Polymeric composites

Experiments were conducted to investigate the degradative effects of ambient and high pressure aqueous environments on unidirectional carbon fiber nylon (AS4/nylon 6) composites. Electrochemical impedance spectroscopy (EIS) was selected for development as a non-destructive method to characterize the degradation phenomena in carbon/nylon composites as result of moisture absorption. EIS data was collected for composites and neat resins as a function of immersion time in ambient and pressurized (6.2 MPa) 3.5% NaCl solution. EIS was also utilized to understand degradative mechanisms when composites were subject to cathodically induced damage. Concurrent EIS and 3-point mechanical loading was also performed on composites to study the changes in the impedance response as a function of loading. A detailed equivalent circuit analysis is also presented in an attempt to elucidate the degradation phenomena in composites. Gravimetric and 3-point mechanical testing data is also presented to study the effect of ambient and pressurized aqueous environments on composites. Scanning electron micrographs of composites are also included to assist in morphological evaluation.

This research evaluated the applicability of electrochemical impedance spectroscopy (EIS) as a non-destructive technique to predict and characterize the degradation of carbon fiber reinforced polymer (CFRP) composites exposed to aqueous environments at ambient and 6.2 $\pm$ 0.3 MPa. Changes in EIS data were related to water uptake into the composite material as a function of exposure time. Electrochemically induced damage (both anodic and cathodic) were also evaluated using impedance measurements. Three point flexure tests with concurrent EIS measurements were employed to study the effect of stresses on water uptake and mechanical degradation. Visual observation of the extent of damage (i.e., fiber-matrix debonding) was made using scanning electron microscopy (SEM) and correlated with EIS observation.

A large number of metal-containing compounds show significant activity against cancer cells and incorporating a metal into a polymer offers several possible advantages. Compounds of the type R2SnCl2 (R = methyl, ethyl, propyl, butyl, t-butyl, octyl and phenyl) were tested for the ability to inhibit the growth of Balb 3T3 mouse fibroblast cells and CAOV3 human ovarian carcinoma cells. Polymers of 2-chloro-1,4-benzenediamine and the same organotin dichloride were synthesized and tested as well. For both monomers and polymers, the pattern of growth inhibition relative to the R group was butyl > propyl = t-butyl = octyl = phenyl > ethyl > methyl. This and other aspects of the structure-activity relationship of the monomers and polymers were examined.

Durability of concrete bridge decks reinforced with conventional structural steel is a major concern in aggressive environments. To address this problem, there have been efforts, in recent years, to develop and evaluate alternatives to conventional steel. One alternative is fiber reinforced polymer (FRP) composite reinforcement. FRP composites have been used successfully in many industrial applications. This thesis investigates short-term mechanical properties of FRP rebars as reinforcement for concrete bridge decks and discusses results of extensive laboratory tests. Four test methods (tension, flexure, shear and bond) are developed and test protocols are proposed for adoption by AASHTO.

Metal containing polymers were synthesized by reaction of organotin and group IVB metallocene dichlorides with kinetin, a plant growth hormone (PGH), via the interfacial polycondensation process. Product yields were in the range of 40--63% and degrees of polymerization were from 20 to 150. The structures of the products were determined using infrared and mass spectroscopy. Further characterization involved determination of solubility, degree of polymerization and electrical conductivity. The biological potential of the products was tested against selected microorganisms and Balb/3T3 cell lines. One of the products showed activity in the 0.2mug/ml range, one hundredth of that of similar compounds. Germination experiments using the PGH incorporated polymers were performed on sawgrass and cattail seeds as well as selected vegetable seeds and compared to a control. Sawgrass germination, typically in the 0--2% range were increased to about 60% through the treatment with kinetin-containing polymers.

Degradation of the Carbon Fiber/Vinylester (CF/VE) polymer matrix composites due to different electrochemical interactions when exposed to seawater or at high temperature had been experimentally investigated. Water uptake behavior of composite specimen was examined based on weight gain measurement. Three point bending test was performed to quantify the mechanical degradation of composite immersed in seawater with different environmental and electrochemical interactions. Finally, Electrochemical Impedance Spectroscopy (EIS) was used to better understanding of the degradation process in CF/VE composite produced by interactions between electrochemical and different environmental conditions. A detailed equivalent circuit analysis by using EIS spectra is also presented in an attempt to elucidate the degradation phenomenon in composites.