STUDY ON THE STRUCTURE, COMPOSITION AND PERFORMANCE OF NATURAL POLYMER

Abstract

The sunflower stem core is one kind of natural polymer material. Its structure presents obvious structure gradient from the center to outer part. This article mainly focuses on the relationship between nature of cell walls and the mechanical properties of sunflower stem core. The mechanical properties recorded by the universal testing machine; the cell wall's chemical composition, the cellulose crystallinity and the microfibril angle were measured using the chemical analysis method and X-ray powder diffraction. Research shows that the Young modulus of outer part is nearly 3 times more than that of center part, while the yield strength is 2.5 times more than that of center part. The main components of the sunflower stem core are cellulose, hemicellulose and lignin. The amount of those three components is about 70% of the total dry weight. The contents in the center and outer part are slightly different. The difference of crystallinity and microfibril angle between the center and outer part are quite small, which are 41.39–41.49% and 29.64–27.20%, respectively. Therefore, the results suggested that the nature of cell walls has little influence to the difference of mechanical properties between the center and outer part, and the cell structure is the main reason.