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Brush Filament & Shape Glossary



Carolina Brush Company predominantly uses fiber from Type 6, Type 6.6, and Type 6.12.  Nylon offers a combination of excellent bend recovery, abrasion resistance, flex fatigue resistance and chemical resistance.  All nylons absorb water is wet conditions, which will reduce their stiffness; up to 30% for Type 6.12, and up to 80% for Type 6.  Nylon has excellent resistance to most substances, including hydrocarbons (such as gasoline, kerosene, and diesel fuel), oils, cleaning solutions, and alkalis.  It is however attacked by oxidizing agents, organic and mineral acids, and aromatic alcohols.  It will absorb small amounts of water, low molecular weight alcohols (e.g., methyl, ethyl, or isopropyl alcohols) and chlorinated solvents, and be plasticized by them.  This may result in a temporary loss of stiffness and tensile strength.  Type 6.12 is more resistant to dilute acids and other water soluble substances than Type 6 of 6.6, thereby making it most suitable for wet applications.

Some diameters of specialty nylon filament such as abrasive impregnated, conductive 6.6 and heat stabilized 6.6 are available.


The top quality polypropylene we use is a versatile filament for a wide variety of applications.  It has excellent wet stiffness and flex fatigue resistance.  It is resistant to most solvents, oils and chemicals and is especially good at resisting strong acids and bases.  It may be attacked by oxidizing agents such as hydrogen peroxide, chlorinated solvents (such as 1,1,1-trichloroethane) and aromatic solvents (such as xylene).  Polypropylene has good bend recovery, but will take a set more easily than other materials.  This issue can usually be addressed with good brush design and reasonable care in handling and packaging.


Fibers made with polybutylene terephthalate polyester (PBT) can be a good substitute for Nylon in some applications.  It has better abrasion resistance than polypropylene, but not quite that of nylon.  It has excellent bend recovery, excellent solvent resistance, and excellent oxidation resistance at higher temperatures.  It has very good resistance to sunlight.  The properties of polyester do not change significantly between wet and dry applications because it does not absorb much water, making it ideal for many wet applications.  It is however attacked by strong alkalis such as concentrated solutions of sodium hydroxide (lye or caustic soda), calcium hydroxide (lime, mortar), ammonia, trisodium phosphate, or sodium carbonate.

Abrasive Filaments

A long wearing abrasive filament impregnated with silicone carbide particles.

Note:  This information is based on our experience and published data.  Some published data has been contradictory, but we believe this information to be true and accurate.  Because of the effects of concentration, time and temperature on solvent and chemical resistance, we suggest that actual trials be conducted in critical applications.

Fiber Property Comparisons

Filament Melting Point (*F) Tensile Modulus (kpsi) Tensile Strength (kpsi) Flicking Action % Bend Recovery Relative Abrasion Resistance
Nylon 6 410 480 53 Excellent 97 Excellent
Nylon 6.6 495 520 48 Excellent 97 Excellent
Nylon 6.12           410 480 42 Excellent 93 Excellent
Polypropylene 320 740 53 Good 75 Fair
Polyester 430 445 31 Excellent 92 Good

Filament Set Resistance Relative Flex Fatigue Resistance Water Absorption % Max Retention of Stiffness in Water Sunlight & UV Light Resistance General Solvent Resistance
Nylon 6 Good Excellent 9 Poor Fair Excellent
Nylon 6.6 Good Excellent 9 Poor Fair Excellent
Nylon 6.12           Good Excellent 3 Good Fair Excellent
Polypropylene Fair Best <0.1 Excellent Poor Excellent
Polyester Good Good 0.5 Excellent Fair Excellent

The above compares in a general way some of the properties of the synthetic filaments we most commonly use to aid in distinguishing between them when selecting the filament best suited for a particular application.

Animal Hair


Produced in Argentina, Canada, China and the United States. Soft to slightly stiff texture. Used primarily on highly polished areas.

Hog Bristle

Imported from Europe and China. Soft to slightly stiff texture. Natural flagging enables brush to reach into cracks to remove fine dust.

Goat Hair

Very fine and soft. Used for very short trim brushes.

Vegetable Fibers


A vegetable fiber produced in Mexico from the Mexican Agave plant. The original color is off-white, but it can be dyed any color, but most often dyed black or grey. Tampico is soft to medium with good water retention and acid resistance.

Bassine Fiber

Bassine fiber is a superior grade of Palmyra fiber. The fibers are coarse and stiff and range in color from dark brown to black. Good water resistance and its coarseness makes it ideal for stiff scrub brushes.

Union Fiber

Union fiber is a mixture of two or more materials – usually Tampico and Palmyra. It has a medium stiff texture and is a mix of light and dark brown fibers.



Available in both straight and crimped forms.

Phoshor Bronze

Alloy composed of mostly copper and brass. Light duty applications that require a soft touch.

Carbon Steel

This wire withstands tougher scrubbing. Is used primarily in wire wheels, scratch brushes and rotary floor brushes.

Stainless Steel

This type wire is the most corrosion resistant wire available in the brush industry


Melting Point is stated as a typical values; actual melting points may vary by 20*F from those stated.  It should be kept in mind that each of these materials will soften and melt over a range of temperatures, and that the useful temperature limit of a fiber is quite a bit lower than the melting point.

Tensile Modulus is a measure of the stiffness of the fiber.  The higher the tensile modulus, the stiffer the fiber.

Tensile Strength refers to how hard one can pull on the fiber before it breaks. A significant reduction in tensile strength indicates deterioration of the fiber.

Flicking Action of springiness is how well a fiber snaps back after being bent.  This is an important consideration for light sweeping and dusting, less so for heavy sweeping and scrubbing.

Bend Recovery is a fiber’s ability to return to its original position after being bent.  Lack of bend recovery is a common mode of brush failure.

Abrasion Resistance is a fiber’s ability to resist being worn away.  Abrasion is another common mode of brush failure.

Set Resistance refers to a fiber’s ability to straighten completely after being moderately flexed for a long period.  This differs from Bend Recovery which is a more severe bending for shorter periods.

Flex Fatigue Resistance describes how many times a fiber may be bent back and forth before it is damaged.

Water Absorption and Retention of Stiffness in Water refer to the tendency of certain plastics to pick up and be plasticized by water, but other materials are not affected.

Sunlight, UV Light will result in rapid degradation of some polymers.

General Solvent Resistance refers to the ability of a fiber to retain its important physical properties when exposed to certain chemicals.