UL 746A:2006 pdf download – Polymeric Materials一Short Term Property Evaluations.
18.6 Method E — peel resistance by T samples
186.1 The primary purpose 01 this method is to determine the relative peel resistance of adhesive bonds
between flexible adherents by means of a T-type specimen.
186.2 T-peel strength is the average load per unit width of bond line required to produce pogressive
separation of two bonded, flexible adherents, under the conditions designated in this test method.
18.6.3 The general form and dimensions of the test specimen are illustrated in ASTM 0 1876.
18.8.3 revised May 30, 2006
186.4 After conditioning, the bent unbonded ends of a test specimen are clamped in the test gnps of a tension testing machine and the peel resistance is to be determined.
19 IdentifIcation Hardness of Rubber and Plastics by Means of a Durometer
19.1 The test method for determination of the hardness of rubber and plastics by means of a durometer
is descnbed in the Standard Test Method for Rubber Property-Durometer Hardness, ASTM D 2240 (ISO
19.1 revIsed May 30. 2006
19.2 ASTM D 2240 (ISO 868) describes a method in which a horizontal specimen is subjected to penetration by force of an indentor. From Ihe hardness measurements obtained, the indentation hardness can be calculated.
19.2 revised May 30. 2006
20 DIelectric Breakdown Voltage and Strength
20.1 The test method for the determination of the dielectric breakdown and strength of insulating malerlals Is described in the Standard Test Methods for Dielectnc Breakdown Voltage and Dielectric Strength of Soled Electrical Insulating Materials at Commercial Power Frequencies, ASTM D 149 (lEG 60243).
20.1 revised May 30. 2006
20.2 Of the tests contained in ASTM 0 149 the following is a summary of the short-lime test.
202 revIsed May 30. 2006
203 In a test chamber, voltage is applied to me specimen at the uniform rate of rise of 500 V/s (a value selected from those suggested in ASTM D 149 until breakdown occurs. Observation of actual rupture or decomposition is accepted as evidence ol voltage breakdown. When physical evidence is not apparent. the voltage is usually reapplied to produce a more positive indication. Tripping the circuit.tweaking device is not a valid criterion for determining breakdown by vl.lue of voltage.
24.1.3 The high-voltage arc-tracking rate is the rate in mm per minute at which a conducting path can be produced on the surface of the material under standardized test conditions.
24.1.4 This test is to determine the ability of a material to withstand repeated high-voltage low-current arcing at its surface without forming a conductive path — a simulation of conditions that might be encountered dunng malfunction of a high-voltage power supply,
242 Apparatus
24.21 The basic components of the test apparatus are to consist of the following:
a) A power transformer rated 250 VA minimum primary 120 VA A — C. root mean square (VAC RMS) 60 lIz: secondary open-circuit volts 5200 VAC RMS.
b) A current-limiting resistor bank (with a variable nominal resistance of 2.2 megohms) capable of limiting the short-circuit current at the electrodes to 2.36 mA.
C) Two test electrodes consisting of a No. 303 staInless steel rod having a diameter of 3.2 mm (118 inch) and an overaJl length of approximately 102 mm (4 inches). The end is to be machined to a symmetrical conical point having an overall angle of 30 degrees. The radius of curvature for the point is not to exceed 0.1 mm at the start of the given test. The electrodes are to be mounted in a common vertical plane, parallel to the axis of the test specimen. orthogonal to one another, and are to have an angle of 45 degrees to the horizontal such that their tips contact the surface of the specimen with a normal force of 0.20 ±0.04 N (20.4 ±4.0 gf). One of the electrodes is to be fixed and the other is to be movable in a horizontal direction to increase the length of the air gap between electrodes, while maintaining the 45-degree angle.
d) A timer is to be incorporated in the test fixture so that the operator can record the length of time of the test.
C) See the schematic diagram of the circuit in Figure 24.1.