Testing tracking resistance

Tracheobronchitis effect on heart, 5 107 Trachoma, 74 338 Tracking resistance testing, 79 587 Traction, 3 726-727 Traction thickener, 22 65 Trade... 

The treatment of HP has become increasingly difficult due to the frequency of antibiotic resistance and recurrence after successful treatment. In Peru, the recurrence rate of the infection is as high as 73% even after successful eradication. In this instance, recurrence is not attributed to antibiotic resistance but to re-infection of patients. In the United States, resistant HP is also of concern. The Helicobacter pylori Antimicrobial Resistance Monitoring Program (HARP) is a multicenter US network that tracks HP patterns of resistance. In 2004, HARP reported that 34% of 347 HP isolates tested were resistant to one or more antibiotics commonly used to treat HP infections.In the US, most antibiotic resistance is associated with metronidazole and clarithromycin, both standard treatment options for HP. Thus, antibiotic resistance and high re-infection rates strongly argue for the development of new therapeutic modalities to prevent and treat HP infections worldwide. 

Testing of polyurethanes for their electrical properties due to the voltages required must be carried out using properly designed equipment. The electrical tests that are normally carried out are resistivity, insulation resistance, electric strength, tracking resistance, power factor, and permittivity. 

Fig. 3.116 Test arrangement for tracking resistance 1 drip-nozzle 2 electrode 3 specimen 4 base. Dimensions in mm...

The resistance to permanent deformation is determined with respect to the wheel-tracking test. The resistance to permanent deformation, expressed accordingly, should be lower than the maximum values of the category (or categories) specified. 

The continuous reading, fixed slip technique is similar to the abovementioned locked wheel skid tester technique but it provides a record of skid resistance along the whole length of the test track surface. It also enables averages to be obtained for specified test segments. Hence, the instantaneous friction reading is recorded and the BFC for each friction length is calculated and recorded. 

The tracking resistance test is conducted by applying two electrodes—with a force of 1 N—to the surface of the specimen. A 0.01% solution of ammonium chloride is... 

Another PPS success story in the electrical/electronics industry concerns use of PPS in televisions.26 Here requirements included high temperature resistance, precision moldability, good arc tracking resistance, and good dimensional stability. Again, numerous materials were tested, but a fiberglass-reinforced PPS compound proved to be the material of choice for a series of pin cushion corrector coils used in color television sets. 

A material s behaviour in the proximity of electrical fields or discharges and the static build-up and dicharge behaviour of a material are tested. Tests include volume and surface resistivity, permittivity, breakdown strength, insulation resistance, power (or loss) factor and tracking resistance. 

ASTM method D 2132 outlines the procedure for determining dust and fog tracking and erosion resistance of electrical insulating materials. The test is carried out in a fog chamber with a standardized dust applied to the sample surface. Failure is characterized by the erosion of the specimen or tracking. ASTM D 2302 also describes the test for differential wet tracking resistance of electrical insulating... 

Despite these limitations, it is desirable to compare the track resistance of different plastics. Typical results with the inclined-plane, liquid-contaminant tracking test (ASTM D 2303) are shown in Table 7. 

The inclined-plane test, ASTM 2303, is most suitable for evaluation of track resistance. Many CTI values have been published by UL (36). The voltage ranges used in tests, 150-600 V for the CTI and 1.5-6 kV for the inclined plane test, have no relationship to operating voltages. The test voltages provide only a comparison and a means for rating. 

Table 7. Tracking Resistance of Polymers Inclined Plane Test ASTM D 2303...

Liquid-eontaminated inclined plane tracking Tests for electrical insulation Resistance to dust and fog tracking Measurement of tracking Resistance to water treeing Traeking index using various electrodes... 

ASTM D2132, Test MethodforDust-and-Fog Tracking and Erosion Resistance of Electrical Insulating Materials, Vol. 10.02, ASTM, Philadelphia, Pa., 1989. 

To enhance the resistance to heat softening his-phenol A is substituted by a stiffer molecule. Conventional bis-phenol A polycarbonates have lower heat distortion temperatures (deflection temperatures under load) than some of the somewhat newer aromatic thermoplastics described in the next chapter, such as the polysulphones. In 1979 a polycarbonate in which the bis-phenol A was replaced by tetramethylbis-phenol A was test marketed. This material had a Vicat softening point of 196 C, excellent resistance to hydrolysis, excellent resistance to tracking and a low density of about l.lg/cm-. Such improvements were obtained at the expense of impact strength and resistance to stress cracking. 

The arc resistance of a polymer is the length of time for which we can apply an electrical discharge to its surface before it breaks down and begins to conduct electricity. Breakdotvn typically takes the form of conductive carbonaceous tracks that are caused by oxidation due to locally high temperatures. Polymers -with lowpolarity typically fare better in this test than polar polymers. Arc resistance is reduced by dirt, moisture, and other surface contaminants. 

In these tests, EA 3580 produced somewhat more impairment in performance of Track Tracing Accuracy (Fig. 34) than in Track Tracing Speed (Fig. 35), suggesting that physical competence may be more resistant than cognitive functions to the effects of anticholinergic drugs with high relative central potency. 

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