CMT Materials, Inc.

Innovative Tooling Materials for Thermoforming

Product Data Sheets

HYTAC Plug Assist Materials

HYTAC Selector Guide

HYVAC Vacuum Fixturing

Tooling and Modeling Board

METAPOR Air Permeable Composites

Machining Tools

HYTAC Inserts

HYTAC Sizing Chart

One of the questions frequently asked about syntactic foam plugs is; "what is the best way to attach the foam plug to a base structure?"

Syntactic foam plug assist materials typically fall in to one of three broad categories - thermoset epoxy, copolymer epoxy or thermoplastic.    

Thermoset epoxy syntactic foams (HYTAC-W, WF, WFT, Rx Series and other standard 350° or 450° epoxy syntactics) generally have poor tensile and shear strength, making direct threading unadvisable.  Failure due to over tightening, improper screw/bolt length, or a cantilevered wobble of the plug is typically catastrophic and results in cracking of the entire plug or pull out of sections too large to repair.

Copolymer syntactic foams (HYTAC-FLX and FLXT) are more durable to impact and production abuse, yet still subject to the same limitations when attaching to a base.

Thermoplastic syntactic foam (HYTAC-B1X) has a toughness that prevents propagation of a failure throughout the entire plug.  A threaded piece that pulls free generally damages the threads only.  It is easy to drill and retap the plug, install a slightly larger thread and have the plug back on the machine in a matter of minutes.

Tests performed by CMT comparing usage of a threaded insert to a scored insert bonded in to place using standard quick cure adhesive, yielded similar tensile pull out values, but with very different types of failure.  Threaded inserts failed catastrophically, destroying the entire plug, while the bonded insert simply pulled out in a failure of the adhesive.    The advantage of the bonded insert is that it may easily be readhered inside the plug.  The disadvantage is that strength is entirely dependent on the quality of the adhesive bond.

Typical threaded insert – Not recommended for use with thermoset epoxy or copolymer syntactic foam. Use only with HYTAC-B1X.

Scored insert available from CMT.  Suitable for use with any syntactic foam.  Available with ¼-20 or 6 mm internal thread.

Click here for a PDF installation guide detailing the process and adhesive to use CMT inserts for HYTAC materials.