NCC/Nano-silver/PLA Composite Film Preparation And Application Of Mulberry Preservation

Nanocellulose is one of the most common materials studied in recent years.It is made by the most common plant fiber, and has excellent performance:high strength, high stiffness, lightweight and biodegradable, can be modified to enhance other materials, with excellent results. Polylactic acid (PLA) is a kind of eco-friendly materials can made by wheat or corn, its degradation products are water and cabon dioxide, because some flaws cannot be mass production. Nano-silver’s antibacterial quality is superior to other silver products, and therefore added to the composite film to improve the material antibacterial properties.In this thesis microcrystalline cellulose (MCC) was used as raw material, using sulfuric acid prepared nanocellulose (NCC), and made acetylated cellulose (ANCC) by adding acetyl groups on NCC to expand its solubility. The composite films with different ratio of ANCC/PLA were prepared by solvent casting method, to find the best mechanical properties, good barrier effect combinations.On the basis of 1%ANCC/PLA film, produce antibacterial films with addition of nano-silver. Characterization methods used in this thesis are:transmission electron microscope (TEM), Fourier transform infrared (FTIR), thermo gravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), mechanical properties, oxygen transmission rate, translucent the performance and haze,etc.The results show that:The NCC and ANCC nanoscale dimensions, a length of about 100 nm, a diameter of about 10-20 nm, NCC thermal performance is lower than MCC and ANCC, and NCC has same crystalline structure MCC. NCC increased crystallinity to 93.16% however ANCC crystallization decreased to 55.42%.A certain amount of ANCC can improve the mechanical and gas barrier properties, almost no effect on the transmittance and haze, heat stability.1%ANCC/PLA film has the best overall performance, ANCC agglomeration effect is not obvious, gets the best mechanical properties, maximum tensile strength is 47 MPa, an oxygen permeation rate of 2.219 ×10-2 cm3/m2×d×Pa, thermal stability the best, high transmittance, low haze.Adding nano-silver can improve the film mechanical properties, thermal stability, barrier properties and antibacterial effect, the combination use of ANCC and nano-silver is better than single adding, but had some influence on the film transmittance and haze. Nano-silver amount of 1% had the best overall performance, ANCC did not agglomerate in the system, had the optimum mechanical properties, thermal stability is excellent, oxygen transmission rate was well. Films had an obvious bactericidal effect against Staphylococcus aureus and Escherichia coli.1% nano-silver PLA films can extend the shelf life of mulberry to 4th day. The sensory evaluation of mulberry, decay index, mass loss rate and titratable acid and other indicators showed that nano-silver added not only reduces the permeability of the material, but also inhibits the growth of bacterias on fruit preservation has greatly improved.