Abstract
In order to clarify the application possibilities of okara, which is a byproduct of tofu production, as moisture absorbing biomass filler, polypropylene (PP) sheets mixed with okara at 33, 40, 51 and 60 wt% were prepared by compression molding. Mechanical properties, including the yield stress and yield elongation, of these sheets decreased with increasing okara mix ratios due to low adhesive strength between okara and PP. In addition, the decrease of elastic modulus was particularly remarkable in PP sheets mixed with 60 wt% of okara because of crack formation on the sheet surface. However, hygroscopicity was improved by mixing okara because the amount of adsorbed vapor increased with higher okara ratios. Furthermore, when these okara mixed PP sheets were kept at 40℃, 93% R.H., mechanical properties and dimension stability decreased while the amount of adsorbed vapor increased significantly in the first 7 days due to voids forming on the sheet surface. However, changes in these properties were considered to be within an acceptable range in practical use. Finally, it was thought that okara mixed PP sheets could be used as a packaging material that suppresses moisture absorption by the contents.
