Recently, Prof. Yano and his research team presented a completely transparent crab-shell, keeping its original shape and substantial morphological detail. An important application of the finding is demonstrated as in the micro- to mm-scale nanostructured crab shell chitin particles that are used to process transparent nanocomposites. The incorporation of chitin particles not only retains the transparency of the matrix resins but also drastically reduces the CTE of the polymer. Moreover, the optical transmittance of the composite is stable over a large range of temperatures despite significant inhomogeneity at the mm-scale and large changes in the refractive index of the resin in its isolated state. Encouraged by the transparent crab powder sheet, the research team undertook the preparation of optically transparent pulp-fiber composites. The pulp-fiber sheet was acetylated, with care taken to maintain a never-dried condition, and it was then dried and impregnated with acrylic resin. Despite the heterogeneous paper structure, the sheet became transparent (see the figure below). Since the nanofibrillation process is not necessary and the dewatering speed of the acetylated pulp fibers is very high, the production efficiency of the optically transparent composites improved drastically.
Fig. 1 Chemically modified pulp fiber sheet (left) and after resin impregnation (right)