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Appendix A This guide is designed to help identify and prevent potential problems as- sociated with epoxy use. If the prevention steps described here do not re- Problem solving guide solve the problem, call the WEST SYSTEM technical staff. Appendix 48 PROBLEM POSSIBLE CAUSES PREVENTION The epoxy mixture has not cured after the recommended cure time has passed. Off ratio—too much or too little hardener will affect the cure time and thoroughness of the cure 1. Remove epoxy. Do not apply additional material over non-curing epoxy. See 5.3.5 Removing epoxy. 2. Check correct number of pump strokes-use equal strokes of resin and hardener. DO NOT add extra hardener for faster cure! 3. Check for correct hardener pump (5:1 or 3:1 ratio) and be sure pumps are working properly. Look for a continu- ous stream of resin or hardener without spitting. 4. Check pump ratio (see pump instructions). Low temperature- Epoxy mix- tures cure slower at low tem- peratures 1. Allow extra curing time in cool weather. 2. Apply heat to maintain the chemical reaction and speed the cure. 3. Use a faster hardener, designed to cure at lower tem- peratures. See 5.3.2 Understanding and controlling cure time. Insufficient mixing 1. Remove epoxy. Do not apply additional material over non-curing epoxy. See 5.3.5 Removing epoxy. 2. Mix resin and hardener together thoroughly to avoid resin rich and hardener rich areas. 3. Add fillers or additives after resin and hardener have been thoroughly mixed. See 5.3.3 Dispensing and mixing. Incorrect products 1. Remove epoxy. Do not apply additional material over non-curing epoxy. See 5.3.5 Removing epoxy. 2. Check for proper resin and hardener. Resin will not cure properly with other brands of hardener or with polyester catalysts. Bond failure Insufficient cure See above. Resin starved joint-epoxy has wicked into porous bonding surfaces Wet out bonding surfaces before applying thickened ep- oxy. Re-wet very porous surfaces and end grain. See 5.4.2 Bonding—Two-step bonding. Contaminated bonding surface 1. Clean and sand the surface following the procedure in 5.4.1 Surface preparation. 2. Sand wood surfaces after planing or joining. Bonding area too small for the load on the joint Increase bonding area by adding fillets, bonded fasteners or scarf joints. Too much clamping pressure squeezed epoxy out of the joint Use just enough clamping pressure to squeeze a small amount of epoxy from the joint. Clear coating turned cloudy Moisture from condensation or very humid conditions reacts with amines in uncured hard- ener 1. Apply moderate heat to partially cured coating to re- move moisture and complete the cure. Avoid overheating. 2. Use 207 Hardener for clear coating applications and for bonding thin veneers that may bleed through to the sur- face. Entrapped air from aggressive roller application 1. Apply moderate heat to partially cured coating to re- lease trapped air and complete the cure. Avoid overheat- ing. 2. Apply coating at warmer temperature–epoxy is thinner at warmer temperatures. 3. Apply epoxy in thin coats. Waxy film appears on surface of cured epoxy Amine blush forms as a result of the curing process Blush formation is typical. Remove with water. See 5.4.1 Special preparation for various materials—Cured epoxy. The hardener has turned red after long storage Moisture in contact with hard- ener and metal container Red color will not affect epoxy performance. Avoid using for coating or exposed areas where color is not desired. APDF Image | Vacuum Bagging Techniques 002150
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