1. Discover the Essential Materials Behind Conveyor Belts: How to Choose the Right One for Your Needs
As a conveyor belt manufacturer, we understand that material selection is the core of conveyor system design. The interaction between surface materials and core materials directly determines the load capacity, service life, and safety of the conveyor belt. In this article, we will systematically analyze the scientific properties of these two materials and the industrial logic behind their selection.
1.1 Basic Components of Conveyor Belts
Conveyor belts are designed using a “sandwich” composite structure, where each layer plays a pivotal role in ensuring the belt’s efficiency and durability. The belt consists of three primary components:
- Surface material layer (0.5-15mm):This is the outermost layer of the conveyor belt and is responsible for providing essential functions such as abrasion resistance, anti-slip, and corrosion resistance. It is the first line of defense against external factors like high temperatures, oil contamination, and wear and tear.
- Core reinforcement layer (1-10 layers):The core provides the tensile strength and impact resistance needed for the conveyor belt. It controls both longitudinal and transverse extension, ensuring the belt’s structural integrity and strength during operation.
- Bonding interface (0.1-0.3mm):This layer, made using RFL impregnating liquid (resorcinol-formaldehyde-latex), ensures that the bond between the surface and core layers is strong, with an interlayer bond strength of ≥8N/mm.
This layered design makes the conveyor belt both flexible and rigid, allowing it to operate effectively in extreme conditions, ranging from -60°C to 400°C.
2. Scientific Classification of Surface Materials
Surface materials must be carefully matched to the physical and chemical properties of the materials they handle. Below is a performance overview of the three main surface materials used in conveyor belts:
| Main Material Type | Hardness | Temperature Range | Abrasion Resistance Index | Aplicable Scenarios |
| Rubber | 60-90 | -40℃~120℃ | ≤90 | Mining/Steel/Port/ heavy-load Conveying |
| PVC | 70-85 | -10℃~80℃ | ≤120 | Food/light Industry/Warehouse/Logistics |
| PU | 80-95 | -30℃~100℃ | ≤60 | Chemical/Oil/Contaminated/ Precision/Sorting |
2.1 Rubber Surface Materials
- Formula Technology:Natural rubber (NR) and styrene-butadiene rubber (SBR) are mixed in a 5:5 ratio to improve tear resistance.
- Function Modification:Adding carbon black (20%-30%) enhances abrasion resistance, while zinc oxide (3%-5%) improves aging resistance.
- Extreme Conditions:In iron ore transportation, the wear-resistant layer thickness needs to be ≥8mm to withstand the impact of transporting 300 tons of ore per hour.
2.2 PVC Surface Materials
- Hygienic Design:Uses non-toxic calcium-zinc stabilizers instead of lead salts and is FDA 21 CFR 177.2600 certified to meet food safety standards.
- Lightweight Advantage:With a density of 1.3-1.5g/cm³, PVC weighs 40% less than rubber, reducing driving energy consumption.
- Surface Treatment:Embossed with diamond or rhombic patterns, increasing the friction coefficient to 0.45-0.6 for better grip.
2.3 PU Surface Materials
- Chemical Stability: The oil expansion rate of ASTM #3 is <5%, and it is resistant to 5% acid/alkaline solutions.
- Precision Processing:With a tolerance control of 0.1mm, PU materials ensure no scratching of electronic components during precision sorting.
3. The Mechanical Properties of Core Materials
The core material of the conveyor belt is the “skeleton system” that provides essential tensile strength (N/mm) and elastic modulus (GPa). Selecting the right core material is critical for ensuring the belt’s strength and durability, especially under heavy loads or in environments with frequent mechanical stress.
3.1 Fabric-Reinforced Core Layers
EP (Polyester-Nylon):
- Weft Tensile Strength: ≥600N/mm (ISO 283 standard)
- Weft Elastic Modulus:≥12GPa
- Application Scenarios:Automotive assembly lines, port bulk material transport
NN (Nylon-Nylon):
- Dynamic Flexibility: Passes 1 million bending tests per DIN 22102 without delamination.
- Moisture Sensitivity: For every 1% increase in moisture content, elongation increases by 0.8%.
3.2 Metal-Reinforced Core Layers
ST (Steel Cord):
- Steel Wire Diameter: 0-12.5mm (corresponding to ST1000-ST6300 grades)
- Pre-tensioning Technology:Initial elongation rate <0.25%, suitable for long-distance, kilometers-long transport.
- Rust Protection:Zinc coating thickness ≥70g/m², passing 720 hours salt spray testing.
3.3 Natural Fiber Core Layers
CC (Cotton-Cotton):
- Breaking Elongation:≥15% (requires periodic tension adjustment)
- Environmental Value:Biodegradable in less than 5 years, with 60% lower carbon emissions than synthetic fibers.
4. How to Choose the Right Conveyor Belt Material
In industrial scenarios, choosing the right conveyor belt material requires a multi-dimensional engineering analysis. Below is a systematic methodology for selecting the right materials for your conveyor belt.
4.1 Key Selection Parameters
- Dynamic Friction Coefficient:The sliding resistance between the material and the belt surface directly impacts conveyor efficiency. For scenarios with inclines exceeding 15 degrees, the friction coefficient must be no less than 0.55. This is typically achieved through surface embossing or optimizing rubber formulations.
- Volume Resistivity: In dust-explosion-risk areas (such as coal mines), material resistivity must be controlled between 10^4~10^6Ω·cm to prevent static accumulation. In food industries, resistivity must exceed 10^12Ω·cm to avoid contamination adsorption.
- Tear Propagation Strength:In applications where sharp materials like metal ores are transported, the tear strength must exceed 30kN/m. Regular polyester fabric conveyor belts (with a tear strength of 15-20kN/m) should be upgraded to steel cord core structures.
- Hydrolysis Resistance:In humid and hot environments (such as Southeast Asia), materials exposed to 85°C and 85% humidity for 1000 hours must retain more than 85% of their strength. Regular PVC materials may lose 40%-50% of their strength under these conditions.
- Fatigue Bending Flexibility:Sorting machines in logistics need to support over 5 million bending cycles, and mining operations require belts that can endure over 2 million impacts. This can be achieved through the synergy of core materials and bonding technology.
4.2 Application-Specific Material Selection Solutions
High-Temperature Metallurgical Scenarios (Coal and Slag Transport)
Steel plants primarily handle the transportation of coke, coal, and high-temperature slag.
- Coke Transport:The surface uses 10mm thick styrene-butadiene rubber (SBR), with 20% carbon black added to enhance wear resistance. The core uses ST1600 steel cord, with a breaking strength ≥1600N/mm, capable of withstanding impacts from falling coke at heights of 3-5 meters.
- Liquid Slag Handling: Contact temperatures can reach 800℃-1000℃. The surface uses ceramic particles embedded rubber (with ≥92% alumina content), and the core is made of glass fiber that can withstand temperatures up to 350℃. The belt is designed with a double-layer hollow structure, incorporating cooling pipes.
Deep Sea Port Salt-Fog Environment
The surface material uses hydrogenated nitrile butadiene rubber (HNBR), which improves salt-fog corrosion resistance by 5 times compared to regular rubber. The core uses glass fiber-reinforced polyester, passing 720 hours salt-fog testing with a strength retention rate of over 90%. The seams are treated with fluoroelastomer paste for secondary vulcanization, with gap width controlled to 0.1mm.
Biopharmaceutical Clean Rooms
The surface is made of solvent-free polyurethane (PU), with a roughness of ≤0.8μm to avoid microorganism retention. The core uses 316L stainless steel mesh, resistant to acid and alkali cleaning agents. The cleanliness requirement is for volatile organic compounds (VOCs) to be below 10μg/m³, and the belt is validated after 200 pH 2-12 cleaning cycles.
5. In-Depth Analysis of Material Properties
5.1 Molecular-Level Characteristics of Surface Materials
- Natural Rubber (NR):The cis-polyisoprene chain structure gives natural rubber high elasticity, with a glass transition temperature as low as -65℃, making it ideal for low-temperature environments. However, its oil resistance is poor, and long-term contact with mineral oils can cause volume expansion greater than 30%.
- Styrene-Butadiene Rubber (SBR): The styrene-butadiene copolymer structure balances abrasion resistance and cost-effectiveness. With a dynamic loss factor of 0.35, it is suitable for mining conveyor applications with medium to high-frequency vibrations.
- Polyurethane (PU):The microphase-separated structure of urethane hard segments and polyether soft segments results in a wear index 50% lower than rubber, and it has an oil expansion rate of less than 5% in oil-contaminated environments.
5.2 Mechanical Behavior of Core Materials
- Polyester-Nylon (EP):
- Weft Tensile Strength: 600-1000N/mm
- Elastic Modulus: 6-12GPa
- Suitable for medium-load scenarios such as port bulk material transport but has weak resistance to heat and humidity.
- Steel Cord (ST):
- Tensile Strength: Up to 6300N/mm
- Elongation:Only 0.1%-0.3%, making it ideal for long-distance transport, and it is treated with galvanization (coating ≥70g/m²) for 720-hour salt-fog protection.
- Aramid Fiber:
- Impact Energy Absorption:Up to 25.6J/mm², which is 5 times higher than steel cord. It is used in extreme-impact areas such as mining crusher discharge points, though it is 3-4 times more expensive than EP materials.
6. Industry Application-Specific Technical Solutions
6.1 Steel Smelting Industry
Coke Transport System
- Pain Points:High hardness (Mohs hardness 3-4) of coke, residual heat of 80-120°
- Solution:
- Surface Layer:10mm SBR rubber with lateral corrugated edges to reduce material impact.
- Core Layer:ST1600 steel cord, with interlayer bond strength ≥12N/mm (ISO 252).
- Edge Reinforcement:Double-layer polyurethane edge to extend lateral wear resistance by 2x.
- Verification:After implementation in Baosteel’s plant, annual maintenance costs were reduced by 18%, and downtime was decreased by 42%.
Blast Furnace Slag Handling
- Pain Points: Liquid slag temperatures can reach 1000°C, and water-quenched slag particles are highly abrasive.
- Solution:
- Surface Layer: 92% alumina ceramic particles embedded in rubber, with a wear rate of only 0.08mm/1000 impacts.
- Cooling Design: Double-layer hollow structure with 15% surface porosity to accelerate steam dissipation.
- Heat Stress Control: Gradient-density rubber matrix to prevent cracking at high temperatures.
- Lifetime Comparison:Traditional rubber belts are discarded after 2 months, while ceramic composite belts last more than 12 months.
6.2 Port Logistics Industry
Ore Unloading System
- Technical Requirements: Salt-fog corrosion resistance, with a throughput of 300 tons/hour.
- Material Combination:HNBR rubber surface + fiberglass core.
- Core Parameters:
- Salt-Fog Testing:Passed 720 hours without cracking (ISO 9227).
- Tensile Strength:EP1000-grade, supports a lifting height of 50 meters.
6.3 Food Processing Industry
Meat Sorting Line
- Hygiene Requirements: Compliant with FDA 21 CFR 177.2600, with a bacterial count of <10 CFU/cm².
- Material Solution:
- Surface:Non-porous PU, with laser-welded seams to avoid bacterial growth.
- Cleaning Design:3° inclined angle and embedded drainage channels, reducing drying time to 15 minutes.
- Antibacterial Treatment:Nano silver ion additives with an antibacterial rate of >99.9% (ISO 20743).
