Date of Graduation

1998

Document Type

Thesis

Abstract

The goal of this research was to find polymeric additives that would significantly decrease the rate of crystallization in nylon 6,6, in order to enhance mechanical properties indirectly. Since miscibility was essential, different classes of materials considered included amorphous and semi-crystalline nylons, and other polymers known to be compatible with polyamides. These additives were blended with nylon 6,6 using solution and melt blending techniques. The change in thermal behavior of the blends was evaluated using data obtained with a Differential Scanning Calorimeter (DSC) and Dynamic Mechanical Thermal Analyzer (DMTA). Reduction in the crystallization temperature (T{dollar}\\sb{lcub}\\rm c{rcub}){dollar} during a non-isothermal DSC run was used as the primary criterion for judging the effectiveness of the additive. Polymers that were particularly promising included amorphous nylons--Trogamid-T and Zytel 330; nylon 6,12 and polyacrylic acid. An unusual finding was that annealing the blend in the melt state promoted additional changes in the melting and crystallization behavior. This was attributed to interchange reactions occurring between the blend components. Later work focussed on the use of nylon additives and studied the influence of the nature and amount of additive, residence time in the extruder, drying time, and the melt annealing time. Both the amorphous and semi-crystalline additives produced significant changes in the thermal behavior on melt annealing, the effect increasing with concentration. It was found that Trogamid-T was more effective in reducing the rate and extent of crystallization of nylon 6,6 when compared with nylon 6,12. The suppression in T{dollar}\\sb{lcub}\\rm c{rcub}{dollar} was more for the as-prepared Trogamid-T blends and also for samples annealed for different times. The extent of interchange reaction, measured by the depression in equilibrium melting point, was linear with respect to the annealing time. Trogamid-T blends appeared to be "nearly miscible" initially, with miscible blends being produced in the twin screw extruder at all concentrations. The {dollar}\\rm T\\sb{lcub}g{rcub}{dollar}-composition curve showed a positive deviation from linear additivity. The single {dollar}\\rm T\\sb{lcub}g{rcub}{dollar} decreased as a function of annealing time in the melt, with the change in {dollar}\\rm T\\sb{lcub}g{rcub}{dollar} being proportional to the additive concentration.

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