Soft Rod for Best Joint-Sealant Performance

Closed cell polyethylene foam is typically used as a joint filler and backing to elastomeric sealants. It has the characteristics of low moisture absorption and compatibility with cold applied sealants. On the other hand, Soft Rod is reticulated closed cell polyethylene foam that compresses easily as a joint filler and backing for sealants. Similar to the closed cell polyethylene foam, Soft Rod has low moisture absorption and will not discolor the sealants or substrates. Soft Rod readily conforms to irregular joints, installs easily and eliminates the bubbling of sealants. When either the closed polyethylene foam or Soft Rod is used, the need for the bond breaker is eliminated.

Soft Rod – the process of application

There are three reasons why there is a need to use backer rods on the joints before sealant is applied.

-        To control the depth of the sealant in proper relation to joint width

-        To provide a backing against which a sealant will be applied; it forces the sealant to the sides of the joint

-        It prevents the 3-sided adhesion so as to ensure the proper functioning of the joint sealant

Proper sizing of the Soft Rod

It is suggested that the Soft Rod must have a diameter that is at least 25% bigger the width of the joint so as to easily achieve the hourglass configuration before sealant application. It is also essential to follow the suggestions of the manufacturer in installing the compressed Soft Rod and well as in the joint-sealant application for best performance.

Tips when applying the Soft Rod

-        The Soft Rod must be applied using a blunt probe or a plain-faced roller to force the backing to the desired depth. Using the table that is usually provided by the sealant manufacturer, the proper rod diameter must be selected and cut to length or used directly from the spool.

-        A template or roller gauge can be used to control the depth at which the Soft Rod should be placed. It is important to follow the suggestions of the sealant manufacturer for the joint-sealant width-to-depth ratio.

-        Generally, the depth of the joint after the Soft Rod has been applied is one half of the width. Very large or small joints vary in terms of depth to width ratio.

-        During the installation, the Soft Rod should not be stretched. It should gently be forced in the joint so that the backing fits tight against the sides of the joint.

-        Surface cleaning is important for proper sealant adhesion. There are instances when priming the surface is required wherein the primer should be applied only to the joint surfaces and allowed to dry before the Soft Rod is installed. The Soft Rod is not a subject for priming.

-        It is important to make any analysis of the water absorption properties of the sealant material based on standard specifications for elastomeric performance. Always make sure that current versions of product data sheet and MSDS are followed. Such standards are not applicable for the Soft Rod.