Thermomechanical Transitions in Polyphosphazenes.
Abstract
Unoriented and oriented samples of two phosphazene homopolymers with chemical structure (NPX2) sub n, where X = CF3CH2O and p-CH3C6H4O, and three unfilled and filled alkoxy-type polyphosphazene copolymers, plus one filled aryloxy-type copolymer were examined using a Rheovibron viscoelastometer. Measurements were made from -120 C to temperatures above the T(1) transition of the respective polymers. The effects of orientation and repeated temperature cycling through the T(1) transition temperatures were studied. The overall physical behavior of these polyphosphazenes was dominated by changes that occurred through the primary softening dispersion and the so-called mosomorphic or T(1) transition region. The enthalpy of the T(1) transition, and the T(1) temperature were investigated by differential scanning calorimetry (DSC) as a function of temperature cycling through the T(1) region. For instance, the change in enthalpy through the T(1) region is about an order of magnitude larger than it is at Tm for the unfilled polyphosphazene homopolymers. The Tg's of the polyphosphazenes were also determined. Density measurements were made on oriented and unoriented specimens using a floatation method. Although an increase in density (and crystallinity) was observed when specimens were cycled through the T(1) transition, no significant difference in density was found between oriented and unoriented materials. Some discussion of the molecular origin of the T(1) mesophase transition is included. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 08, 1980
- Accession Number
- ADA088119
Entities
People
- I. C. Choy
- J. H. Magill
Organizations
- University of Pittsburgh