Anti-Aging Agents for Rubber: PPD and TMQ Systems

Rubber products degrade through two primary mechanisms: thermo-oxidative aging and ozone cracking. Without antidegradant protection, NR and SBR compounds lose elasticity and develop surface cracks within months of outdoor exposure.

PPD (p-Phenylenediamine) Antidegradants

PPDs are the most powerful antiozonants and antioxidants for diene rubbers.

Key PPD types:

• 6PPD: Industry standard for tires; excellent dynamic ozone protection. Typical loading: 1–3 phr.
• IPPD: Good static ozone protection; lower cost than 6PPD.
• 77PD: Low-volatility; suitable for high-temperature applications.

TMQ (Polymerized 2,2,4-Trimethyl-1,2-Dihydroquinoline)

TMQ is a non-staining antioxidant that protects against thermal and oxygen aging. Suitable for light-colored compounds where PPD staining is unacceptable. Typical loading: 1–2 phr.

Combined Protection

For severe ozone and thermal exposure (tires, conveyor belts, automotive hoses):

• 6PPD: 2 phr + TMQ: 1 phr + Physical antiozonant wax: 2–5 phr

Environmental Considerations

6PPD degrades to 6PPD-quinone (6PPD-Q), which is highly toxic to coho salmon (LC50 <0.1 µg/L). Regulatory scrutiny increasing.

HMEChem supplies 6PPD, IPPD, TMQ, and wax antiozonants for tire, automotive, and industrial rubber applications.