Over time, tires (passenger, truck, agricultural, on- and off-road) start to display a brownish blooming on the surface, especially on the sidewall. This can also occur on the tread surface of larger tires, giving a very poor appearance in some cases. The blooming is generally uniform in appearance, tacky and powdery, and is highly visible against the black background of the tire. In other cases, the blooming may appear as differently sized spots and may be localized in areas where there is a concentration of mechanical stress.
The typical reaction of a compounder to the blooming is "it looks bad, but the antiozonants/antioxidants are still doing their job".
It's now worth asking if the compounder could do something better today that would maintain the same level of ozone protection but overcome the brownish appearance forever?
In order to improve the appearance of a premium tire, a non-blooming and non-staining antioxidant is required such as Addivant's high molecular weight, slow migrating additive molecule, DURAZONE® 37 antiozonant.
To reduce the blooming on tire sidewalls and treads, caused by plasticizers in the rubber compound formulation, Addivant's DURAZONE® 37 antiozonant is recommended, in combination with a reduction in the wax and 6PPD level, the elimination of DPPD/DTPD and of IPPD from the formulation.
For white-filled, colored, and non-black filled compounds with diene rubber, DURAZONE® 37 antiozonant is once again the non-staining, non-blooming and slow migrating additive of choice.
Is there a solution? The answer is "YES" !!!
We should add here that Addivant's solution is both new and novel, and especially applicable to the premium tire segment and to cars that represent a status symbol for their owners. By this we mean exclusive cars such as the sports-luxury and SUV segment, whose owners will not accept blooming or poor appearance of the tires on their expensive vehicles.
What about trucks and tractors? These cost hundreds of thousands of Euros and must also have perfect looking tires, without any molding defects or blooming. This is especially true for tractors since the tractor tires are completely exposed outside the tractor chassis.
The second challenge is presented by a recent switch from aromatic oil extracts, commonly used as plasticizers and extenders in rubber compounds, to other oils that are free from, or contain limited levels, of polycyclic aromatic compounds (PAHs). The new oils are less viscous than the aromatic extracts, making them more fluid and this fluidity encourages the blooming of common antiozonants and leads more quickly to a poor tire surface appearance.
The third challenge relates to silica-based compound, or white-filled compounds. The simple question is: can the blooming derived from a classic PPD-based antiozonant package, which may be clearly visible in light colored compounds, be avoided?
The solution to achieving an improved tire appearance is the adoption of a non-blooming and non-staining, high molecular weight and slow migrating additive molecule, DURAZONE® 37 antiozonant.
DURAZONE® 37 antiozonant can be used in tire formulations where the good appearance of the sidewall and tread is a must, this includes the premium passenger tire segment and also the truck and agricultural tire segment. Since DURAZONE® 37 antiozonant is effective under static ozone attack as well as under dynamic conditions, it can be formulated with a lower level of paraffin wax to further reduce blooming and improve the appearance. Additionally, a combination of DURAZONE® 37 antiozonant with a reduced level of 6PPD is recommended for short-term protection under dynamic conditions. In such formulations, DPPD/DTPD can be omitted and the result is excellent protection under dynamic and static ozone attack conditions, together with the desired good appearance of the tire sidewall and negligible levels of blooming.
An increased level of blooming may be observed in tires where non-aromatic oils are used due to the recent ban in the EU market. The increased blooming is driven by the high fluidity of MES or T-DAE oil and by their lower solubility in rubber compared to the aromatic extract DAE oil. In order to counteract this blooming caused by the plasticizers, the adoption of DURAZONE® 37 antiozonant is recommended in combination with a reduction of the wax and 6PPD level and the elimination of DPPD/DTPD as well as IPPD from the formulations. This will lead to a considerable improvement in the tires appearance.
For white-filled, colored, and non-black filled compounds with diene rubber, the non-staining, non-blooming and slow migrating additive of choice is again DURAZONE® 37 antiozonant.