DuPont Filamentsf

Filament Performance in Brushes

“The Global Choice for Premium Brush Filaments”

Tynex • TynexA • Orel • Chinex

Technical Information

Tynex®, Tynex® A, Chinex®, and Orel® are DuPont registered trademarks for its filaments that are used inpremium quality brushes. Applications are:

• Tynex® level filaments for toothbrushes• Tynex® fine filaments for cosmetic brushes• Tynex® tapered filaments for paintbrushes• Tynex® A abrasive filaments for floor care and industrial brushes• Chinex® synthetic bristle for paintbrushes• Orel® polyester tapered filaments for paintbrushes

Much of the data presented in this bulletin is pertinent to a variety of brushes and brush filaments. Butparticular emphasis is placed on DuPont filaments that are now manufactured in ISO 9002-qualified plantsworldwide.

Introduction

DuPont has produced nylon monofilaments for over 50 years. Currently, most of these filamentsare used in toothbrushes, paintbrushes, and cosmetic and abrasive filament brushes. We havegathered pertinent technical data over the years concerning brushes made with synthetic filaments.This technical bulletin summarizes and revises data presented in past publications.

Contents

Stiffness of Nylon Filaments ....................................................................................... 1

Abrasion Resistance and Factors That Affect Brush Wear Rate ................................. 5

Bend Recovery ............................................................................................................ 9

Fatigue Resistance and Factors That Affect Flex Life ................................................ 13

Filament Identification ................................................................................................ 16

Chemical Resistance of Nylon Filaments .................................................................... 21

Stiffness of Nylon Filaments

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Whether a brush does the job for which it wasdesigned usually depends on a number of factorssuch as brush configuration, abrasion resistancebend recovery, or, perhaps most important, stiffnof the brush. Brush stiffness in turn depends almentirely on filament stiffness, which is affected bythe following factors.

Modulus versus StiffnessThree factors (modulus, diameter, and trim lengthaffect the filament property that we call stiffness.The confusion about the property of stiffness resufrom using the word “stiffness” interchangeablywith “modulus.”

Modulus is a physical property of a material thatcan be defined as resistance to deformation or,more simply, as resistance to bending. Modulus ibased on a unit area (1 in2) and is, therefore,independent of the diameter of the sample used make the determination. Modulus (stiffness forequal caliper and length) is one of the inherentproperties of the material, i.e., just as polyethylenhas a unique modulus, Tynex® has a unique modu-lus. In other words, every material has a specificmodulus and it is usually different from any othermaterial.

If we attempt to bend two different sized (diameterods of the same material, we would say that onestiffer than the other. What we feel is a combinatiof modulus and size. The modulus is the same foboth, but the larger size of one makes it feel stiffethan the other.

A third factor that affects stiffness is length. A shofilament feels stiffer than a long filament of thesame size and composition.

Factors Affecting ModulusMoistureAll filaments are affected to some extent by moisture. Figure 1 shows the effect of moisture onmodulus for Tynex®. As can be seen from thegraph, 66 nylon is stiffer than Tynex® when dry, butTynex® is stiffer when wet. This is caused by thelower moisture absorption of Tynex®, whichabsorbs only 3% moisture when saturated. At ab68% relative humidity, the modulus of Tynex® and66 nylon are equal. Type 6 nylon becomes verylimp when wet and does not make a good brush-filling material. In fact, it is used for fishing line.

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Figure 1. Stiffness versus Relative Humidity ofNylon Filament at 23°C (73°F)

Although nylons absorb some water, they do notabsorb as much moisture as natural hair bristle(horse hair and hog bristle). The natural fibers notonly absorb more water than Tynex®, but theyabsorb it much faster, as shown in Figure 2. Thisfigure shows percent stiffness retained versus timein water. After only 10 min in water, natural hairbristle loses 40% of its stiffness, whereas it takes10 hr for Tynex® to lose 28% of its stiffness.

Table 1 lists wet and dry moduli for several brush-filling materials. Also listed are the wet-to-drymodulus ratios.

Table 1Brush Moduli

Tynex Natural Hair612 Nylon 66 Nylon Bristle

Dry Modulus, psi 580,000 650,000 680,00023°C (73°F) and50% RH

Wet Modulus, psi 420,000 240,000 410,00023°C (73°F) and100% RH

Wet-to-Dry 72 37 60Ratio, %

Tynex612 Nylon

66 Nylon

10 20 30 40 50 60 70 80 90 100200

300

400

500

600

700

800

Relative Humidity, %T

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Figure 2. Stiffness Retained versus WettingTime␣ for 10-mil Filaments and FibersSubmerged in Water at 23°C (73°F)

Changing the caliper of the filament will compen-sate for a high or low modulus. Thus, the wet-to-dry modulus ratio is a more important factor thanactual modulus levels in selecting a filler for bush

66 Nylon

Natural Hair

Tynex

0 1 2 3 4 5 6 7 8 9 1030

40

50

60

70

80

90

100

Wetting Time, hr

Sti

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ess

Ret

ain

ed, %

6

Figure 3. Stiffness versus Temperature for Nylon Filame

–12(10)

100

200

300

400

900

1,000

1,100

1,200

1,300

500

600

700

800

–7(20)

–1(30)

4(40)

10(50)

16(60)

21(70)

27(80)

32(90)

Tempe

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that will be used under various moisture conditioA filler with a low wet-to-dry ratio would be toostiff under dry conditions if designed for wetconditions.

TemperatureAll filaments are less stiff at elevated temperaturthan they are at room temperature. Figure 3 showsthe typical effect of temperature. Nylon filamentsare about twice as stiff at 0°C (32°F) as they are atroom temperature. The change in stiffness is muless above room temperature than it is below rotemperature. It should be pointed out that eventhough nylon filaments become stiff at low tem-peratures, they do not become brittle.

Brush StiffnessEffect of Caliper and Trim LengthThere are many combinations of filament diameand trim length that will result in a brush withsimilar stiffness.

Figure 4 presents this information graphically. Foexample, let us suppose a given brush has a trimof 2 in and is filled with 10-mil (0.010-in) filamenDraw a line on the chart from 2 in on the trimlength scale to 10 mil on the diameter scale. Nowhere this line crosses the reference line. Assum

nt (Humidity Controlled)

38(100)

43(110)

49(120)

54(130)

60(140)

66(150)

71(160)

77(170)

82(180)

88(190)

rature, °C (°F)

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that a new brush with a 21/2-in trim length and thesame stiffness is required. Draw a line from thispoint on the trim length scale through the crossovpoint on the reference line to a new diameter. In texample shown on the chart, the line is drawn to tdiameter scale at 14 mil. Therefore, assuming thefilling material used is the same, a brush with a21/2-in trim filled with a 14-mil filament will havethe same stiffness as the original brush with a 2-intrim filled with 10-mil filament.

The answer is only an approximation because tufstiffness is also affected by the way in which thebrush is made (i.e., staple set, wire drawn). Also,because tuft stiffness is a function of the 2nd powof the filament diameter, even a small deviationwill have a large effect on stiffness. This chart canbe used for any type of level filament as long asboth brushes are filled with the same type offilament.

Brush Construction VariablesBrush construction plays a big part in determiningbrush stiffness. Figure 4 is for brushes of likeconstruction. It would be impractical to develop achart that includes all of the various brush construtions. In most brushes, one filament touches anotand, therefore, does not function as an individualfilament but as a family of filaments. Their interaction varies with each type of construction (strip

Figure 4. Nomograph for Relating Trim Length andFilament Caliper for Equal Brush Stiffness

Reference Line

Fila

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, mil

Trim

Leng

th, in

Existing Brush

Desired Brush

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/3 4

/1 2

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brush, tuft-staple set, tuft-wire drawn, tuft-adhesiveset, etc.). This interaction will also vary with tuftsize, trim length, and the rigidity of the tuft in thebrush.

Crimping is one way to increase the apparent mas(bushiness) of the filaments. Natural bristles, as aresult of their rough surfaces, have more interactiobetween fibers than noncrimped nylon filament. Abrush filled with crimped nylon filament morenearly duplicates the “feel” of a natural fiber brushand gives the bushiness usually associated with anatural fiber.

Calculation of Brush StiffnessThe following equation is a basic engineeringformula that relates the factors controlling stiffnessfor a filament held at one end, such as in a brush.

Brush StiffnessEquation 1: D =

Where: D = Deflection of filament, in

W = Weight (or force causingdeflection), lb

L = Length of filament, in

E = Modulus of filament, psi

I = Moment of inertia of the crosssection of the filament, in4

I = 0.0491d4 for round filament

d = Diameter of filament, in

Round FilamentFor a round filament, Equation 1 becomes:

D =

The following conclusions can be drawn fromEquation 2:• The stiffness (resistance to bending) of a single

round filament fixed at one end is proportional tothe 4th power of the diameter.

• The stiffness of a single round filament fixed atone end is inversely proportional to the 3rd poweof the length of that filament.

Tufts of FilamentIn most cases, brushes are made up of tufts offilaments rather than single filaments. In the case a tuft, Equation 2 becomes:

D =

where N is the number of filaments per tuft.

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3 EI (1)

WL3

0.1473 Ed4 (2)

WL3

0.1473 Ed4N (3)

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The area of a round filament is πd2/4, and,therefore, the number of filaments, N, for a givesize tuft is inversely proportional to the 2nd powof the diameter of the filament.

The following conclusions can be drawn for tuftstiffness:• The stiffness (resistance to bending) of a tuft o

round filament is proportional to the 2nd poweof the filament diameter.

• The stiffness of a tuft of round filament is in-versely proportional to the 3rd power of thelength of that tuft.

From these conclusions we can write the followiformula, which relates filament diameter and trimlength of one brush to filament diameter and trim

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length of another brush for equal brush stiffness,given that the filaments are of the same polymertype:

13 L3

d2 D2

Where: 1 = Trim length of existing brush

d = Filament diameter of existing brush

L = Trim length of desired brush

D = Filament diameter of desired brush

By substituting the known values in the aboveequation and assuming either a new trim length odiameter, the one remaining unknown can becomputed. This equation can be solved graphicaby using the nomograph in Figure 4.

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Abrasion Resistance and Factors That AffectBrush Wear Rate

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The abrasion resistance of a brush filament is oftthe controlling factor in brush life. This is particu-larly important if the brush is used for polishing orcleaning and is rotated or operated mechanicallyagainst an abrasive surface. The abrasion resistaof different materials used as brush fillers varieswidely. Resistance to abrasion is an outstandingproperty of nylon filaments.

Inherent Abrasion Resistance ofBrush-Filling MaterialsThe abrasion rate of a brush-filling material isprimarily an inherent property of that material. Inthe case of synthetic filaments, it is essentially aproperty of the material from which the filament ismade and is only slightly influenced by the procesof filament manufacture. The best way to comparthe relative abrasion resistance of one material toanother is to measure the rate of wear (abrasionrate) of the materials in question under identicalstandard test conditions. Table 2 shows compara-tive data obtained during testing.

The method used to obtain the data involves theuse of 2-in long twisted-in-wire brushes, 13/4 inin diameter, filled with 0.012-in diameter filament.The brushes are rotated against sandpaper for agiven period of time. The change in brush weightor weight loss is the abrasion rate (expressed inmg/hr).

Tynex® and nylon filaments, in general, have amuch lower abrasion rate than any of the naturalmaterials and are about 50% better than the nextbest economical man-made filament commerciallavailable.

Table 2Test Data

Abrasion Rate, AbrasionMaterial mg/hr Ratio*

Tynex 612 Nylon 40 1.0066 Nylon 46 1.15Polyester 60 1.50Hog Bristle 160 4.00Tampico 220 5.50

*Based on Tynex = 1

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Filament SizeThe larger the filament, the faster it will wear, allother factors being constant. Figure 5 showswhere abrasion rate is plotted versus filament sizAbrasion rate is directly proportional to the cross-sectional area of the filament or the square ofthe filament diameter. Brush stiffness is alsodirectly proportional to the square of the filamentdiameter. Thus, abrasion rate is proportional tobrush stiffness.

Therefore, for the longest life, a brush should be stiffer than necessary to do the job for which it wadesigned. Because stiffness is proportional to thesquare of the filament diameter, a small increasecaliper will result in a much larger abrasion rate.For example, the abrasion rate is almost doubledgoing from 10-mil (0.010-in) filament to 14-mil(0.014-in) filament, all other factors being constan(Figure 5).

Figure 5. Effect of Filament Diameter on AbrasionRate of Tynex

5 10 15 20 25 30

25

50

75

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175

Filament Diameter, mil

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Figure 6. Effect of Brush Speed on Abrasion Rateof Tynex

Brush SpeedAs would be expected, the abrasion rate increaseas the brush speed increases (Figure 6).

The rate of abrasion increases in a straight linewith increasing speed up to a point (for example,2,400 rpm in Figure 6). Above this level, the rateof abrasion increases rapidly. A certain amount omaterial is removed each time a filament comes contact with the abrasive surface. Therefore,increasing the number of contacts (increasing thespeed) increases the abrasion rate. The departurfrom a linear relationship above a certain speed iprobably a combined effect of heating by frictionand impact abrasion. At the higher speeds (greatimpact force), it is reasonable to assume that momaterial is torn away per contact with the abrasivsurface.

Applied LoadAgain, as would be expected, abrasion rate in-creases as the applied load on the brush is incre(Figure 7). The effect of filament diameter can alsbe seen in this graph.

In Figure 7, the abrasion rate varies directly andlinearly with the applied load. At much higherapplied loads, the abrasion rate increases muchfaster than the applied load. This departure fromlinear behavior is a result of excessive deflectionof the filament, which greatly increases the contaarea between the filament and the abrasive surfa

0 1,000 2,000 3,000 4,000

25

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75

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125

150

Brush Speed, rpm

Ab

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Rat

e, m

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1

Figure 7. Effect of Applied Load on Abrasion Rateof Tynex

Figure 8. Effect of Brush Fill Weight on AbrasionRate of Tynex

0 2 4 5 6 10

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75

Brush Fill Weight, g

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Fill WeightFigure 8 shows that the rate of abrasion is constawhen fill weight is changed over a three-fold rangThis is at first surprising, but can be explained byremembering that with diameter constant, the ratof abrasion varies with the load per filament.Doubling the number of filaments will halve theload per filament and, hence, halve the abrasionrate. However, there are twice as many filamentends subject to abrasion, so the overall rate isconstant.

Although the weight loss is independent of fillweight, the trim loss is proportional to fill weight.This means that within the range explored, theweight of material worn away will be the sameregardless of the fill weight. The lighter the fill, thefaster the brush will lose trim length.

0 100 200

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200

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400

300 400

18 mil Tynex

12 mil Tynex

6 mil Tynex

Applied Load, g

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TemperatureSurprisingly, there is little effect on abrasion rate onormal atmospheric temperature variation. Abra-sion rate increases as temperature increases. Theeffect of temperature over the range –40 to 66°C(–40 to 150°F) is shown in Figure 9.

The effect shown in Figure 9 is actually a com-bined effect of temperature and stiffness as causeby temperature. As discussed previously (“Stiffnesof Nylon Filaments”), temperature has a markedeffect on the stiffness of nylon monofilament.Stiffness decreases as temperature increases, anabrasion rate decreases with decreased stiffness.Therefore, abrasion rate should decrease with ristemperature, except for the fact that there are otheffects of temperature (such as softening) that tento increase abrasion rate. The grand total effect oall these factors results in a modest increase inabrasion rate as temperature rises.

Figure 9. Effect of Temperature on Abrasion Rateof Tynex

Another point to remember is that the filament tipsare heated by friction against the abrasive surfaceand, therefore, the filament tip temperature in somapplications may be somewhat independent ofambient temperature.

HumidityThe effect of relative humidity on abrasion rate isshown in Figure 10. The effect of humidity onabrasion rate is similar to that of temperature. It isa combined effect of humidity and stiffness changcaused by humidity.

In many cases, the ambient temperature and relahumidity rise and fall together. Therefore, becausa rise in humidity reduces the abrasion rate and a

–18(0)

–46(–50)

10(50)

38(100)

66(150)

25

50

75

Temperature, °C (°F)

Ab

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Rat

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g/h

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11

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Figure 10. Effect of Relative Humidity on AbrasionRate of Tynex

rise in temperature increases the abrasion rate, thtwo effects tend to cancel each other. This being case, the effect of temperature and relative humidity can be neglected under most conditions.

Trim LengthIn the abrasion test used to obtain this data, the trlength was held constant. Trim length as such hasno effect on the abrasion rate of a brush. It does,however, affect the abrasion rate of a brush inpractice because it affects the stiffness of the bruswhich does affect the abrasion rate.

All other factors being constant, abrasion ratevaries inversely with trim length, which is to saythat as trim length increases, abrasion rate de-creases. Therefore, trim length is certainly a factoto consider with respect to brush life.

Abrasive SurfaceThe type of surface being brushed is probably themost important factor in the abrasion rate of a givmaterial. In order to study different types of sur-faces, a series of tests were run on various gradesandpaper. The results are interesting in thatabrasion rate is maximum on a sandpaper surfacewith a grit size of about No. 180. Coarser or finersandpaper gives a lower abrasion rate, as shownFigure 11.

The sandpaper that gives the maximum abrasionrate has abrasive particles of about 5-mil (0.005-indiameter. As the particle diameter approaches zethe rate of abrasion approaches zero. Here againeffect of filament diameter can be seen.

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20

40

60

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Rat

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40 60 80 100

Relative Humidity, %

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Figure 11. Effect of Abrasive Grit Size on AbrasionRate of Tynex

The phenomenon of abrasion is rather complicateand not fully understood. One explanation for thedome-shaped curves of Figure 11 might be thateach grain of abrasive functions independently astiny cutting tool. The amount of material removedis the volume removed by a single contact betweetool and work, multiplied by the number of tools.The volume removed per contact is proportional tthe square of the grit diameter. The number of toois inversely proportional to the first power of thegrit diameter. Therefore, the abrasion rate would proportional to the first power of the grit diameter.This is the case for grit diameters below 5 mil inFigure 11. The fact that the abrasion rate drops ofrather than increases above 5 mil is because theparticle size is approaching the diameter of thefilament. As this happens, the filament tends tomove to one side rather than be abraded by theparticle. Therefore, the abrasive particle size thatgives maximum abrasion rate will depend on thesize of the filament being abraded. This is shownFigure 11, where the maximum abrasion rate(“hump” in curve) moves to the right as filamentdiameter increases.

SummaryThe data presented in this bulletin were derivedfrom tests designed to simulate high brush wear-rate conditions, using a twisted-in-wire brushrotated mechanically against an abrasive surface

6 mil Tynex

12 mil Tynex

18 mil Tynex

2 4 6 8 10

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Grit Height, mil

Grit Size

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320 240 180 120 80

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The various factors affecting brush wear rate are:• filament or brush-filling material• filament stiffness• brush speed• load on the brush• brush fill weight• temperature• humidity• brush size• abrasiveness of surface being brushed

The effect of each factor on brush wear rate wasmeasured by keeping all the others constant.Several general conclusions may be drawn from tdata in this bulletin. The more important conclu-sions are listed below.

• With all factors held constant, abrasion resistancof a filament is an inherent property of thematerial itself.

• With all factors held constant except filamentstiffness . . .– the stiffer the brush filling of the same materia

the faster it will wear.– because stiffness is proportional to filament

size, the larger the filaments used, the faster tbrush will wear.

• With all factors held constant except brush speethe faster a brush rotates, the faster it will wear.

• With all factors held constant except load . . .– the higher the applied load, the faster the brus

will wear.– when the applied load is increased to a point

that causes excessive deflection of the brushfilaments, wear rate increases more rapidly ththe proportional increase in load.

• With all factors held constant except fill weight,within limits the wear rate of a brush based onweight loss is independent of brush fill weight.However, trim loss is proportional to fill weight.

• With all factors held constant except temperaturand humidity, abrasion rate increases with risingtemperature and decreases with rising relativehumidity. In the case where temperature andhumidity rise together (most atmospheric condi-tions), the effects of these two variables canceleach other.

• With all factors held constant except brushdiameter, the shorter the trim length, the faster abrush will wear.

• With all factors held constant except abrasivesurface, the wear rate of a brush is greatly influ-enced by the relationship of the filament size usto the abrasive surface being brushed.

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Bend Recovery

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A desirable property in a brush-filling material isgood bend recovery. This depends not only on thmaterials used as brush fillers, but also on thefilament size and the environmental conditions.The bend recovery of the many materials nowbeing used as brush fillers varies widely. High berecovery is an outstanding property of DuPontTynex® nylon filaments.

What Is Bend Recovery?Recovery can be described as the ability of amaterial to return to its original shape after defor-mation. Recovery of brush-filling materials isusually determined by measuring the ability of thefilaments to straighten out after bending. Bendrecovery is sometimes confused with fatigueresistance, which is a measure of a material’sresistance to breaking, splitting, or completefracture after many cycles of flexing.

Figure 12a shows a brush filler that has good benrecovery. Figure 12b shows matting caused bylow bend recovery. In Figure 12c, the filament onthe right has failed in fatigue, and the one in thecenter has failed because of low bend recovery.

Bend Recovery of PolymersThere are many recovery tests used to characterman-made fibers and filaments. Tensile, torsionacreep, work, elastic, and dynamic recovery are atests that are used in the textile trade. All of thesetests are similar, but vary in their discriminatingpower for specific applications. The bend recovertest seems most applicable for characterizing brufilling materials.

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Figure 12. Bend Recovery

Figure 12a Figure 12b

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Metal recovers completely from bending providedthe yield stress is not exceeded. Stressing aboveyield point causes permanent deformation, whicheasily predicted from a stress–strain relationship the material. Recovery for polymers, such as nylois not as simple.

Polymer MoleculesAll man-made filaments are composed of polymemolecules. This means that the molecules areextremely large compared with ordinary moleculesuch as a molecule of water (H2O). Polymermolecules consist of a combination of atoms,usually carbon, hydrogen, and oxygen, but sometimes nitrogen, chlorine, or fluorine. Polymermolecules exist because carbon atoms have achemical affinity for one another and form longchains of hundreds or thousands of atoms. Thesecarbon chains are the backbone of most polymermolecules; however, some have links of oxygen onitrogen connecting many short chains of carbonatoms. These chains may also have side groupsattached at regularly spaced intervals. These sidegroups on the polymer chains and the differentatoms in the backbone are what account for mosthe difference among man-made filaments.

These polymer chains could be thought of as a mof cooked spaghetti. They act like coils and en-tangled springs. If the molecules are entirelyrandom and without order, the polymer is said tobe amorphous. If, however, there are regions in tmass where the molecules are regularly packed,then it is a crystalline polymer. Nylon is such apolymer.

Figure 12c

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OrientationOrientation involves cold drawing the polymer,which lines up the molecules more or less paralleto the filament axis. Orientation not only tends tocreate order in the amorphous region, but alsoorders the crystalline regions with respect to thefilament axis. The high strength of nylon filamentcomes from this orientation process.

It is this semi-ordered mass of cold springs withwhich we are dealing when we talk about recoveof nylon. Small and rapid deformation of nylon isperfectly elastic or springlike and results in com-plete recovery. This is because the polymer mol-ecules can be compressed, elongated, uncoiled,bent a certain amount without causing relativemotion of the molecules with one another.

With greater deformation (the amount depends otemperature and the time under deformation),movement of chains or chain segments over oneanother occurs. Opposing this is a chemical attration of neighboring chains or chain segments.When stress is applied, there is always a separaof neighbors; however, as the separation becomelarge, true flow may set in, and neighbors may slpast one another irreversibly.

Because of points of attraction between chains,tension will extend the chain segments to the poiwhere some of the bonds between neighbors wilbreak and reform with another neighbor in aposition of zero stress. When the material is al-lowed to recover (load removed), the extendedchain segments resume their initial randomly coilposition. This in turn puts tension on the newbonds, causing them to break and reform with thoriginal neighbors. The extent to which the chainsegments can resume their initial random positioand the extent to which the original neighbors carebond determines the recovery of a material.

CreepAs mentioned, when a polymer such as nylon isdeformed and held at constant stress (load), thechain segments are extended and bonds arestretched. The polymer is uncomfortable in thisposition, and the various chain segments willrearrange themselves in a direction of lower stresif enough time is allowed. If the load continues tobe applied, chain movement continues—in thedirection of the applied load. This phenomenon,called creep, is largely irreversible, causing permnent deformation.

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Stress RelaxationIf the polymer is deformed and held at constantstrain (deformation) instead of constant stress, thesame chain segment rearrangement occurs. Ifallowed enough time, they will finally find posi-tions of zero stress or nearly so. Having done so,they will continue in their new positions even afterthe material is released. This phenomenon is callestress relaxation, or stress decay, and is reallyanother form of creep. To reach zero stress requira very long period of time, perhaps years. Forshorter periods of time, rearrangement is less thacomplete, and many chain segments can return toor in the direction of, their original position. Thisaffords partial recovery.

These processes are both time- and temperature-dependent. Therefore, a polymer will have morecomplete recovery from deformation at roomtemperature than if the material is deformed andheld at an elevated temperature for the same lengof time. A polymer will also deform easier andrecover faster at elevated temperatures than at rotemperature.

Factors Affecting Bend RecoveryThe following is a detailed discussion of the factoraffecting bend recovery of brush filaments.

Inherent Bend Recovery of BrushFilamentsBend recovery of a material is partly an inherentproperty of that material and partly influenced bythe manufacturing process. In the case of man-made filaments, the raw materials from which theyare manufactured prescribe a range for bendrecovery. Bend recovery can be changed within thrange by filament manufacturing techniques.

A relative measure of the bend recovery of onematerial to another may best be obtained by takinmeasurements of the materials in question underidentical standard test conditions.

Comparative data for several materials are shownTable 3.

Table 3Inherent Bend Recovery

(Standard Test)

Material Bend Recovery, %

Tynex 612 Nylon 92Type 66 Nylon 90Hog Bristle 92Tampico 40Polystyrene 35Polypropylene 75Polyvinylidene Chloride 82

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TemperatureBend recovery of Tynex® is maximum at roomtemperature and slightly above. Bend recovery of66 nylon is more temperature-sensitive than that Tynex®.

Table 4Bend Recovery versus Temperature

Bend Recovery, %Tynex

Temperature, °C (°F) 612 Nylon 66 Nylon

–18 (0) 86 760 (32) 87 87

23 (73)* 92 9038 (100) 92 9066 (150) 92 8679 (175) 91 85

*Denotes standard test conditions

HumidityThe bend recovery of Tynex® is unaffected bychanges in relative humidity.

Table 5Bend Recovery versus Relative Humidity

Bend Recovery, %Relative Humidity Tynexat 23°C (73°F), % 612 Nylon 66 Nylon

100 91 8250* 92 9010 92 91

*Denotes standard test conditions

StrainSmall and rapid deflection of nylon is perfectlyelastic or springlike and results in complete recovery. The larger the strain, the lower the bendrecovery.When larger filaments are deflected, theare strained more, which results in higher stress.

Table 6Bend Recovery versus Filament Caliper

Bend Recovery, %Tynex

Filament Caliper, in 612 Nylon 66 Nylon

0.008 97 940.012* 92 900.020 90 89

*Denotes standard test conditions

15

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Time Under LoadThe longer a filament is held in a deflected posi-tion, the less complete the recovery.

Table 7Bend Recovery versus Time Under Load

Bend Recovery, %Tynex

Time Under Load, min 612 Nylon 66 Nylon

1 95 934* 92 90

10 92 9230 92 91

120 91 90

*Denotes standard test conditions

Relaxation TimeThe longer a filament is allowed to relax, the morecomplete the recovery.

Table 8Bend Recovery versus Relaxation Time

Bend Recovery, %Tynex

Relaxation Time, min 612 Nylon 66 Nylon

1 78 763 83 82

10 87 8630 90 9060* 92 90

120 92 91

*Denotes standard test conditions

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SummaryThe more important factors affecting bend recovare:

• temperature

• humidity

• total strain (deflection)

• strain rate

• time under load

• relaxation time

The effect of each factor on bend recovery wasmeasured by keeping the others constant. Severgeneral conclusions may be drawn from the datathis bulletin. The more important conclusions arelisted below:• With all factors held constant, a fundamental

bend recovery value may be obtained for eachmaterial. This is an inherent property of thatmaterial.

16

• With all factors held constant, except one . . .– bend recovery is maximum for Tynex® at room

temperature or slightly above and lower ateither higher or lower temperatures.

– bend recovery of Tynex® is less temperature-sensitive than that of 6 nylon or 66 nylon.

– humidity has no measurable effect on the berecovery of Tynex®.

– the greater the deflection, the lower the bendrecovery for a given material.

– small and rapid deformations of nylon are pefectly elastic and result in complete recovery

– the shorter the time under load, the higher thbend recovery.

– the longer the relaxation time, the higher thebend recovery.

Fatigue Resistance and FactorsThat Affect Flex Life

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The fatigue resistance of a brush-filling material isoften the controlling factor in brush life. This isparticularly true if the brush is heavily loaded andoperated mechanically, as is the case for manyindustrial brushes. Personal and household brushgenerally are not heavily loaded or subjected tocontinuous flexing, and, therefore, their mode offailure is usually not fatigue, but rather bendrecovery. Fatigue resistance (or flex life) dependsnot only on the materials used as brush fillers, bualso on the filament size, brush construction, andthe environmental conditions. The fatigue resis-tance of the many materials now being used asbrush fillers varies widely. High fatigue resistanceis an outstanding property of DuPont Tynex® nylonfilaments.

What Is Fatigue Resistance?Fatigue is the most misunderstood and confusingphysical property of a material, whether metal orplastic. Fatigue resistance is a measure of amaterial’s resistance to breaking, splitting, orcomplete fracture after many cycles of flexing.Fatigue failure starts as a small crack and growswith each additional flexing until catastrophicfailure occurs.

Fatigue resistance is often confused with bendrecovery or matting resistance. Bend recovery is ameasure of how completely a material returns to ioriginal shape after bending (flexing). Fatigueresistance is a measure of whether or not thematerial breaks after repeated flexing. Figure 13shows two different types of brushes that havefailed in fatigue.

Figure 13. Fatigue Resistance

Bottle brush before and after use; Vacuum cleaner brushused brush shows fatigue failure showing fatigue failure

17

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Factors Affecting FatigueResistanceThe following is a more detailed discussion of thefactors affecting fatigue resistance of brush-fillingmaterials. A general discussion of fatigue followsthis section.

Inherent Fatigue Resistance ofBrush FilamentsFatigue resistance of a material is partly an inhereproperty of that material, but is also greatly influ-enced by the manufacturing process. In the case man-made filaments, the raw materials from whicthey are manufactured prescribe a range for fatiguresistance values. Fatigue resistance can be markedly changed within this range by filament manu-facturing techniques.

A relative measure of the fatigue resistance of onematerial to another may best be obtained by makimeasurements of the materials in question under identical set of test conditions.

Comparative data for several materials are shownTable 9.

Table 9Inherent Fatigue Resistance

Material Fatigue Resistance, %

Tynex 612 Nylon 9866 Nylon 90Hog Bristle 40Horse Hair 10Tampico 10Polypropylene 98Polystyrene 30Polyvinylidene Chloride 20Polyvinyl Chloride

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TemperatureFatigue resistance of Tynex® decreases withdecreasing temperature, as shown in Table 10.

Table 10Fatigue Resistance versus Temperature

Fatigue Resistance, %Temperature, °C (°F) Tynex 612 Nylon 66 Nylon

49 (120) 99 9223 (73)* 98 900 (32) 97 85

–18 (0) 90 80

*Denotes standard test conditions

HumidityHigh humidity increases the fatigue resistance ofTynex®. However, 66 nylon is more humidity-sensitive than Tynex®, as shown in Table 11.

Table 11Fatigue Resistance versus Relative Humidity

Fatigue Resistance, %Tynex 612 Nylon 66 Nylon

100 100 100 50* 98 90

0 97 85

*Denotes standard test conditions

DeflectionThe larger the filament deflection, the poorer thefatigue resistance. For a given filament size, thelarger the deflection of the filament, the higher thestrain in the filament and, correspondingly, thehigher the stress. Naturally, the higher the stress,the poorer the resistance to breakage.

Filament SizeAt constant strain, the larger the filament size, thelower the fatigue resistance. This can be seen in Table 12 data, which lists total number of impactsrequired to produce 2% failure.

Table 12Tynex Caliper versus

Number of Impacts to Failure

Total NumberFilament Caliper, in of Impacts

0.012 107,0000.016 60,0000.022 32,0000.032 15,000

Relative Humidityat 23°C (73°F), %

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Therefore, in order to obtain equivalent results foany diameter filament of the same material, thestandard test is run for shorter periods of time forlarger filaments.

Flexing RateStrain rate, within the range tested, does not affethe fatigue resistance of Tynex® 612 nylon or 66nylon, as shown in Table 13.

Table 13Fatigue Resistance versus Strain Rate

Fatigue Resistance, %Tynex 612 Nylon 66 Nylon

500 99 90750 97 90

1,000* 98 901,250 98 91

*Denotes standard test conditions

The Mechanism of FatigueFailuresMan noticed early in his use of metals that after aperiod of satisfactory use a part would sometimesfail, even though the loads were relatively low.Such a failure would usually occur suddenly, sucas a ductile steel axle snapping off as if it werebrittle. This type of fracture always showed a dullarea surrounded by an area of bright crystals.

Such a fracture was naturally considered evidencthat repeated twisting or bending had caused a pof the metal to crystallize. This explanation wasso simple that it became firmly entrenched andis still used to this day by some to explain afatigue failure, although the theory has longbeen disproved.

Fatigue failure occurs in almost every type ofmaterial: metals, plastics, and rubbers. Fatigueis an unfortunate word to describe this type offailure, because materials do not get tired, and thdo not recover when rested. Regardless, the term“fatigue” has become firmly entrenched in materi-als terminology.

The mechanism of fatigue failure is now morethoroughly understood. Under repeated stress, amaterial yields at one or more micro sites. Thisyielding occurs because of weakness or highresidual stresses in the molecular structure. Wheyielding of plastic occurs, segments of moleculesslip past others and break atomic bonds, whichresults in submicroscopic cracks. These cracksfrequently cause areas of stress concentration. Athe working stress is repeated, the cracks spread

Strain Rate(Impacts per min)

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usually inward from the surface. Over time, thereso little sound material left that the normal appliestress exceeds the strength of the remaining matrial. This is when catastrophic failure occurs.

SummaryThe data presented in this bulletin were derivedfrom tests designed to predict the performance ofilling material in a brush with respect to fatiguefailure. The test method used does not exactlysimulate brush use, but rather measures the fundmental property (fatigue) of the material.

The more important factors affecting fatigueresistance are:• type of filling material• filament diameter• temperature• humidity• deflection

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The effect of each factor on fatigue resistance wmeasured by keeping the other constant. Severageneral conclusions may be drawn from the dataThe more important conclusions are:

• With all factors held constant, a fundamentalfatigue resistance value may be obtained for efilling material.

• With all factors held constant, except one . . .– high humidity increases the fatigue resistanc

of Tynex®.– low temperatures reduce the fatigue resistan

of Tynex®.– fatigue resistance of Tynex® is less

temperature- and humidity-sensitive thanthat of 66 nylon.

– the smaller the filament, the higher the fatiguresistance.

– the larger the deflection, the lower the fatiguresistance.

– flexing rate, within the range tested, has noeffect on fatigue resistance.

9

Filament Identification us

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There are many types of man-made filaments intoday throughout the brush industry. Many of thefilaments used in the manufacture of brushes aresimilar in appearance and “feel,” but have widelyvarying properties, depending on the material frowhich the filaments are made. Even within familygroups, there are wide differences. This is espe-cially true of the several types of nylon being useby the brush industry.

For example, Tynex® nylon filament has a low leveof moisture absorption and, thus, retains most ofstiffness in water, in water-based paints, and inaqueous solutions. On the other hand, type 6 annylon filaments absorb greater amounts of moistand lose much of their stiffness in aqueous medi

Identification ProblemsThe brushmaker or brush buyer may at any timepresented with a brush filled with an unknownfilament that he or she wants to identify. Identifiction is more difficult today because of the wide-spread use of man-made filaments and the fact tmost of these filaments are similar in appearanc

This bulletin presents a simplified identificationprocedure that a brushmaker can use to identify filament in question. It also defines a method foridentifying the type of nylon. These tests do notrequire elaborate or expensive equipment nor dothey require special training by the person doinganalyses.

Identification ProceduresThe selection of an identification procedure for aparticular brush filament depends on the nature the sample, the experience of the person doing tidentification, and the equipment available. Quiteoften, the person analyzing the filament has a goidea as to what the material is, and all that may bnecessary is a spot test to confirm this opinion.

20

TableFilament Burn

Filament

Nylon (All Types) BluePolyesters YelloPolypropylene BluePolystyrene (and Styrene Copolymers) YelloPolyurethane SmoPolyvinylidene Chloride YelloAnimal Hair Doe

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Burning TestOne of the most useful spot tests is the burning teMost filaments display a characteristic burningbehavior, and, if controls of known samples areused, the burning test can be very useful. The uscontrols is very important because some of thedescriptions listed on the following page tend to bsubjective.

A gas Bunsen burner is probably the most effectisource of heat to use for a burning test, but evenmatch can be used. The best technique is to holdfilament by one end with forceps or pliers, andbring it slowly into the side of the flame until itignites (or not more than 10 sec if it does not burnTable 14 lists typical burning behavior of severalfilaments.

Note: Molten plastics are very hot and can givepainful burns if they contact the skin.

Filament on left is nylon; filament on right is poly-styrene. Note that nylon is barely burning and isstarting to melt and drip. Polystyrene burns vigor-ously and gives off black smoke.

Figure 14. Burning Filament

14ing Behavior

Observation

flame, yellow top, melts and drips, burned wool odorw flame, smokes, drips

flame, yellow top, drippings may burn, paraffin odorw flame, smoke, black specks in the airkes, chars, sharp odorw flame, ignites with difficulty, green spurts

s not burn, odor of singed hair

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Solubility and Float TestsIf one does not have an idea as to the identity of filament, or if it seems desirable to confirm theresults of the burning tests described in Table 14,solubility and float tests are commonly used and extremely helpful. These tests are best carried ouwith about 4 oz of solvent and one or more of thefilaments. Some materials take several hours todissolve, and occasional stirring or shaking helpsMost solvents are flammable, and some (likehydrochloric acid) are corrosive. Tests should becarried out in a well-ventilated room.

The identification plan shown in Figure 15 sepa-rates most of the materials used for man-madefilaments. However, there are some less frequenused materials that may react to the solubility andfloat tests in the same way as the commonly usematerials listed. If there is any doubt about any

2

Figure 15. Identification Scheme for Filament Family Ty

Unknow

Group I

Group II-B-1

Soluble

Polyvinyl Chloride—Polyvinyl Acetate Copolymer

Polystyrene

Polyvinylidene Chloride,Polyurethane,

Polyester

Sinks

Concentrated Hydro

Acetone

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material, its melting point and/or specific gravityshould be checked for a positive identification. Itmight even be necessary to send the unknownmaterial to a well-equipped laboratory for identification, if it should happen to be particularly rare.

The general identification scheme for the solubiland float tests is shown in Figure 15. This schemerequires the following materials, which are avail-able from drug stores or chemical supply houses

• water• acetone (flammable)• concentrated hydrochloric acid (same as muria

acid). This is commonly sold as 37–38% acid,with a specific gravity of 1.19. (Acids arecorrosive)

• 90% concentrated formic acid

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Group II-A Group II-B

Group II-B-2

Insoluble

Group II

Nylon, Polypropylene,Polyurethane, Polyester,Polyvinylidene Chloride

Nylon (Types 6,610, 612, 66, 11)

Polypropylene Nylon, Polyurethane,Polyester,

Polyvinylidene Chloride

Floats

Floats

Sinks

chloric Acid

Water

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Group I—Soluble in AcetoneAcetone dissolves filaments made from polystyre(and most styrene copolymers) and polyvinylchloride-polyvinyl acetate copolymer. Solubilitytests should be run on a few filaments in about 4 of acetone. Occasional stirring or shaking helpssolution, and at least 1 hr should be allowed forsolution to take place.

Group II—Insoluble in AcetoneAcetone will not dissolve filaments made fromnylons, polypropylene, polyurethane, polyesters,or polyvinylidene chloride.

Group II-A—Floats in WaterThe polypropylenes can be quickly identified,because they are the only commonly used man-made brush filaments that float in water. Thus, ifthe filament is insoluble in acetone and floats inwater, it is polypropylene. In making float tests, thfilaments should be poked below the surface of thliquid to completely wet them. Polyethylenefilaments would also be in Group II-A and can bedistinguished from polypropylene filaments bymelting point.

Group II-B—Sinks in WaterThe nylon, polyurethane, polyester, and polyvinylidene chloride filaments are insoluble in acetoneand sink in water. The nylons can be distinguishefrom the other three types, because they float inconcentrated hydrochloric acid; the polyurethanespolyesters, and polyvinylidene chlorides sink.

Group II-B-1—Sinks in ConcentratedHydrochloric AcidPolyester, polyurethane, and polyvinylidenechloride filaments sink in concentrated hydrochlo-ric acid after they have been poked below thesurface of the liquid with a glass stirring rod.

Group II-B-2—Floats in ConcentratedHydrochloric AcidAll the principal types of nylon used as brushfilaments (types 610, 612, 66, 6, and 11 nylons)will float in concentrated hydrochloric acid. Thesefive types of nylons can be separated by the idenfication scheme given in Figure 16.

Float tests of filaments in acid should be run bydropping small lengths of filament in the acid raththan by pouring acid into the glass container on toof the filaments. This is because concentratedhydrochloric acid causes some filaments to softenand stick to the walls or to the bottom of thecontainer, which could obscure the results of thefloat test.

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The success of the float test in acid depends on tacid maintaining its specific gravity of 1.18 to 1.19which it has when purchased. When not in use, thacid should be kept in a closed glass container, ait must not be contaminated with water or othermaterials that dissolve in it.

Soluble in Concentrated Hydrochloric AcidType 66 and type 6 nylons are soluble in concen-trated hydrochloric (or muriatic) acid, usuallywithin 1 hr. These tests are run by putting a fewlengths of filament in about 4 oz of the acid. (Acidare corrosive and should not be allowed to come contact with the skin. If this happens accidentallythe exposed areas should be washed immediatelwith water.) If the filament is either 66 or 6 nylon,it should be completely soluble by this test and nomerely deformed or partially dissolved.

Softens in Concentrated Hydrochloric AcidThe 610 nylon will not dissolve in this concentrateacid within 1 hr, but it may start to soften and sticto the sides of the container. After being in the acovernight, the 610 nylon will have lost its shapeand will have a jellylike appearance.

Behavior in Dilute Hydrochloric AcidThe type 66 and 6 nylons that were soluble inconcentrated hydrochloric acid can be distinguishfrom each other by their behavior in dilute hydro-chloric acid. This acid is made by pouring one paof acid (by volume) into two parts of water. (Al-ways pour acid slowly into water; never pour wateinto acid.) Type 6 nylon will dissolve in this diluteacid within 1 hr at room temperature; type 66 nylowill not dissolve.

Insoluble in Concentrated HydrochloricAcidType 11 nylon is virtually unaffected by concen-trated hydrochloric acid, even after standingovernight. It is clearly distinguished from the othetypes of nylon by this behavior.

Insoluble in Concentrated Formic AcidThe 610 nylon will dissolve in this concentratedacid within 1 hr. The 612 nylon will start to softenbut will not dissolve even after 24 hr of exposure.

Figure 16. Identification Scheme for Nylon Filaments

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est

Nylon Filaments (Types 6, 610, 612, 66, 11)

Type 66Type 6

Type 11

Type 6 Type 66 Type 610 Type 612

Concentrated Hydrochloric Acid (37 to 38%)

Soluble (1 hr)

Soluble (1 hr) Soluble (1 hr)Insoluble (1 hr) Insoluble

Insoluble (Overnight) Softens (Overnight)

Dilute Hydrochloric Acid(1 part acid—2 parts water)

Formic Acid90% Concentration

Type 612 (Tynex)Type 610

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Specific GravitySpecific gravity (also known as relative density)can be used for either primary or supplementalidentification of many materials. The identificationschemes outlined in this bulletin make frequent usof specific gravity.

The specific gravity of the sample is compared withe specific gravity (known) of a liquid by deter-mining whether the sample sinks or floats in theliquid. A wide variety of liquids may be employed.

For example, water (specific gravity 1.0) is used tidentify polypropylene; concentrated hydrochloricacid (specific gravity 1.18) is used to identifynylons.

Another useful specific gravity solution is a satu-rated solution of ordinary table salt in water. (Addsalt to water until no more will dissolve and undis-solved salt is on the bottom of the container.) Thissolution has a specific gravity of 1.19 at roomtemperature. Nylons will float in this solution;polyesters and polyurethanes will sink.

23

Melting PointEach type of man-made filament has its characteistic melting point. Some of these are listed inTable 15. A melting point apparatus is a useful tofor supplemental identification of filaments that anot clearly identified by other tests described in tbulletin. A good model can be selected from alaboratory supply store.

Even without a melting point apparatus, someidentification of materials by melting point can bemade on an electric iron. For example, consider problem of identifying two brushes, one made ofTynex® (melting point 210°C [410°F]) and one of66 nylon (melting point 257°C [495°F]). The endsof a filament from each brush could be jabbedagainst the face of an electric iron while the ironwas being heated stepwise from the lowest to thhighest temperature setting. The filament that firleft a sticky residue on the iron would be Tynex®,which is the lower melting of the two.

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Table 15Specific Gravity and Melting Point

Melt Point*

Filament Specific Gravity °C °F

66 Nylon 1.14 257 495

612 Nylon (DuPont Tynex) 1.06 210 410

610 Nylon 1.08 216 420

6 Nylon 1.14 218 425

Polyurethane 1.21 170 338

Polyvinylidene Chloride 1.75 165 330

Polystyrene 1.06 163 325

Polyethylene 0.91–0.96 110–138** 230–280

Polypropylene 0.89 165 330

Polyester Filament (Polyethylene Terephthalate) 1.38 250 482

Polyester Filament (Polybutylene Terephthalate)(DuPont Orel) 1.32 216 420

Hog Bristle 1.32 None None

Tampico 1.22 None None

* Approximate melting points are reported. It is a characteristic of most plastic materials that they do not melt sharply, butsoften over a range of temperatures.

**Depends on type

Chemical Resistance of Nylon Filamentse

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Nylon filaments are outstanding in their resistancto a wide range of solvents and chemical solutioHydrocarbons and oils have no effect, and thecommon organic solvents (alcohols, chlorinatedhydrocarbons, ketones, esters) have either no efor a temporary and small effect on stiffness, whicis recovered when the solvent evaporates.

Aqueous solutions of most chemicals, includingalkalies such as lye, have no effect other than thtemporary effect of the water itself on the stiffnesof nylon filaments. Horse hair and hog bristle, onthe other hand, dissolve in alkalies.

Materials that do affect nylon filaments usually dso by some degree of solvent action. Phenol(carbolic acid) and formic acid will slowly dissolvnylon. Other acids, such as acetic (organic) andhydrochloric (mineral) acid, degrade and embrittnylon. Weak solutions of these acids at roomtemperatures attack nylon very slowly, givingfilaments an appreciable life in such solutions.Food acids, including vinegar, have no appreciabeffect on nylon.

2

TablChemical Solutions Havin

Chemicals

Water, Distilled

Ammonium Hydroxide (Ammonia Water)

Paintbrush Cleaner (Alkaline Detergent)

Potassium Carbonate, 20% (Potash)

Salt Water (Sodium Chloride 4%)

Soap (Fels Naphtha)

Sodium Carbonate, 20% (Cleaning Agent)

Sodium Chloride (Saturated) (Salt)

Sodium Cyanide, 10% (Metal Cleaning Agent)

Sodium Hydroxide, 20% (Strong Alkali)

Sodium Hypochlorite, 1% Chlorine (Bleaching Agent)

Sodium Perborate, Saturated (Bleach, Deodorant)

Trisodium Phosphate, 20% (Strong Cleaner)

Surfactant, 2%

Typical Detergents

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Horse hair and hog bristle are degraded by mosorganic and mineral acids.

The resistance of nylon filaments to various chemcals are given in Tables 16 and 17.

EffectsThe effects of the chemicals tested on nylon werdivided into three groups: no effect, temporaryeffect, and permanent effect. The principal temprary effects were loss of modulus and tensilestrength. The permanent effects were a drop intensile strength or, if serious degradation occurrebrittleness and low elongation.

Chemical Solutions—No EffectSome chemical solutions have only a temporaryeffect due to the water present. The original propties are regained upon drying out.

5

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Comments

Slight decrease in stiffness and tensile strength

No effect other than that of water

No effect other than that of water

No effect other than that of water

No effect other than that of water

No effect other than that of water

No effect other than that of water

No effect at 24°C (75°F); not tested higherNo effect other than that of water

No effect other than that of water

No effect other than that of water at thisconcentration; probably degraded at very highconcentration

No effect other than that of water

No effect other than that of water

No effect other than that of water

No effect other than that of water

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Common Solvents—No EffectThe following common solvents have little or noeffect on nylon:• amyl acetate (lacquer solvent)• butyl acetate (lacquer solvent)• cottonseed oil (food oil)• gasoline• kerosene• lard• linseed oil (paint drying oil)• naphtha (VMP) (paint thinner)• naphtha (xylol) (paint remover)• toluene (paint remover)• turpentine (paint thinner)

Common Solvents—Temporary EffectThe following common solvents cause a temporloss of stiffness, which is rapidly regained uponevaporation of the solvent from the filament:• acetone (paint remover)• ethyl alcohol, 95%• ethylene dichloride (degreasing agent)

2

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• isopropyl acetate (lacquer solvent)• methyl alcohol (shellac solvent)• methyl acetate (lacquer solvent)• methyl ethyl ketone (paint remover)• trichlorethylene (degreasing agent)

Paints containing any of these solvents wouldprobably cause brushes of Tynex® to becomefloppy temporarily. However, the use of any ofthese solvents to clean such brushes would beperfectly satisfactory. Brushes with greater inherstiffness can be made of Tynex® to compensate forthis condition.

Chemicals or Solvents—Permanent EffectSome chemicals or solvents have a permanenteffect on Tynex® filaments. However, some arefrequently used with success at normal roomtemperatures and low concentrations.

6

27

Table 17Chemicals or Solvents Having a Permanent Effect

Chemical Principal Effects Comments

Acetic Acid Loss of stiffness Effect at a minimum in concentrations under 10% at 24°CBecomes weak (75°F). Fails completely upon prolonged exposure at

99°C (210°F).

Diglycolic Acid Loss of stiffness Little effect 1–5% concentrations. Fails completely uponBecomes weak prolonged exposure at 99°C (210°F).

Formic Acid Loss of stiffness 66 nylon—significant effect even at 5% level at 24°C (75°F).Becomes weak Fails completely upon prolonged exposure at 99°C (210°F).

Tynex—little effect at 90% level at 24°C (75°F). Failscompletely at 90% level upon prolonged exposure at99°C (210°F).

Hydrochloric Acid Loss of stiffness Below 5% level and at 24°C (75°F) effect is about same as(Muriatic Acid) Becomes weak water alone. Degrades rapidly at elevated temperatures of

higher concentrations.

Hydroxyacetic Acid Loss of stiffness Moderate effect up to 63°C (145°F). Fails completelyBecomes weak upon prolonged exposure at 99°C (210°F).

Lactic Acid Loss of stiffness Only slight effect up to 63°C (145°F) at 15% concentration.Becomes weak Fails upon prolonged exposure at 99°C (210°F).

Dilute Phenol Loss of stiffness Little or no effect at 1% level at 24°C (75°F). Effect(Carbolic or Cresylic Acid) Becomes weak more pronounced at elevated temperatures or higher

concentrations.

Oxalic Acid, 10% Loss of stiffness Little effect at 24°C (75°F). Seriously degraded upon(Strong Cleaning Agent) Becomes weak prolonged exposure at 63°C (145°F).

Phosphoric Acid Loss of stiffness Insignificant effect at 24°C (75°F) up to 20% concen-Becomes weak trations. Fails upon prolonged exposure at 99°C(210°F).

Sulfuric Acid Loss of stiffness Little effect at 24°C (75°F) up to 20% concentration. FailsBecomes weak completely at 63°C (145°F).

Zinc Chloride, 50% Loss of stiffness Little effect up to 63°C (145°F). Dissolves at 99°C (210°F)Becomes weak upon prolonged exposure.

DuPont FilamentsPrinted in U.S.A.

The DuPont Company assumes no obligation or liability for any advice furnished by it or results obtained with respect to this product. All such adviceis given and accepted at the buyer’s risk. DuPont warrants that the material itself does not infringe the claims of any United States patent; but no licenseis implied nor is any further patent warranty made.

CAUTION: Do not use in medical applications involving permanent implantation in the human body. For other medical applications, see “DuPontMedical Caution Statement,” H-50102.

Europe,Middle East, AfricaDuPont FilamentsP.O. Box 31065NL-6370 AB LandgraafThe NetherlandsTelephone: 31-45-532·91·91Fax: 31-45-532-79·48

Asia PacificDuPont FilamentsChe Gong Miao Industrial AreaDistrict No. 5Shenzhen, GuangdongPeoples Republic of ChinaPost code: 518040Telephone: 011-86-755-330-7848Fax: 011-86-755-340-0755

North AmericaDuPont FilamentsRoute 892Building 158Washington, WV 26181Telephone: (800) 635-9695Fax: (304) 863-2779

For more information about DuPont filaments or the name of a brushmaker whomight fill your needs, contact one of the DuPont offices below:

DuPont FilamentsWilmington, DE 19898

f

DuPont FilamentsTynex A Abrasive Filaments

Floor Care BrushesIndustrial Brushes

Tynex FilamentsToothbrushes

Cosmetic Brushes

Tynex, Chinex, Orel Tapered FilamentsPaintbrushes

South AmericaDuPont FilamentsP.O. Box 26Al. Itapecuru, 506Alphaville06454-080 C.P. 263Barueri—S.P.BrazilTelephone: 55-11-7266-8744Fax: 55-11-7266-8513

www.dupont.com/filaments

IntroductionContentsStiffness of Nylon FilamentsAbrasion Resistance and Factors That Affect Brush Wear RateBend RecoveryFatigue Resistance and Factors That Affect Flex LifeFilament IdentificationChemical Resistance of Nylon Filaments