Osmotic blistering, a form of composite failure that is a particular problem in marine applications, occurs when water penetrates and encounters a pocket of uncured resin. This results in a blister of acidic fluid under pressure that will eventually break through to the surface. Repair of the blisters requires grinding out the blisters, thoroughly drying the hull, and patching the craters.
In many layered composites such as yacht hulls or turbine blades, the structural risk can be particularly insidious if structural weaknesses occur within internal layers, hidden from view. This could lead to possible catastrophic failure without warning in mission critical or high performance applications, such as yacht or car racing, if no external signs of structural weakness are presented.
For design engineers using vacuum infusion for greater quality, consistency, and performance than wet/hand lay-up or vacuum bagging offers, it is ironic that general-purpose spray adhesives can potentially negate these qualities.
An adhesive product developed specifically for the vacuum infusion process called Infuzene presents a solution by crosslinking with the resin to provide greater interlaminal shear strength. Offered by Port Orchard, WA-based Westech Aerosol, a specialty industrial adhesives manufacturer, the vacuum infusion-specific adhesive was developed to hold dry materials onto structural surfaces, including vertical and tight radius work, during the vacuum infusion process.
As a high strength, high temperature, solvent-based vacuum infusion enabler for industrial use, it is designed to safely fuse laminating materials to structural core surfaces, forming a continuous matrix without structural weakness. Since it will not interfere with the curing process of vinyl esters, polyester or styrene resins, it allows resins to obtain maximum tensile shear strength. The adhesive crosslinks and hardens along with the ester or styrene resins to form an integrated structure.
In recent tests conducted by a leading independent university composites testing lab, results indicated the vacuum infusion-enabling adhesive provided a stronger bond in the vacuum infusion process than the leading general-purpose spray adhesive. Based on ASTM 2344 short beam shear strength testing standards, the results indicate that the composite with Infuzene was up to 30% stronger in interlaminar shear strength than the same composite with the leading alternative.
While the vacuum infusion-enabling adhesive is primarily used for fiberglass, its crosslinking properties with resin also provide greater interlaminar shear strength for carbon fiber (graphite) and Kevlar materials. A canister system with a reusable gun and hose eliminates the need for air-assisted application systems and allows continuous application for large projects when a 13-ounce can is insufficient.
For the most recent test results, including information from the independent study, call 800-674-2010; Fax 360-674-2053; visit www.ok2spray.com; or write to Westech Aerosol Corporation at 5405 Constance Dr. SW, Port Orchard, WA 98367.