Mix 20-50% reclaimed rubber with fresh rubber compound to get a workable balance of properties and material conservation, rather than using reclaim alone. A 100 kg batch at 50% reclaim saves 50 kg of virgin rubber, which at 2-5 kg of dry rubber per tree per year is the output of 10-25 tree-years. The more reclaim, the weaker the result, so use the low end for parts that carry load and the high end for mats and mounts.
Part of Rubber Processing
Combining reclaimed and virgin rubber into practical compounds.
Blending Trades Strength For Rubber Saved
Reclaimed rubber alone keeps only 50-70% of the strength of virgin rubber, per the carrier. Blending dilutes that loss with fresh rubber while still stretching the supply. The carrier gives a single figure: 20-50% reclaimed rubber in the blend. The corpus gives no rule for how strength varies with the blend, and this article does not invent one.
| Blend | Reclaim share | Where it fits |
|---|---|---|
| Light | toward 20% | Parts that carry some load: gaskets, seals |
| Heavy | toward 50% | Mats, mounts, low-pressure parts |
The row assignments follow from the carrier’s statement that reclaim suits floor mats, vibration mounts and low-pressure gaskets; they are a reading, not a corpus table.
What You Need
- Reclaimed rubber from Devulcanization Methods.
- Fresh rubber, sheet or crepe; see Smoke Curing (RSS) and Crepe Rubber Production.
- A two-roll mill and its stop; see Compound Mixing.
- Curing ingredients, adjusted by trial: the reclaim may carry residues from its first life and from the reclaiming agent, and the corpus gives no correction.
- A set of test strips and the tests in Quality Testing.
Method: A Blend
Step 1: Choose the blend from the table above.
Step 2: Weigh the reclaim and the fresh rubber to the chosen ratio.
Step 3: Mill them together until the sheet is one colour and texture. Add the curing ingredients last, following Compounding Recipe.
Step 4: Cure a trial strip and test it for stretch, snap-back and compression set.
Step 5: Adjust and repeat until the strip meets the grade the product needs.
Worked Example
Batch of 100 kg at 20-50% reclaim: 20 kg to 50 kg of reclaim and so 80 kg to 50 kg of fresh rubber. Fresh rubber saved against an all-fresh batch is the reclaim amount, 20-50 kg. At 2-5 kg of dry rubber per tree per year (carrier), 50 kg of reclaim stands for 50 ÷ 5 = 10 to 50 ÷ 2 = 25 tree-years of tapping; 20 kg stands for 4 to 10 tree-years.
Common Mistakes
- Treating the blend as a recipe. It is a starting point; test every batch.
- Skipping the milling time. A streaky sheet cures unevenly.
- Using the blend for critical seals. Keep the share low or avoid it.
Safety
The mill nip
Blending is done on a two-roll mill, where a hand or sleeve drawn into the nip cannot be pulled out. Use the paddle, keep the stop bar within reach and do not work alone; see Compound Mixing for the stop and coast-down requirements.
What’s Next
- Learn next: Essential Rubber Products — where blended rubber goes
- Combine with: Quality Testing — grading the result