Structural Bonding

114
Thread Sealing
Choosing a thread sealant
When choosing a thread sealant, there are several factors
that need to be considered. The single most important
question is substrate. Are you dealing with plastic threads,
metal threads, or a combination of both? Plastic threads
usually require a different sealant than metal threads. In
some instances, the environment becomes a factor. If the
application requires the sealant to be in contact with harsh
chemicals, then a chemically resistant sealant should be
chosen. In other cases, the type of thread comes into play.
For example, if the fitting to be sealed has large coarse
threads, then a sealant with more gap fill should be chosen.
Similarly, a low viscosity sealant would be better suited for
fine threads. When choosing a sealant, it is important to
consider all of the factors. The following chart will help
guide you through your choices.
Why use a solvent-based sealant on plastic fittings?
Anaerobic sealants work when they harden in the absence
of air and the presence of a metal surface. On the other
hand, solvent-based sealants harden when the solvent
evaporates. In the case of plastic fittings, you must rely on a
solvent-based sealant since there are no metal surfaces to
cure the adhesive. Similarly, in those cases when joining
metal to plastic fittings, solvent-based sealants are
recommended. Because only half of the substrate is metal,
anaerobic sealants may produce inconsistent cure.
This chart should not be used to specify products without specific
testing. It is recommended that you conduct on-part testing to
ensure product performance before specifying any thread sealant.
Loctite® Adhesives and Sealants Product Specialists are available to
assist you with new product designs, or to help you re- engineer an
existing application for improved performance and cost savings.
They can also set up testing of your parts at the Henkel Customer
Engineering Center. For application assistance, call 1-800-LOCTITE
(562- 8483) or visit www.loctite.com and select “Contact Loctite.” In
Canada, please call 1-800-263-5043.