HYDRATION AND PLASTICIZATION EFFECTS IN CELLULOSE-ACETATE - A SOLID-STATE NMR-STUDY

The conjoint effects of water and diethyl phthalate (DEP) plasticizer on molecular motion in cellulose acetate (CA) have been examined. H-1,C-13 and cross polarization NMR data reveal a number of interesting features. As in other hydrated polymers, there are different types of water ranging from tightly bound to bulk-like water in CA. Both tightly and loosely bound water can act as a plasticizer. In CA which is devoid of DEP, water preferentially interacts with carbonyl groups in the side chains whereas in the plasticized and filled polymer, water associates with oxygen atoms in both main and side chains via weak hydrogen bonding. Hydration significantly enhances chain motions but, as expected, reduces the ability to cross-polarize carbons and protons. Information is obtained on the relaxation behaviour of CA and the manner in which it is affected by water and DEP plasticizer. From a practical point of view, it is significant that water and plasticizer act in concert to alter the properties of the material quite dramatically. That these property changes can be induced, for example, by climatic changes in humidity has important bearing on the processability of the material.