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Plastic Calking Materials.


pdf icon Plastic Calking Materials. (13870 K)
Tregoning, J. J.; Milliken, K. A.; Hockman, A.; Sligh, W. H.; Kessler, D. W.

BMS 033; 25 p. January 20, 1940.

Keywords:

plastics; specifications; weather effects; tests; installations; performanc evaluation; limestone; synthetic resins

Abstract:

One phase of this study was concerned with the development of test procedures and the accumulation of data to form the basis of a specification. By inspection of several installations and numerous specimen joints after exposure to the weather for several years, it was decided that tests for shrinkage, rate of hardening, bond, tenacity, staining, and slumping tendency afford a good basis for predicting the performance. Since calking compounds are commonly used in contact with porous materials whose absorptive properties materially affect the performance, it is necessary to employ an accessory porous material in the tests. For this purpose a certain limestone has been selected because of its uniformity. The test procedures have been so devised that three specimens are prepared for each sample and on these eight properties are determined. A study of the composition of proprietary compounds has shown that a large variety of formulations are used. Oils most commonly used are fish, soybean, linseed, and tung. Cottonseed and rapeseed oils were employed in some mixtures whereas there were a few brands in which the vehcile consisted of rosin, tallow, or synthetic resin. In a considerable number of the proprietary compounds, the volatile content was too high for good performance. A study of compositions in relation to performance has indicated that pretreatment of the oil is of first importance, and that considerable care must be exercised in selecting fillers as well as keeping the volatile content very low. Certain factors which may affect the performance of plastic calking materials in service have been studied. Compounds that give good service in one type of masonry do not always give similar results on all other types. Often very porous masonry absorbs less of the vehicle than much denser materials do. Capillary forces of the pores seem to be of considerable importance. A compound may be satisfactory in wide joints but fail in narrow joints. Primers have been found to have some value in reducing shrinkage of mixtures of pronounced staining characteristics, but they may affect the bond adversely. Good mixtures do not require primers.