Study On Propeties Of Polylactic Acid And Nanocomposite Of Polylactic Acid

Poly (L-lactic acid) (PLLA) was a typical green polymer since it wasproduced from renewable resources, corn starch, and could be degraded tolactic acid, then became carbon dioxide and water under compost conditionafter usage. PLLA was nontoxic, bioabsorbable and biocompatible. It also hadgood mechanical properties and could be processed by traditional processingmethods. It would be possible that PLA take place of some current polymersof petroleum base. Researched the factors that will influence on properties ofprocessing in processing would be propitious to apply and process polylacticacid. The product of polylactic acid that act as current polymer was littlebecause the stress, brittleness, barrier properties, heat-resistant properties ofpolylactic acid limited the field of application, it will improve the propertiesthrough nanometer material modification. The degradable law of PLA wasresearched will be propitious to apply it and dispose the waste.It was investigated that water content, shear stress and processingtemperature affected on properties of processing of polylactic acid.Researched the thermal kinetics of polylactic acid by the curve of TG-DTG,by right of the method of Friedman and Ozawa, it was found that theactivation energy was 118．36 kJ/mol and 128．4 kJ/mol, reaction order n=1．Polylactic acid/nanometer calcium carbonate, clay, silicon dioxide andtitanium dioxide composites were produced by a twin screw extruder,through mechanical test, water vapor permeability, vicat softening point test,it was found that nanometer calcium carbonate that was disposed by stearicacid composites could rather enhanced strength, tough, water barrierproperties, and thermal stability of polylactic acid; scanning electronmicroscopy (SEM) showed Nanometer calcium carbonate was dispersedevenly in nanocomposites when the content was less than 9wt%; differentialscanning calorimeter(DSC), Wide-angle X-ray diffraction(WXRD) and polarizing microscope(POM) indicated crystalline degree increased andcrystalline temperature, crystalline time, crystalline size decreased ofpolylactic acid when nanometer calcium carbonate was filled in.The degradable law of PLA was researched through experiment ofenvironment, it was found that the degradable speed of mesomer polylacticacid(PDLLA) was faster than leveisomer polylactic(PLLA), the degradablespeed became more fast when polyethyleneglycol was interfused PLA. Thedegradable speed was the most rapid when PLA was put in alkaline buffersolution, and the degradable speed was the most slow when PLA was put inacidic buffer solution.