Accession Number:

ADA026113

Title:

Low-Frequency Thermomechanical Spectrometry of Polymeric Materials: Tactic Polymethylmethacrylates.

Descriptive Note:

Technical rept. Jul 75-Jun 76,

Corporate Author:

PRINCETON UNIV N J

Personal Author(s):

• Stadnicki,S. J.
• Gillham,J. K.
• Hazony,Y.

Report Date:

1976-06-01

Pagination or Media Count:

47.0

Abstract:

A computerized and automated torsional pendulum has been used to characterize amorphous polymethylmethacrylates at about 1 Hz in the temperature sequence 473 to 93 to 473 K. The effects of thermal prehistory, temperature cycling, water content and tacticity are demonstrated. In particular, a comparison of the out-of-phase shear modulus G versus temperature for syndiotactic, atactic and isotactic polymer specimens shows that the intensity of the glassy-state beta loss peak decreases with increasing isotactic content while the temperature of its location remains the same. Extrapolation suggests that completely isotactic polymer would not display a beta loss peak. The shape and location of the G data at low temperatures indicate that the basic mechanism of the beta process is the same for the three polymer samples and support the validity of the extrapolation. The effect of tacticity is reflected also in the glass transition region the isotactic sample has its Tg about 65 C lower with greater intensity than the syndiotactic polymer. Author

Descriptors:

• *PHASE TRANSFORMATIONS
• *POLYMETHYL METHACRYLATE
• *AMORPHOUS MATERIALS
• THERMOMECHANICS
• COMPUTERIZED SIMULATION
• LOW TEMPERATURE
• SPECTROMETRY
• TRANSITION TEMPERATURE
• LOW FREQUENCY
• THERMAL CYCLING TESTS

Subject Categories:

• Plastics
• Solid State Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE