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(Au gus t 1] , 1966)Theoreti ca l equ a ti o ns ar e de ve lo pe d for typi cal decompositions of polyme rs including th ose in whi c h the vola tilization does not folJ ow a simpl e "re action orde r" a nd those made up of a composite of seve ral reac tions of diffe rin g e ne rgies of ac tivation. The e ffects of orde r, activation ene rgy, heatin g ra te and te mpe ra ture de pe nd e nce upon th e calc ulated th ermogram s is illu strated. The lite rature on th ermogravim e tri c kine ti cs is c riti cally re vi ewed and coalesced into a logi cal and cohere nt de velopme nt stressin g the inte rrelation of me th ods a nd e mplo yin g a co ns iste nt sys te m of nota tion . As a res ult , a nu mbe r of impro ved me th ods and ne w me thod s for the a nalys is of kineti c data a ppli ca ble to th e co mpl e x sys te ms me nti oned a bove are developed . It is co nc lu de d th at me thods involvin g a va riabl e rate of hea tin g or invo lving seve ra l the rm ogra vime tri c traces at d iffe re nt ra tes of hea tin g a re capa bl e of es tabli s hing th e unique ness of kine ti c pa ra me te rs. A ne w me th od of de te rminjn g init ial pa ra me te rs from rate·conve rs ion data is de veloped . A novel co nce pt is e mpl oyed of programmin g reac ti on va ri a bles (i n thi s case, th e heatin g ra te) in a ma nne r whi c h great ly simplifies th e mathe mati cs of the kin e ti c s'ys te m and whic h shows pro mise of a wide ra nge of a pp lj ca bilit y in th e area of rate processes. Ke y Word s : Degrad a tion, no ni sothe rm al kine ti cs, polyme rs, pyrolys is, th e rm a l deco mp os iti o n, th e rmogra vim e try, th e rm olys is, sta bilit y of po lyme rs.

cording to some recent theories of the osmotic second virial coefficient in the limit of large excluded volumes, i.e., for high molecular weight polymer molecules in thermodynamically "good" solvents, the ratio A2M%,/(Rl,)'/* should attain an essentially constant value. Qualitatively the constancy of this ratio is an expression of the expectation that the interactions of polymer molecule pairs in such media resemble collisions of spheres whose volumes are proportional to (7?2W)V2. If, then, the volumes of the equivalent hydrodynamic spheres observed viscometrically are also proportional to (i?2w)'/' the ratio AtMw/[rj] should be another constant. _The ratio is plotted against log Mw in the center graph of Fig. 7 for the ten polyvinylacetate fractions in methyl ethyl ketone. Over this molecular weight range the ratio is a constant equal to 4.4 X 1024.A plot of A-iM^I [77] against log M-w for the samesystem in the lower graph of Fig. 7 reveals a remarkably constant value, 1.39, for this ratio over the molecular weight range 246,000 to 3,460,000.Here again data of Howard19 have been used to extend the observations to lower molecular weight polymer fractions.It may therefore be stated empirically that the thermodynamic interaction of a pair of high molecular weight polyvinylacetate molecules in methyl ethyl ketone is similar to the collision of spheres having effective volumes proportional to (A!2W) This observation, coupled with the validity-of the equivalent hydrodynamic sphere treatment of limiting viscosity numbers, yields an empirical relation among the quantities AMw and [17]. It has been found40 that this relation is valid for several polymers in thermodynamically good solvents, and similar magnitudes for the ratio A2MW/ [77 ] are observed.

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Nucleophilic reactions of hexafluorob enzene and related polyfiuorobenzenes were studied in detail. R eaction of hex a fluorobenzc nc with hydroxides, alco holates, aqueous amines, and organolithium co mpounds led to the substitution of one 01' more fluorine atoms. The stru ctures of the products were determined, using near infra red a nd nuclear m agnetic resonance spectra. Fluorine is replaced more readily than chlorin e, bromine, iodine, or other groups. I n the ma jo rity of the products in which two of the fluorin es in hexafluorobenzene we re replaced, t he substituting groups were p a ra to eac h other. However, depe nding on the reagents other orientation effects were noted . The reaction mechanis ms we re a fun ction of reagents a nd co nditions. The mo t prcvalent mecha ni sm is presuma bly the di splace me nt of a fluoride anion by another anion, probably via the fo rmation of transition co mplexes of difl'erent lifetimes. Howeve r, simple ionization 0 1' attack by neutral species may occ ur under some co nditions. The diazotization a nd oxidation of pentafluoroan il ine were also inv estigated.

Thermal decomposition s of various nylon samples havin g difTcrenL molec ular weights and composition were investigated by several procedures: ( I ) Th e raLc of volaLiliulLion at temperatures between 310 0 and 380 0 C; (2) t he analysis of the volatile produets by mass spectrometry; and (3) a direct m eas urement of volaLili zing m aterial obtained by eHtTying out the pyrolysis within the ionization chamber of a m ass spectromeLer.AcLivation energies based on the rates of volatilization for the variolls amples varied from 15 to 42 kilocalories. The rate behavior, i. e., the observaLion of maxima inLhe rateversus-conversion plots, is close to that given by theory for random d composiLion. The different activatio n energies appear to be the res ul t of a hydrolytic mec hanis m which is sensi t ive to trace polymerization catalysts. Increases in rates were obtained when sulfuric and phosphoric acids were a dded to nylon. The flucLuaLion s found in activation energies, find the production of CO2 indicate that a hydrolytic decomposition mechani sm may be contributing to the over-all process. It appears evident that, compared to a pure hydrocarbon chflin, the polyamides are much more sllseeptible to thermal decomposition.

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