Properties of Composites of Unbeaten Birch and Pine Sulphate Pulps with Bacterial Cellulose

Abstract

The possibility of modifying the structure and properties of fibrous papermaking pulps with bacterial cellulose was investigated. For this purpose, three ways of obtaining specific composites were developed. The first one consisted in making the biosynthesis of bacterial cellulose in Acetobacter xylinum culture in the presence of fibres of papermaking semiproducts; the second one involved the addition of suitably disintegrated bacterial cellulose film to different papermaking pulps; and the third one consisted of joining semi-product paper sheets with bacterial cellulose film by putting the bacterial cellulose film on a sheet of paper and drying it in laboratory apparatus of the Rapid-Koethen type. The most important structural and strength properties of fibrous semi-products and their composites with bacterial cellulose were determined and compared. It was observed, among others, that composites produced according to the first two methods (i.e. in acetobakter xylinum culture and as a result of the addition of bacterial cellulose to a fibrous semi-product) in general show higher static and dynamic strength indices than semi-products used for composite production. The joining of sheets of two kinds of cellulose (i.e. fibrous semi-product and bacterial cellulose) gives a two-layered composite characterised above all by higher static strength properties than unbeaten pulps and, at the same time, a higher tear resistance in comparison with bacterial cellulose. Joining bacterial cellulose with pulp fibres, irrespective of the joining method, increases the apparent density of the semi-product.