A functionalized polyphosphazene, poly[bis(carboxylatophenoxy)‐phosphazene], was blended with a structural polyurethane via reactive mixing of the polymer with diisocyante and diol prepolymers. The thermal stabilites of the resultant foams were analyzed by thermogravimetric analysis (TGA). The char yields at both 400°C and 600°C increased relative to the pure polyurethane upon increasing the amount of polyphosphazene from 5 wt% to 20 wt%. At higher incorporations, the char at 400°C remained the same, but the char at 600°C continued to increase. The combustion behavior of these foams was analyzed both qualitatively, by a horizontal flame test, and quantitatively, by oxygen index (OI) measurements. Both of these tests indicated an increase in flame resistance at loadings of 20 wt% and above.

SUMMARY: Equilibrium constants determined from low molecular weight mixtures are used to predict the phase behavior of analogous polymer blends. Due consideration is given to intramolecular screening and functional group accessibility, factors that are a direct consequence of chain connectivity.

We recently reported the results of a comprehensive infrared study of the self-association of methacrylic acid copolymers. 1 Values of equilibrium constants that describe the number of hydrogen-bonded carboxylic acid dimers formed at equilibrium were determined and found to be a strong function of chain stiffness. In this note, we present some further spectroscopic results involving miscible blends of poly(tetrahydrofuran) (PTHF) with one of these random styrene-co-methacrylic acid copolymers that contains 9 mol % methacrylic acid (denoted STMAA{9}).At a given temperature, above the glass transition temperature and below the onset of anhydride formation, the carbonyl groups of STMAA{9} exist in a state of dynamic equilibrium, oscillating between isolated "free" (non-hydrogen-bonded) and hydrogen-bonded carboxylic acid dimers (there is also a transient "opendimer" intermediate state that has been detected in dilute solution studies, but not in polymer work 1 ). This equilibrium may be simply depicted as

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Equilibrium constants determined from low molecular weight mixtures are used to predict the phase behavior of analogous polymer blends. Due consideration is given to intramolecular screening and functional group accessibility, factors that are a direct consequence of chain connectivity.