The Preparation, Properties And Characterizations Of Starch-based Biomaterials

Recently,natural biomaterials have received increasing attention in many counties and by a number of scientists,especially the topics of energy crisis aggravation and environmental pollution.Starch,as an abundant raw material,has been used in the field of biomaterials,but the application of raw starch in the preparation of starch-based biomaterials such as packaging films and agricultural plastic films is limited because of its multi-hydroxyl and regular crystal structure of native starch gragules.In this paper, full-biodegradable films,agricultural plastic films,and pet toys were prepared by using starch with different sizes,modified starch and intensifiers.The structures of various biomaterials were characterized by Fourier transform infrared spectrometry(FTIR), differential scanning calorimetry(DSC),X-ray photoelectron spectrometry(XPS),X-ray diffraction(XRD),and scanning electron microscopy(SEM).And at on time,the mechanism of starch modification was discussed.The main contents,results and conclusions of thesis are as follows:1.The mechanism of modified starch-based biodegradable packaging film using nano silicon dioxide(nano-SiO₂)The microstructure,atoms constitute aggregation,and thermal properties of a modified starch-based biodegradable packing film with the addition of nano-SiO₂ were characterized and analyzed.The mechanism of modification was also discussed by FTIR, XPS,XRD and DSC:not only extensive intermolecular hydrogen bonds but also C-O-Si bonds were generated among nano-SiO₂ and starch-PVA;therefore,a dense network structure was formatted among the molecules of nano-SiO₂,starch,and PVA.Further results revealed the essential reasons for the improved properties of the ST-PVA film using nano-SiO₂.2.The preparation technology for a starch-based biodegradable packing film modified by nano-SiO₂The paper systematically studied the dispersion method of nano-SiO₂ and the plasticization and crosslinking technology of starch.The results indicated that ultrasonic dispersion was a good method for dispersing nano-SiO₂.Nano-SiO₂ could homodisperse in ST-PVA films under the condition of pulsing on 3s,pulsing off 2s,and 50%swing intension for 12 min.Since the optimum content of nano-SiO₂ was 1.5%, then the water resistance,tensile strength,breaking elongation,and environmental suitability of ST-PVA films could be obviously improved.The optimal contents of compound plasticizers were determined with water(4%),glycol(3%),and glycerol (9%),respectively by employing orthogonal experiment and comprehensive assessment method in fuzzy mathematics.Glyoxal was an effective crosslink agent to starch.The optimal crosslinking conditions are the following:glyoxal content of 2.5%;pH 9; reaction temperature at 80℃;and reaction time of 30 minutes.The mechanical properties of the starch-based biodegradable packing film reached the Chinese standard of GB/T 4456-1996(the Chinese standard of polythene packing film),and these products had great environment suitability and biodegradability.3.The properties of micronized starch and its application in biodegradable filmTo improve the miscibility of starch and PCL,micronized starch was prepared by an ultrasonic airflow pulverator,then it was hydrophobically modified.The results showed that the particle size of starch decreased obviously,and the surface became irregular.With the micronization degree increasing,the hydrogen bonds were fractured within starch molecules,the surface activity of the starch molecules was increased,and crystallinity was decreased.However,further research indicated that excessive micronization would make aggregate starch.Micronized starch of 300mu was suitable considering the production cost.The conditions of double plasticization modification determined that the content of polyethylene glycol(PEG)(Mn=6000) as a PCL plasticizer was 6%according to the weight of PCL,and the optimal content of triethanolamine was 4%,polyglycol (Mn=400) 3%,and glycerol 2%as starch plasticizers according to weight of ST, respectively.The field experiment results of sweet corn crops showed that the starch-based biodegradable films,which could substitute for the non-degradable PE film, had effects on performance in terms of heat retention,water retention,preferable biodegradability,and increased yield.4.The diesterified starch and its application in pet toyThe microstructure,thermal properties,and crystal structure of diesterified starch, namely,the starch of phosphorylation and acetification,were studied systematically.The pet toys were prepared by further treatment in terms of enhancement,plasticization,and crosslinking.The results indicated that the transparency rate was improved,and the freeze-thaw stability and degree of expansion were also increased.The crystallinity of diesterified starch decreased compared with natural starch.However,water retention and the heat-resistant stability of starch were improved when the content of the compound plasticizers of water and glycerol were 12%,respectively,the crosslink agent of polyphosphate was 2%,the intensifiers of glutin were 20%according to the weight of double-esterification starch,and the hardness and elasticity of the pet toy were 14042.55g and 0.936,respectively.The creative achievements of this work were as follows:1.Starch was modified by nano-SiO₂ with high surface activity which was dispersed by ultrasonic dispersion,and the properties of the starch-based packaging film were improved.Furthermore,it was found that a hydrogen bond and a chemical bond exist among nano-SiO₂ and starch-PVA.2.According to thermodynamic principles,the crystallinity and clustering behavior of starch particles were decreased.The disordering and reactivity of starch were increased by mechanical force action.Micronized starch was yielded through the modification of hydrophobicity and double plasticization,and the full-biodegradable films with good mechanical and degradable properties were prepared using the film blowing method.3.Starch-based edible pet toy was prepared using diesterified starch,The texture properties of starch pet toy were characterized by a texture analyzer.