ASTM proposes new standard for rCB storage

WEST CONSHOHOCKEN, Pa.—ASTM International has proposed a new standard that offers parameters for storage of recovered carbon black.

The trend toward rCB—typically produced using tire pyrolysis on EOL tires—is growing in the tire, rubber goods, plastics, pigment and many other industries.

However, scaling up production and producing rCB that grades as a drop-in replacement have been hurdles in preventing greater use of the more sustainable additive.

As such, ASTM's rCB committee (D36) has proposed the standard (WK73460) to "guide users of rCB on how long the material can be stored and the effect that prolonged storage might have on rCB."

"Many substances have a 'best before date' that guides users when a substance loses some of its original performance or properties," said Joe Hallett, ASTM member. "This guidance does not prevent use after this date but informs users that extra checks may be required before use to ensure it is still suitable for their application."

According to Hallett, the purpose of the proposed standard, in part, is to prevent "unnecessary disposal of good material."

Even so, after 12 months, the material should be checked to ensure it is still suitable for use, Hallett said.

Interested parties are invited to join in the development of WK73460.

In particular, the committee is seeking data from users and producers indicating that the performance of their products is not affected by age.

Like other ASTM standards regarding rCB, this effort relates to the United Nations Sustainable Development Goal No. 12 on responsible consumption and production.

Recovered carbon black has gained momentum over the past several years, in both the number of rCB suppliers and in interest from major tire manufacturers, for its green credentials.

About 65 percent of tire makers cite rCB as the "best material to achieve sustainability goals," according to a Smithers report on sustainable CB production methods.

Early in 2023, ASTM International approved another standard that helps classify recovered carbon black.

"This ASTM item will be arguably the most useful standard for recovered carbon black," Martin von Wolfersdorff, a Berlin-based consultant on the rCB industry, told Rubber News at the time. "It will help producers to know what to produce and buyers to know what they purchase."

According to ASTM, the standard, approved Jan. 31, 2023, and officially known as D8474, spawned out of the D36 committee (the D24 committee conducts tests and classifications for standard furnace black).

Within the D36 committee is a subcommittee, D36.70, known as "rCB Testing in Rubber," which counts tire majors such as Continental A.G., Bridgestone Corp. and Michelin, and CB suppliers Birla Carbon, Cabot Corp. and Orion S.A., as participants.

Essentially, the D8474 classification provides quality control via a test that can help differentiate rCBs.

According to ASTM, the test is a thermogravimetric technique that determines organic residue, overall fixed carbon content and ash content in rCB.

To date, rCBs have been refined from the non-virgin material that comes from a pile of tires into semi-reinforcing grades, including N700, N600 and N500 grades.