns, they need to be used cautiously in modern formulations. When selecting such materials, performance benefits, compliance requirements, and environmental impact should all be evaluated.

6. How should rubber antidegradants be selected?

Antidegradant selection should be judged from five aspects: rubber type, aging environment, appearance requirements, migration risk, and verification method.

6.1 Start with the rubber type

Rubber type or system	Main aging sensitivities	Antidegradant selection focus
Natural rubber	Thermo-oxidative aging, ozone aging, flex-fatigue aging	Amine antidegradants, protective waxes, and secondary antioxidant systems when needed
Styrene-butadiene rubber	Thermo-oxidative aging, ozone aging, dynamic cracking	Combined systems of p-phenylenediamines, quinoline antidegradants, and protective waxes
Butadiene rubber	Ozone aging, flex-fatigue aging, thermo-oxidative aging	Antiozonants and dynamic-fatigue protection systems
Nitrile rubber	Thermo-oxidative aging, extraction by oil media, metal contact	Thermo-oxidative antidegradants, low-extraction protection systems, and metal-deactivation approaches
Ethylene-propylene-diene rubber	Heat, light, long-term outdoor exposure	Phenolic antidegradants, secondary antioxidants, and weathering protection systems
Specialty rubbers such as silicone rubber and fluororubber	High temperature, media exposure, and special service conditions	Verification based on dedicated formulations, processing methods, and service standards

6.2 Then consider the service environment

Service scenario	Main failure risks	Selection focus
Tire sidewall	Ozone cracking, flex-fatigue aging, outdoor aging	Combined use of p-phenylenediamine antiozonants, antidegradant RD, and protective waxes
Rubber hose	Thermo-oxidative aging, ozone aging, extraction by media, dynamic deformation	Amine or phenolic systems, with extraction by media verified
Conveyor belts and transmission belts	Flex-fatigue aging, thermo-oxidative aging, crack propagation	Coordination of anti-flex-cracking antidegradants, fillers, and curing system
Sealing rings	Compression set, thermo-oxidative aging, oil media	Low-extraction, low-migration protection systems compatible with service media
Wire and cable sheathing	Thermo-oxidative aging, copper-induced degradation, weathering, electrical properties	Heterocyclic antidegradants, phenolic antidegradants, and secondary antioxidant systems
White or light-colored rubber	Discoloration, staining, thermo-oxidative aging	Low-staining systems based on phenolics, heterocyclic antidegradants, and phosphites
Medical or food-contact rubber	Migration, odor, toxicology, and regulatory requirements	Low-migration, low-extraction antidegradants with clear compliance documentation

6.3 Then consider appearance and contact requirements

For dark-colored rubber, high-efficiency amine antidegradants may be prioritized. For white, light-colored, transparent, medical, food-contact, or electronic-contact products, low-staining, low-migration, and low-odor protection systems should be prioritized.

If rubber products require subsequent bonding, coating, printing, or encapsulation, the surface migration of antidegradants and protective waxes should be carefully considered. Excessive migration may cause adhesion failure, coating craters, surface whitening, or contact staining.

6.4 Finally, consider migration and extraction

Antidegradants need appropriate migration to protect the rubber surface, but excessively fast migration may cause blooming, contact staining, and environmental release. Oil, water, solvents, and cleaning agents may extract antidegradants, reducing long-term protection. Therefore, migration and extraction should be included in the evaluation of seals, hoses, medical rubber, and outdoor rubber.

7. Common misconceptions when using rubber antidegradants

7.1 Misconception 1: The more antidegradant added, the better

Excessive antidegradant dosage may lead to blooming, discoloration, increased odor, contact staining, reduced adhesion, and higher cost. For migratory antiozonants, insufficient dosage may result in inadequate surface protection, while excessive dosage may cause surface exudation.

7.2 Misconception 2: One antidegradant can solve all aging problems

Thermo-oxidative aging, ozone cracking, flex-fatigue aging, metal-catalyzed aging, and extraction by media are not the same type of failure. Dark-colored dynamic products, light-colored products, seals, cable sheathing, and food-contact products require different protection priorities. The same antidegradant system cannot simply be applied to all products.

7.3 Misconception 3: Only tensile strength after aging matters

Rubber product failure does not necessarily first appear as a decline in tensile strength. Ozone cracks, increased hardness, decreased elongation at break, surface blooming, color change, swelling in media, and adhesion failure may all occur earlier. Antidegradant evaluation should select indicators according to the intended use of the product.

7.4 Misconception 4: Treating low-staining claims as equivalent to safe applicability

“Non-staining” mainly means that the material causes less staining of rubber color and contact surfaces. It does not necessarily mean low toxicity, low migration, or suitability for all scenarios. Whether an antidegradant can be used still needs to be judged based on formulation compatibility, migration and blooming, extraction by media, regulatory requirements, and environmental transformation products. Food-contact, medical, long-term skin-contact, and outdoor-release applications require separate safety and compliance evaluations.

7.5 Misconception 5: Ignoring the curing system

Sulfur curing, peroxide curing, and resin curing differ in their compatibility with antidegradants. Some free-radical scavenging antidegradants may affect peroxide crosslinking efficiency. Therefore, the curing curve, crosslink density, initial properties, and aged properties should all be checked together.

8. Future research directions for rubber antidegradants

8.1 Low-migration and low-extraction antidegradants

Traditional small-molecule antidegradants can easily migrate, bloom, or be extracted by media. Low-migration, reactive, polymer-bound, or carrier-immobilized antidegradants can help extend protection duration and reduce surface staining and environmental release.

8.2 Research on antiozonant alternatives

Antidegradant 4020 still has important value for tire safety and ozone-cracking resistance, but the environmental risk of 6PPD-quinone has driven the screening of alternatives. Alternative research should not compare only ozone-cracking performance; it should also examine dynamic fatigue, tire safety, migration behavior, transformation products, toxicological risk, and cost.

8.3 What needs to be verified when naturally derived antidegradants are used in rubber formulations?

Natural polyphenols, lignin, tannins, and plant extracts have antioxidant potential. However, when used in rubber formulations, their thermal stability, compatibility with rubber, dispersibility, color impact, odor, batch-to-batch stability, and effects on curing and aged properties still need to be verified. Natural origin does not mean that they can directly replace traditional industrial antidegradants. Only after they show stable performance in formulation processing and aging tests are they suitable for further application evaluation.

8.4 Multi-factor aging evaluation

Actual rubber products often experience heat, oxygen, ozone, light, humidity, stress, and media exposure at the same time. Future formulation evaluation should make greater use of combined aging approaches, such as conducting ozone-cracking tests after heat aging or performing flex-fatigue tests after liquid immersion, so that selection decisions are not misled by a single test result.

9. Product Selection Guide for Rubber Antidegradants: From Aging Pathway Identification to Protection-System Design

Research or experimental objective	Recommended table to consult first	Why start with this table	Recommended linked table	Selection guidance
Establish a basic selection framework for rubber antidegradants	Table 1 and Table 2	Table 1 focuses on amine antidegradants, which are suitable for understanding antiozonation, flex-crack resistance, and thermo-oxidative protection in dark-colored rubber; Table 2 focuses on phenolic antidegradants, which are suitable for understanding low-staining protection, light-colored systems, and thermo-oxidative protection	Table 3 and Table 4	First determine whether the target aging pathway is ozone aging, flexing, thermo-oxidative aging, copper-induced degradation, or extraction by media, and then select the corresponding protection type
Study antiozonation and flex-crack protection for dynamic rubber products such as tire sidewalls, hoses, and belts	Table 1	The p-phenylenediamine and aromatic amine products in Table 1 are directly related to ozone cracking, dynamic cracking, and thermo-oxidative aging	Table 3 and Table 4	Amine antidegradants can be combined with paraffin wax and quinoline antidegradants to observe the combined changes after static ozone exposure, dynamic flexing, and heat aging
Compare structural differences and protective effects among different amine antidegradants	Table 1	Table 1 covers p-phenylenediamines, diphenylamines, naphthylamines, and alkylated aromatic amines, which can be used to compare the influence of aromatic amine structure, alkyl substitution, and molecular size on protection performance	Table 4	Quinoline antidegradants can be included to compare differences among amine antidegradants in antiozonation, thermo-oxidative protection, and discoloration tendency
Build a thermo-oxidative aging protection system for dark-colored industrial rubber	Table 4	The polymerized quinoline and ethoxyquin in Table 4 can be used for thermo-oxidative aging and long-term heat-resistance studies; benzimidazole products are suitable for metal-contact, copper-induced degradation, and thermo-oxidative stability studies	Table 1 and Table 3	Quinoline or benzimidazole products can be combined with aromatic amines, phosphites, or thioesters to observe changes in tensile strength, elongation, and hardness after aging
Develop protection systems for light-colored, low-staining, or appearance-sensitive rubber	Table 2	Table 2 focuses on hindered phenols, bisphenols, thiobisphenols, and polymeric phenolic antidegradants, which are suitable for studies on color stability and low-staining protection	Table 3 and Table 4	First use phenolic antidegradants to establish thermo-oxidative protection, and then select auxiliary protection components according to whether metal contact, long-term heat aging, or extraction by media is present
Study the structural effects of phenolic antidegradants in rubber thermo-oxidative aging	Table 2	Table 2 includes small-molecule hindered phenols, bisphenols, thiobisphenols, and high-molecular-weight hindered phenols, which can be used to compare the effects of molecular weight, bridged structures, and phenolic hydroxyl environments on antioxidant persistence	Table 3	Phosphite or thioester secondary antioxidants can be combined to observe property retention after aging and migration behavior in blended systems
Design combined systems of hindered phenols and secondary antioxidants	Table 3	Table 3 focuses on phosphite and thioester secondary antioxidants, which can be used to decompose hydroperoxides and improve the completeness of thermo-oxidative aging protection	Table 2	Use phenolic antidegradants first as the primary antioxidant component, then add phosphite or thioester products to compare aged properties between single-additive and combined systems
Study physical ozone protection on rubber surfaces	Table 3	Paraffin wax in Table 3 can be used for surface-barrier protection studies and is suitable for evaluating the effect of wax films on static ozone cracking and storage aging	Table 1	Paraffin wax can be combined with p-phenylenediamine antiozonants to compare the synergistic effects of chemical protection and surface physical protection
Study wire and cable, metal-contact rubber, or copper-induced degradation protection	Table 4	The benzimidazole antidegradants in Table 4 are closely related to metal-catalyzed aging, copper-induced degradation protection, and thermo-oxidative stability	Table 2 and Table 3	Experiments can be designed around metal contact, hot-air aging, and retention of electrical properties to observe the effects of antidegradants on aged mechanical properties and appearance
Compare low-migration, extraction-resistant, or long-term heat-aging protection approaches	Table 2	The high-molecular-weight hindered phenols and polymeric phenolic antidegradants in Table 2 are suitable for studies on low volatility, low migration, and long-term protection	Table 3	Thioester or phosphite secondary antioxidants can be added, followed by evaluation of retained protection after treatment with oil, water, or solvents
Study environmental transformation products and analytical methods for antidegradants	Table 4	Table 4 includes the quinone oxidation product of Antidegradant 4020, making it suitable for studies on tire wear particles, leachates, and ozone-oxidation transformation	Table 1	Starting from Antidegradant 4020 itself, ozone oxidation, sample pretreatment, and quantitative analytical methods can be established to track parent-compound consumption and oxidation-product formation
Conduct control experiments for rubber antidegradant formulation screening	Table 1, Table 2, Table 3, and Table 4	The four tables cover amines, phenolics, secondary antioxidants, protective waxes, quinolines, benzimidazoles, and environmental transformation products, making them suitable for building control combinations based on different protection mechanisms	Select according to the experimental objective	Control groups can include a no-antidegradant group, single-antidegradant group, combined-antidegradant group, and simulated target service-condition group to compare thermo-oxidative aging, ozone aging, flexing, migration, and color change

Table 1｜Amine Antiozonants, Flex-Crack-Resistant Antidegradants, and Thermo-Oxidative Antidegradants

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Alkylated diphenylamine thermo-oxidative antidegradant	68411-46-1	A304374	Irganox 5057	Reagent grade	Used to study the role of liquid aromatic amines in rubber thermo-oxidative aging, oil-phase compatibility, and synergy with phenolic antidegradants; applicable to thermal-stability screening of dark-colored rubber and elastomers.
p-Phenylenediamine antiozonant	793-24-8	N137371	N-(1,3-Dimethylbutyl)-N′-phenyl-1,4-phenylenediamine (6PPD)	≥98% (GC)	A commonly used antiozonant and flex-crack-resistant protective agent in tires, hoses, belts, and dynamic rubber products; can be used to study ozone cracking, thermo-oxidative aging, and antidegradant migration behavior.
p-Phenylenediamine antioxidant antidegradant	74-31-7	D102501	N,N′-Diphenyl-p-phenylenediamine	≥98%	Used for studies on rubber thermo-oxidative aging and structural effects of amine antidegradants; can serve as a screening and control sample for p-phenylenediamine antidegradants.
Aromatic secondary amine antidegradant	90-30-2	P110559	N-Phenyl-1-naphthylamine	≥98%	Can be used in studies on thermo-oxidative protection of natural rubber and synthetic rubber; suitable for comparing the differences between naphthylamine structures and diphenylamine or p-phenylenediamine antidegradants.
Diphenylamine high-temperature antioxidant antidegradant	10081-67-1	B152187	4,4′-Bis(α,α-dimethylbenzyl)diphenylamine	≥98%	Used for studies on high-temperature oxidative stability of rubber, elastomers, and polymers; can be used to compare the influence of bulky diphenylamine structures on thermo-oxidative protection and volatilization loss.
Alkylated diarylamine antioxidant antidegradant	15721-78-5	B303010	Bis(4-(2,4,4-trimethylpentan-2-yl)phenyl)amine	≥97%	Used to study the role of alkyl-substituted diarylamines in rubber heat stability, oxidation induction period, and low-volatility antioxidant systems.
p-Phenylenediamine antioxidant antidegradant	93-46-9	D121460	N,N′-Di-2-naphthyl-1,4-phenylenediamine	≥96%	Can be used for thermo-oxidative aging studies of dark-colored rubber and comparative experiments on amine antidegradant structures; suitable for observing the influence of aromatic substitution on rubber discoloration and antioxidant effect.
p-Phenylenediamine antiozonant	101-72-4	I157651	4-Isopropylaminodiphenylamine	≥95%	Commonly used to study p-phenylenediamine antiozonation and flex-crack protection; can be compared with Antidegradant 4020 in terms of antiozonant efficiency, discoloration tendency, and migration behavior.

Table 2｜Hindered Phenols, Thiobisphenols, and Polymeric Phenolic Antidegradants

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Polymeric hindered phenol antidegradant	68610-51-5	P477159	Poly(dicyclopentadiene-co-p-cresol)	Solid	Used to study the role of polymeric phenolic antidegradants in rubber thermo-oxidative aging, low migration, and extraction-resistant protection; suitable for screening light-colored or low-staining systems.
Small-molecule hindered phenol antidegradant	128-37-0	D104366	2,6-Di-tert-butyl-4-methylphenol	Ultrapure grade, ≥99.5% (GC)	Can be used for studies on thermo-oxidative stability of rubber, latex, and polymers; suitable as a basic control for hindered phenolic antioxidants.
Hydroquinone-type hindered phenol antidegradant	88-58-4	B107613	2,5-Di-tert-butylhydroquinone (DBHQ)	Moligand™, ≥98%	Used to study the role of hydroquinone structures in free-radical scavenging, thermo-oxidative aging inhibition, and antioxidant systems for light-colored rubber.
Styrenated phenolic antidegradant	61788-44-1	T1067100	Styrenated phenol	Mixture	Used for studies on thermo-oxidative aging resistance, discoloration prevention, and low-staining protection in rubber and elastomers; can serve as a phenolic antidegradant screening option for light-colored rubber.
Bisphenol-type hindered phenol antidegradant	119-47-1	M124850	2,2′-Methylenebis(6-tert-butyl-4-methylphenol)	≥99%	Used for thermo-oxidative aging studies of light-colored rubber, latex, and elastomers; can be used to compare the effect of bisphenol structures on antioxidant efficiency and migration behavior.
Bisphenol-type hindered phenol antidegradant	88-24-4	M158327	2,2′-Methylenebis(6-tert-butyl-4-ethylphenol)	≥98% (GC)	Used in low-staining rubber protection systems; can be used to evaluate the influence of ethyl-substituted bisphenol structures on thermo-oxidative aging, color stability, and compatibility.
Thiobisphenol antidegradant	96-69-5	T162247	4,4′-Thiobis(6-tert-butyl-m-cresol)	≥98%	Combines phenolic hydroxyl antioxidant activity with a sulfur-bridged structural feature; can be used for studies on rubber thermo-oxidative aging, long-term heat resistance, and low-staining antioxidant systems.
High-molecular-weight hindered phenol antioxidant	6683-19-8	P473547	Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)	≥98%	Used in low-volatility and low-migration antioxidant systems; applicable to experiments on retention of mechanical properties before and after aging in rubber, thermoplastic elastomers, and polymers.
High-molecular-weight hindered phenol antioxidant	2082-79-3	I106561	Irganox 1076	≥98%	Used for studies on thermo-oxidative stability of rubber and elastomers; suitable for evaluating long-term aging protection when compounded with phosphite or thioester secondary antioxidants.
Bisphenol-type hindered phenol antidegradant	85-60-9	B152804	4,4′-Butylidenebis(6-tert-butyl-m-cresol)	≥97% (HPLC)	Used in rubber thermo-oxidative aging and low-staining protection systems; can be used to compare the effect of butylidene-bridged bisphenol structures on antioxidant persistence.

Table 3｜Phosphite and Thioester Secondary Antioxidants and Physical Protective Waxes

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Phosphite secondary antioxidant	25448-25-3	T303233	Triisodecyl Phosphite (mixture of isomers)	Mixture of isomers	Used to decompose hydroperoxides and improve processing heat stability; can be combined with hindered phenols or amine antidegradants to study combined antioxidant systems in rubber.
Thioester secondary antioxidant	693-36-7	D137678	Dioctadecyl 3,3′-Thiodipropionate	≥90% (HPLC)	Used for long-term thermo-oxidative aging protection studies; can act synergistically with hindered phenolic antidegradants to evaluate strength retention and hardness changes after aging in rubber and elastomers.
Thioester secondary antioxidant	123-28-4	D154974	Didodecyl 3,3′-Thiodipropionate	≥90%	Used in secondary antioxidant systems and peroxide-decomposition pathway studies; can be used to compare the compatibility and extraction resistance of thioesters with different alkyl chains in rubber.
Phosphite secondary antioxidant	26523-78-4	T486960	Tris(nonylphenyl) phosphite	—	Used for rubber processing stability and secondary protection against thermo-oxidative aging; can be combined with phenolic antidegradants to evaluate the antioxidant efficiency of blended systems.
Physical protective wax	8002-74-2	P434228	Paraffin wax	Melting point ≥65 °C (ASTM D 87)	Used for physical surface isolation against ozone and storage protection in rubber; can be combined with p-phenylenediamine antiozonants to evaluate static ozone-cracking protection.

Table 4｜Quinolines, Benzimidazoles, Nickel Salts, and Environmental-Research-Related Products

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Quinoline thermo-oxidative antidegradant	26780-96-1	P192432	Poly(1,2-dihydro-2,2,4-trimethylquinoline)	Softening point: 80–100 °C	A commonly used thermo-oxidative antidegradant in dark-colored rubber; can be used in studies on retention of aged mechanical properties and combined protection systems for tires, hoses, belts, and related products.
Benzimidazole antidegradant	583-39-1	M111104	2-Mercaptobenzimidazole	≥98%	Used for studies on rubber thermo-oxidative aging and copper-induced degradation protection; suitable for screening protection systems for wire and cable, metal-contact rubber, and light-colored rubber.
Nickel salt antiozonant	13927-77-0	N159261	Dibutyldithiocarbamic Acid Nickel Salt	≥97% (T)	Used for studies on rubber antiozonation and weathering protection; can be used to evaluate the protective effect and formulation compatibility of metal-salt antidegradants in outdoor rubber products.
Quinoline antioxidant antidegradant	91-53-2	E114373	Ethoxyquin	≥90%	Used for studies on antioxidant stability of rubber and polymers; can serve as a small-molecule quinoline antidegradant control to compare the protective differences between polymerized quinoline and small-molecule quinoline types.
Research target for antidegradant transformation products	2754428-18-5	P1430591	6PPD-Q	Moligand™, ≥99%	Used for studies on the ozonation product of Antidegradant 4020, tire wear particle leachates, and environmental toxicology analysis; suitable for method development, quantitative standard calibration, and transformation-pathway verification.

Note: The products listed above are representative Aladdin products. More product specifications can be searched on the Aladdin official website by product name, CAS number, or catalog number.

References

[1] Xu J., Hao Y., Yang Z., Li W., Xie W., Huang Y., Wang D., He Y., Liang Y., Matsiko J., Wang P. Rubber Antioxidants and Their Transformation Products: Environmental Occurrence and Potential Impact. International Journal of Environmental Research and Public Health, 2022, 19(21):14595. DOI: 10.3390/ijerph192114595.

[2] Tian Z., Zhao H., Peter K. T., Gonzalez M., Wetzel J., Wu C., et al. A ubiquitous tire rubber-derived chemical induces acute mortality in coho salmon. Science, 2021, 371(6525):185–189. DOI: 10.1126/science.abd6951.

[3] ISO 188:2023. Rubber, vulcanized or thermoplastic — Accelerated ageing and heat resistance tests.

[4] ISO 1431-1:2024. Rubber, vulcanized or thermoplastic — Resistance to ozone cracking — Part 1: Static and dynamic strain testing.

[5] ISO 1817:2024. Rubber, vulcanized or thermoplastic — Determination of the effect of liquids.

[6] ISO 37:2024. Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties.

[7] ISO 48-2:2018. Rubber, vulcanized or thermoplastic — Determination of hardness — Part 2: Hardness between 10 IRHD and 100 IRHD.