Two Modified Treatment Methods for Pretreated Corn Stalk and Its Composites with Modified Lignosulfonate
Keywords:Corn stalk, Pretreatment, Laccase-vanillin system, Polyethylenimine-glutaraldehyde, Ultrasound, Chemical and mechanical properties
Effects of two different modified treatments were investigated relative to the chemical and mechanical properties of pretreated corn stalk particles and their composites prepared with a modified lignosulfonate (ML) binder. Corn stalk particles (CP) first were prepared by treating corn stalk particles with oxalic acid in ultrasonic conditions (pretreated corn stalk particles, PCP). These particles were then modified by treatment with either laccase-vanillin system with ultrasound (LU) or polyethylenimine-glutaraldehyde with ultrasound (PU), and the surface chemistries of the modified PCP and mechanical properties of LU-PCP/ML composites and PU-PCP/ML composites, such as modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), 24-h thickness swelling (TS), and crystallinity were compared. Both modified treatments dramatically enhanced the mechanical properties of the composites. The MOR, MOE, and IB of the PU-PCP/ML composites were improved by up to 148%, 81%, and 62%, respectively, compared to LU-PCP/ML. Moreover, the 24-h TS of the LU-PCP/ML composites was reduced by 16%. These results show that the pretreatment method of CP and ultrasonic collaborative treatment of PCP can effectively improve the properties of its composites. Modified PCP with PU was more favorable for surface chemical and mechanical properties.