Long-Chain Silane-Modified Cotton Straw for the Preparation of Polyethylene Composite Board

Abstract

Biomass-plastic composites (BPC) have become prominent for achieving high-value biomass applications and reducing reliance on traditional polymers. Silanization was a powerful method to improve the interfacial compatibility between biomass and plastics. In this study, dodecyltrimethoxysilane (DDTMS), a long-chain silane coupling agent rarely used to modify biomass, was selected to adjust the contact angle of cotton straw (CS), and the process was optimized using the Box–Behnken design (BBD). All contact angles of the modified CS (MCS) exceeded 117°, surpassing those achieved with short-chain silane coupling agents. Analysis of variance from the BBD highlighted the significance of the CS/DDTMS mass ratio and reaction temperature in increasing contact angles. Under optimal conditions, the contact angle of MCS reached 132°. Silane functionalization also enhanced the thermal stability of CS. The MCS with higher contact angles could be used to produce MCS/polyethylene composite boards that demonstrated significantly better thermal stability than native CS/polyethylene boards. The maximum tensile strength of these boards was 24.63 MPa with a strain of 25.3%. Additionally, MCS/polyethylene composite boards exhibited improved resistance to swelling and lower hygroscopicity compared with CS/polyethylene boards. These findings highlighted the potential of DDTMS-based silanization as a robust strategy for developing high-performance BPC.