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 fe atures. As in other hydrated polymers, there are different types of wa ter 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 devoi d of DEP, water preferentially interacts with carbonyl groups in the s ide chains whereas in the plasticized and filled polymer, water associ ates with oxygen atoms in both main and side chains via weak hydrogen bonding. Hydration significantly enhances chain motions but, as expect ed, reduces the ability to cross-polarize carbons and protons. Informa tion is obtained on the relaxation behaviour of CA and the manner in w hich it is affected by water and DEP plasticizer. From a practical poi nt of view, it is significant that water and plasticizer act in concer t to alter the properties of the material quite dramatically. That the se property changes can be induced, for example, by climatic changes i n humidity has important bearing on the processability of the material .