THE MISCIBILITY AND MORPHOLOGY OF HEXAMINE CROSS-LINKED NOVOLAC POLY(EPSILON-CAPROLACTONE) BLENDS/

The miscibility and morphology of novolac/poly(epsilon-caprolactone) ( PCL) blends before and after curing were investigated by optical micro scopy, differential scanning calorimetry (d.s.c.) and FT i.r. It was f ound that PCL is miscible with uncured novolac resin, as shown by the existence of a single glass transition temperature (T-g) in each blend . FT i.r. studies revealed that hydrogen bonding interaction in novola c/PCL blend occurs between the hydroxyl groups of novolac and the carb onyl groups of PCL, which is responsible for the miscibility of the no volac/PCL blends. However, remarkable changes occurred after the novol ac/PCL blends were cured with hexamine (HMTA), which can be considered to be due to the dramatic changes in chemical and physical nature of novolac resin during the cross-linking. Phase separation in the initia lly miscible novolac/PCL blends occurred after curing with 15 wt% HMTA (relative to novolac content). The phase structures of the cured blen ds show composition dependence. The cured novolac/PCL blends with novo lac content up to 70 wt% were observed to be partially miscible, where as the 90/10 cured novolac/PCL blend was found to be miscible. The cur ing reduces the intermolecular hydrogen-bonding significantly, but the re still exists a considerable amount of residual intermolecular hydro gen bond in the cured blends with its strength much lower than that in the uncured blends. The morphology of the novolac/PCL blends was rema rkably affected by curing. The curing results in the disappearing of t he T-g behaviour of novolac, owing to less mobility of the novolac cha in segments. Copyright (C) 1996 Elsevier Science Ltd.