The moisture absorption characteristics of crosslinked vinyl terminated polyethers compared with epoxies

Processable and practically useful thermosetting resins are almost invariably highly polar. For this and other reasons they can absorb considerable moisture, which affects their physical, electrical and mechanical properties. Crosslinked vinyl terminated oligomeric polyethers (VTPs) of very low polarity are described and their moisture absorption characteristics are compared with those of a standard amine cured Epikote 828® epoxy resin cured with metaphenylene diamine (MPD). The equilibrium moisture absorption of the vinyl terminated polymers is about one‐tenth of that of the epoxy system, but their diffusivity is higher. The dependence of the equilibrium uptake on temperature, relative humidity, specimen thickness and oligomer proportions is discussed. The effect of moisture saturation on the d.c. volume resistivity is considered. Moisture prevents the resin from obeying Ohm's law.