Brush bodies
Brush bodies
Generalites
The filaments are attached to a rigid support that forms the ‘brush body’.The materials used are mainly synthetic, but also natural or metallic.
| Item | PS | A | Tmax | Tmin | R | RE | RC | D | FDA | Main use |
|---|---|---|---|---|---|---|---|---|---|---|
| PVC | 1.40 | 0.05 | +60 | -5 | 55 | 10¹⁵ | XX | 80 | Brushes without special specifications | |
| PA | 1.13 | 10 | +95 | -30 | 70 | 10¹¹ | X | 75 | ✓ | Food |
| PP | 0.91 | 0.03 | +100 | 0 | 35 | 10¹⁷ | XX | 70 | ✓ | Food, humid or climatically aggressive environment, large roller brushes |
| PE | 0.96 | 0.02 | +80 | -50 | 28 | 10¹⁶ | XXX | 65 | ✓ | Large flat brushes, climatically aggressive environment |
| POM | 1.41 | 0.50 | +100 | -50 | 65 | 10¹⁵ | X | 80 | ✓ | Food, precision machining |
| PET | 1.34 | 0.50 | +110 | -20 | 55 | 10¹⁴ | XX | 80 | ✓ | Food, precise processing and aggressive environment |
| PTFE | 2.18 | +120 | 25 | 10¹⁸ | XXX | ✓ | Food, warm environment | |||
| PEEK | 1.32 | 0.50 | +180 | -20 | 95 | 10¹⁶ | XX | High operating temperatures | ||
| PUR | 1.30 | +85 | -20 | 43 | XXX | 40 | Belt brushes | |||
| WOOD | 0.72 | 25 | +300 | 130 | 10¹² | X | 60 | High temperatures, light brushes | ||
| MULTISTRATE | 0.67 | 37 | 10¹² | X | 65 | High temperatures, linear brushes | ||||
| LEATHER | 0.85 | 60 | +110 | -30 | - | XX | 40 | Large belt brushes | ||
| ALUMINIUM | 2.70 | - | +200 | 300 | 2.8 x 10-⁶ | XX | - | Rigid, antistatic brushes | ||
| BRASS | 8.50 | - | +280 | 420 | 7 x 10-⁶ | XXX | - | Brush body with high mechanical resistance | ||
| STEEL | 7.85 | - | +450 | 500 | 1.2x10-⁵ | X | - | Motorized brushes | ||
| STAINLESS STEEL | 7.90 | - | +600 | -150 | 515 | 1.2x10-⁵ | XXX | - | ✓ | Motorized brushes, food use |
PS: specific weight (Kg/dm³)
A:water uptake (%)
T max: maximum operating temperature (°C)
T min: minimum operating temperature (°C)
R: tensile breaking load (N/mm²)
RE: electrical resistance (Ohm cm)
RC: chemical resistance (X = poor, XX = sufficient, XXX = good)
D: hardness (ShD)
FDA: for food use according to Food and Drug Administration (U.S.A.) Room temperature only
All synthetic materials are available in sheets, solid and perforated bars, and in some cases also in shaped profiles.
PVC
Hto excellent handling and cold dimension stability. However, it cannot be used in hot environments or for food use. Its deformability with temperature can be exploited to perform excellent hot-mounting of perforated bars on metal pipes.
PA (Nylon)
It has good mechanical and elastic properties, but is less workable than PVC and tends to deform during processing. It is well suited for food use (only at room temperature).
PP
It has lower mechanical properties than PA and is also available in tubes, making it suitable for the manufacture of large roller brushes, where other products would waste a lot of material. It also lends itself well to injection moulding. It withstands chemicals well.
PE
As it is a soft material, it allows high processing speeds and is also relatively light, making it suitable for building large slab brushes. It also has a low coefficient of friction. It withstands chemicals well.
POM (Acetal Resin)
It is a material widely used in brushes of higher technical value, as it has excellent workability, dimensional stability, temperature resistance and is suitable for food use. Available in H (homopolymer) and C (copolymer) versions.
PET
It has similar characteristics to POM, plus it has good resistance to chemicals.
PUR (polyurethane)
It is often used in the construction of belt brushes due to its deformability. It is also used as a coating for metal cores.
PTFE (Teflon)
It is used as a temperature-resistant material and when sliding on metal surfaces or shafts is required.
PEEK
It is a technological material that is used exclusively for its resistance to high temperatures.
Wood
Before the advent of synthetics, wood was practically the only material used to make industrial brushes. But even today, due to its ability to withstand high temperatures and its lightness, it is still a material used in technology. It is of fundamental importance to use only carefully seasoned wooden boards, to avoid bending and breaking during brush work.
Multi-layer
It has great dimensional stability and flatness, and has the advantage of being available in sheets of various thicknesses. Marine plywood can also work in water.
The diagram shows how a plywood board returns to normal from the situation of maximum water absorption.
Leather
It is another material used for belt brushes, and has about the same hardness as PUR. With leather, belts of considerable width can be made, and it is often laminated with a layer of nylon or PP to increase its rigidity. The most commonly used leather is the one treated with chrome.
Aluminium
It makes it possible to build very strong and light brush bodies, and at the same time is soft enough to be inset with automatic machines, albeit much faster than plastics. It has high dimensional stability. It is also an excellent electrical conductor, which is why it is also used in the manufacture of anti-static brushes.
Brass
It has high mechanical strength and great stability even at very high temperatures. It also has excellent handling.
Steel
It is mainly used as a core for roller brushes in the form of tubes, shafts, bushings, flanges. Or it is used as a body for hand-sewn brushes. There are many steel grades available for brush bodies, including stainless steel (AISI 304), in bar or plate format.
Synthetic materials have a hardness characteristic of the polymer of which they are made.
When a batch of synthetic rods or sheets enters the factory, its hardness is also checked by means of a durometer on the Shore D scale (or Shore A for softer materials such as PUR).
Hardness is also indirectly related to other characteristics such as the breaking load R. Each material has a range of acceptability, if the result falls outside this range it is rejected.
This control eliminates faults due to incorrect material manufacture, thus guaranteeing consistent quality in the supply of brushes. In the case of metal bodies, whether turned or milled, quality control is of the dimensional type; various high-precision instruments are used for this purpose.
Frequent questions
The special feature of the brush is that the work surface is made up of millions of individual elements, which are the ends of the individual filaments.
This gives the brush an adaptability that no other element, however deformable, can have.
It depends on various factors. In a nutshell, it can be said that 2 mm is a good compromise. The important thing is that the filaments of the brush work “at the tip” and not on the side.
Depending on the materials used and the dimensions, there is a tensile limit load that a single bunch can withstand.
Beyond this limit the bunch comes off, therefore the brush must be calculated according to the use. This limit can be greatly increased by building “sewn” or “tied” brushes by hand, where a continuous steel wire is placed instead of a single anchor element.
It can only happen if the brush has a manufacturing defect, like any other type of object (e.g. a roller made with silicone flakes, one of which is defective and breaks).
When it is important that no contamination occurs, it is advisable to use synthetic (non-natural) fibers with a diameter greater than or equal to 0.15 mm.
Virtually all degrees of hardness can be had, from very soft to very hard. In fact, the hardness is given by the combination between the diameter of the filament, its free length and the density of the bunches.
Of course, we can provide FDA or FOOD GRADE certifications and filament traceability.
Unfortunately not, as it is the machine + brush assembly that must be ATEX certified, not just the brush.
However, it is possible to supply the materials that the certifier requires, e.g. conductive bases, conductive filaments, etc.
Generally speaking it is possible, but it is necessary to evaluate if it is economically convenient, and it is not always. Furthermore, in the case of a punched brush, it is not advisable to regenerate the brush more than twice in order not to reduce the holding of the bunches.
