Findings

Change in Dimension—All three material types decreased in dimension after the first four-week cycle of testing, as shown in Table 8.

Change in Weight—The following charts show two responses to the cycles of wetting and drying; the percentage gain and loss in each period of water immersion or drying, and the general trend of samples’ weight loss or gain over an extended period. For materials with a relatively high solvent content, the general trend of losing weight is likely due to solvents being released from the specimen.

Material Type lUM-ltl—1-Component, Modified Urethane #1—Setting aside one anomalous data point, the greatest gain in weight in a seven-day period of water immersion was 8.8 %. The specimens exhibited a general trend to lose weight during the test period, with the average weight stabilizing after approximately 56 days. Refer to Fig. 7.

TABLE 8—Average dimensional change during a four-week test cycle.

Material

Height

% Change

Width

1UM-#1

1.4

1.1

lUM-#2

3.4

2.1

2U-#1

0.8

0.6

FIG. 7—Specimens of material type IUM-#1. Weight change through three test cycles.

Material Type IUM-#2—1-Component, Modified Urethane #2—The greatest change in weight in a seven-day period of water immersion was a loss of 3.6 %. The specimens exhibited a general trend to lose weight during the test period, with the average weight stabilizing after approximately 56 days. Refer to Fig. 8. The material did not complete curing during the test period. Throughout the 84-day test period an oily film was noted on the surface of water that held specimens of this material. In the field, the authors have observed a tacky condition in this material several years after installation.

Material Type 2U-#l—2-Component, Unmodified Urethane #1—Apart from two anomalous high val­ues, the greatest gain in weight in a seven-day period of water immersion was 4.8 %. The specimens exhibited little change in weight during the test period, with the average weight stabilizing after approxi­mately 28 days. Refer to Fig. 9.

Conditioning Environment—It is reasonable to expect some differences in the performance of cold liquid-applied materials when they are installed in different conditions of temperature and humidity. Liquid materials do not spread as easily when cold; single component materials depend upon moisture for curing.

Research by Mailvaganam et al. [4] studied the effects of curing temperature and humidity on the properties of cold liquid-applied deck coatings, which are similar to the products addressed in this paper. The CMHC researchers cured specimens in temperature and humidity controlled conditions: 30, 50, and 85 % RH and 5, 22, and 38°C (41, 72, and 100°F). They found that membrane properties, including permeability, were significantly affected by varying the temperature and humidity of installation and curing.

We conducted a set of tests in addition to the one described above. Samples for both sets of tests were prepared and cured for the first three days in a contractor’s unconditioned warehouse during a time when the exterior temperature ranged from 8 to 16°C (46 to 61 °F). Following the initial cure, samples were

FIG. 8—Specimens of material type lUM-#2. Weight change through three cycles.

conditioned for periods of one, two, and three weeks. Half of the samples (described in the Figs. 7-9 were held at standard conditions, while the other half were conditioned in an un-insulated and unconditioned garage at a time when exterior temperatures ranged from 5 to 21 °С (41 to 70°F).

As shown in Fig. 10, the results of this testing did not reveal consistent differences between specimens cured in standard conditions versus those cured in an unconditioned garage. These samples shared a common environment for initial cure, which may be the time when cold liquid-applied materials are most sensitive to weather fluctuations.