ELJEN Products List EJ-500 Optical Cement distributed by
EJ-500 is a clear and colorless epoxy cement with refractive index at 1.57.  It is ideal for optically bonding plastic scintillators and acrylic (PMMA) light guides.  It is equally effective with PYT (polyvinyltoluene) or polystyrene based scintillators and may also be confidently used for making butt joints of optical fibers with polystyrene cores. EJ-500 has a degree of flexibility making it useful for optically bonding glasses or the above plastics to glass windows.
EJ-500 is fully cured at room temperature (20°C) with a working life of 60 minutes.  The mixed cement takes 3-4 hours to set and 24 hours to harden, although it takes several days to achieve complete cure.  It may also be used to cement metal or ceramic parts to plastic scintillators or PMMA light guides.
Thoroughly mix 4 parts by weight resin to one part by weight of hardner (3 parts to 1 part by volume).   Allow air bubbles to rise before applying by setting aside for 15~20 minutes.   Apply to both surfaces to be joined.  
The adjacent surfaces may be protected with tape.  Best results are achieved with a thin epoxy joint typically 0.01" (0.25 mm) thick.  
For bonding plastic scintillators and/or light guides, the surfaces to be joined should be lightly sanded with a 400 grit silicon carbide paper, cleaned with methanol or isopropanol, and dried.

  Typical Properties
Mixed viscosity 800 cps EJ-500 Optical Transmission
Bond Strength 1800psi ( 126.5kg/cm2 )
Dielectric Strength 16. 5volt/µm
( 420 volt/mil )
Specific Gravity, cured 1. 17
Service Temperature -65°C to +105°C
Volume resistivity, @25°C 1 x 1014 ohm-cm
Thermal expansion coeff. 7. 2 x 10-5/°C
NASA outgassing properties 1.69% mass loss, 0.04%
condensed volatiles

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