Research Of The Mechanism For Weakening The Hydrogen Bond In Starch

Starch Plastics is an important measure of solution white trash.It has become a research hotspot, for wide variety of sources and degradability. Due to the defect of starch itself, so it hard to process, affecting the application process of starch as biodegradable plastic. It is a better method for adding accessory ingredient to improve the processability of starch. However, many factors that affect the starch plastics are not very definite at the present time. For this reason, this article explores several aspects as follows:First, adding some different types and different amount of plasticizer into the natural starch, in the mixer torque rheometer melt blending, then press into a standard sample by vulcanizing press.Using Fourier transform infrared spectroscopy to study hydrogen bond between plasticizer of the starch and glycerol, urea etc. and find that in starch form hydrogen bonds mainly is the oxygen atom of C-O-C group and the hydrogen atom of the C-O-H group ; and it will form hydrogen bonds between excessive plasticizer, and reduce hydrogen bonding of plasticizer and C-O-C ,then compared with the amide polyol plasticizer plasticizing effect of plasticizers obtained amide plasticizer and starch can form more stable hydrogen bonds, weakening the effect of hydrogen bonds in the starch is more evident.Using X-ray diffraction, qualitatively study and compare the crystallization of the natural starch and plasticized thermoplastic starch plastic. A model for the crystallization of natural starch, because there are a large number of hydrogen bonds formed. Adding plasticizers no crystallization occurred after processing, which is due to the amide plasticizers can form stronger hydrogen bonds with starch, comparing with plasticizer of glycerol and other polyols,the molecular interaction of starch is so small and the starch molecules is so supple that it's not easy to left residual stress to produce induced crystallization in the machining process. By scanning electron microscopy (SEM),observe the fracture surface of the sample , using differential scanning calorimetry (DSC) analysis the glass transition temperature and the viscous flow temperature of thermoplastic starch materials, to find that the T g and T f of the amide plasticizer material is lower than the polyol plasticizer. By thermal gravimetric analysis (TG) of the thermal stability of plasticizer plastics material and find that the starch amide plasticizer plasticized plastic thermal decomposition temperature is much higher than the polyol plasticizer plasticized materials, and weight loss to be wider platform. Therefore, compared to polyol plasticizer, plasticizer amide molecules in the starch tends to disorder because of oxygen double bond to oxygen atoms as the electron density increases, the hydrogen bond acceptor of greater electronegativity, they weaken the starch more hydrogen bonds, and with starch to form more stable hydrogen bonds.In order to solve the problem of starch hard to process, the mainly ploblem is how to weaken the hydrogen bonds in the starch. Through using substance with strong electronegative atom and strong positively charged hydrogen atom, And using some substances with larger electron density as plasticizers, it is able to make a good role with starch, and weaken the hydrogen bonds in starch. And some small molecules plasticizers with good penetration (such as: water) also to appear a strong plasticizing capacity with starch.