Sandia National Laboratories
One of the most vital parameters related to thermosetting encapsulants is the parameter known as the working time of the resin which can be defined as the amount of time required for a resin to reach an unmanageably high viscosity at a given temperature. Typically, long working times are desired for two reasons. Firstly, short working times can result in premature gelation of the resin resulting in void spaces in encapsulated parts. Secondly, formulations with short working times typically exhibit fast kinetics making them prone to auto-acceleration and are susceptible to thermal run-away if handled in large quantities. Currently used curatives, such as D230 and Ancamine Z, exhibit different working times when used in conjunction with epoxy resins, such as Epon 828, due to the structural differences between the two. The aliphatic amines found in D230 exhibit rapid kinetics and short working times while the aromatic amines in Ancamine Z exhibit the opposite. Additionally, as Ancamine Z has recently been documented to be hazardous, a replacement curative exhibiting a comparable working time is desired.
To this end, much effort has been invested in researching new thermosetting resin formulations with tunable kinetics. Such systems are attractive in that different encapsulation applications which require varied working times could potentially all use the same base formulation but with different catalyst loadings.
Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.