Preparation And Characterization Of Novel Nanocellulose/PLA Composites Via Aerogel Procedures

At present there is significant interest for the development of environmentally friendly polymers and polymer based composites from renewable resources. Worries about greenhouse gas emissions produced by using fossil fuel composed with low degradability of polymers derived from fossil fuel has led to increase in research to develop degradable polymers and composites. Poly(lactic acid) and cellulose are two such examples of degradable polymers that come from renewable resources.The production of nanocellulose with controlled structure from plant resources with facile availability and well sustainability in purpose of application of suitable material for various biomedical applications and energy storage devices is very important in science and engineering. Up to now, many methods for isolating nanocellulose from various plant fibers such as mechanical and chemical procedures had been explored. Furthermore, in recent years, natural fiber reinforced biopolymer nanobiocomposites have attracted great interest, both in academia and industry. In this case, the most important factor in obtaining good fiber reinforcement in the composite is the strength of adhesion between the matrix polymer and the fiber which can be effect on their properties. Whereas the main drawbacks of natural fiber reinforced polymer composites are their hydrophilicity, low weathering resistance that adversely affect the fiber/matrix interface and leads to degradation, and delamination of composites. Since, fibers are hydrophilic in nature, therefore, are inherently incompatible with many well-known and popular in composite manufacturing resins such as PLA. Overall, the main objective is to develop an understanding for relationships between processing, different kinds of material, different concentration of PLA to produce nano/micro cellulose composites and properties of the resulting materials in order to assess the potential of these new nontoxicity, biocompatibility, and biodegradability materials.In this work, firstly, bamboo nanocellulose through mechanical and chemical procedures via four kinds of acid system have been prepared and the effects of both method on the morphology, structure and properties of the prepared materials have been studied,In this case based on the Scanning electronic microscopy (SEM) results both methods work well and both lead to a relatively appropriate degree of fibrillation. The main advantage of mechanical method is that no single chemical additive was used. Also as TGA results, it was noticed that the decomposition temperature of nanocellulose by mechanical defibrillation started at about 240? and that of nanocellulose obtained by different kinds of chemical defibrillation started at about 280? which is indicated that the different kinds of chemical defibrillation compare to mechanical defibrillation lead better thermal stability in the bamboo nanocellulose. Moreover, it was clear that there was no significant difference in the spectra of nanocellulose from different kinds of acid hydrolysis as well as compare to that of mechanical procedure.Secondly, nano/micro fibrillated cellulose (NFC/MFC) networks via aerogel procedure from the different lignocellulosic materials (sugarcane bagasse, bamboo and cedar) have been prepared through mechanical defibrillation methods. Additionally, nanocomposite from resulting materials reinforced by different concentration of PLA (6 and 12%) during freeze-drying have been produced by the following steps procedures. The main objective is to develop an understanding for relationships between processing, different kinds of material, different concentration PLA to produce nano/micro cellulose composites and properties of the resulting materials. The thermal performance of nano/micro cellulose networks, aerogels and biocomposites has been compared with the performance of different cellulosic materials and different concentration of PLA in order to assess the potential of these new nontoxicity, biocompatibility and biodegradability materials.According to the BET results the average fibril size for nanocellulose/PLA composites were approximately 430nm obtained from several SEM images whereas, the width of nanoparticles and pore size distribution shows the void diameters ranging from the single digit nano to micrometer range. The characteristics of nanocellulose/PLA composites was obviously on the increasing thermal stability by introducing 6% concentration of PLA into the nanocellulose/PLA composites.Finally, the highest crystallinity of nanocellulose/PLA composites were found to be around 3.5% for sugarcane nanocellulose/PLA composites with 6% content of PLA. Also, the crystallinity of nanocellulose/PLA composites slightly decreased by increasing more content of PLA to 12% in bamboo and sugarcane bagasse nanocellulose/PLA composites.The pore volume of the nanocellulose/PLA composite aerogels was calculated in range of 73.0-95.0% which is appropriate for such a kind of materials and the specific surface was in range of 2.771 m2/g to 23.014 m2/g by SSA values were obtained in highest point for 12% loading concentration level.