SECTION VII C - MODIFYING EPOXY WITH FILLERS 0Epoxies formulated for coating and fiberglassing are too thin to serve as gap-filling adhesives. They can be modified by the addition of thixotropes to form non-sagging pastes very useful as gap filling glues. These pastes can be further modified with the addition of microballoons to form putties for fairing and hole filling. Wood flour can be used to make filleting putty for stitch-and-glue boat construction. All these solid dusty additives are called fillers. Fillers change the flow and density characteristics of the epoxy system. Each filler changes the liquid resin and hardener in ways that make epoxy useful for other applications besides coating or fiberglassing.
SECTION VII D - BONDING WITH EPOXY 0The mixed viscosity of coating and fiberglassing epoxies is not high enough to make good gap filling adhesives. Thixotropic agents like silica thickener (Cab-O-Sil, Aerosil), plastic minifibers, and wood flour are used to thicken the epoxy and change the flow characteristics. These fillers will turn the epoxy from translucent to opaque depending on the type and amount used. Silica thickener and plastic minifibers make the epoxy whitish while wood flour turns it reddish-brown. Silica thickener makes a smooth material while epoxy thickened with plastic minifibers or wood flour will be coarse. Microballoons and microspheres should not be used in adhesive formulations as they reduce tensile strength.
SECTION VII E - FILLETING, FAIRING, AND MOLDING WITH EPOXY RESIN 0
The SilverTip Series contains two putty materials: SilverTipEZ-Fillet, a wood-flour filled putty, and SilverTip QuikFair, a microballoon filled putty. Neither involve user added fillers and powders. As described elsewhere these have other advantages beyond simply eliminating the use of obnoxious, dusty powders. We suggest that most epoxy users will be better off using these rather than whipping up a batch of "homebrew" epoxy putties. Once mixed SilverTip EZ-Fillet and SilverTip QuikFair are used as described below.