35 methods to improve ozone resistance of rubber products

Ozone erosion of rubber often occurs on the surface. The concentration of ozone in the air around us is increasing year by year. The erosion of rubber products subjected to certain strains by ozone results in the formation of cracks, which ultimately lead to the complete failure of the rubber parts.

1. Wax based anti ozone agents

To improve the ozone resistance of the rubber material under static conditions, various wax blends are usually added, such as low molecular weight paraffin, high molecular weight paraffin, or microcrystalline wax blends. These blends are limited to improving the static ozone resistance of the rubber material. If too much is added, it will actually reduce the dynamic ozone resistance of the rubber material.

2. Phenylenediamine PPDs anti ozone agent

Phenylenediamine PPDs are highly effective anti ozone agents that can impart excellent ozone resistance to rubber materials even under dynamic conditions.

In many cases, 6PPDs are also used as effective anti ozone agents under dynamic conditions.

Combining 6PPD (long-term effective) and 77PPD (short-term effective) can comprehensively improve the ozone resistance of the rubber compound.

3. Microcystic PPD

For 6PPD, microencapsulation technology can be considered, and cellulose acetate can be chosen as the microcapsule agent. Adding microencapsulated 6PPD to the adhesive can protect it from ozone corrosion for a long time and prevent the outward migration of 6PPD.

4. Wax/PPDs

To achieve good ozone resistance of the adhesive under both static and dynamic conditions, a wax is selected and an anti ozone agent such as 6PPD is used.

5. NBC anti ozone agent

Nickel dibutyldithiocarbamate (NBC) is a good static ozone inhibitor for NBR, CR, and SBR, but it is not suitable for use as a rubber compound under dynamic conditions.

6. Molecular weight and solubility of anti ozone agents

An effective anti ozone agent must be compatible with the rubber material and must be able to migrate to the surface to prevent ozone erosion. Usually, its migration speed depends on its molecular weight and solubility in the solvent

7. 6QDI

In sulfur cured diene rubber compounds, N-phenyl-N, -1,3-=methylbutyl quinoline imine (6QDI) should be used as an ozone inhibitor because after vulcanization, it will chemically bind with the rubber main chain or carbon black, improving the ozone resistance of the rubber compound. Therefore, there are reports that in some cases, 6QDI has better antioxidant effects than 6PPD/TMQ. There are also reports that 6QDI will partially convert into 6PPD and play a role in resisting ozone erosion.

8. 77PD

77PD (alkyl PPD) is mainly used for static ozone protection and short-term protection. Under dynamic conditions, it is often not used alone and is usually used in combination with alkyl and aryl PPDs to provide good ozone resistance of the adhesive under both static and dynamic conditions. Usually, 6PPD and 77PD are used in a 2:1 ratio (mass ratio), with the former for dynamic ozone protection and the latter for static ozone protection

9．TMQ/6PPD

If TMQ is not sufficient for ozone resistance or fatigue protection, 6PPD [N-phenyl-N '- (1,3-dimethylbutyl) - p-phenylenediamine] can be used in combination. This is particularly important for rubber materials that are first exposed to an oxygen environment and then exposed to an ozone environment. Therefore, it is common to use TMQ in combination with 6PPD. I

10. Non coloring formaldehyde anti ozone agent

For white or colored adhesives, non coloring antioxidants can be used. It is possible to consider using cyclic aldehyde antioxidants (Bayer's VulkazonAFS) as ozone inhibitors for various rubber compounds.

According to reports, compared with p-phenylenediamine antioxidants, bis - (1,2,3,6-tetrahydrobenzaldehyde) - pentaerythritol formaldehyde can endow CR, IIR, CIIR, BIIR and other rubber compounds with higher ozone resistance.

11. Butyl rubber and halogenated butyl rubber

Butyl rubber and halogenated butyl rubber themselves have good ozone resistance.

Butyl rubber with low unsaturation, such as 0.8% (molar concentration), has better ozone resistance because low unsaturation reduces the chance of ozone erosion.

12. DNPD/Zn0 sulfurized BIIR

Using zinc oxide and N, N, N-di-B-naphthyl-p-phenylenediamine (DNPD) or Goodrich's product Agerite White to vulcanize brominated butyl rubber can endow the rubber compound with good ozone resistance.

13．BIMS

Brominated isobutylene styrene rubber (BIMS) has better ozone resistance than some butyl rubber or halogenated butyl rubber because BIMS is fully saturated.

Replacing some halogenated butyl rubber or EPDM with BIMS in the sidewall compound of ternary blended tires based on NR can significantly improve ozone resistance and fatigue crack growth resistance.

14. Dihydroxime vulcanization of butyl rubber

The butyl rubber material is vulcanized with oxime, which can improve the ozone resistance of the rubber material.

15. Alkyl phenol disulfide sulfurized halogenated butyl rubber

When blending halogenated butyl rubber with other unsaturated elastomers, using alkylphenol disulfide for vulcanization can significantly improve the ozone resistance of the rubber compound.

16. EPDM and EPM

Both EPDM rubber and EPDM rubber have good ozone resistance.

17. High gloss ozone resistant adhesive

To achieve high glossiness on the surface of rubber products, a polymer blend containing a high saturation main chain should be selected. The blend contains these saturated components and has good ozone resistance without the need to add anti ozone agents. If anti ozone agents are used, the phenomenon of "frost spraying" will occur, which will affect the gloss of the product when it migrates to the surface. This saturated main chain elastomer

18. Avoid using NR

If strong ozone resistant agents are not used, the ozone resistance of natural rubber materials will be poor, so blends of NR and other ozone resistant elastomers are generally used.

19. NR with covering adhesive

The all natural rubber engine bracket installed on the engine has two layers of covering rubber on its surface, with the bottom layer being a cross-linked chloroprene and octene polymer mixed in a certain proportion, and the top layer being a cross-linked halogenated butyl rubber/octene polymer. The two layers of covering rubber on the surface of the rubber bracket can effectively resist the erosion of natural rubber by ozone and thermal oxidation, mainly because it reduces the main chain breakage caused by the diffusion of ozone and oxygen into the natural rubber. The fatigue test results show that the fatigue frequency of this rubber engine bracket with two layers of covering rubber is significantly increased.

20. NR/EPDM blend

Among the sulfurized NR/EPDM compounds containing sulfur and peroxide, EPDM gives the rubber compound better ozone resistance.

For NR/EPDM blends, increasing the amount of EPDM will improve the ozone resistance of the blend material. In theory, the optimal dosage of EPDM is between 35% and 40% (mass fraction) (EPDM becomes the continuous phase). As the amount of EPDM increases, co vulcanization becomes a problem and can lead to a decrease in performance. Research has found that the dispersed micro areas of EPR in NR can reduce the ozone cracking of the rubber material. The optimal dosage of EPR in NR is 35% -45% (mass fraction), which can effectively improve the ozone resistance of the rubber material.

21. NR/CIIR blend

In NR/CIIR blends, the proportion of CIIR can be higher, and its compatibility with NR is better than that of EPDM and NR. However, EPDN is equivalent to an anti ozone agent added to NR, so sometimes it is necessary to blend the three to obtain a rubber compound with good physical properties and ozone resistance.

According to reports, the ozone resistance of chloroprene rubber can reach 50pphm (50 X 10-8), and adding 1-2 parts (by mass) of diarylphenylenediamine ozone inhibitor can improve the ozone resistance of CR rubber to 100pphm. However, this antioxidant will shorten the scorch safety period of the rubber material and should be mixed with the vulcanizing agent.

23.CR/EPDM alloy

In the CR/EPDM=70/30 (mass ratio) blend, 10 parts (mass ratio) of Escor acid ternary copolymer compatibilizer (ethylene methacrylate acrylic acid ternary copolymer) is added. This rubber compound has good resistance to Demacia (flexural) incision growth, heat resistance, and ozone resistance, and is strongly recommended for use on conveyor belts.

24. Mixable PU and SBR blend

Gradually adding mixable PU to SBR rubber can effectively improve its ozone resistance.

25. Epichlorohydrin rubber

Epichlorohydrin rubber itself has good ozone resistance.

26. Silicone rubber

Silicone rubber is an elastic material with good ozone resistance.

27. Polyacrylate rubber

Polyacrylate rubber is an elastic material with good ozone resistance.

28。CM

Chlorinated polyethylene elastomer is an elastomer with good ozone resistance.

29. CSM

Chlorosulfonated polyethylene rubber itself has good ozone resistance.

30. Polyurethane elastomer

A prominent advantage of polyurethane elastomers compared to general diene rubber is their good ozone resistance.

31. HNBR

HNBR can still be sulfurized with sulfur because it still has some unsaturated bonds, and if oxidized, it will improve its ozone resistance.

32. NBR/PVC blend

After blending NBR with PVC, its ozone resistance will be significantly improved. After melting and blending NBR pure rubber with plasticized PVC in an internal mixer, granulation is carried out for future mixing and blending. It was found that lotion polymerized PVC (used as plastic sol) was most suitable for blending with NBR, which could make the rubber compound have better ozone resistance and stress-strain properties. In NBR/PVC blends, increasing the amount of PVC can improve the ozone protection of the rubber material.

33. NBR/EPDM blend

If NBR adhesive with good oil resistance is combined with 30 parts (by mass) EPDM; Mixing can improve its ozone resistance, but it will reduce its oil resistance. However, the compatibility between NBR and EPDM is poor. If they cannot be well mixed, the performance of the vulcanized blend will be poor. Therefore, it is important to choose a suitable vulcanization system to ensure compatibility between the two. For example, Wood and Mass found that dithiocarbamate salts have long-chain alkyl groups and can be used in sulfurization systems. In addition, Bergstrom's research found that, o， 2 parts (mass fraction) of sulfur, 0.5 parts (mass fraction) of CBS, and 2.5 parts (mass fraction) of 40% DCP masterbatch are good vulcanization systems for NBR/EPDM. Mitchell's research found that mixing EPDM with carbon black to form a base rubber, and then mixing it with NBR, can improve compatibility and other properties.

34. Talc powder

Research has found that talc powder can endow rubber materials with certain ozone resistance.

35. White carbon black

Adding white carbon black to sidewall compounds filled with EPDM and carbon black can effectively improve the ozone resistance, tear resistance, and crack growth resistance of the compound.