EPDM Recycled Rubber

1. Definition and Basic Concept
EPDM Recycled Rubber is a plastic, re-vulcanizable rubber material produced primarily from post-industrial or post-consumer waste products containing Ethylene Propylene Diene Monomer (EPDM) rubber, through a series of physical, chemical, or mechanical reclamation processes.
• Core Feedstock: Primarily sourced from scrap EPDM products such as automotive weather-stripping (door/window/trunk seals), roofing membranes, heat-resistant hoses, cable jacketing, and rubber playground/track surfaces.
• Essence: It represents the circular reprocessing of EPDM rubber resources, serving as a crucial pathway for reducing raw material costs and minimizing solid waste and environmental impact. It is not virgin EPDM and exhibits performance trade-offs.
2. Manufacturing Process
The typical production process for EPDM recycled rubber involves the following key stages:
1. Sorting & Collection: Separating EPDM scrap from other rubber types (e.g., NR, SBR) is a critical pre-treatment to ensure purity and performance consistency.
2. Shredding & Cleaning: Large scrap pieces are shredded into chips and washed to remove contaminants like sand, metal, and fabric.
3. Fine Grinding: The chips are further pulverized into fine rubber powder (typically 20-80 mesh).
4. Reclaiming/Devulcanization: This is the core process, aiming to break down the three-dimensional crosslink network (S-S and C-S bonds) in the vulcanized scrap, restoring plasticity and re-vulcanizability. Common methods include:
◦ Dynamic High-Temperature Process: Applying high pressure, heat (180-220°C), and shear stress in an internal mixer or reactor.
◦ Extrusion Process: Utilizing the high temperature and shear of a twin-screw extruder for continuous reclaiming.
◦ Chemical Reclaiming: Using reclaiming agents/activators (e.g., aromatic oils, pine tar, disulfides) to facilitate bond cleavage. Due to EPDM's saturated backbone, it is more resistant to devulcanization than unsaturated rubbers, often requiring harsher conditions or specialized agents.
5. Refining & Filtration: The reclaimed mass is homogenized and sheeted out through a refiner mill, which also filters out any remaining hard impurities.
6. Sheeting & Packaging: The final material is sheeted, cut, and packaged for shipment.
3. Key Characteristics (vs. Virgin EPDM)


Property
EPDM Recycled Rubber
Virgin EPDM Rubber
Fundamental Properties
Retains the core inherent qualities of EPDM: excellent ozone, weathering, aging resistance, and electrical insulation. This is its primary value proposition.
Excellent ozone, weather, aging resistance, and electrical insulation.
Mechanical Strength
Significantly Reduced. Tensile strength, elongation at break, and tear strength are notably lower.
High.
Temperature Resistance
Degraded, especially under continuous high-temperature service. Upper service temperature limit is lowered.
Excellent, typically -40°C to 150°C.
Processing
Lower Mooney viscosity, better flow, easier mixing and molding,lower shrinkage.
Requires mastication, higher Mooney viscosity, compounding adjustments needed for processing.
Color
Typically black or dark grey. Production of light-colored compounds is virtually impossible.
Can be compounded in any color.
Consistency
Batch-to-batch variability is higher.Performance depends heavily on feedstock source, purity, and reclaiming process.
Consistent and uniform across batches.
Odor
May have a slight odor from the reclaiming process.
Neutral.
4. Primary Applications
Due to its cost/performance balance, EPDM recycled rubber is predominantly used in mid-to-low-end applications where ultimate physical properties are not critical, but basic weatherability is required.
1. Building & Construction:
◦ Underlayment or backing layer for roofing membranes.
◦ Sealants, gaskets, and expansion joint fillers.
◦ Low-grade rubber flooring, mats, and anti-fatigue pads.
2. Automotive (Non-Critical Parts):
◦ Base compound or partial replacement in window channels and trunk seals.
◦ Non-fluid resistant, low-heat gaskets in the engine compartment.
3. Industrial Goods:
◦ Outer cover of low-pressure, non-critical hoses.
◦ Electrical insulating pads, filler layer in cable sheathing.
◦ Miscellaneous molded rubber goods, mud flaps.
4. General Use:
◦ Blending with virgin EPDM, NR, or SBR to reduce compound cost and improve processing.
◦ Manufacturing of low-grade molded seals, grommets, and buffers.
5. Advantages and Disadvantages
• Advantages:
◦ Low Cost: Significantly cheaper than virgin EPDM, its primary advantage.
◦ Environmental Sustainability: Promotes resource conservation and waste reduction.
◦ Superior Processability: Reduces energy consumption during mixing, shortens cycle times, and improves production efficiency (filler dispersion, flow).
◦ Retains Key Properties: Preserves EPDM's essential weathering resistance for cost-effective applications.
• Disadvantages:
◦ Compromised Mechanical Properties: Unsuitable for high-performance, high-strength applications.
◦ Performance Variability: Inherent inconsistency due to variable feedstock; quality control is challenging.
◦ Potential Contaminants: Risk of unknown chemical carryover from the original products.
◦ Color Limitation: Cannot be used for light-colored or bright compound.
6. Guidelines for Use
1. Compound Reformulation: Formulations must be rebalanced when using recycled rubber, especially the curing system (types/amounts of accelerators and sulfur), as it contains residual curatives and fillers.
2. Strategic Blending: It is most effectively used in blends with virgin rubber. The blend ratio must be optimized via testing to achieve the best cost/performance balance.
3. Rigorous QC Testing: Incoming batches should be tested for key properties (Mooney viscosity, hardness, tensile strength) to ensure production stability.
4. Clear Application Scope: Its use should be strictly defined for non-critical, performance-tolerant products. It is not suitable for safety-critical components.