Rubber Magnets: The Ultimate Guide

Rubber magnets are magnets renowned for their flexibility, which is achieved by blending powder drawn from magnetic materials like ferrite and rare earth materials with rubber. Other polymer binders like plastic can also be used.

Advantages of Rubber-Coated Magnets

Rubber-coated magnets exhibit unique features and from these features, numerous advantages are born. Underneath are the main advantages that have seen the demand for rubber magnets proliferate immensely:

  • Flexible and thus can be twisted and customized to take different forms allowing their use in distinct applications.
  • Can operate normally at low temperatures as well as high temperatures (-40°C to 80°C.)
  • Their corrosion resistance is impressively strong thanks to the rubber polymer binders added.
  • They are relatively low-cost, especially when compared to permanent magnets.
  • Rubber magnets can retain magnetism even when exposed to certain levels of demagnetization forces.
  • These magnets are relatively safe
  • They contain supplementary features like threaded stems and sockets, which make installation easier.

The Composition of Rubber Magnets

Rubber magnets are the end products of magnetic materials (in powder form) combined with polymer binders. Here are the main ingredients used to make rubber-coated magnets.

Magnetic Powder

At the base of rubber magnets, lies magnetic powder which is primarily drawn from ferrite compound (iron oxide). The ferrite is often supplemented by other elements like strontium and barium.

Alternatively, rare earth magnetic materials can be crushed and their powder utilized as the base of rubber magnets. The magnetic powder is the force behind the rubber magnets’ magnetic capabilities.

Polymer Binder

The powdered magnetic particles must be enjoined and this is achieved with the aid of polymer binders. The most commonly utilized polymer binders in rubber magnets include polyvinyl chloride (PVC) and flexible plastics. The binder is responsible for the flexibility exhibited by rubber-coated magnets.

PVC Molecular Formula
PVC Molecular Formula

Other additives may be injected into rubber magnets to elevate specific features like coloration and physical strength.

Magnetic Properties of Rubber Magnets

Rubber magnets can be differentiated from conventional inelastic magnets easily.

This is because they possess distinct characteristics like elasticity and corrosion resistance. Underneath are the primary properties that set apart rubber magnets from typical magnets.

· Magnetic Strength

Rubber magnets are primarily designed for applications that prioritize flexibility rather than strong magnetic forces. As such, they exhibit relatively inferior magnetic strengths compared to rigid magnets like neodymium magnets. This means that their maximum energy product (BHmax) is comparatively lower.

· Flexibility

Although they do not exhibit strong magnetic forces like conventional rigid magnets, rubber magnets are unmatched when it comes to flexibility. They can be bent, twisted, or even molded into varying shapes depending on the respective scenario. The elasticity property is enabled by the flexible polymer binders added to the magnetic powder.

· Coercivity

Rubber magnets tend to lose their magnetic powers more easily compared to other magnet types. This, however, does not mean that they are easily demagnetized because they can retain their magnetism even under the presence of stronger magnetic fields. Comparing their resistance to demagnetization to rare earth magnets is however a mismatch.

· Corrosion Resistance

Compared to other magnets, particularly those made from metallic materials, the corrosion resistance of rubber magnets is relatively high.

Despite containing ferrite compounds, they contain polymer binders, which protect the magnetic powder from oxidation and corrosion. This makes them ideal for use in rough environments and it also prolongs their service life.

· Temperature Stability

Rubber magnets can function at high levels despite being subjected to rough temperatures. They retain their functionality even at temperatures as low as -40°C and as high as 80°C.

However, their maximum operating temperature and curie temperature are comparatively lower in comparison to rare earth permanent magnets.

Classifications of Rubber Magnets

Rubber or flexible magnets are essentially classified into two; isotropic and anisotropic rubber magnets. Here is a brief look at these two prominent categories of rubber magnets.

· Isotropic rubber magnets

Isotropic flexible magnets are generally manufactured by pouring the magnetic material powder on a rubber matrix uniformly for mixing. They have magnetic field lines flowing in a uniform direction since the magnetic domains are randomly oriented. Isotropic flexible magnets tend to showcase weaker magnetic forces relative to anisotropic rubber magnets. They however demonstrate higher elasticity.

· Anisotropic Rubber Magnets

In anisotropic rubber magnets, the magnetic domains are uniformly aligned and this is because they are magnetized during the curing process.

This equips them with more powerful magnetic forces, unlike isotropic magnets. They are however weaker when it comes to flexibility. Anisotropic flexible magnets are therefore commonly utilized in applications prioritizing stronger magnetism rather than elasticity.

Types of Rubber Magnets

The demand for rubber magnets is continually growing and this is partly being driven by the variety of options available.

Today, they are available in a range of forms, sizes, and properties, ensuring that every use scenario has a tailor-made magnetic solution.

· Threaded Stem Rubber Magnets

Threaded stem rubber magnets contain a metal stem, which makes it easier to fix the magnets on specific surfaces or objects.

They are versatile and their application fields transcend both indoor and outdoor applications. Furthermore, they exhibit great magnetic powers and are quite long-lasting. Threaded stem flexible magnets are mainly used to hold signage and in assembling processes.

Threaded Stem Rubber Magnet
Threaded Stem Rubber Magnet

· Internal Thread Rubber Magnets

These rubber magnets can be identified by a threaded hole in the magnet’s center. The role of the threaded socket is to hold bolts and other fasteners.

This makes them perfect for holding temporary fixtures on objects as well as mounting protective covers on equipment. They can be easily unmounted and are highly resistant to corrosion.

Internal Thread Rubber Magnet
Internal Thread Rubber Magnet

· Countersunk Hole Rubber Magnets

Countersunk hole magnets consist of a depression or hole within the magnet whose primary role is to facilitate flash mounting. This depression also prevents the projection of bolts being fastened onto the rubber magnet. They are mainly utilized to secure decorations and hold signage.

Countersunk Hole Rubber Magnet
Countersunk Hole Rubber Magnet

· Screw-Socket Rubber Magnets

These rubber magnets feature a threaded socket as well as a threaded stem. This diversifies their applications by providing more mounting options. Screw-socket rubber magnets are powerful and they are ideal for holding objects in varying settings.

Screw Socket Rubber Magnet
Screw Socket Rubber Magnet

Rubber Magnet Manufacturing Process

Rubber magnet manufacturing involves blending magnetic materials in powder form with polymer binders. This makes the magnetic material flexible consequently opening up more use scenarios. Here is a step-by-step breakdown of rubber magnet manufacturing:

· Ingredient Preparation

The process of manufacturing rubber magnets commences with the collection and preparation of the main ingredients.

Besides, these ingredients are magnetic material powder, polymer binders, and optional additives. The amounts are precisely calculated to ensure uniformity in the rubber magnet’s magnetism.

· Mixing

With all the ingredients in place, the magnetic powder is placed in a mixer and the polymer binder is added. The two compounds are then mixed thoroughly until a uniform distribution is achieved.

· Calendaring

The resulting mixture is then injected into a calendaring machine where rollers flatten and shape the mixture. This results in flat sheets or rubber magnetic material evenly sized.

· Magnetization

The evenly sized material collected from the calendaring machine is then introduced to power magnetic fields. This helps align the magnetic domains of the magnetic material resulting in active magnetic forces. This can be repeated severally to ensure optimal magnetization.

· Curing

The curing process involves subjecting the magnetic material to controlled heat. Varying heating methods can be employed to achieve curing but the most common involves using ovens.

· Shaping

Consequently, the magnetized material is cut into smaller pieces as per the design demands. Laser cutting is often used to cut rubber magnets into different shapes and designs.

· Surface Treatment

Although this step is optional, it is often utilized. Surface treatment can include adding protective coatings or printable materials for branding.

· Quality Control

Finally, the rubber magnets are subjected to multiple tests to guarantee quality. The magnetic strength is measured as well as the magnet’s elasticity.

Rubber Magnet Manufactering Process
Rubber Magnet Manufacturing Process

Limitations of Rubber Magnets

Rubber magnets are known and revered for their flexibility and versatility. These unique features, however, come at a cost. Here are the main limitations of rubber-coated magnets.

  • They have comparatively inferior magnetic forces compared to permanent magnets. This is understandable because they are built to suit applications that prioritize flexibility rather than magnetic strength.
  • Their demagnetization resistance is also comparatively low. This is because they do not necessarily generate strong magnetic fields.

Applications of Rubber Magnets Today

  • Signage and Promotional Materials: They are commonly used to hold promotional materials like posters on different surfaces.
  • Industrial Applications: In industrial settings, they are often used to provide magnetic functions to seals and gaskets as well as conveyor systems.
Rubber Gaskets
Rubber Gaskets
  • Educational Settings: They are prominently used in classrooms to hold magnetic boards and puzzles. They are also used as learning aids.
  • Magnetic Closure: Contemporary wallets and pulses feature rubber magnets, which facilitate secure closing as well as ease the process of opening and closing.
Apair of Magnetic Closure
Apair of Magnetic Closure

Additional Applications

  • Retail displays
  • Vehicle signage
  • Magnetic business cards
  • Magnetic calendars
  • Magnetic whiteboards
  • Magnetic strips
  • Magnetic labels
  • Magnetic sensors
  • Art and craft
  • Refrigerator magnets

Rubber magnets come with a different set of properties compared to conventional hard magnets. This has consequently broadened their application fields, thereby driving up their demand.

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