Electrical Property of Polymers to Determine Resistance to Conductivity
When electric current travels across an insulator's surface, it can become conductive due to damange, erosion or other factors. Arc resistance is a measure of the time required to make an insulating surface conductive under a high voltage / low current arc in carefully controlled laboratory conditions.
In other terms, arc resistance is the ability of the plastic material to resist the action of a high voltage electrical arc and resist the formation of a conducting path along its surface under a given time.
It is used for differentiation among similar material with respect to their resistance to the action of high voltage low current to the surface of the insulation. It is also a critical property while selecting polymer for insulation applications since lose in insulation can lead to devastating consequences in certain application areas.
This electrical property is usually stated in terms of time required for plastics surface to become electrically conductive, the values are therefore reported in seconds (s).
Arc resistance as a polymer property can used for the following applications, amongst many other.
- Preliminary screening of plastic materials for applications susceptible to electric arcing
- Quality control testing after field experience and other types of simulated service arc tests to establish a correlation
- Detecting the changes in insulation behavior of formulation due to contamination, thermal and chemical decomposition and erosion
For example, arc resistance is a key E&E performance need. Electrical tension may cause a tracking current to flow on plastics surfaces, especially if they are contaminated with humidity, dirt or chemicals. Small arcs can be generated at irregular interruptions along this current path causing a thermo-mechanical effect that erodes the material's surface. Tracking resistance indicates how well the surface of a plastic material resists damage caused this way. Arc resistance is closely connected with tracking resistance.
Under the influence of an arc (which may be generated by a short circuit) the plastic should not form a conductive bridge and should, if possible vaporize, so as to extinguish the arc. Due to closeness of contact pins and sockets these parts must have good tracking resistance.
Check out more on Arc Resistance:
» How to measure Arc Resistance?
» Plastics Failure Due to Electric Arc & Methods to Improve Arc Resistance
» Arc Resistance Values of Several Plastics
How to Measure Arc Resistance?
The most generally used standard tests to calculate arc resistance is
ASTM D495 (
of course there exists several other methods as well, but they are not discussed here). ASTM D495 test method evaluates dry, uncontaminated samples, Test Methods ASTM D 2132, D 2303, and D 3638 involve wet, contaminated specimens.
Schematic High Voltage, Low Current Dry Arc Resistance Test
ASTM D495-14 - Standard Test Method for High-Voltage, Low-Current, Dry Arc Resistance of Solid Electrical Insulation
This test method covers, in a preliminary fashion, the differentiation among similar materials w.r.t their resistance to the action of a high-voltage, low current arc close to the surface of insulation. This arc tends to form a conductive path in that location or may cause the material to become conducting due to the localized thermal and chemical decomposition and erosion.
The arc resistance of a material is determined by this method by measuring the total elapsed time of operation of the test until failure occurs.
There are
four general types of failure which have been observed:
- Many inorganic dielectrics become incandescent, at which point they are capable of conducting the current. However, when cooled, they return to their earlier insulating condition
- Some organic compounds burst into flames without formation of a visible conducting path in the substance
- Some organic compounds fail by tracking (i.e. a thin wiry line is formed between the electrodes)
- Some compounds experience carbonization of the surface until sufficient carbon is present to carry the current
Generally, this method is not used in product design or material specifications. However, the results obtained in the test are values only used to distinguish materials of nearly identical composition such as identification, quality control and development.
Plastics Failure Due to Electric Arc & Methods to Improve Arc Resistance
Upon subjected to electric arc, many inorganic materials become incandescent thus, resulting in electric current conductivity. When cooled, they become insulators again. Another factor includes carbonization of the surface once there is enough carbon to conduct the electric current across the material. Additionaly, factors such as degree of ionization, length and cross-section of the arc define arc resistance of the given material.
Different plastics have different arc resistance performance.
Thermoset phenolics tend to carbonize easily and therefore have relatively poor arc resistance. While, on the other hand, alkyds, melamine and fluorocarbons are excellent arc resistance materials
The arc resistance of thermoplastics can be improved substantially by the addition of reinforcements such as fiber glass, minerals and other inorganic fillers.
Commercially Available Electrically Insulating Polymer Grades
Arc Resistance Values of Several Plastics
Click to find polymer you are looking for:
A-C |
E-M |
PA-PC |
PE-PL |
PM-PP |
PS-X
Polymer Name |
Min Value (sec) |
Max Value (sec) |
ABS - Acrylonitrile Butadiene Styrene |
60.0 |
120.0 |
ABS Flame Retardant |
60.0 |
60.0 |
ABS High Heat |
45.0 |
85.0 |
ABS High Impact |
45.0 |
85.0 |
ABS/PC Blend - Acrylonitrile Butadiene Styrene/Polycarbonate Blend |
0.00 |
120.0 |
ASA - Acrylonitrile Styrene Acrylate |
60.0 |
120.0 |
CA - Cellulose Acetate |
50.0 |
300.0 |
CP - Cellulose Propionate |
175.0 |
190.0 |
ECTFE - Ethylene Chlorotrifluoroethylene |
50.0 |
50.0 |
FEP - Fluorinated Ethylene Propylene |
165.0 |
180.0 |
HDPE - High Density Polyethylene |
100.0 |
180.0 |
HIPS - High Impact Polystyrene |
20.0 |
100.0 |
HIPS Flame Retardant V0 |
60.0 |
120.0 |
LCP Glass Fiber-reinforced |
124.0 |
182.0 |
LCP Mineral-filled |
145.0 |
183.0 |
LDPE - Low Density Polyethylene |
130.0 |
160.0 |
PA 11, Conductive |
70.0 |
130.0 |
PA 11, Flexible |
70.0 |
130.0 |
PA 11, Rigid |
70.0 |
130.0 |
PA 12 (Polyamide 12), Conductive |
70.0 |
130.0 |
PA 12, Fiber-reinforced |
70.0 |
130.0 |
PA 12, Flexible |
70.0 |
130.0 |
PA 12, Glass Filled |
70.0 |
130.0 |
PA 12, Rigid |
70.0 |
130.0 |
PA 6 - Polyamide 6 |
118.0 |
125.0 |
PA 6-10 - Polyamide 6-10 |
120.0 |
120.0 |
PA 66 - Polyamide 6-6 |
130.0 |
140.0 |
PA 66, 30% Glass Fiber |
60.0 |
135.0 |
PA 66, Impact Modified, 15-30% Glass Fiber |
85.0 |
135.0 |
PA 66, Impact Modified |
95.0 |
125.0 |
PAR - Polyarylate |
125.0 |
125.0 |
PBT - Polybutylene Terephthalate |
124.0 |
125.0 |
PBT, 30% Glass Fiber |
10.0 |
130.0 |
PC (Polycarbonate) 20-40% Glass Fiber |
30.0 |
120.0 |
PC - Polycarbonate, high heat |
110.0 |
120.0 |
PCTFE - Polymonochlorotrifluoroethylene |
350.0 |
400.0 |
PE - Polyethylene 30% Glass Fiber |
140.0 |
140.0 |
PEEK - Polyetheretherketone |
40.0 |
40.0 |
PEEK 30% Glass Fiber-reinforced |
30.0 |
40.0 |
PEI - Polyetherimide |
128.0 |
128.0 |
PEI, 30% Glass Fiber-reinforced |
85.0 |
85.0 |
PEI, Mineral Filled |
140.0 |
140.0 |
PESU - Polyethersulfone |
20.0 |
120.0 |
PESU 10-30% glass fiber |
75.0 |
75.0 |
PET - Polyethylene Terephthalate |
75.0 |
125.0 |
PET, 30% Glass Fiber-reinforced |
94.0 |
125.0 |
PETG - Polyethylene Terephthalate Glycol |
75.0 |
125.0 |
PFA - Perfluoroalkoxy |
180.0 |
180.0 |
PMP 30% Glass Fiber-reinforced |
120.0 |
120.0 |
POM - Polyoxymethylene (Acetal) |
200.0 |
220.0 |
POM (Acetal) Impact Modified |
120.0 |
120.0 |
POM (Acetal) Low Friction |
126.0 |
183.0 |
PP - Polypropylene 10-20% Glass Fiber |
75.0 |
100.0 |
PP, 10-40% Mineral Filled |
100.0 |
130.0 |
PP, 10-40% Talc Filled |
100.0 |
130.0 |
PP, 30-40% Glass Fiber-reinforced |
60.0 |
75.0 |
PP (Polypropylene) Copolymer |
135.0 |
180.0 |
PP (Polypropylene) Homopolymer |
135.0 |
180.0 |
PP, Impact Modified |
135.0 |
180.0 |
PPA – 30% mineral |
119.0 |
121.0 |
PPA, 33% Glass Fiber-reinforced |
119.0 |
121.0 |
PPA, 33% Glass Fiber-reinforced – High Flow |
0.00 |
0.00 |
PPA, 45% Glass Fiber |
124.0 |
126.0 |
PPE - Polyphenylene Ether |
53.0 |
80.0 |
PPE, 30% Glass Fiber-reinforced |
120.0 |
120.0 |
PPS - Polyphenylene Sulfide |
124.0 |
124.0 |
PPS, 20-30% Glass Fiber-reinforced |
120.0
|
127.0
|
PPS, 40% Glass Fiber-reinforced
|
34.0 |
34.0 |
PPS, Glass fiber & Mineral-filled |
116.0 |
182.0 |
PS (Polystyrene) 30% glass fiber
|
40.0 |
85.0 |
PS (Polystyrene) Crystal |
60.0
|
80.0
|
PSU - Polysulfone
|
60.0 |
120.0
|
PSU, 30% Glass finer-reinforced
|
100.0 |
100.0 |
PTFE - Polytetrafluoroethylene
|
200.0 |
300.0
|
PVC Rigid
|
60.0 |
80.0 |
PVDF - Polyvinylidene Fluoride |
50.0 |
70.0 |
SAN - Styrene Acrylonitrile |
100.0 |
150.0 |
SAN, 20% Glass Fiber-reinforced |
60.0 |
75.0 |