Dm. Price et Z. Bashir, A STUDY OF THE POROSITY OF WATER-PLASTICIZED POLYACRYLONITRILE FILMS BY THERMAL-ANALYSIS AND MICROSCOPY, Thermochimica acta, 249, 1995, pp. 351-366
In a previous study, the morphology of water-plasticised polyacrylonit
rile (PAN) film, made by compression moulding moist polymer powder, wa
s discussed. The X-ray diffraction pattern of the plasticised film was
different from that of dry PAN and this led to the suggestion that hy
drated polymer crystallites had been formed by a portion of the water.
The location of the remainder of the water was unknown. In this work,
the thermal behaviour of the water-plasticised PAN at sub-ambient tem
peratures has been examined. When the film was cooled below room tempe
rature, two distinct exothermic peaks were observed at -17 degrees C a
nd -38 degrees C due to the formation of ice. By analysing the data in
terms of thermoporometry, which has been more widely used to study th
e freezing of condensates in porous ceramic materials, it was conclude
d that the water-plasticised films had a micro-porous morphology. The
DSC results suggested a bimodal distribution of pore sizes, but scanni
ng electron microscopy revealed a third category of pores with larger
size. These large pores were not detected by calorimetry because they
were not fully filled with water.