Thermal characterisation of cellulose based materials: Investigation of water content

Natural polymers, as cellulose, with hydrophilic groups such as hydroxyl groups have various strengths of interaction with water. Cellulose is a structurally heterogeneous polymer, consisting of paracrystalline and amorphous domains. Water can interact with the amorphous domains, but it is excluded almost completely from the crystalline regions. The purpose of this study was to estimate the amount of bulk free water in cellulose based materials, as linen, cotton and paper, by measuring the heats of vaporisation. Moreover the amount of free water in oxidised and grafted samples has been determined by DSC and this quantity has been compared with that found in the corresponding native materials. In oxidised cellulose the water content increases with decreasing the degree of crystallinity; the oxidation, being a degradative reaction, modifies the amorphous content in the cellulose. In presence of acrylic grafted polymer, the free water content is reduced and this reduction is related to the grafting yields.