BIOCATALYTIC MODIFICATION OF CORN STARCH TO IMPROVE THE PHYSICAL AND MECHANICAL CHARACTERISTICS OF CARDBOARD
Introduction. In recent years in connection with the expansion of paper and cardboard production, the requirements for physical and mechanical properties of these materials have increased due to the conditions of their production and applying. However, the strength of cellulose-based fibrous materials is significantly less than the strength of the fibers from which they are made, since the bonds between the single cellulose fibers in paper and cardboard are weak. The surface treatment of paper and cardboard with starch containing a lot of linear polymers will increase the deformation properties of these materials, because these polymers can penetrate into the structure of paper and cardboard, fill the inter-fiber space and form a greater amount of hydrogen bonds among the single cellulose fibers. The goal of this study was to determine the effect of amylose and other linear polymers amount in the corn starch on the cardboard physical and mechanical properties. Starch paste containing dry matter in an amount of 2% with the added enzyme preparations was incubated for 3 hours at a temperature of 50 ° C with constant stirring. Then, the starch paste was applied to the cardboard surface and dried by the convective method. Determination of the deformation properties of materials was carried out with obtaining of the load-elongation indicator diagram and the stress-strain dependence diagram. It is known that the percentage of amylose in corn starch is small. However, a three-hour treatment of starch paste with the pullulanase enzyme allows to increase the content of amylose and other linear polymers in the paste in 3 times. It is possible to conclude that the effect of corn starch enzymatic treatment on the cardboard deformation properties are interrelated with the content of linear polymers in the chemical composition of starch. These linear polymers are responsible for the formation of additional cross-links among cellulose fibers. Starch paste treatment with the pullulanase allows to increase the percentage of linear biopolymers in the starch and to obtain a cardboard with the increased structural rigidity both in the longitudinal and transverse fiber directions.