1. Thermoplastics vs heat-vulcanisable elastomers
- Heat-vulcanised elastomers (rubber, vulcanised silicones) form a permanent cross-linked network; unlike thermoplastics (TP and TPE), they cannot be remelted.
- The polymer chains can slide slightly under tension but are quickly held back. A whole network of bridges and chains forces them to return to their original position.
- The formation of bridges, known as CROSS-LINKING, prevents any return to a plastic state and makes it difficult to recycle vulcanised elastomers.
- Thermoplastics are recyclable: they can be ground and remelted without any significant loss of properties, but within certain limits to guarantee the performance of the final product.
2. Recovery options for vulcanised elastomer waste
A. Mechanical recycling 🔧
Recycling industries produce a “powder” by grinding and sieving. The finest particles obtained are approximately 0.05 mm.
Incorporating this “rubber powder” into a formulation will result in:
- a reduction in the cost price of the mixture.
- maintains chemical resistance, provided that the powder has the same base elastomer as the formulation.
- a significant reduction in mechanical properties (elasticity, tear resistance)
This solution is recommended for the manufacture of low-tech parts.
For information, elastic coatings for roads or sports facilities are a market for recycling rubber elastomers (tyres, etc.).
More than 50% of waste is used in this way.
B. Chemical recycling/devulcanisation 🧬
Vulcanised waste is mechanically crushed and then laminated in the presence of chemical agents that break the bonds created by vulcanisation and depolymerise the material.
The incorporation of this “regenerated” rubber (up to 20–50%) into a formulation will result in:
- a reduction in the cost price of the mixture.
- maintenance of chemical resistance, provided that the “regenerated” material has the same base elastomer as that of the formulation.
- a significant reduction in mechanical properties.
This solution is recommended for the manufacture of non-technical parts.
C. Pyrolysis🔥 : material and energy recovery
Pyrolysis involves heating elastomer waste in the absence of oxygen in order to break it down thermally without combustion. This process makes it possible to recover:
- oils that can be used as fuel or raw materials,
- gas for energy production,
- recycled carbon black,
- and, depending on the case, metal residues (wires, reinforcements, etc.).
This solution is mainly developed for used tyres, and offers prospects for other complex or unsorted waste.
D. Combustion🔥
When elastomer waste (manufacturing scrap, cores or end-of-life products) cannot be reused or recycled mechanically or chemically, energy recovery is a relevant and regulated alternative.
Elastomers (natural rubber, SBR, EPDM, silicone, etc.) have a high calorific value – often comparable to that of coal or heavy fuel oil – making them particularly attractive as a substitute fuel in certain industries.
Typical uses:
- Cement plants: shredded elastomer waste is co-incinerated in very high-temperature furnaces (1,400–1,600°C), leaving no solid residue.
- Incineration units: waste mixed with household waste or non-hazardous industrial waste is used to fuel steam boilers, often used for district heating.
🏭 CHEVALIER CLERET & ELTEC
Injection moulding limits waste to a minimum
This type of technology generates very little material loss and, when the process is direct injection, there is virtually no material loss.
As the quantities of waste represent only a small percentage of the material used, they are not recycled and are destroyed by combustion, thus generating heat for district heating.
🔗 Please do not hesitate to contact us for further information.