Views: 0 Author: Site Editor Publish Time: 2026-05-20 Origin: Site
EPDM colorful granules are elastic granular materials made from EPDM rubber compounded with multiple additives, processed through mixing, vulcanization, and granulation. As a core material for outdoor sports and leisure facilities, they exhibit excellent UV resistance, aging resistance, elasticity, and environmental friendliness. Unlike single-component materials, EPDM granules are a typical composite system where each component undertakes specific functions. The reasonable collocation of ingredients is the key to balancing the material’s processability, performance, and cost. This paper will dissect the composition of EPDM colorful granules in detail and analyze the role of each component in the system.
EPDM is a terpolymer synthesized from three monomers: ethylene, propylene, and diene (usually ethylidene norbornene or dicyclopentadiene). Its molecular structure is saturated except for the diene crosslinking sites, endowing it with outstanding resistance to ozone, UV radiation, and high-temperature aging.
Ethylene content: 45%–75%, determining the material’s hardness and mechanical strength; higher ethylene content increases rigidity and wear resistance.
Propylene content: 20%–50%, regulating low-temperature flexibility to avoid brittleness in cold environments.
Diene content: 2%–8%, providing crosslinking sites for vulcanization, enabling the rubber to form a stable three-dimensional network structure and maintain elasticity under stress.
In high-quality EPDM colorful granules, the EPDM rubber content is generally 20%–40% (by weight). As the continuous phase of the composite, it acts as the "skeleton" of the material, undertaking the following core functions:
Providing fundamental elasticity and resilience, ensuring the shock absorption performance of sports surfaces.
Binding all fillers and additives together, maintaining the structural integrity of the granules.
Determining the material’s weather resistance and aging resistance, directly affecting the service life (5–10 years) of the granules.
Fillers are the most abundant auxiliary components in EPDM granules, with a content of 30%–60%. They are divided into reinforcing fillers and inert fillers, which reduce cost, improve processability, and enhance physical properties.
Component: Precipitated calcium carbonate (CaCO₃), the most common filler in EPDM granules.
Function:
Reducing production cost significantly as a low-cost extender.
Increasing the hardness and dimensional stability of the granules without reducing elasticity.
Improving the dispersion uniformity of pigments and additives.
Components: Precipitated silica, talc powder, kaolin, etc., with a content of 5%–15%.
Function:
Enhancing the tensile strength, tear resistance, and wear resistance of EPDM rubber.
Improving the UV shielding performance and delaying aging.
Application: Mainly used in high-end EPDM granules for professional sports tracks and high-frequency use playgrounds.
Paraffinic white oil is the primary plasticizer for EPDM granules, with a content of 5%–15%. It is a non-volatile, low-aromatic mineral oil with good compatibility with EPDM rubber.
Reducing the viscosity of EPDM rubber, improving mixing processability and filler dispersion.
Enhancing the low-temperature flexibility of the granules, preventing cracking in cold climates.
Adjusting the hardness of the finished granules to meet the elasticity requirements of different scenarios.
Color pigments are the key to the bright and durable color of EPDM granules, with a content of 1%–5%. High-quality granules adopt through-dyeing technology (uniform color inside and outside), achieved by adding pigments during compounding.
Inorganic pigments: Iron oxide (red, yellow, black), titanium dioxide (white), chromium oxide (green), etc. Advantages: excellent UV resistance, light fastness, and heat resistance, not easy to fade; widely used in outdoor EPDM granules.
Organic pigments: Phthalocyanine (blue, green), azo pigments (red, orange), etc. Advantages: bright color and high tinting strength; used for special color customization, but with slightly poorer weather resistance than inorganic pigments.
To improve pigment dispersion, color masterbatches (pigments pre-dispersed in EPDM carrier resin) are often used instead of raw pigments. They avoid pigment agglomeration, ensure uniform color of granules, and improve color stability.
Vulcanization is the process of crosslinking EPDM rubber molecules into a network structure, which transforms plastic rubber into elastic rubber. The vulcanizing system accounts for 1%–3% of the total composition.
Sulfur is the most common vulcanizing agent for EPDM granules, matching with accelerators to form an efficient curing system.
Common accelerators include thiazoles (MBT), sulfenamides (CBS), etc., which reduce vulcanization temperature, shorten curing time, and improve crosslinking efficiency.
Forming a stable crosslinked network of EPDM molecules, endowing the granules with permanent elasticity and shape stability.
Improving the mechanical strength and aging resistance of the material.
A small amount of functional additives (0.5%–2%) are added to optimize specific properties of EPDM granules.
Components: Hindered amines (HALS), phenolic antioxidants, etc.
Function: Absorb UV radiation, block the oxidation reaction of rubber molecules, and prevent color fading, cracking, and performance degradation caused by long-term outdoor exposure.
Function: Promote the uniform dispersion of fillers and pigments, reduce friction during processing, and improve the surface smoothness of granules.
Function: Delay the aging process of EPDM rubber, prolong the service life of granules, and maintain stable elasticity and color.
The performance of EPDM colorful granules depends on the synergistic effect of all components rather than a single ingredient. The typical composition ratio (by weight) of high-quality EPDM granules is as follows:
表格
Component | Content Range | Core Function |
|---|---|---|
EPDM rubber | 25%–35% | Elastic skeleton, binding fillers |
Calcium carbonate | 40%–50% | Cost reduction, hardness adjustment |
Paraffinic white oil | 8%–12% | Plasticization, low-temperature flexibility |
Color pigments/masterbatches | 2%–4% | Coloration, color stability |
Vulcanizing system | 1%–2% | Crosslinking, elasticity formation |
Functional additives | 0.5%–1.5% | UV resistance, aging resistance |
Adjusting the ratio according to application scenarios:
Professional sports tracks: Increase EPDM content (35%–40%) and reinforcing fillers to enhance wear resistance and elasticity.
Ordinary playgrounds: Appropriately increase calcium carbonate content to reduce cost while ensuring basic performance.
High-temperature and strong UV regions: Increase UV stabilizers and inorganic pigments to improve weather resistance.
EPDM colorful granules are a sophisticated composite material system with EPDM rubber as the matrix, calcium carbonate as the main filler, white oil as the plasticizer, pigments as the colorant, and a vulcanizing system plus functional additives as the auxiliary. Each component has clear division of labor and synergizes with others, jointly determining the material’s elasticity, weather resistance, color stability, and mechanical properties.
With the increasing demand for outdoor sports and leisure facilities, the optimization of EPDM granule composition will focus on high EPDM content, low VOC, and enhanced environmental performance. In-depth understanding of the composition and functional mechanism is conducive to improving product quality, reducing costs, and promoting the sustainable development of the EPDM material industry.
