Belts carrying hot clinker, sinter or coke see cover temperatures well above those of a general belt. The cover rubber must resist heat ageing and hardening. Reverse engineering a failed or competitor belt cover usually answers a simple question: what polymer system is it?
Separate the cover from the carcass
Peel or cut the cover from the fabric. Remove any skim layer and adhesive. Sample from the middle of the cover thickness, away from surface that may have been aged by heat.
Polymer candidates
- EPDM for the best heat and ozone resistance in belting, with peroxide or high-accelerator sulfur cure.
- SBR/BR or NR/SBR for low-cost covers where heat is moderate.
- IIR (butyl) blends for some heat- and ozone-resistant covers.
IR and DSC separate these quickly: EPDM has no double-bond bands and a Tg near −50 °C, butyl shows the gem-dimethyl doublet, SBR/BR shows phenyl and butadiene bands.
What the aged part tells you
A cover from a failed belt has been aged. Look for:
- Loss of extractable oils and antioxidants. Compare extractables at the surface and the core.
- Hardness gradient across the thickness. A hard, cracked skin over a softer core is classic heat ageing.
- Carbonyl growth in IR at the surface, a sign of oxidation.
Filler system
Heat-resistant covers use carbon blacks with moderate structure, with mineral fillers or calcium carbonate to cut cost. A very high ash fraction with low reinforcing black suggests a cost-engineered cover.
Cure and antidegradants
- Peroxide cure shows very low sulfur and no accelerator residues.
- Sulfur-cured covers show an accelerator profile and antidegradants such as polymerised dihydroquinoline or a benzimidazole, chosen for heat resistance. Chromatography of the extract identifies them.
Matching target
Heat ageing is the property that counts. Compare hardness change and elongation retention after ageing at the duty temperature for the same period. A compound that matches the fresh profile and loses properties faster in ageing is not a match.
