In modern industries such as industrial manufacturing, smart home appliances, 자동차 전자, and advertising signage, 고무 자석 have become indispensable polymer composite magnetic materials due to their excellent flexibility, easy machinability, and stable magnetic performance.
Essentially, a rubber magnet is an isotropic or anisotropic high-density composite material produced by combining high-remanence ferrite magnetic powder (magnetic filler) with synthetic rubber (polymer matrix) and various additives through advanced compounding technology. As a unique material that combines both magnetism and elasticity, its manufacturing process integrates the disciplines of powder metallurgy and polymer processing.
This article provides a comprehensive overview of the modern manufacturing process of 고무 자석, tracing every step from raw mineral materials to high-precision finished products.
1. The Foundation of 조작: Raw Material Formulation and Modification
The overall performance of a rubber magnet depends not only on advanced processing equipment but also on its carefully designed formulation. The first production stage requires precise proportioning and surface modification of inorganic magnetic powder and organic polymer materials.
1.1 Selection of Magnetic Fillers and Polymer Matrix
Strontium/Barium Ferrite Calcined Powder
Ferrite magnetic powder is the primary source of magnetic properties and typically accounts for 85% 에게 92% of the total material composition.
Isotropic rubber magnets generally use cost-effective barium ferrite powder with moderate magnetic energy.
High-performance anisotropic rubber magnets utilize strontium ferrite powder with superior crystal orientation, higher remanence, and stronger coercivity.
Synthetic Rubber and Chlorinated Polyethylene (CPE)
Serving as the continuous matrix that encapsulates magnetic particles, common polymer materials include chlorinated polyethylene (CPE), 니트릴 고무 (NBR), and EPDM rubber.
이들 중, CPE has become the most widely used base material because of its excellent weather resistance, ozone resistance, flame retardancy, and outstanding magnetic powder loading capacity.
1.2 Surface Coupling and Additive Formulation
Surface Chemical Coupling Treatment
Ferrite magnetic powder is an inorganic hydrophilic particle, while CPE is an organic hydrophobic polymer. Direct mixing often results in poor interfacial bonding.
To improve compatibility, titanate or silane coupling agents are added to form a molecular protective layer on the magnetic powder surface, converting its hydrophilic properties into lipophilic characteristics and significantly improving particle dispersion within the polymer matrix.
Functional Additives
To optimize flexibility and prevent thermal degradation, formulations also include carefully controlled amounts of:
- Stearic acid (lubricant)
- Plasticizers such as DOP (hardness adjustment)
- Antioxidants
- Anti-aging stabilizers
2. Mixing and Pelletizing: Achieving Uniform High-Filler Composite Materials
Converting raw materials into dense pellets with excellent processing characteristics is essential before molding. The objective at this stage is to eliminate magnetic powder agglomeration and achieve microscopic uniform dispersion.
2.1 High-Shear Internal Mixing
The modified ferrite powder, CPE, and additives are loaded into an internal mixer simultaneously.
Under high-temperature and high-pressure conditions, rotor-generated shear force, compression, and frictional heat soften the CPE matrix. Mixing temperatures are generally maintained between 110°C and 140°C.
The intensive mixing process uniformly encapsulates the high-density magnetic particles within the polymer network, forming a homogeneous composite melt.
2.2 Twin-Screw Extrusion Pelletizing
The mixed compound is transferred into a co-rotating twin-screw extruder, where it undergoes further conveying, homogenization, and degassing to remove volatile components.
The molten material is extruded through die holes into continuous strands and immediately cut into pellets using water-cooled or air-cooled hot cutting systems, producing highly uniform rubber magnetic pellets with diameters of approximately 3–5 mm.
3. Core Forming Processes: Two Parallel Manufacturing Routes
Depending on the final product shape, rubber magnets are manufactured using either calendering or extrusion technology.
3.1 Calendering Process: Manufacturing Precision Rubber Magnetic Sheets
The calendering process is primarily used to produce rubber magnetic sheets or rolls with thicknesses ranging from 0.2 mm to 5.0 mm.
Preheating and Plasticizing
The magnetic pellets are softened and remelted in a two-roll mill, forming continuous plastic sheets with good ductility.
Precision Multi-Roll Calendering
The material passes through three-roll or four-roll calender machines, where successive rolling reduces thickness layer by layer.
Precise roller gap adjustment and temperature control are critical for achieving smooth surfaces and maintaining thickness tolerances typically within ±0.03 mm.
3.2 Extrusion Process: Continuous Production of Profiled Magnetic Strips
Extrusion is widely used to manufacture refrigerator door seals, automotive sealing strips, curtain magnetic strips, and other customized magnetic profiles.
Single-Screw Extrusion
Magnetic pellets are fed into a single-screw extruder, where screw rotation generates pressure that continuously transports and melts the material.
Die Forming and Magnetic Orientation
The molten material passes through specially designed profile dies to produce customized cross-sectional shapes.
For anisotropic rubber magnets, a strong external magnetic field is applied as the material exits the die while still molten.
This orientation process aligns the ferrite particles along their easy magnetization direction, significantly improving magnetic properties compared with isotropic materials.
The extruded profiles are subsequently cooled and shaped in water tanks.
4. Post-Processing and Finishing
하지만 molded rubber magnets have obtained their physical shape, they remain magnetically neutral until magnetization and additional finishing processes are completed.
4.1 High-Voltage Pulse Magnetization
The cooled magnetic sheets or strips are transferred into a magnetizing machine.
High-voltage capacitor discharge generates an extremely strong pulse magnetic field, typically exceeding 1.5 Tesla, aligning the internal magnetic domains and activating permanent magnetism.
Depending on application requirements, products may receive:
- Single-side multipole magnetization
- Double-side magnetization
- Axial magnetization
Magnetization pole spacing directly determines the final surface magnetic strength (Gauss value).
4.2 Surface Laminating and Anti-Stick Treatment
PVC Film and Adhesive Lamination
Because rubber magnets naturally appear dark brown, colored PVC films, PP glossy films, UV films, or high-strength adhesive tapes such as 3M adhesive are laminated onto the non-magnetic side to satisfy printing and bonding requirements.
UV Protective Coating
For exposed magnetic surfaces, special UV anti-stick coatings are applied and instantly cured using ultraviolet equipment.
The protective layer improves wear resistance while preventing oxidation, powder shedding, and adhesion during storage.
4.3 Precision Slitting, Die Cutting, and Packaging
Large magnetic rolls are slit into narrower rolls using computerized slitting machines or die-cut into customized shapes by automatic punching equipment.
After quality inspection, finished products are packaged with magnetic shielding materials or separator boards to prevent contamination by ferrous particles during transportation.
5. 결론
Modern rubber magnet manufacturing represents a sophisticated integration of materials science, polymer chemistry, and magnetic engineering.
From raw material modification and high-shear mixing to pelletizing, calendering or extrusion forming, and finally high-voltage pulse magnetization, every manufacturing step is closely interconnected. Precise temperature control and magnetic field management ensure the excellent quality and performance of the final product.
A comprehensive understanding of this manufacturing process enables industrial customers to evaluate material selection, custom specifications, technical feasibility, and cost efficiency more scientifically, providing reliable and flexible magnetic solutions for a wide range of industries.
