*3.3. Morphology*

SEM micrographs of pea fibers before and after ISMS treatments are displayed in Figure 3. Native PeaF displayed compact and thick blocks, and some fiber blocks with a smooth surface were distributed (Figure 3A). ISMS treatment could effectively alter the microstructure of the pea fiber, and compared to native PeaF, the structure of the ISMS-treated PeaF became looser and thinner. There was a flattened structure with some band-like sheets at the edge for Pre-PeaF (Figure 3B). After ISM treatment at low pressure, the fibers were highly distorted, and ISM-60 PeaF was tightly packed into a flat plate with a large surface (Figure 3C). When the treatment pressure reached 90 MPa, the fibers were torn into flat lamellas with interwoven filaments (Figure 3D). Furthermore, the appearance of a flimsy and crimped flake-like structure was observed for ISM-120 PeaF (Figure 3E) and ISM-120-T2 PeaF (Figure 3F), implying that a greater degree of breaking pea fiber was induced by high treatment intensity. The change of SEM morphology was more clear than the observation of CLSM images to illustrate the effect of ISMS treatment on the pea fiber, further implying that mechanical effect initiated by ISM could destroy and break the architecture of the pea fiber. High-density energy could be produced by ISM treatment owing to powerful shear, turbulence, high-velocity impaction, high-frequency vibration, instantaneous pressure drop and cavitation forces which contributed to disrupt the pea fiber. As ISM treatment intensity increased, different degrees of damage and disruption forms of the fiber were observed. It was possible that the varied strength of mechanical forces exerted an effect on tearing the fiber when different treatment intensities were imposed. The appearance of a multi-branched flake-like structure most likely provided an explanation for the changes in the absorption properties of the fiber.

**Figure 3.** SEM micrographs. Magnification was 800×.
