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Quality inspection of insulation materials

Our insulating housings are made from various thermoplastic materials. Depending on the application, the best-suited material is selected based on its electrical and mechanical properties. All plastics used by Phoenix Contact are RoHS-compliant. All plastics used at Phoenix Contact have been listed with UL (Underwriters Laboratories Inc.) in the USA.

Quality features of insulation material

Thermoplastics
The majority of our insulating housings are made from thermoplastic materials. Roughly speaking, these can be divided into amorphous and semi-crystalline substances. Thermoplastics are processed using the efficient and environmentally-friendly injection molding process. They have good recycling properties and can be re-used. We use many materials that are modified in different ways to meet the demanding requirements of electrical and electronic modules, devices, and systems with regard to their mechanical, thermal, and electrical properties. The thermoplastic is halogen free, i.e., there is no formation of combustion fumes that can lead to corrosive condensation alone or in conjunction with humidity. It also contains no silicone compounds, formaldehyde, PCB or PCT.

Behavior of plastics under the influence of temperature (operating temperatures)
All plastics undergo a process referred to as thermal aging when they are subjected to heat over long periods. This process causes changes in the mechanical and electrical properties of the material. External influences, e.g., radiation, additional mechanical, chemical or electrical stresses, amplify this effect. Special tests on samples can yield characteristic data which provides a good means of drawing comparisons between different plastics. However, applying these characteristics to an evaluation of molded plastic parts is only possible to a limited extent, and can only give the designer a rough guide when it comes to selecting a plastic material. IEC 60947-7-1/EN 60947-7-1 specifies a permissible temperature increase of 45 K for terminal blocks under nominal load. Phoenix Contact terminal blocks satisfy this requirement.

Inflammability characteristics of plastics (UL 94)
The inflammability tests for plastics have been defined by the Underwriters Laboratory (USA) in regulation UL 94. This applies to all areas of application, particularly in electrical engineering. A horizontal or vertical test is carried out at the test laboratory to determine the inflammability of the plastic material with a naked flame. In order of increasing flame-retardant behavior, the evaluation classes are HB, V1, V2, V0. Test results are recorded on “yellow cards” and are published annually in the Recognized Component Directory.

Thermoplastics: non-reinforced polyamide, PA
We use the modern, semi-crystalline insulation material, polyamide, which is now an essential component in electrical engineering and electronics. It has long occupied a leading position and is authorized for use by the relevant approval authorities such as the CSA, KEMA, PTB, SEV, UL, VDE, etc. Polyamide has excellent electrical, mechanical, and chemical properties, even at high operating temperatures. Brief peak temperatures up to approximately 200°C are permitted as a result of heat aging stabilization. Depending on the type (PA 4.6, 6.6, 6.10, etc.), its melting point is in the region of 215°C to 295°C. Polyamide absorbs moisture from its surroundings, on average 2.8%. However, this moisture is not crystallization water in the plastic itself, but chemically bonded H2O groups in the molecular structure. This makes the plastic flexible and resistant to breakage, even at temperatures as low as -40°C. As per UL 94, PA has a flammability rating of V2 to V0.

Thermoplastics: fiberglass-reinforced polyamide, PA-F
Fiber-reinforced polyamides feature greater rigidity and hardness as well as operating temperatures higher than those of non-reinforced materials. This means that they are also suitable for use in applications such as surge protection. Reinforced polyamide absorbs less moisture than the non-reinforced material. Otherwise, the properties are largely the same. As per UL 94, fiber-reinforced polyamides have a flammability rating of HB to V0, although V0 materials are usually only available in black.

Thermoplastics: ABS
We use the thermoplastic molding compound ABS for products which must have good impact and notched impact properties in addition to high mechanical stability and rigidity. The products are characterized by their resistance to chemicals and stress cracking due to their special surface quality and hardness. The characteristic thermal properties provide good dimensional stability at both low and high temperatures. Products made from ABS can be coated with metal surfaces, e.g., nickel. As per UL 94, the molding compound used has a flammability rating of HB to V0.

Thermoplastics: polyvinyl chloride, PVC
PVC is resistant to salt solutions, diluted and concentrated lyes, and to most diluted and concentrated acids except for fuming sulfuric acid and concentrated nitric acid. PVC is flame-retardant even without fire protection equipment (B1 according to DIN 4102 to UL 94 V0).

PropertiesUnit/
level
Polyamide
PA
Polyamide
PA
Polyamide
PA-GF
Polyamide
PA-GF
Polycarbonate
PC-GF
Continuous temperature, DIN IEC 60216[°C]< 130< 125120120130
Temperature for use (without mechanical load)[°C]-60-60-60-60-60
Electric strength, IEC 60243-1 / DIN VDE 0303-21[kV/cm]600600550475175
Resistance to creepage, IEC 60112 / DIN VDE 0303-1CTI...GoodGoodGoodGoodGood
Tropical and termite resistance      
Specific contact resistance
IEC 60093 / VDE 0303-30, IEC 60167 / VDE 0303-31

[Ω cm]

1012101210121012> 1014
Surface resistance
IEC 60093 / VDE 0303-30, IEC 60167 / VDE 0303-31
[W]1010101010121012> 1014
Flammability rating UL 94 V0V2V0HBV0
PropertiesUnit/
level
Polyamide
PA
Polyamide
PA
Polyamide
PA-GF
Polyamide
PA-GF
Polycarbonate
PC-GF
Continuous temperature, DIN IEC 60216[°C]< 130< 125120120130
Temperature for use (without mechanical load)[°C]-60-60-60-60-60
Electric strength, IEC 60243-1 / DIN VDE 0303-21[kV/cm]600600550475175
Resistance to creepage, IEC 60112 / DIN VDE 0303-1CTI...GoodGoodGoodGoodGood
Tropical and termite resistance      
Specific contact resistance
IEC 60093 / VDE 0303-30, IEC 60167 / VDE 0303-31

[Ω cm]

1012101210121012> 1014
Surface resistance
IEC 60093 / VDE 0303-30, IEC 60167 / VDE 0303-31
[W]1010101010121012> 1014
Flammability rating UL 94 V0V2V0HBV0
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Insulation material properties – IEC 60210-1 / UL 746 B

In the following tests, an increased load on the terminal block is simulated over a longer period of time. The behavior of plastics at constantly higher temperatures is described with respect to their tensile strength and insulation properties. IEC 60216 and UL 746 B specify a temperature index that allows conclusions to be drawn regarding the service life of plastics under thermal loads. Characteristic values are specified for these two properties:

  • Mechanically as a TI value according to IEC 60216
  • Electrically as an RTI value according to UL 746 B

IEC 60216 – TI value
The tensile strength is measured over 5000 hours and the result is extrapolated to 20,000 hours. After 20,000 hours, the temperature at which the tensile strength has decreased by half is recorded.
UL 746 B – RTI value
The RTI value indicates the highest operating temperature before a disruptive discharge occurs under certain test conditions. The polyamides used by Phoenix Contact are classified as follows:

 UL 94 V2UL 94 V0
TI105°C125°C
RTI125°C130°C

Ceramic terminal blocks, for example, are available for use at higher temperatures.

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Surface inflammability – ASTM E 162

Surface inflammability test  

① Radiant heater ② Flame ③ Plastic sample

The spread of a fire under the influence of heat is tested and evaluated in the above standard. To evaluate the surface inflammability of plastics, a “flame spread index” is devised according to ASTM E 162 to provide information on flame propagation under given test conditions.

For this purpose, a sample (152 mm x 457 mm x maximum 25.4 mm) is irradiated with a heat source (815°C) at an angle of 30° and ignited with a naked flame at the top end. During the 15-minute duration of the test, the time in which the flame front reaches two measuring points that are 76 mm apart is determined. The product of this flame propagation time and a calculated heat development factor yields the “flame spread index”. In the American railroad sector, the maximum limit value is 35. The drip behavior of the plastic is also observed and evaluated during the test. Terminal blocks from Phoenix Contact achieve a flame spread index of 5 and produce non-burning droplets. The terminal blocks therefore lie well below the approved maximum values of the Federal Railroad Administration (FRA) of the US Department of Transportation.

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Smoke gas generation – ASTM E 662

Smoke generation in the smoke density chamber  

① Radiant heater ② Flame ③ Plastic sample

Standard ASTM E 662 specifies a procedure for evaluating the specific optical density of the smoke (smoke opacity) during an open fire or a smoldering fire. For this purpose, the percentage of light transmitted in relation to the burning chamber volume is observed. Testing is carried out on a sample (76 mm x 76 mm x maximum 25 mm) in a smoke density chamber defined by the NBS (National Bureau of Standards) (see figure). The test object is irradiated with a heat of 2.5 W/cm². The following processes are then simulated for 20 minutes:

  1. Burning with a naked flame
  2. Smoldering fire, avoidance of a naked flame

There are special limit values for the optical smoke density of both processes that are recorded after 1.5 and 4 minutes.

a. Specific optical smoke density (Ds1.5) – limit value 100
b. Specific optical smoke density (Ds4) – limit value 200
c. Maximum smoke density (Dm) during the 20 minutes

The polyamides used for Phoenix Contact terminal blocks satisfy all the requirements of the Federal Railroad Administration (FRA) of the US Department of Transportation in accordance with ASTM E 662.

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Behavior in fire – NF F 16-101

NF F 16-101 describes the behavior in fire of plastics on the basis of two indices (I and F). As such, the following tests are performed: glow-wire test, oxygen index, smoke gas opacity, smoke gas toxicology.

IndexOxygen indexGlow wire
I 070%960°C, no flame formation
I 145%960°C, no flame formation
I 232%960°C, no flame formation
I 328%850°C, no flame formation
I 420%850°C, no flame formation

1. Determination of index I (0 - 4) Index I is determined from the results of the glow-wire test and the oxygen index using the following table. Here, I 0 is the best classification and I 4 the worst.
2. Determination of smoke index F (0 - 5) This is based on the smoke gas opacity and the smoke gas toxicity. The following concentrations in [ppm] are considered critical:

Carbon monoxide (CO) – 1750
Carbon dioxide (CO2) – 90,000
Hydrochloric acid (HCl) – 150
Hydrobromic acid (HBr) – 170
Hydrogen cyanide (HCN) – 55
Hydrofluoric acid (HF) – 17
Sulfur dioxide (SO2) – 260

Based on the test results, a smoke index is documented and can be assigned to classes F 0 - F 5 depending on the value. Here, F 0 is the best classification and F 5 the worst. Terminal blocks from Phoenix Contact attain classification I 2/F 2.

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Smoke gas toxicity – SMP 800-C

SMP 800-C describes the maximum permissible values of toxic smoke gases when a plastic is burned. In comparison with BSS 7239 (Boeing standard), this standard specifies more precise measuring methods for the qualitative and quantitative determination of toxic smoke gases that result when a test object is completely burned. The smoke gases of these measurements are taken from the NBS test chamber of the ASTM E 662 test. The same time scheme is valid here as in ASTM E 662. Data is recorded over 20 minutes. SMP 800-C limit values of toxic smoke gases in [ppm]:

Carbon monoxide (CO) – 3500
Carbon dioxide (CO2) – 90,000
Nitric oxides (NOX) – 100
Sulfur dioxide (SO2) – 100
Hydrochloric acid (HCl) – 500
Hydrobromic acid (HBr) – 100
Hydrofluoric acid (HF) – 100
Hydrogen cyanide (HCN) – 100

The polyamides used by Phoenix Contact are many times below the critical concentrations.

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Halogen-free flame protection – DIN EN ISO 1043-4

Color variants  

Color variants

Halogens are the chemical elements fluorine, chlorine, bromine, and iodine. One property of halogen compounds is the reduction in the degree of inflammability when used in plastics. The relationship between released toxic gases and halogens has been defined in fire safety investigations. Terminal blocks from the CLIPLINE complete system are made of polyamide 6.6 (PA 6.6) with fire protection classification UL 94 V0. Melamine cyanurates are used instead of flame protection agents that contain halogen. Phoenix Contact terminal blocks are therefore, without exception, entirely free of halogens.

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Comparative tracking index (CTI) – DIN EN 60112

Creepage on the test piece  

Creepage

Humidity and contamination facilitate the formation of creepage distances on the plastic surface. The formation of creepage distances refers to the occurrence of conductive connections between neighboring potentials. Consideration is given to the dependence of the potentials on their voltage differences under electrolytic influences. The CTI value of a plastic indicates the extent to which this creepage distance formation is prevented. Two platinum electrodes are placed 4 mm apart on a test piece measuring 20 mm x 20 mm x 3 mm. A test voltage specified by the standard is applied to both electrodes. A test solution is then dripped onto the electrodes by a test apparatus at a rate of one drop every 30 seconds. The test evaluates the maximum voltage value at which 50 drops are applied without a short-circuit current > 0.5 A. The plastics used by Phoenix contact are classified in the highest test voltage category with a CTI value of 600.

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Glow-wire test – IEC 60695-2-11

Glow-wire test on a terminal block  

Glow-wire test

In the event of overload, conductive metal parts of the terminal block or connected conductors can heat up considerably. This additional heat affects the plastic housing. The glow-wire test simulates this source of danger for electrical components. A glow wire is heated to a specific temperature of 550°C, 650°C, 750°C, 850°C or 960°C. As shown in the figure, the glow wire is then pressed onto the thinnest point of the test object housing at a right angle. A force of 1 N is applied. The test is deemed to be passed: – When no flame or glowing process occurs during the test – When the flames or glowing processes are extinguished within 30 seconds of the glow wire being removed – When the tracing paper beneath the glow wire is not ignited by falling drops of burning substances The polyamides used by Phoenix Contact as housing materials all satisfy the requirements of the glow-wire test at 960°C (highest level).

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Needle flame test – IEC 60947-7-1/-2

Needle flame test on a terminal block  

Needle flame test

As far as the use of terminal blocks is concerned, behavior in fire when in direct contact with a source of ignition is a major criterion. Such sources of ignition could be electric arcs along a creepage distance, for example. Terminal blocks must not aid or accelerate fires and the plastics must have self-extinguishing properties. This fire test simulates the behavior of the components when directly subjected to an external source of ignition. In the test, a naked flame fed with butane gas is held to an edge or surface of the test object at an angle of 45° for 10 seconds (see figure). The behavior of the test object without a source of ignition is then observed. The test is deemed to be passed:

  • When the flames or glowing processes are extinguished within 30 seconds of the flame being removed.
  • When the tracing paper beneath the test object is not ignited by falling drops of burning substances.

All Phoenix Contact terminal blocks pass the needle flame test thanks to the high-grade plastics used and their structural design.

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Calorific value of the plastic – DIN 51900-2/ASTM E 1354

Due to experience with catastrophic fires, technical systems are increasingly also classified according to the amount of heat dissipation in the case of fire. The reason for this is to limit heat generation in relation to the area.

Fire load

The fire load is defined as the amount of energy released over a particular area during burning. The fire load value is usually expressed in MJ/m². The higher the calorific value and the presence of a substance, the greater the amount of energy released during burning. The calorific values of polyamides are relatively high. For this reason, the calorific values of terminal blocks are also increasingly included in the fire load determination. Calorific values of the plastics used by Phoenix Contact according to:

DIN 51900-2: ASTM E 1354: 
Polyamide 66 V2Approx. 30 MJ/kgPolyamide 66 V2Approx. 22 MJ/kg
Polyamide 66 V0Approx. 32 MJ/kgPolyamide 66 V0Approx. 24 MJ/kg
  For comparison: heating oilApprox. 44 MJ/kg

To calculate the fire load of individual components, the calorific value of each polyamide must be multiplied by the weight of the part.

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Inflammability classification – UL 94

Test setup according to UL 94  

Test setup according to UL 94

UL 94 describes inflammability tests that have gained particular importance in the field of electrical engineering. Behavior in fire is the main focus. Items are classified according to either UL 94 HB (Horizontal Burn) or UL 94 V (Vertical Burn). The test setup is such that the 94 V0/1/2 classifications are stricter than the 94 HB classification.

UL 94 V0/1/2

After conditioning, the test bar is vertically clamped and flame-treated several times for 10 seconds at a time. In between the flame treatments, the time until the test bar is extinguished is measured. Afterwards, the afterburning times and the drip behavior are evaluated. The plastic used for Phoenix Contact terminal blocks satisfies the higher-grade criteria for classification as a V0 material.

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ClassificationUL 94 V0UL 94 V1UL 94 V2
Burning time after each flame treatment< 10 s< 30 s< 30 s
Total burning time after ten flame treatments< 50 s< 250 s< 250 s
Glowing time after the second flame treatment< 30 s< 60 s< 60 s
Complete burn-offNoNoNo
Ignition of the absorbent cotton under the sampleNoNoNo

PHOENIX CONTACT (Pty) Ltd.

36 Lyn Road
P.O. Box 916
ZA-Ferndale 2160
+27/11/801-8200

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