Study On The Preparation And Properties Of Nanocellulose Crystal/Poly (Lactic Acid)Biodegradable Composites

Nanocellulose crystal (NCC) becomes an ideal filling reinforcing material of composite polymer materials because of the light weight, low price, and the properties of its excellent biodegradability, renewability and excellent mechanical properties. Nanocellulose crystal is prepared by acid hydrolysis microcrystalline cellulose. NCC modified by grafting and coupling agent to achieve better dispersion and compatibility of poly (lactic acid)(PLA). The composite film is preformed by the mixing mill and the vulcanizing machine, and the best film preparation process parameters was optimized through comparing the film mechanical properties, barrier properties, and thermal properties. The PLA film and NCC/PLA film were degraded by the acid solution, alkali solution, and ultraviolet light irradiation. The degradation mechanism was researched by gravimetric analysis, scanning electron microscopy (SEM) observation and X-ray photoelectron spectroscopy (XPS) analysis of the degraded film. The results as follows:(1) Acid hydrolysis microcrystalline cellulose to get the nano-cellulose, the particle size of which are most less than100nm, which fits the nanoscale requests; the infrared spectra results showed that the graft modification of nano-cellulose and coupling agent modified nano-cellulose molecular structure in each group have absorption peaks in corresponding position, indicating that the two modified methods all succeed.(2) By studying the film properties which can be influenced by the four parameters——the NCC content, the temperature of mixer, platen time and the modified methods of NCC, the results show that the optimal film prepared process parameters are:the NCC content of5%, mixer temperature of190℃, vulcanizing machine platen time of4minutes, NCC modified by adding the silane coupling agent kh560. Under these conditions, the comprehensive performance of the film is optimal.(3) TGA results showed that the film in alkaline environment degraded fastest and in acidic conditions faster, slower rate of degradation in UV irradiation; and NCC/PLA film rate of degradation is slightly larger than that of PLA film, indicating that NCC enhance the degradation performance of the composite film. XPS results suggest that the PLA films depredated in acidic conditions the—C—O—,—C=O firstly depredated resulting in the O/C decreasing, the—C—C—degradation rate in other conditions is relatively fast, causing the increase of O/C; the NCC/PLA film degraded in the three conditions, the degradation rate of—C—C—is relatively faster causing the increase of O/C.