Dissertation > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > General issues > Products and testing

Preparation, Structure and Properties Characterization of TPS/EVA Biodegradable Plastic

Author LiuChang
Tutor LiXinFa; ChenJinZhou
School Zhengzhou University
Course Materials Science
Keywords Thermoplastic Starch Thermo-mechanical properties Thermal degradation Kinetics Water Resistance Biodegradability
CLC TQ320.7
Type Master's thesis
Year 2009
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Diminishing oil resources as well as the growing of the "white pollution" make the oil as the main raw material of plastic faceing a very embarrassing situation.The appearance of starch-based plastic and puting into use alleviate the contradiction effectively,but starch-based plastic also has some diadvantages,such as the high cost,the poor degraded performanceand the mechanical properties in using and the low water resistance.Thermoplastic starch with a lower melting process temperatur can be obtained after the glycerol plasticizing.It can be used in disposable plastic bags and disposable tableware and other fields.The obtained starch plastic film has shortcomings in the production process,such as poor plasticity,poor sealing,poor water resistance,low mechanical properties.In order to improve these disadvantage,we used thermoplastic starch and smaller molecular weight EVA and EAA prepared a series of different resins and resin contenting different starch biodegradable plastics,and the aggregation structure,thermal properties,processing performance,thermo-mechanical properties, mechanical properties,water-resistant performance and the performance of bio-degradable be testing and characterization.Through the research,we found that:1.According to X-ray diffraction pattern analysis and polarizing microscope,we found that TPS and TPS / EVA / EAA biodegradable plastic is still a state of coexistence of crystal phase and amorphous phase,but there is a significant reduction in crystallinity,minimum to 15%.According toDSC,we found that the melting point of TPS and TPS / EVA/EAA biodegradable plasticwas lower than the original starch’s,which was in favor of amending it’s thermoplasticity and heat sealing ability.2.According to infrared spectroscopy,we knew that after plasticized by the plasticizer,starch molecules and the plasticizer molecules and the EVA / EAA intermolecular association through hydrogen bonding,such as the formation of a different molecular structure of the original material.3.DMA test showed that with the increasing of temperature and frequency,TPS / EVA biodegradable plastics and TPS’s temperature which was corresponding to changing peaks and storage modulus were very similar;TPS / EAA biodegradable plastic’s temperature which was corresponding to changing peaks and storage modulus were moving to the high temperature;with the increasing of temperature and frequency,TPS / EVA biodegradable plastics and TPS / EVA / EAA biodegradable plastic’s temperature which was corresponding to changing peaks and storage modulus were moving to lower temperature;All of these showed that thermoplastic starch had a better compatibility with EVA.There was a strong and broad absorption peak of internal friction in the low temperature zone,and glass transition temperature was basically lower than -30℃,which showed that the series of biodegradable starch plastics had good low temperature toughness and cold resistance.4.The thermal degradation of TPS and TPS / EVA / EAA starch biodegradable plastics in the in nitrogen moved to high-temperature with increasing heating rate,and thermal degradation process was divided into two steps.Its thermal degradation curve of the first step in the process complied with the type of slowdown in the mechanism of border control,and the second step complied with the thermal degradation curve of the type of slowdown in the proliferation of three-dimensional(Ginsting-Brounshtein equation) mechanism.The balance thermal degradation temperature ofTPS / EVA / EAA starch biodegradable plastics in the N2 atmosphere showed as below:The first step in thermal degradation:Too= 262.67℃,Tpo = 272.82℃C,Tfo = 309.30℃;The second step in thermal degradation:Too= 428.32℃,Tpo=452.16℃,Tfo= 466.52℃.All of this showed it had a good thermal Stability in the same kind of biodegradable plastics.5.Starch in the case of glycerol as a plasticizer can reduce the glass transition temperature and thermal degradation temperature,the plastic can be processed at about 140℃;EVA and EAA can be used as the strengthening of thermoplastic starch flexibilizer plastic which can improve its mechanical properties,in the actual production its content can be changed based on actual needs;when EAA and EVA compound used in plastics starch,because of its compatibility with plastics starch,it has a better effect than the alone effect of EVA or EAA,the thermoplastic starch obtained has the best mechanical properties in the scope of study.6.With the EVA / EAA content increasing and the composition changes,the two-phase system interfaces are becoming more and more vague,from the definition of"sea-island" structure gradually developed into a vague "sea - the sea" structure.7.The addition of glycerol,not only can improve the thermoplastic starch,but also can reduce balance water absorbption of biodegradable plastic,and with the glycerol content increased,the balance water absorbption gradually reduces,when the glycerol content is more than 25%,the change is less;The addition of EVA / EAA can improve the water resistance.When the water temperature is low,its water balance is significantly lower than thermoplastic starch’s;with the increasingof water temperature,the water absorption of the biodegradable plastics increas gradually; added the EVA / EAA resin,the time required to reach the balance water absorbption of the biodegradable plastic extends effectively.8.After filling soil tested and proven method,it shows that:starch biodegradable plastics have a very good biodegradability in the five-month weight loss of up to 25%~40%;colony grows on the surface of the degradation sample,which indicatg that the campaign materials are in support of micro-organisms growth,its degradation ability is confirmed;with study,we found that the degradation degree of the biodegradable plastics has a great relationship with the thickness of the materials;the microbial degradation happens from the surface to the inside of the sampel.

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