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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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