Flexible Magnets 
The FLEXMAG™ division of Arnold Magnetic Technologies produces flexible magnetic
sheet and strip (rubber magnets) for use as advertising specialties or printed magnets (refrigerator magnets, car signs, labels) by commercial printers (we don’t sell the advertising magnets, we sell the bulk material in roll and sheet form) as well as OEM uses including sensing magnets, motor magnets, biomedical surgical drapes, doors (shower and other), robotic guidance and automotive sound deadening.
MANUFACTURING PROCESSES
There are three processes used in manufacturing flexible magnets. They include extrusion, calendaring, and a combination of the two. The extrusion process is widely used for "profile extrusion" or magnets with an irregular cross-section. The calendering process involves the rolling of pelletized compound between two rollers to form a continuous sheet. The combination extruder/calender process invloves a little of both processes to achieve the desired magnet. Each process has advantages and limitations.
Flexmag manufactures five primary grades of extruded or calendered product and many more representing customer-required variations. Energy products range from 0.6 to 1.4 MGOe (4.8 to 11.1 kJ/m3). Thickness of extruded sheet is from 0.010" to 0.063" (0.25 to 1.60 mm). Extruded profiles are available in a wide range of shapes. Calendered sheet is also available. For profile extruded and calendered sheet, please contact us for size capability details.
Flexmag uses, primarily, a polyethylene binder system. Many variants are available including newer formulations with nitrile rubber. Again, please contact us to discuss your specific requirements.
The Plastiform Division of Flexmag Industries produces continuous rolls of calendered sheet and strip product in thicknesses of 0.020" to over 0.375" (0.51 mm to over 9.5 mm). Energy product for ferrite materials ranges from 1.0 to 1.6 MGOe (8.0 to 12.7 kJ/m3). The binder choices include nitrile rubber, Nordel and Natsyn. The material is generally vulcanized, but is also available unvulcanized. Rare earth flexible NdFeB magnets are available in higher energy products.
Sheet can be stamped, slit, punched, laminated, or sanded to profile the edges or achieve close thickness tolerance. Magnetized sheet is available in several pole per inch (ppi) configurations from 4 to over 12 ppi, optimized for specific applications. More poles per inch increase the holding strength, but reduce the reach of the field. Fewer poles per inch increase the distance at which the magnet attracts, but reduces the ultimate holding strength. Pole per inch capability is also a function of the thickness of the sheet, thicker sheets having fewer ppi.
TEMPERATURE CHARACTERISTICS
Both the polyethylene and nitrile rubber binders are capable, with ferrite, of use up to 120°C. Higher temperatures are possible, but with some dimensional change (usually shrinkage) and with loss of flexibility. Testing of nitrile with ferrite has been conducted up to 150°C.
The presence of rare earth metal powder, however, greatly reduces the temperature capability. Rare earth material is so strong that at elevated temperatures (when the binder is soft), the magnet will self-deform, literally tearing itself apart. It is imperative that flexible rare earth not exceed the recommended use temperature.
REMEMBER: bonded magnets are truly engineered products, tailored to meet your needs by experienced Arnold engineers.