Soluble, thermally stable phosphorus containing polyimides have been synthesized to controlled molecular weights and well-defined phthalimide endgroups via solution imidization. They were characterized by intrinsic viscosity, DSC, TGA, and thermomechanical measurements. Molecular weight control was successful and these polyimides were thermally stable via dynamic TGA up to 500°C. Flame resistance was suggested by the 10-20 % of char yield observed in air at 750°C. Good tensile modulus (500-550 ksi) via stress-strain measurements and excellent adhesion to Ti-6AI-4V substrates through single lap shear tests was demonstrated. Investigations of the effects of molecular weight and end group on thermal and mechanical properties of reactive amine terminated and non-reactive phthalic anhydride terminated PMDA-mBAPPO polyimides were pursued. Polyimides with non-reactive end groups do not crosslink and, hence, were essential for controlled processability. Rheological behavior was investigated with a parallel plate type viscometer and the results confirmed the thermoplastic nature of these systems. Phenyl ethynyl endcapped polyimides were synthesized for a broad based investigation of their processibility and mechanical properties. Thermally stable soluble polyimide oligomers were synthesized via the poly(amic acid) precursor route followed by subsequent solution imidization. These polyimides were successfully crosslinked upon heating, without the evolution of volatile products. The phenyl ethynyl endcapped polymers (T_cure ~ 350-400°C) exhibited a wider processing window above Tg, relative to the unsubstituted acetylene endcapped polymers (T_cure ~ 200°C). Studies of the chemorheological behavior of these polyimides as a function of varying temperatures and times were conducted. This research allows the conclusion that high Tg, thermostable, and solvent resistant new networks suitable for structural adhesives and matrix resins have been identified. This was proven by characterization of these novel networks. Ninety-nine percent gel fraction networks were observed after cure at 380°C for 60 minutes. Thermomechanical properties such as tensile properties, adhesion properties, creep behavior, and heat distortion temperatures have been generated which illustrate the excellent dimensional stability and mechanical properties achievable at optimum crosslink density. Polyarylene ether sulfones were also studied which demonstrated the desirable combination of excellent thermal stability and good mechanical properties. Biphenyl-based polysulfones were synthesized and endcapped with 3-phenyl ethyny] functional groups. High Tg, thermostable, ductile and solvent resistant networks were prepared after curing at 380°C. Thermo-mechanical behavior, including tensile properties and dynamic mechanical analyses have been determined and are reported in this thesis. / Ph. D.

Fiber reinforced polymeric composites (FRPC) have superior physical and mechanical properties, such as high specific strength, light weight, and good fatigue and corrosion resistance. They have become competitive engineering materials to replace conventional metallic materials in many important sectors of industry such as aircraft, naval constructions, ships, buildings, transportation, electrical and electronics components, and offshore structures. However, since FRPC contain polymer matrix, the polymer composites and their structures are combustible. FRPC will degrade, decompose, and sometimes yield toxic gases at high temperature or subject to fire conditions. The objective of this study is to design and optimize fire retardant nanopaper by utilizing the synergistic effects of different nanoparticles. A paper-making technique that combined carbon nanofiber, nanoclay, polyhedral oligomeric silsesquioxanes, graphite nanoplatelet, and ammonium polyphosphate into self-standing nanopaper was developed. The fire retardant nanopaper was further incorporated into the polymer matrix, in conjunction with continuous fiber mats, through resin transfer molding process to improve fire retardant performance of structural composites. The morphology, thermal stability, and flammability of polymer composites coated with hybrid nanopaper were studied. The cone calorimeter test results indicated that the peak heat release rate of the composites coated with a CNF-clay nanopaper was reduced by 60.5%. The compact char material formed on the surface of the residues of the CNF-clay nanopaper was analyzed to understand the fire retardant mechanism of the nanopaper. The financial support from Office of Naval Research is acklowdged.

Step-growth polymerization enabled the synthesis of novel polyester regioisomers and pendant functionalized polyetherimides (PEI)s. Novel monomers incorporated at targeted mol % produced series of polyesters and PEIs, suitable for systematic analysis of key polymer properties. Subsequent compositional, thermal, mechanical, and rheological characterization forged structure-property relationships to further understand the influence of composition on performance. Altering regiochemistry is a subtle way to maintain the same polymer composition but tune desired properties. Similarly, introducing functional pendant groups expands the property profile of common industrial polymers and installs a handle for secondary chemistry after synthesizing the main polymer. Both altering regiochemistry and adding pendant groups alters polymer properties without the need for large changes in synthetic requirements or reaction conditions, ideal for industrial adoption. Incorporation of a kinked bibenzoate (BB)-based diester monomers into the commonly utilized linear regioisomer afforded processable amorphous and semi-aromatic (co)polyesters. BB-(co)polyesters with ethylene glycol (EG) possessed improved barrier performance compared to poly(ethylene terephthalate) (PET) while improving on mechanical properties, including tensile and flexural modulus/strength, rivaling bisphenol-A polycarbonate (BPA-PC). Replacement of EG with 1,4-cyclohexanedimethanol (CHDM) improved thermal properties closer to BPA-PC, while enabling melt rheological analysis due to its amorphous morphology. Time-temperature superposition (TTS) analysis produced master curves provided insight into the entanglement molecular weight (Me) and entanglement density. More kinked structures possessed a lower Me and more entanglements. Introducing kinked monomers posed the question of cyclic speices generation during polymerization, common in step-growth reactions. Thus, systematic incorporation of meta-substituted hydroxyethylresorcinol and para-substituted hydroxyethylhydroquinone regioisomers into PET analogues enabled the characterization of cyclic formation due to monomer regioisomers. Increased meta substitution produced increased amounts of cylic species, analyzed by size exclusion chromatography (SEC). Adding functionality to high performance polyetherimides (PEI)s is difficult due to the high temperatures required for processing. The lack of thermal stability for commonly utilized H-bonding/reactive groups limits viable moieties. Utilizing the high temperture processing, PEIs incorporating pendant carboxylic acids reacted in the melt to form branched PEIs. These branched PEIs exhibited steeper shear thinning as well as improved flame resistance, limited in thin film commercial PEIs. / Doctor of Philosophy / My research focused on making new plastics (polymers) for use in consumer and performance markets. Typical applications utilizing these plastics include food packaging, consumer goods, automotive, aerospace, microelectronics, construction, and medical devices. Large changes such as intricate new chemicals used to make the plastics increase the difficulty in incorporating these new materials into existing synthesis and processing techniques and infrastructure. Thus, my research revolved around subtle changes to the chemical structure of the plastic, suitable for easy industrial adoption while also improving targeted properties necessary for the aforementioned applications. Polyesters are a class of polymers commonly used for food packaging and consumer goods. Thus, improving gas barrier performance and mechanical integrity/strength is crucial when designing new polyesters. Changing the bond angles through the linear versus kinked nature of the polymer chain imparts processability and improved gas barrier, compared to commercial poly(ethylene terepthalate) (PET), commonly used in food packaging applications. The density of the polyesters is also increased, which improves mechanical strength. The specific structures used also increased the thermal resistivity compared to PET. This higher thermal resistivity enables use in applications where high temperature cleaning such as steam sterilization and dish-washing could deform products or processing such as filling food packaging containers with hot foods. Similar types of polymers which possess much higher thermal resistivity are classified as high performance polymers. One class of these include polyetherimides (PEIs). The specific chemical structures and their high thermal resistance makes them great candidates for applications in automotive, aerospace, and microelectronic applications; although, these same properties make these polymers very difficult and expensive to process into the desired parts. Thus, adding functionality to the polymer by putting specific chemical groups off of the main chain enabled easier processing and improved other polymer properties. Adding the functionality to these polymers allowed them to react and change structure at high temperatures (during processing) to achieve a different shape, thus improving desired properties, such as how easy they flow like liquids at high temperatures and processing conditions. Another benefit realized from this change during processing was the improvement of flame resistance. Due to the chemical structure of the PEIs, they inherently possess resistance to catching on fire, remaining on fire, and dripping flaming material. Although PEIs typically possess good flame resistance, thin films or small parts made from these polymers do not possess the same flame resistance and can produce flaming drips, undesirable for applications requiring flame resistance. Chemically modifying these polymers with the aforementioned functionality and processing them increased the flame resistance to eliminate flaming drips and lessen the amount of time the polymer was on fire.

Flamskyddsmedel har visat sig ha en stor påverkan på både miljö och hälsa. Den grupp flamskyddsmedel som i stor utsträckning har använts sedan slutet på 70-talet till början av 00-talet för textilier är polybromerade difenyletrar (PBDE). De är halogenerade ämnen som är svårnedbrytbara, persistenta, i vissa fall även bioackumulerande och toxcistiska. Studier har visat att dessa ämnen upptäckts i både miljö och i människokroppen. Människan exponeras av dessa ämnen, framförallt genom damm och livsmedel. I synnerhet feta fiskar eftersom PBDE drar sig till organismer och fettvävnader. I takt med att brandkraven i många länder ökar är behovet av ett substitut för bromerade flamskyddsmedel stort. Flera typer av PBDE är idag förbjudna i Europa men problemet kvarstår då det fortfarande existerar i importerade produkter. För att komma ifrån flamskyddsmedel i lös inredning, exempelvis soffor och madrasser skulle ett barriärmaterial innehållande naturligt flamskyddade material vara ett bra substitut.   För lös inredning är det viktigt med komfort, det fanns i studien ett intresse av att se hur naturligt flamskyddat material tillsammans med ull betedde sig vid en flamspridning. Ull i sig har en hög komfort och har ett naturligt flamskydd på grund av sitt höga LOI. För att uppnå ett resultat på vilken FR-fiber som skulle studeras vidare tillsammans med ull, har flamtester på Kevlar, Nomex, Protex och Flamestop utförts. De är uppbyggda med olika typer av naturligt flamskydd i form av aramider, modakryl och fosfor behandlad viskos.   Med resultatet från flamtesterna utfördes vidare tester och analyser på tre kombinationer av Flamestop/Ull, innehållande tre olika procentsatser. Testmetoder i form av antändning och flamspridning har utförts på de olika kombinationerna, för att göra det möjligt att analysera om hur de flamskyddade materialet uppförde sig tillsammans med ull. Samt om det gjorde någon skillnad vilken procentandel Flamestop kombinationen innehöll.   Resultatet av testmetod för antändning på tre spridda procentandelar Flamestop/Ull som erhölls, var att en högre procentandel Flamestop gentemot ull gjorde det möjligt för materialet av självslockna i ett tidigt stadie. I flamspridningstestet visade det sig att procentandelarna inte gjorde någon skillnad för spridningens framfart. Det gick att utläsa av testerna att proverna med flamskydd i vinkelrät riktning mot flammans riktning bildade ett skyddande skikt av förkolnad fosfor från Flamestop. Flamman och Flamestop i längsgående riktning resulterade i större skada på materialet. För att göra det möjligt att undersöka mer om riktningen på det flamskyddade materialet hade det varit intressant att studera flamspridningen med materialet i både väft och varp. / Flame-retardants have a great impact on the environment and health. Polybrominated diphenyl ethers (PBDE) are the group of flame-retardants that mainly has been used since its entrance in the late 70s until the early 00s. PBDEs consist of Organobromine compounds, different types of halogenated compounds, which are highly resistant to degradation, persistent and in some cases even bioaccumulative and toxic. It has been ensured in previously studies that PBDEs has been found in the human body and in the environment. Humans are exposed every day to these pollutants through dust, food and especially from fatty fishes, as living organisms and fatty tissues are easily attracted to PBDE. A lot of the existing PBDE are forbidden in Europe; however, the issue still exist as imported products can contain PBDE. As the fire safety regulations in many countries increases, it is necessary to find a substitute for flame-retardants. To lessen or completely remove flame-retardants in loose interiors, as couches and mattresses a barrier-material could be a good substitute.   Comfort is an important component for loose interiors; in this study there was an interest to see how a material with inherent natural flame resistance behaved with wool. Wool, that has a good comfort and a natural resistance of flame, due to its high LOI. To decide which FR-fibre that will be looked into and analysed in this essay an ignition test on Kevlar, Nomex, Protex and Flamestop were made. These materials have different structures of flame resistance, in form of aramids, modacrylic and phosphorus viscose.   Three different percentages of Flamestop/Wool were created from the results of the previous mentioned ignition test. These three percentages were weaved into a plain weave, tested and analysed. Ignition and flame spread were tested on the weaves, analysed to see how the natural flame resistant material behaved together with wool and if there were any differences when comparing the different test specimens.   The result of the ignition and flame spread tests showed that the percentages of Flamestop played a role in the ignition test; the ability to extinguish was greater with a higher percentage of Flamestop in the weave. It was not possible to see a difference in the test of flame spreading. The test specimens with the FR-fibre perpendicular to the flames direction showed a better result than the test specimens with the FR-fibre in a longitudinal direction to the flame. It would be of interest to study weaves with FR-fibres in both directions of warp and weft.