STP1249

    Assigning the Glass Transition Temperature in Oriented Poly(ethylene terephthalate)

    Published: Jan 1994


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    Abstract

    Thermoplastics like poly(ethylene terephthalate) (PET) can be melt processed into sheet and film formats for a variety of applications. Fabrication of these formats often involves application of a drawing process which can include drafting, tentering, heat setting, detentering, and heat relaxation. These various components add a thermomechanical history to the PET that will influence the glass transition. Thermomechanical analysis (TMA) in both the compressive mode and the tensile mode along with differential scanning calorimetry (DSC) techniques have been applied to a series of seven PET films generated using different drawing processes applied with an Iwamoto Biaxial Stretcher on extruded sheet from a single source. These measurements were undertaken to assign a glass transition temperature for each film. The assigned temperature ranged between 70°C and 94°C. Orientation and heat setting increased the temperature assigned as Tg while detentering both increased and lowered Tg on a direction-specific basis. Both the measurement technique and the assignment protocol employed to determine Tg contributed to differences in the assigned value. DSC results suggested the presence of two amorphous domains (mobile and constrained) in the film oriented uniaxially without constraint. TMA data demonstrated the assigned Tg may be direction specific and not a bulk property in oriented PET films.

    Keywords:

    differential scanning calorimetry (DSC), thermomechanical analysis (TMA), mobile amorphous domain, rigid amorphous domain, glass transition, glass transition temperature (, Tg, ), poly(ethylene terephthalate) (PET), tensile mode, compressive mode, softening point (, Ts, ), uniaxial orientation, biaxial orientation


    Author Information:

    Moscato, MJ
    Analytical chemist, Analytical Services, and research associate, Material Science and Engineering, Eastman Kodak Company, Rochester, NY

    Seyler, RJ
    Analytical chemist, Analytical Services, and research associate, Material Science and Engineering, Eastman Kodak Company, Rochester, NY


    Paper ID: STP15378S

    Committee/Subcommittee: E37.01

    DOI: 10.1520/STP15378S


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