Materials and methods: The experimental RCSs were prepared as two separate parts. Invariable Part 1: 30% wt. of bisphenol A/F epoxy resin and 70% wt. of ZrO2 filler. Variable Part 2: 30% wt. of AH, SOP and 70% wt. of ZrO2. Both parts were mixed together until homogeneous paste was obtained. Samples A-E included different AH (25% wt) and 5% wt. of SOP. A: 1,3-Diaminopentane, B: Diethylenetriamine, C: Poly(m-xylenediamine) (MXDA), D: trimethylenepropane tris(poly(propylene glycol) amine) (TMTP), E: Polypropylene glycol block-polyethylene glycol block amine terminated (PPPEA). Samples F-J were prepared with 30% of the same AHs respectively as in samples A-E and not included the SOP. All samples were polymerized at 370C during 24 hours and then tested for post-curing reaction using the DSC device (Mettler Toledo) from 250C to 2500C at the heating rate 50C/min.. All samples were tested for the Glass Transition temperature (Tg) using the DSC, scanned from -500C to 2500C at the heating rate of 100C/min after 24 hours and again after 7 days in 370C.
Results: No post-curing effect was observed for any of the samples. The Tg values after (24 hours) and 7 days are: A (61.340C) 77.230C; B (62.120C) 75.540C; C (45.830C) 47.910C; D (40.560C) 41.660C; E (-13.030C) -10.200C; F (67.390C) 81.480C; G (69.230C) 78.510C; H (49.980C) 50.400C; I (45.090C) 47.110C; J (-6.980C) -5.100C.
Conclusions: As the AH is longer, linear and low amine content molecule like the PPPEA , the Tg is lower and more stable during first 7 days. SOP reduces significantly the Tg for relatively short periods.