Coagulation size of freezable water in poly(vinyl alcohol) hydrogels formed by different freeze/thaw cycle periods
(875-880) Polymer Journal 43 #11 (2011)
Abstract
Nakano and Nakaoki of Ryukoku University, Japan, studed the coagulation size of freezable water in a poly(vinyl alcohol) (PVA) hydrogel as a function of the freeze/thaw cycle period using thermal analysis.  The melting temperature of ice in the gel shifted to a lower temperature than that of normal ice.  This temperature depression can be interpreted in terms of the coagulation size of freezable water in the gel.  For longer freeze/thaw cycle periods, the coagulation size became larger. In addition, the weight content of freezable water estimated from the melting enthalpy of ice increased with an increasing length of the freeze/thaw period.  These results suggested an expansion of the coagulation size of freezable water.  It was concluded that the coagulation size of freezable water expands and the aggregation of PVA increases as a result of lengthening the freeze/thaw cycle.  (RDC 11/11/2011)