What is the heating loss value for recovered carbon black

Heating loss (also called loss on heating, tested by ASTM D1509 / ISO 1126 at 125 °C for 1 hour) measures mass loss mainly from adsorbed moisture plus small amounts of low-boiling volatile organics on rCB surface, as referenced at rcb-mill.com. This must not be confused with high-temperature volatile matter (tested at 550 °C or 950 °C, which captures tar, PAH and surface organic residues).

Typical heating loss (125 °C, wt%)

1. High-quality thermally devolatilized rCB (tire / battery grade)
   0.2 – 1.0 wt%
   Battery-grade rCB is strictly controlled below 0.3 wt%, because moisture will cause gas generation inside lithium-ion cells.
2. Standard commercial dry-processed rCB (rubber & masterbatch grade)
   1.0 – 2.0 wt%
3. Poorly processed crude pyrolysis char / untreated rCB
   

   2.0 wt%, sometimes up to 4–6 wt% if stored under high humidity or with residual light tar.

For reference: Virgin furnace carbon black heating loss is normally <1.5 wt%.

What affects rCB heating loss

1. Surface porosity: Higher BET / porous rCB absorbs more moisture from ambient air, raising heating loss.
2. Thermal post-treatment: Inert thermal devolatilization removes tar and reduces hygroscopic surface functional groups, lowering moisture uptake.
3. Storage and packaging: Unsealed rCB readily absorbs water vapor in humid environments. Sealed inert packaging keeps heating loss stable.
4. Surface chemistry: Acidic surface groups (before thermal treatment) increase water adsorption.

Difference: Heating Loss (125°C) vs Volatile Matter (high temperature)

• Heating loss @125°C: mostly moisture, used for routine QC and sample pre-treatment.
• High-temperature volatile matter (TGA / 550 °C): residual tar, PAH, organic deposits. For premium rCB this target is <2–3 wt%. Crude char may reach 8–16 wt% volatiles.

Impact on end applications

• Rubber compounding: Heating loss >2% may create bubbles / porosity during vulcanization and affect curing stability.
• Color masterbatch / coatings: Excess moisture causes foaming and surface defects during extrusion or curing.
• Li-ion battery conductive rCB: Heating loss (moisture) must be minimized. Even small amounts of water react with electrolyte and reduce cell safety and cycle life.

Test principle

Following ASTM D1509 or ISO 1126:

1. Weigh rCB sample, heat in oven at 125 °C for 60 min.
2. Cool inside a desiccator to avoid re-absorbing moisture.
3. Calculate mass loss percentage = heating loss value.

Summary table