Exploring the macroscopic and microscopic characteristics of rice stalk for utilization in bio-composites.

In the present study, the macroscopic and microscopic structure, chemical composition and mechanical properties of rice stalk were explored and the corresponding interfacial bonding strength with high-density polyethylene (HDPE)/polylactic acid (PLA) were evaluated. The stalk is composed of core and sheath. The epidermal tissue under the outer surface of core is thicker than that of the sheath, which is an important factor contributing to its mechanical properties. FT-IR, SEM and mapping reveals a hydrophobic outer surface of the stalk covered with a waxy and silicon layer. The inner surface of stalk is smoother compared with the outer surface and the core inner surface had the best wettability. The mechanical properties indicate that it is necessary to maintain a longer core of rice straw in composites because of its higher tensile strength than the sheath. The inner area of the rice stalk is exposed because of its stronger shear strength when pulling out of matrix than outer surface. PLA is chosen as the matrix because of its better compatibility with the rice straw than HDPE. In addition, the protruded bumps enhance the mechanical locking with matrix. This study provides strong support for design and manufacture of straw-reinforced green composites. [Display omitted] [ABSTRACT FROM AUTHOR]