Effect of citric acid on properties of (3-mercaptopropyl)trimethoxysilane modified xylan/polyvinyl alcohol composite film

In order to improved the defects of xylan-based films such as strong hygroscopicity and low mechanical strength, a collaborative modification protocol of citric acid (CA) and MPTMS-modified xylan (MSMX) was proposed. Xylan from sugarcane bagasse was firstly modified by (3-mercaptopropyl)trimethoxysilane (MPTMS), and then citric acid was used as crosslinking agent or plasticizer. The MSMX/PVA/CA films were prepared by casting method and the effects of citric acid content on the structure and packaging performance of the composite film were studied. The results show that with the increase of CA content, the cross-linking degree of MSMX/PVA/CA films increases and the internal structure becomes more dense, which lead to the significant enhancement of mechanical properties and water vapor barrier performance. Meanwhile, the hydrophobicity of the MSMX/PVA/CA films is improved with the decrease of hydrophilice groups. When CA content is 20% (mass fraction), the tensile strength of MSMX/PVA/CA film is 41.8 MPa, water contact angle is 82°, and the water vapor transmittance reaches 2.79×10-13 g·cm·cm-2·s-1·Pa-1, which is 37.79% lower than that of film without CA. The addition of CA improves the moisture barrier properties and mechanical strength of xylan composite films, which makes it have a potential application in the field of food and drug packaging.