Preparation,Modification And Application Of Polylactic Acid Composite Based On Improved Processing And Mechaniclal Properties

As a good biocompatible polymer with good strength and modulus performance,PLA will be used very widely in the medical area,environmental area and industrial fields.This thesis focuses on improvement of processability and usability as well as application of PLA,designed and prepared polylactic acid/polyethylene glycol(PEG),polylactic acid/multi-walled carbon nanotubes(MWCNT)/polyethylene glycol and polylactic acid/hydroxypropyl methylcellulose(HPMC)/polyethylene glycol composites.The structure and properties of three composites were determined and analyzed,results are as follows:Universal tensile testing machine was used to test mechanical properties of composites obtained by different molecular weight of PEG blended PLA.We found that composites have good flexibility.Using polarizing microscope to observe the slices of test samples we found PEG is good compatible with PLA.Futhor Differential Scanning Calorimetry(DSC)shows that adding PEG decrease the glass transition temperature(T_g)of PLA,that was why PLA had excellent flexibility.So PLA/PEG composites can become the basis material of later research.Added HPMC and functioned MWCNT into PLA/PEG respectively to make a contrast,and study them effect on all performances of PLA/PEG composites.Compared with HPMC,MWCNT had better dispersity in PLA/PEG composites.That's one of the reasons that composites had increased performance.Further results of DSC exhibited that there is natural synergy between PEG and MWCNT results the transformation of crystallization behavior.Although rheological properties confirmed that increasing the weight ratio of MWCNT will destroy the collaborative network of PLA/PEG composites,all the composites of rheological properties still better than pure PLA.From macro and micromechanical properties we can learn that the mechanical properties of PLA composites improved significantly.According to micro mechanics performance testing,it is further confirmed that composites are possible to become microneedle materials.The result of microlevels of test samples displayed those different levels of dispersion and incorporation in micro injection molding products,which is the responsible for high performance and easy processing of PLA composites.Composite materials design provided the resource in microneedle processing.CAE software Moldflow was used to simulate the flow behavior of the micro injection molding microneedle products,especially for microneedle products with different shapes and different feed stages.According to filling simulation,we can develop a better understanding of microneedle products with different shapes and different feed stages have the influence onfilling stage.Then we used Moldflow simulated results to search the optimal technological condition and designing scheme,and adopt UG software to design micro injection mould for the next polymer processing to lay a solid foundation.