Preparation And Properties Of Starch-based Carbonaceous Materials And Membrane Materials

Starch is a natural polysaccharide, which is easy to get and biodegradable. Starch can be a replacement for fossil energy to prepare functional materials in many fields. Porous carbonaceous materials have many applications such as adsorption, cell electrodes and catalysis. Porous materials with excellent properties can be prepared from starch by carbonization, at the same time they can be composited with nanoparticles to obtain composite materials. Starch can also serve as natural raw of packaging materials. But nature starch exhibit poor water resistance and low mechanical strength which limit its applications. So we need modification to get modified starch.The porous carbonaceous materials were prepared from cornstarch and montmorillonite by the method of sol-gel and carbonization. The resulting composite materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Their adsorption properties were tested with methylene blue and the cation exchange capacity was also investigated. It was found that cornstarch and montmorillonite were composited in the form of intercalated structure. The adsorption data indicated that the composites demonstrated a superior adsorption capacity and a faster rate of adsorption. The porous carbonaceous materials exhibited excellent cation exchange capacity.Potato oxidized starch was prepared using sodium hypochlorite as oxidant. Influences of different reaction conditions on carboxyl content and transmittance of potato oxidized starch were studied including reaction time, amount of oxidant and pH. Besides, we prepared starch films using glycerol as plasticizer and evaluated these films for their mechanical properties, permeability of water vapor (WVP) and oxygen barrier property (OPC). The optimal condition was:7mL of sodium hypochlorite, pH=8.3 and reaction for 2h at 40 ℃. As we can see from the SEM, the particles of oxidized potato starch became smaller and uniform in size and films of oxidized starch were dense and homogeneous after being oxidized by sodium hypochlorite. It was found that this method could also reduce the viscosity of starch. Moreover, films made with oxidized starch had higher tensile strength and better water vapor and oxygen barrier property when compared to native starch films.Cassava hydroxypropyl starch was prepared by epoxy propane in alkaline conditions. We got different molar degree of substitution of the starch by changing the amount of epoxy propane. Compared with native starch, hydroxypropyl starch exhibited better transmittance and anti-retrogradation. The transmittance of starch paste reached 60% and the viscosity was from 300 to 350 mPa·s. After etherification, the tensile strength of starch films was slightly decreased, but the elongation at break was significantly improved. Hence the toughness of the films was greatly increased. The toughness increased to 1.5 times of the native starch films when the molar degree of substitution was 0.17. The hydroxypropyl starch films avoid the shortcomings of native starch films, such as brittleness and poor flexibility. The hydroxypropyl starch films showed higher barrier property and more homogenous and dense structure.