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STRUCTURE PORPERTY RELATIONSHIPS OF HIGH PERFORMANCE POLYBENZOXAZINES

Liu, Jia
http://rave.ohiolink.edu/etdc/view?acc_num=case1407514371

Abstract Details

2014, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science and Engineering.
Polybenzoxazines is a newly developed thermosetting resin which shows great commercial potential because they have mechanical and physical properties comparable or even superior to conventional phenolic, epoxy, bismaleimide and polyimide resins. This dissertation focuses on exploring the structure-property relationships of high performance polybenzoxazines including the processability, reactivity, flame retardancy and polymerization kinetics. Chapter 1: This chapter highlights the scope and motivations of recent studies on developing high performance polybenzoxazine resins meanwhile fundamentally understanding the structure property relationships of these materials. Chapter 2: In this chapter, a new approach has been developed to enhance the processability of main chain type benzoxazines. Oligomeric benzoxazines are synthesized through end cap approach. Reduced melt viscosity is achieved while maintaining the major advantages of main chain type polybenzoxazines. A series of bisphenol F based oligomeric benzoxazines with different end groups are synthesized and characterized. Chapter 3: To evaluate the isomeric effect on benzoxazine chemistry and properties, the pure bisphenol F isomeric monomers (2, 2’-, 2, 4’- and 4, 4’-substituted) are synthesized and characterized. Unexpected large increase, which is opposite of many such effect reported in the literature, in the glass transition temperature (Tg) was observed from 2, 2’-substituted to 4, 4’-substituted benzoxazine. Predicted Tg of the polymer based on the known isomer mixtures is calculated by the generalized Fox equation. The dependence of Tg, monomer reactivity, thermal stability and crosslink density of benzoxazine upon molecular architecture are discussed. Chapter 4: In this study, we first demonstrated that through incorporating amide group on the ortho position of oxazine ring, polybenzoxazoles (PBOs) can be obtained upon thermal treatment. The most attractive feature of this approach is its structural transformation from polybenzoxazine into a more thermally stable cross-linked polybenzoxazole without the harmful consequences of traditional polybenzoxazole synthesis, such as the use of poly (phosphoric acid) as solvent. Besides, the flame retardancy of these resins are expected to be higher than conventional polybenzoxazines due to the incorporate of heat-resistant oxazole moiety. To examine the thermal property and flame retardancy of these resins, a series of benzoxazines containing amide group in the backbone with a significant degree of aromaticity have been synthesized and characterized. Systematic manipulation of diamine structure has allowed the structure-property relationship of polybenzoxazines examined. Thermal stability and flammability are characterized by thermogravimetric analysis (TGA) and microscale combustion calorimetry (MCC), respectively. The experimental results are fitted to the major thermal decomposition processes contributing to the specific heat release rate histories Q¿(T). This family of materials shows one of the lowest heat release capacity values of all polymers indicating the excellent flame retardancy. Chapter 5: This study focus on understanding benzoxazine network development by simultaneously monitoring chemical and physical changes through the advanced Rheo-FTIR technique. Main-chain type bisphenol A-jeffamine based benzoxazine is used as model compound due to its low melt viscosity. The role of methyl resorcinol (MR) is evaluated upon increasing temperature. Ring opening activity is shown to be accelerated under the presence of MR, the polymerization is found to be a multi-stepped process. Homopolymerization and copolymerization occurs with a transition temperature around 120oC. Both phenoxy and phenolic type benzoxazine is observed by monitor the change of ATR spectra. Phenoxy structure is further rearranged to phenolic structure at higher temperature. Activation energy of each polymerization step is calculated and reaction mechanism is proposed. Appendix A: This work is focused on the complementary information obtained from advanced in situ Fourier transform infrared (FTIR) spectroscopy and rheological measurements to correlate the structural changes with rheological properties upon polymerization of different organically modified montmorillonite clay/vinyl ester composites prepared by in situ polymerization. The microstructure and morphology of the nanocomposites were examined by X-ray diffraction and transmission electron microscopy. The effect exerted by the presence of organic clay on the polymerization reaction of a vinyl ester based polymer matrix was evaluated. In situ and ex situ rheo-FTIR measurements were compared to demonstrate the accuracy of this technique. Appendix B: This study focus on understanding swelling behavior of polyvinyl chloride (PVC) pipe cements prepared by different resin and solvent types. The rheological behavior, under dynamic shear and extensional conditions are determined and compared. Commercial available PVC cements with different resin type, concentration, solvent combination and fumed silica content were thoroughly investigated in this study. We found that morphology of PVC granule plays a role on response to solvent changes. In general, tetrahydrofuran (THF) is a better solvent for all grades of PVC examined, while cyclohexanone (CYH) serves as an effective swelling solvent. Both dimethyl sulfoxide (DMSO) and cyclododecanone (CDDK) system can't dissolve PVC as well as THF/CYH system. CDDK, in particular, is the worst for dissolving PVC. Adding fumed silica significantly increases both viscosity and elasticity.
Joao Maia (Advisor)
Ishida Hatsuo (Committee Member)
David Schiraldi (Committee Member)
Xiong Yu (Committee Member)
257 p.
Engineering; Polymers
polybenzoxazines, structure-property relationship

Recommended Citations

Citations

  • Liu, J. (2014). STRUCTURE PORPERTY RELATIONSHIPS OF HIGH PERFORMANCE POLYBENZOXAZINES [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1407514371

    APA Style (7th edition)

  • Liu, Jia. STRUCTURE PORPERTY RELATIONSHIPS OF HIGH PERFORMANCE POLYBENZOXAZINES. 2014. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1407514371.

    MLA Style (8th edition)

  • Liu, Jia. "STRUCTURE PORPERTY RELATIONSHIPS OF HIGH PERFORMANCE POLYBENZOXAZINES." Doctoral dissertation, Case Western Reserve University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1407514371

    Chicago Manual of Style (17th edition)

case1407514371
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This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.