Relative humidity, ageing tests

In order to demonstrate that HER compared to butanediol-based elastomer has better physical and mechanical properties at elevated temperatures, cast elastomers with 95% stoichiometry have been made from an MDI terminated polyester prepolymer (Baytec MS-242) extended with butanediol and HER-HP (from INDSPEC Chemical Corporation). Test specimens were cut from a sheet post cured at 110 °C for 16 hours, for the tensile, tear, DSC and DMA determinations. In the preparation of material for the dry heat aging evaluation, tensile, DSC and DMA samples were placed in an air oven with the temperature controlled within 2 °C of the set point and aged for 28 days at 100 °C, 21 days at 120 °C and 14 days at 135 °C. Then, all the samples were stored for at least seven days at room temperature and 50% relative humidity before testing. 

The hydrolytic stability of various polymeric materials can be determined by a hardness measurement before and after exposure to high relative humidity aging. This technique for comparing hydrolytic stability is known as the Gahimer and Nieske procedure. See Fig. H. 6. A time period of 30 days in the 100°C, 95 percent RH test environment corresponds to a period from 2 to 4 years in a hot, humid climate. 

Testing the Pressure-Sensitive Properties. The tests were performed after aging for 1 day at constant temperature (22°C) and relative humidity (50%). Testing methods are shown in Figure 31. 

Borup et al. [254,255,258] have studied the corrosion of DLs. They aged different types of hydrophobic treated DLs for around 1,000 hours in deionized water at 80°C. After these aging tests, the samples were fuel cell tested at different relative humidities. It was observed that the DLs that were aged behaved like hydrophilic DLs they showed the best performance under dry conditions and the worst under high-humidity conditions due to flooding. On the other hand, hydrophobic DL materials that were not aged showed the lowest performance during dry conditions and the best... 

The basic mission of the Physics and Biology Laboratories is to test paper treated with products used in the restoration process. Physics is in an air-conditioned room, maintained at 60% relative humidity at 21°C, equipped with machines for testing folding endurance, tensile, and burst strength of paper. Biology runs tests, primarily with culture media, to determine the susceptibility of the treated paper to attack by microorganisms these are identified and a determination is made on how to avoid or eradicate them. Aging chambers are available for tests made by the laboratories. 

A much more recent development is the morpholine process in which fifty books per hour are treated in an evacuated chamber with morpholine-water vapor (12). In its present form, it was effective on 95% of the papers treated, prolonging their life on average by a factor of 4-5 (Figure 7). Though it does not leave a titratable alkaline reserve in the paper, acid papers treated in this manner aged in the presence of 5 ppm S02 at 75 °C and 60% relative humidity deteriorate more slowly than if untreated. Recent tests of twenty treated books at the Library of Congress show that their pH has not declined in two years. The equipment for the process was set up in the Virginia State Library where 35,000 books were treated in the first seven months of operation. 

For each paper, both Foldur Kraft and newsprint, there were ten sample sets and one unwashed set, which was used as a control. The air dried samples were subjected to accelerated aging in humid (90°C/50% relative humidity) and dry (100°C) circulating air ovens for one, two, three, and five weeks. At regular seven-day intervals one sheet from each sample set was removed and tested. 

The data in Table VI shows that the Allied Superior paper improved in folding endurance test values as the relative humidity was increased. This occurred in all instances except for the paper that was aged seven days and tested at 30% relative humidity. 

The stuccos prepared in the laboratory were aged at ZTC and 65% relative humidity for various periods of time. Two stucco properties, that is, consistency and disintegration, were determined immediately after calcining and after various periods of aging. These tests were continued until equilibrium values had been reached the times required to reach these values are given in Table 1. The consistency test methods and the techniques to obtain particle size data, as well as the treatment of these data, are described briefly below. 

The effect of panel age on formaldehyde release was investigated in the first study summarized in Table I, and this variable was evidently very important with respect to the formaldehyde levels measured. As noted in the Remarks column in the table, formaldehyde levels ranged from 0.1 - 0.3 ppm for freshly manufactured specimens, while levels in the range of only 0.05 - 0.1 ppm were associated with matched specimens that had been aired out for 90 days at 23 C and 44% relative humidity. This aging effect is consistent with the theoretical considerations discussed earlier and with test results to be presented later in this report. 

---