| Polylactic acid (PLA) is one kind of biodegradable environmentally friendly products after fully biodegradable polymer, which also has a number of good features such as high mechanical strength, excellent transparency. However, there are some limitations. Compared with the petrochemical plastic, PLA is crisp and has slow crystallization as a kind of linear homopolymer. Therefore, this article adopts the method of fiber composite toughening. Respectively, polylactic acid was enhanced by leather fibers, expandable graphite(G) or carbon nanotube (PLA/G/MWCNTs), with melting method or solvent method to prepared a series of PLA composite materials, for their mechanical and crystalline performance. Their thermal stability was also studied in this experiment.Firstly, poly (lactic acid) and leather powder composite materials were prepared by using silane coupling with melting or solvent method. Fourier infrared spectroscopy (FT-IR), scanning electron microscope (SEM), differential scanning calorimetry (DSC), polarizing microscope (POM) and thermal gravity analysis (TGA) measures were all used to characterize composite materials. In order to exploring the silane coupling agent treatment on the properties of polylactic acid/leather powder system, SEM was used to study the microstructure and surface properties of polylactic acid/leather powder system. And finally polarizing microscope (POM) was applied to obtaining photos for the crystallization performance of the composite material. Results showed that coupling agent silane were grafted on the surface of the large molecules polymer and SLFs, and the composite material prepared by superiordid prepared much better than the one by melting method in terms of bending modulus. Compared with PLA/SLFS, when scrap leather fibers(SLFs) content weight was5%, PLA polymer adding silane modified scrap leather fibers (MSLFs) were greatly improved in modulus of bending modulus and impacted to a certain degree, meanwhile the crystallization rate constant was decreased. Based on fracture surface photos taken by SEM, MSLFs, becoming the PLA crystallization nucleating agent according to the results of crystallization pictures taken by POM, were spread evenly in the PLA matrix as grafting,. Within the scope of this study, compared with pure PLA, PLA who was grafted, whatever prepared by melting method or solvent method, the SLFs/PLA composite materials performed without significant change in glass transition temperature,(Tg) and melting temperature (Tm) since SLFs joined in PLA matrix material when taken thermal stability test by thermogravimetric measurements.The second experiment was about modified PLA with nanometer materials. The present study prepared a battery of PLA composites in melting and mixing process, within the expanded graphite, obtained by adopting the method of thermal reduction oxidation method preparation, or a mixture of graphite/carbon nanotubes, through the ultrasonic mixing method. In order to get composites properties tested, Poly (lactic acid)/expanded graphite composits and PLA/G/MWCNTs nanocomposites were measured by FT-IR for grafting, TGA for thermal stability, DSC and PLA for crystallization, and SEM for microstructure ofln this study, there was a discussion on the dosage, the process and the structure of graphite and multi-walled nanotubes, who might play greatly effects on properties of nanocomposites. Meanwhile, there was also an exploration related to the possibility of modification of poly (lactic acid)/expansion graphite oxide/carbon nanotube composite system, and the preparation method. Research results showed that the PLA/G/MWCNTS was better than the expansive graphite oxide with polylactic acid composite material, in the mechanical properties, crystallization, thermal stability and performance. Particularly, when the mass fraction of G/MWCNTS25system was0.3%of composites, the bending modulus was2.3MPa, and the crystallization rate constant was0.46, respectively. |
PDF Full Text Request