# The Triboelectric Series (sometimes also called The Electrostatic Series).

Copy from TriField Meters (AlphaLab). The TriboElectric Series

When two different materials are pressed or rubbed together, the surface of one material will generally steal some electrons from the surface of the other material. The material that steals electrons has the stronger affinity for negative charge of the two materials, and that surface will be negatively charged after the materials are separated. (Of course the other material will have an equal amount of positive charge.) If various insulating materials are pressed or rubbed together and then the amount and polarity of the charge on each surface is separately measured, a very reproducible pattern emerges. For insulators, the table below can be used to predict which will become positive v.s. negative and how strong the effect will be.

This table can be used to select materials that will minimize static charging. For example, if uncoated paper (with a positive charge affinity value of +10 nC/J) is squeezed by a pinch roller made of butyl rubber (@-135 nC/J), there will be about 145 pico coulombs of charge transfer per joule of energy (associated with pinch and friction). This is about 20 times more than 7 nC/J, which is the static charge per joule that results from squeezing paper with a roller made of nitrile rubber (@+3 nC/J). In general, materials with an affinity near zero (e.g. cotton, nitrile rubber, polycarbonate, ABS) will not charge much when rubbed against metals or against each other. The table can also be used (with other formulas) to predict the static forces that will arise between surfaces, and to help select materials that will create an intentional charge on a surface. See further information on interpretation below the table.

TriboElectric Table

Column 1 (this col.): Insulator name. Col.2: Charge affinity in nC/J (nano ampsec/wattsec of friction). Col.3: Charge acquired if rubbed with metal (W=weak, N=normal, or consistent with the affinity). Col.4: Notes. Affinity nC/J Metal effect Triboelectric Table Tests were performed by Bill Lee (Ph.D., physics). ©2009 by AlphaLab, Inc. (TriField.com), which also manufactured the test equipment used. This table may be reproduced only if reproduced in whole. Polyurethane foam

+60

+N

All materials are good insulators (>1000 T ohm cm) unless noted.

Sorbothane

+58

-W

Slightly conductive. (120 G ohm cm).

Box sealing tape (BOPP)

+55

+W

Non-sticky side. Becomes more negative if sanded down to the BOPP film.

Hair, oily skin

+45

+N

Skin is conductive. Cannot be charged by metal rubbing.

Solid polyurethane, filled

+40

+N

Slightly conductive. (8 T ohm cm).

Magnesium fluoride (MgF2)

+35

+N

Anti-reflective optical coating.

Nylon, dry skin

+30

+N

Skin is conductive. Cannot be charged by metal rubbing.

Machine oil

+29

+N

Nylatron (nylon filled with MoS2)

+28

+N

Glass (soda)

+25

+N

Slightly conductive. (Depends on humidity).

Paper (uncoated copy)

+10

-W

Most papers & cardboard have similar affinity. Slightly conductive.

Wood (pine)

+7

-W

GE brand Silicone II (hardens in air)

+6

+N

More positive than the other silicone chemistry (see below).

Cotton

+5

+N

Slightly conductive. (Depends on humidity).

Nitrile rubber

+3

-W

Wool

0

-W

Polycarbonate

-5

-W

ABS

-5

-N

Acrylic (polymethyl methacrylate) and adhesive side of clear carton-sealing and office tape

-10

-N

Several clear tape adhesives are have an affinity almost identical to acrylic, even though various compositions are listed.

Epoxy (circuit board)

-32

-N

-35

-N

Sometimes inaccurately called "neoprene" (see below).

Solvent-based spray paints

-38

-N

May vary.

PET (mylar) cloth

-40

-W

PET (mylar) solid

-40

+W

-55

-N

Slightly conductive. (10 T ohm cm). Filled rubber will usually conduct.

Gum rubber

-60

-N

Barely conductive. (500 T ohm cm).

Hot melt glue

-62

-N

Polystyrene

-70

-N

Polyimide

-70

-N

Silicones (air harden & thermoset, but not GE)

-72

-N

Vinyl: flexible (clear tubing)

-75

-N

Carton-sealing tape (BOPP), sanded down

-85

-N

Raw surface is very + (see above), but close to PP when sanded.

Olefins (alkenes): LDPE, HDPE, PP

-90

-N

UHMWPE is below. Against metals, PP is more neg than PE.

Cellulose nitrate

-93

-N

Office tape backing (vinyl copolymer ?)

-95

-N

UHMWPE

-95

-N

Neoprene (polychloroprene, not SBR)

-98

-N

Slightly conductive if filled (1.5 T ohm cm).

PVC (rigid vinyl)

-100

-N

Latex (natural) rubber

-105

-N

Viton, filled

-117

-N

Slightly conductive. (40 T ohm cm).

Epichlorohydrin rubber, filled

-118

-N

Slightly conductive. (250 G ohm cm).

Santoprene rubber

-120

-N

Hypalon rubber, filled

-130

-N

Slightly conductive. (30 T ohm cm).

Butyl rubber, filled

-135

-N

Conductive. (900 M ohm cm). Test was done fast.

EDPM rubber, filled

-140

-N

Slightly conductive. (40 T ohm cm).

Teflon

-190

-N

Surface is fluorine atoms-- very electronegative.