Thesis
Grafting modification of polylactic acid and its application for compatibilization of polymer blends
Washington State University
Master of Science (MS), Washington State University
2016
Handle:
https://hdl.handle.net/2376/102214
Abstract
Polymer blending is the most often used approach to achieve tunable performance for polylactic acid (PLA) materials. However, poor interfacial interaction and low compatibility exist between PLA and most other polymers, leading to unsatisfactory performance of the resulting polymer blends. To address such problems, functionalization of PLA via grafting reaction and use of the functionalized PLA as compatibilizer for PLA blends is an effective route. In this thesis research, PLA was functionalized by free radical initiated melt grafting reaction. The effects chemical structure of monomer, reducing agent and St co-monomer, on grafting efficiency were investigated. Six monomers of which two were prepared by ourselves were studied for the grafting reaction. The results indicated that grafting efficiency was highly dependent on reactivity and physical state of the monomer. To solve the problem of low reactivity caused by "cage effect", a novel redox initiation system was employed by combining organic peroxide with a reducing agent - Sn(Oct)2. Addition of Sn(Oct)2 in the initiation system resulted in great increase in grafting efficiency. By introducing St as co-monomer, grafting efficiency was dramatically improved for maleic anhydride (MA), itaconic anhydride (IA) and 4-methacryloxyethyl trimellitate anhydride (META), but decreased for the other monomers. Maximum grafting efficiencies were observed for MA and IA when Sn(Oct)2 and St were used together. In addition, molecular weight of the grafted PLA was also affected by these three factors. Particularly, initiation with the redox system resulted in large reduction in molecular weight for the grafted PLA. Among the six anhydride grafted PLA polymers, MA grafted PLA (PLA-g-MA), was selected for investigating reactive compatibilization for PLA blends. Again, Sn(Oct)2 was used for catalyzing the interaction between maleic anhydride grafted polyethylene (PE-g-MA) toughener and ethylene-methyl acrylate-glycidyl methacrylate (E-MAe-GMA) compatibilizer. The blend systems compounded with single- (E-MAe-GMA) and dual-compatibilizer (PLA-g-MA and E-MAe-GMA) were prepared. The change in rheological behavior indicated that epoxy-anhydride curing reaction was successfully catalyzed by Sn(Oct)2. Studies of morphological structure and mechanical properties demonstrated that PLA-g-MA could further enhance interaction between the crosslinked ethylene dispersed phase (PE-g-MA/E-MAe-GMA) and PLA matrix under the catalysis, resulting in improved toughening effect.
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Details
- Title
- Grafting modification of polylactic acid and its application for compatibilization of polymer blends
- Creators
- Wangcheng Liu
- Contributors
- Jinwen Zhang (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525182001842
- Language
- English
- Resource Type
- Thesis