Why does epoxy yellow over time?


All resins will discolor over time. Epoxy, polyurethane, acrylic, etc.…they will all break down eventually with UV exposure.The epoxy resin itself (Part A) is an aromatic chemical structure, which in simple terms means the chemical bonds are susceptible to UV. UV stabilizers can be added to slow down the discoloration which increases the life of the epoxy. Discoloration is not only an aesthetic issue; it affects the transmission of light through the epoxy.

EB-107LP-2 is a low viscosity, long pot life epoxy system. A USP Class VI certified product, EB-107LP-2 is preferred by many medical device manufacturers for its extremely long work life and biocompatibility. Applications include matching layers in acoustic technology and underfill epoxy for PCB applications. Due to its unique chemical formulation, EB-107LP-2 resists yellowing for much longer than the life of LEDs making it a non-yellowing epoxy.

Product Specifications

No.of Components 2
Mix Ratio by Weight 100/35
Mixed Viscosity @RT(cps) 200-500
Pot Life @25°C(100 gram) >8 hrs
Recommended Cure 3 hrs @ 65°C
Alternate Cure 24-48 hrs @ 25°C
Color Clear
Specific Gravity 1.1
Hardness(Shore) D-82
Refractive Index 1.53
Lap Shear Strength @25°C(psi) 2300
Tg(°C) 82
CTE(Below Tg)10-6/°C 61
Service Temp.Range -55°C to 200°C
Thermal Conductivity(W/m°K) NA
Volume Resistivity(500 V) >10^14

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