Enhanced Toughness of Reed (Phragmites australis) Stalk with Polyethylene Glycol

Reed (Phragmites australis) is a cosmopolitan grass that is often the dominant species in the ecosystems it inhabits. It is widely used in furniture decoration as reed weaving products. However, the application of reed is limited due to its brittle nature and susceptibility to cracks. To increase the toughness of reed stalk, sodium chlorite (NaClO2) was used to remove the lignin from reed stalk, and then polyethylene glycol with different molecular weights (PEG 600, PEG 1000, PEG 2000, and PEG 4000) was used as a plasticizer. The micromorphology, crystal structure, and surface chemical composition of the modified reed stalk were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The bending strength and dynamic thermomechanical analysis (DMA) of the reed stalk were evaluated. The results showed that the delignified reed stalks plasticized with PEG 1000 or PEG 2000 showed better dimensional stability and toughness, and the smallest elastic modulus (133.268 MPa) was obtained when the samples were treated with PEG 2000. The results of thickness swelling showed that the dimensional stability increased after PEG modification. This research may provide the theoretical basis for the modification of reed stalk.