Study On The Biodegradation And Desizability Of Grafted Starch Sizes

In order to study the intrinsic relationship between the chemical structure of the grafted starch and the aerobic biodegradability of the grafted starch, it lays a foundation for the design of the molecular structure of environment friendly grafted starch size. The graft copolymerizations of granular cornstarch with acrylic acid(AA), acrylamide(AM), methyl acrylate(MA), ethyl acrylate(EA), butyl acrylate(BA), methyl methacrylate(MMA) and butyl methacrylate(BMA), respectively, were undertaken in aqueous dispersion using Fe2+-H2O2 initiator to obtain grafted starch sizes with different chemical structure. The structure, morphology and thermal stability of the starch graft copolymers were characterized by infrared spectroscopy(FT-IR), scanning electron microscopy(SEM) and thermogravimetric analysis(TGA). The relation between chemical structure of grafting branches and aerobic biodegradability of grafted starch sizes was examined in terms of COD, BOD5 and BOD5/COD. And the effect of grafting ratio on the biodegradability of grafted starch was studied via varying their grafting ratios. The results showed that the graft copolymerization changed the structure, morphology and biodegradability of starch and was able to improve the thermal stability of starch. The biodegradability of grafted starch decreased with the increase in the number of carbon atoms of alkyl the various units of starch grafted polyacrylate branches. The presence of ?-methyl in the units disfavored the biodegradability while a negative correlation was presented between the biodegradability and grafting ratio as the ratio increased.The sizing properties of grafted starch have been conducted by many researchers. As a temporary binder, the sizing agent not only has a good performance in sizing, but also, it is easy to be desized. However, previous studies have not been carried out on the desizing properties of the grafted starches systematically. So it changes the grafting monomer in this study, a series of similar grafting ratio of grafted starches with different molecular structure were synthesized to examine their influence on the desizing properties of grafted starch. The structures of starch graft copolymers were characterized with X-ray diffraction(XRD). The desizing properties of grafted starch were studied by using three kind of desizing methods namely enzyme desizing, alkali desizing and oxidative desizing. Also, the relationship between the desizing properties of grafted starch and the molecular structure of grafting branches, the effect of molecular structure of grafting branches on swellability, moisture regain of grafted starch film and the time required for breaking the film in water were studied. In addition, S-g-PMA and S-g-PAM with different grafting ratios were prepared by varying the amount of monomer charged. The regularity of their desizability and the variation of the grafting ratio were also discussed. The investigation results showed that the crystallinity of starch film was decreased when graft modification to starch. The hydrophilic grafted branches introduced were able to improve the desizability of starch, increased the water-solubility of starch film, the swellability of starch films were increased. The time required for breaking the film in water decreased, moisture regain increased. However, the introduction of hydrophobic grafted branches, reduced the desizability of starches, decreased the swellability of starch films, increased the time required for breaking the film in water, reduced the moisture regain of starch films. The desizability of grafted starches was decreased with the increasing of hydrophobicity of grafting branches. Hence, it is helpful to design and produce grafted starch sizes with easy desizability when we select the suitable monomer and its amount. Finally, by a comparative experiment of S-g-PAM, S-g-PMA with S-g-PEA, the sizing properties of S-g-PAM and S-g-PMA were evaluated. The results showed that S-g-PAM was able to enhance the tensile strength and abrasion resistance, and display low loss in elongation at break.