UL 746 Series – 746A / 746B / 746C / 746D / 746E
Section 1: General
One of the most referenced Standards for evaluation of Polymeric Materials is the UL 746 series. [Polymeric materials can also be referred to as plastics.] The series consist of 6 linked Standards.
- UL 746A: Standard for Polymeric Materials – Short Term Property Evaluations
- UL 746B: Standard for Polymeric Materials – Long Term Property Evaluations
- UL 746C: Standard for Polymeric Materials – Use in Electrical Equipment Evaluations
- UL 746D: Standard for Polymeric Materials – Fabricated Parts
- UL 746E: Standard for Polymeric Materials – Industrial Laminates, Filament Wound Tubing, Vulcanized Fibre, and Materials Used in Printed-Wiring Boards
- UL 746F: Standard for Polymeric Materials – Flexible Dielectric Film Materials for Use in Printed-Wiring Boards
As a testing laboratory for EIM and EIS, ELTEK Labs conducts testing to 746A and 746B. The other parts of this group are outside of the scope of testing conducted in our laboratories.
Section 2: UL 746A Test Performed at ELTEK Labs
UL 746A: Standard for Polymeric Materials – Short Term Property Evaluations
2.1 Short Term tests refer to the expected length of time for the test to be performed. This usually means the test specimens are to be tested in the “as made” condition. Test can be performed on test specimens which have undergone various pre-conditioning or even some length of thermal aging.
2.2 UL 746A consist of a wide range of individual tests. For the total the tests conducted by ELTEK Labs are:
- Section 10 – Tensile Properties of Thermoplastic Polymeric Materials (Per ASTM D638 / ISO 527)
- Section 12 – Tensile Properties of Thin Polymeric Sheeting (Per ASTM D882 / ISO 527-3)
- Section 13 – Izod Impact Test (Per ASTM D256 / ISO 180)
- Section 14 – Tensile Impact Test (Per ASTM D1822 / ISO 8256 )
- Section 15 – Charpy Impact Test (Per ASTM D6110 / ISO 179-2)
- Section 16 – Flexural Properties of Polymeric Materials (Per ASTM D790 / ISO 178)
- Section 19 – Bond-Strength Properties of Adhesives
- Per ASTM D1002 / ISO 45487 for Metal-to-Metal
- Per ASTM D1876 for Peel Resistance of Adhesives (T-Peel Test)
- Section 20 – Identification Hardness of Rubbers and Plastics by Means of a Durometer (Per ASTM D2240 / ISO 868 Shore A and Shore D ranges)
- Section 21 – Dielectric Breakdown Voltage and Strength (Per ASTM D149 / IEC 60243)
- Section 22 – DC Resistance of Conductance of Insulating Materials (Per ASTM D 257 / IEC 60167 For Surface Resistance / Volume Resistance / Insulation Resistance)
- Section 23 – High-Voltage, Low Current, Dry Arc Resistance Performance Level Categories of Solid Electrical Insulation (Per ASTM D495)
- Section 24 – Comparative Tracking Index and Comparative Tracking Performance Level Categories of Electrical Insulation Materials (Per ASTM D3638)
- Section 25 – High-Voltage Arc-Tracking-Rate Performance Level Categories of Solid Electrical Insulating Materials
Material Distortion Under Load
- Section 30 – Ball Pressure Test
Resistance to Ignition of Polymeric Materials
- Section 32 – Hot Wire Ignition (Per ASTM D3874)
- Section 33 – High-Current Are Resistance to Ignition Performance Level Categories
- Section 34 – High-Voltage Arc Resistance to Ignition Performance Level Categories
- Section 35 – Glow-Wire Ignitability Test (Per IEC 60695-2-13 )
- Section 38 – Method for Measuring Water Absorption of Polymeric Materials (Per ASTM D570 / ISO 62)
The list of tests can be used to evaluate all types of chemistries; such as thermoplastic polymers, thermoset polymers, PA 6, PA 6-6, Polycarbonates, ABS, Epoxy, Polyurethane, Polyesters, Polypropylene, and basically all types of polymeric materials. Refer to UL 746 A and B for more details.
Section 3: UL 746B Test Performed at ELTEK Labs
UL 746-B: Standard for Polymeric Materials – Long Term Property Evaluations
3.1 Long Term tests refer to the expected length of time for the test to be performed. This usually means the test specimens are to be tested are to undergo some length of thermal aging prior to testing. For UL 746B tests the general requirements are for thermal aging to be started at four or more elevated temperatures. The most common minimum length of time for which the thermal aging is to be conducted is 5000-hours. This does not mean that all long term thermal aging projects can be completed within the minimum 5000-hour requirement; the length of time needed for completion is to be agreed upon by all parties involved.
3.2 Long Term Thermal Aging, abbreviated as LTTA, is also known as Thermal Aging, Thermal Decomposition, Thermal Index Rating or TI, and/or Relative Thermal Index Rating or RTI.
3.3 There are three common properties used for TI and RTI projects.
- Mechanical Properties
- Tensile or flexural strength (but not both)
- Impact Strength (Izod, Tensile or Charpy, one but not more than one)
- Electrical Properties [Dielectric Strength]
- Flammability Properties
All of these properties are performed at ELTEK Labs.
The test methods are the same as described in UL 746A for the specific property.
3.4 There are two sampling techniques or procedures.
- Fixed Temperature
- Fixed Time Frame Method [FTFM]
Both techniques are performed at ELTEK Labs.
The preferred test sampling method is the Fixed Time Frame Method. The Screening Test is very helpful in determining which may be the preferred sampling technique.