Plastic Calking Materials.
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.
