| Summary: | 博士 === 大同大學 === 材料工程學系(所) === 97 === In this research, poly(lactic acid)/poly(vinyl alcohol)/maleic anhydride-g-poly(lactic acid)(denoted as PLA/PVA/MA-g-PLA) blends were prepared by compounding to study the thermal properties. The FTIR and μ-FTIR were employed to demonstrate the grafting of MA on PLA, and the grafting degree of MA-g-PLA was 1.625×10-4 mol/g measured by a titration method. A thermal analyzer, DSC, showed that the PLA/PVA blends should be a meta-stable system. However, the affinity from the compatibilizer MA-g-PLA could make the PLA/MA-g-PLA/PVA blends become a stable system. Besides, the crystallinity of PLA blends appeared a significantly increase from amorphous state to crystallinization of 33% as addition of compatibilizer was 2.5g. There were two melt peaks at 147℃and 153℃ to show the sheet shape β-phase and helix shape α-phase. The reason was confirmed that PLA resulted in more β-phase crystallization by adding the compatibilizer. A weak crystalline peak was appeared in the blend after a annealing treatment at 80℃. Then, some strong crystalline peaks were observed when the annealing temperatures were from 90℃ to 130℃. The XRD results demonstrated the onset temperature of recrystallinization of PLA blends.
In previous studies, starch/glycerol(GA) blends presented those characters such as low tensile strength、low elongation and poor melt flow ability. Therefore, aim of this study was to improve above disadvantages by modifying starches. A variety of modified starches, which was treated by hydrolysis and acid hydrolysis(0.1M、0.3M、0.5M citric acid solution). Tensile strength of blend with 50wt% hydrolysis starch was 3.75MPa, but the elongation could reach to 225%. The mechanical properties of starch/GA blends were obviously improved by adding modified starch. The MFI of blends increased to 300g/10min when the addition of acid hydrolysis starch (0.3M CA-starch) was 70wt%. The melt flow ability of blends had a significant improvement. The crystallinty of 0.1M CA-starch presented a decreased and then crystallinity of modified starch increased as acid solution was 0.3M and 0.5M. The crystalline behaviors of modified starches were also studied by ultrasonic treatment at 46 KHz of frequency. The ultrasonic treatment could prove the energy to break hydrogen bonds between molecular chains, and the melt flow ability of blends was obviously improved. The MFI of blends increased from 0.5g/10min to 5.5g/10min when the time of ultrasonic treatment increased from 0min to 10min. The SEM micrographs of blends also showed the growth process of fungi on the surface of specimens during the biodegradation.
Calcium carbohydrate which was treated by titanium coupling agent ( denoted as Ti-CaCO3 ) was also added to improve hydrophilicity and melting flow behavior in the starch blends. SEM micrographs showed that there were a lot of holes in the native starch/ hydrolysis starch blends. Moreover, Ti-CaCO3 dispersed uniformly in the native starch/ hydrolysis starch blends when the addition of Ti-CaCO3 reached to 25wt%. The enthalpy of blend with 5wt% Ti-CaCO3 decreased from 213J/g to 109J/g in the DSC measurement. The reason was considered that coupling agent on the surface of CaCO3 plasticized excessively molecular chains. The blend also presents a high MFI (melt flow index) to 70g/10min when the addition of Ti-CaCO3 reached to 25wt%. Furthermore, the blends with Ti-CaCO3 presented an excellent hydrophobility. Water contact angle of blend increased from 60° to 95° as the addition of Ti-CaCO3 was 15wt%. Beside, biodegradation of the blends were not affected by adding Ti-CaCO3. Weight loss of native starch/hydrolysis starch blend with Ti-CaCO3 was between 50% and 75% after the biodegradation for one week.
|
|---|
