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NAVORD REPORT C255

THE SPECIFIC HEAT OF THERMOSETTING POLYMERS (U)uLJcL-

U -

14 JANUARY 1£59

F ASTIIL.7- D - 1

U. S. NAVAL ORDNANCE LABORATORYWHITE OAK, MARYLAND

NAWr D Report 6255

THE SPECTFIC hEAT OF THEFMOSP-'TTNl FOLYMFPS

Prepared by:

R. W. WarfieldM. C. PetreeP. Donovan

AlbRACT:Specific eat, as a fu'ction of temperature has teenover the range of 301C to 160'C for a number of thermosetting polymers.The data were obtained by means of an adiabatic calorimeter. In agreementwith theory, +.n6 specific heats of the polymers showed a progressiveincrease with increasing temperature. In many cases large increasesin specific hoat have been observed which are indicative of second ordertransitions within the polymer.

CDISTRY RSESARCH DEPARTwENTU. S. NAVAL O RP,'ACE LA BORA1)RY

White Oak, Maryland

- i

NAV)RD Report 6255 lb January 1959

This report contains data on specific heats as a function of temperaturefor a number of therinosetting polymers. In many cases the results areindicative of second order transitions which occur within the polymer*This study was made under Project NlOa-l-56 as part of a general polymerinvestigation.

ML A. PTESONCaptain, USNCoinander

By direc ton V

ii

NAWRD Report 6255

A C1 O '4LDGEY- FN TS

The authors would like to express their appreciation to Dr. P. W. Ericksonand Mr. Thomas Wade for assistance in the experimental part of this work.

li i

NAVOir) }-eport 6255

CONTETSPage

Introduction . . . . . . . .

Theory . . . . . . . . . ... .* .0 0 * * 0 a * * a 2Experimental . . . . * . . . . . . . .. . . . . . . . .. 3

Method • * • • • . . . .

Materials . . . . ... . . . . . . . . . . . . . . . . . 4Results ............. 4

Discussion . .. . .. . • • • • a •. • •. • a

Conclusions . . . . . . . . . . . . . . • • . . . . ..

Pecomnmendations . . . . ... . . . . . . . . . . • • . • 8Appendix I .... . ... . .. . . . . . . 9

I LLI ISTRATTON S

Fig-ure 1. S pe ifi Heats of Epoxide PolymersFigure 2. Spccific H CaA. o P PlyAmiip-R.poxide and an Epoxide PolymerFipnn 3. Specific Heats of Two Epoxide Polymers and a Polyester PolymerFigure L. Specific Heats of an Epoxide Polymer and Diallyl PhthalateFigure 5. Specific Heats of Fpoxide PolymersFigure 6. Specific Heats of Polystyrene and Polyethylene

Table I. Temperature Range of Second Order Transitions, Tg

IV

NAWT) Report 6255

REF -M CES

1. Clanpitt, B. H., German, D. E., and Galli, J. R., J. PolymerSci., 27o 515 (1956)

2. Got. ', Che. High Polymers (Japan), 12, 34h (1955).

'der zh B., and Dole, M. J. Polymer Sci., 2h4, 201 (1957).

L. Ueberreiter, K., and Otto-Laupenmuhlen, E., Z. Naturforachg,

8A, 664 (1953).

5. Gast, T., Kuntstoffe, L3, 15 (1953).

6. Furukawa, G., and RP -Jly, R. J. Res. Nat. i3ur. Stand. 56,3 285, (1956).Furukawa, 0., an -,! ikey, R., ibid, 51, 321 (1953).Furukawa, G., McCos',ey, R., and King, R., ibid, L9, 273 (1952).

7. Boyer, R. F., and Spencer, R. S., in Advances in Colloid Science,

Interscience, New York, N. Y., 1946 pp. 2-12.

8. * 3kkedahl, N., and Matheson, H., ibid., 15, 503 (1935).

9. R.ford, S., and Dole, M.,q J.A.C.S., 77, 4774 (1955).

1.0 Van Amerongen, G. J., in Elastomers and Plastomers, edited by

R, 7 oizrink, Elsevier, N,.r York, N. Y., 1950, pp. 219-222.

11. Fox, T,; ., and Loshack, S., J. Polywr Scie., 15, 371 (1955).

12. Warfield, R. W., Donovan, P., and Petree, M. C., NavOrd #6094.

An Adiabatic Calorimter for the Determination of the SpecificHeats of Casting Resins.

13. Willbourn, A. H., Trans. Faraday Soc., 5h4, 717 (1958).

lh. Homer, A. H., Cohen, F., and Kohn, L. S., Modern Plastics, 35, 10,Sept (1.957)

15. Weiss, H. K., Ind. F7 Chin., L9, 1089 (1957)

16. Jones, R. V., and Boeke, P. J., Ind. Env. Chem., ', 155 (1956)

17. Shell Chemical Corp., Technical Bulletin on Diallyl Phthalate,(1949) pp. 31.

18. Floyd, D. E.j Peerman, D. E.; and ;ittcott, H., J. Applied Chem.,7, 250 (1957).

19. Pow Chemical Co., Technical B1UXetin on Styron 666, (1955), PP.3.

V

NAW)TRP Report 6255

THF SPFCIFTC HEAT OF THERMOSETTING POLYMERS

TN T PU DuTT7 OF,

1. A knowledpe of the specific heat, of thermosetting polymers isbecoming more important with increasing use of these materials, oft,.under high temperature conditions. Values of specific heat (hereafterreferred to as Cp) determined as a function of temperature can be usedin calculating heats of polymerization of polymers using the techniquesof Oifferential thermal analysis (Reference 1) and adiabatic calorimetry(Reference 2). In addition, thermal diffusivities may be calculatedfrom the Cp data when the thermal conductivity and the density are known.The changes of Cp with temperature are indicative of changes in theelectrical and mechanical properties of these materials and are frequentlyrelated to the second order transitions.

2. Some uork As been done on determining the Cp of syntheticpolymers but a systematic study of the thermal properties of thermosettingpolymers has not been previously undertaken. Dole and co-workers (Refer-ence 3) have determined Cp for polyethylene and a number of other syntheticpolymers, and polystyrene has been studied by Ueberreiter and Otto-Laupenmuhlen (Reference L). Gast (Reference 5) has studied the Cp ofpolyvinyl chloride. Furukawa, Bekkedahl and co-workers at the NationvolBureau of Standards have deter-med Pp for a nuber of" po!y- (Refer-ences 6 and 7). In addition, a number of values of Cp have been reportedbut with no information as to the temperature at which +he determinationwas made or of the method that was used.

3. A calorimeter was constructed for the pu-pose of d .. i. thewCp of thermosetting polymers. The design of this instrument was based onthe maIntenance of adiabaticity between the polymer sample in the calori-meter vessel and the calorimeter wall during the Cp determination. Thetemperature of the cured polymer sample was increased continuously bymeans of an embedded resistance coil which was connected to a source ofenergy. Adiabatic conditions were maintained by electrically heating thecalorimeter wall at such a rate that the wall temperature was within 1Cof the temperature of the polymer sample at all times durinp the determi-nation. This calorimeter was designed to obtain engineering data with.a minimum of effort and could be operated by a single technician. Thedata obtained were estimated to be accurate to wthin 5%.

n. The work reported upon herein wao part of a long-term study ofthe -mosetting polymers being conducted in al effort to obtain a more basicunderstanding of the thermal, electrical. and mecbanical properties ofthese materials. In additions a study was being conducted using thermaland electrical methods tc get Information on the polymerization ch'aracter-istics of these compounds. The extent to which the physical propertiesof the solid polymer are influenced by the manner in which the polymeri-zation is conducted was also being stud ed. The results of this Cp

1

NARD report 6255

investigation indicate that Cp determination mide as a function oftemperature are real functions of the structure of the polymer a..d canbe used in studying the thermal and mechanical properties of thermo-setting polymers.

THEORY

5. The theory of the specific heat of linear polymers has receiveda lizited treatment by Boyer and Spencer (Reference 7). These investi-gators attributed the increase in Cp Arth temperature to increasingderees of freedom within the po2,mer. The molecules in the solid-ibrate about their equilibrium positions with an amplitude which increaseswith increasing temperature. As the temperature is raised these newdegrees of freedom are slowly activated and absorb heat energy. Theooserved effect of these new degrees of freedom, 4- +'he increase in Cpof the polymer. A theoretical treatment of the Cp of thermosettingpolymers has not been made. In this class of polymer the problem iseven more complex as the entire polymer is crossllnked and vibrationsand rotations occur only with difficulty.

6. The increase in Cp with temperature is only of lixited interestWhe. Compared to the fact that in many polymers there are rather abruptincreases in Cp over relatively narrow temperature ranges. This rapidincrease in Cp has been observed by many investigators (References 3, 7and 8) and can be attributed to a second order transition, Tg, occurringwithin the polymer. This transition which occurs upon heating a polymermanifests itself as a change in the temperature dependence of a largenumber of physical properties. At this temperature point, or morecorrectly, in this temperature range, a discontinuity occurs in the thermo-dynamic quantities such as specific heat, thermal conductivity and thermalexpansion. As the temperature is raised through this region, a processtakes place not involving latent heat, which results in larger values ofthe thermodynamic quantities and in a charge in the general physical proper-ties of the material. In general, when the material is above the transitiontemperature it becomes solter and mor e as contra.-ted to its hardbrittle character at lower temperature.

7. There is no simple physical explanation that will completelydescribe Tg in terms of the structure of a polynme- and which can beapplied to all polymers. For linear polynners, Tg increases approximatelyin proportion to the secondary valance force per u.i t length of polymerchain (Reference 7). However, bulky groups and strong polar groups leadto higher Tg values (Reference 7). It has been considered by some workersin this field that Tg is an internal melting point, above which the polymerstill preserves the external characteristics of a solid while behaving inpart like a liquid. As the polymer is heated and Tg is reached, sectionsof long polymer chains move further apart and are able to move more freelyabout the length of the chain (Reference 7). This new vibration and

2

NAVODTh P.eport 6255

rtation which occurs at TR can account for the increase in Cp, Alford

and Dole (Reference 9), wAo studied Tg in poiyvinyl chloride, concludedthat the large increase !n Cp at Tg could not be entirely the result ofadditional vibrations in the solid; other factors such as interchaininteractions involving a potential energy were suggested as being involved.

8. Van Az-eronzen (Reference 10) has concluded that the temperaturerange of Tp in linear polymers is mainly deternined by the strength of thesecondary valence enerries and by the "Lfexi ity of -the chain. In thermo-setting polynmers the higher values of Tg are primarily determined by theAxtent of crosslinking. This has been shoun by Fox and Loshack (Refer-ence i) who pointed out that crosslinking involves the exchange of second-ary bonds for primary bonds.

EXPEERIMi} TAL

A. Method

9. The adiabatic calorimeter, the calorimeter vessel, the temperaturemonitorinr and controlling instrumentation, and a detailed description ofthe techniques used to determine the Cp of thermosetting polymers have beenpreviously described (Reference 12). In addition, the calibration of thecalorimeter was described and the results of a Cp determination on poly-ethylene were compared with the results obtained on the same material byWunderlich and Dole (Reference 3).

10. The adiabatic calorimeter consists of three closed concentriccylinders separated by dead air spaces. Placed around the inner cylinderis a heating oil of nichrome resistance wire. The two 3ther cylindersand the dead air spaces serve to insulate the inner cylinder and preventloss or gain of heat during a Cp determination. The cylindrical polymersample containing an encapsulated heating coil and thermocouples is placedin the inner cylinder of the calorimeter. The heating coil in the polymersample is connected to a source of power and the temperature of t sampleis %hus raised at a uniform rate. This increase in temperature is measuredat 300 second intervals by means of the encapsulated thermocouples. Adia-baticity is maintained by heating the inner cylinder of the calorimeter ata rate so that it temperature is always within 1°C of that of the polymersample. This prevents loss or gain of heat by the sample.

11. In each case the polymer was extensively postcured before Cpwas determine1. Each Cp determination was conducted in duplicate and insome cases additional determinations were made. The Cp was cplculated by-jeans of Equaticn '

Cp = I2Rt (1)6.185 M(& T)

NAW)RD Report 6255

,x+ i is the current ' amperes, R is the tcpcrature dependent resistance

of tne heating coil in ohms, t the time in seconds, M the mass of thepolyner in grams, (1 T) the rise in temperature of the polymer in 'C,and the constant L.185 is the mechanical equivalent of heat in 'oulesper calorie.

B. Mate r--

12. The amorphous thermosetting polymers studied in this investigationconsisted of a number of commercially available compounds. Many of thesecompounds were casting resins. All the polymers were prepared for studyby the methods described in Reference 12. In addition to the therno-setting polymers, two thermoplastic polymers, polyethylene and polystyrenewere used to check the accuracy of the calorimeter. The polymers studied,the polymer type, the curing agent used a 1 the manufacturer are shownin Aptnendix I.

C. Results

13. 'ivures 1 to 6 are plots of the Cp as a function of the temperaturefor the polymers studied. Inspection of these plots shows that in eachcase the Cp increased with an increase in temperature. In one case (Epon828 cured with m-phenylene diamine) this increase in Cp was approximate3ylinear. This indicates that no sharp transitions occur within the polynerover the temperature range considered. However, in many of the polymersstudied the Cp, after an initial linear interval, suddenly increases andthen assumes an approximately constant value which is much less temperaturedependent. In two cases (polyamide-EPL 2795 and diallyl phthalate) theCp changes throughout the temperature range considered. The rate of changewas not constant yet no second order transition was indicated.

I~~ Published values of Tv for thermosetting polymers are nonexistent,but in the case of polystyrene, a thermoplastic polymer, Boyer and Spencer(Reference 7) reported a Tg value of 81'C. The value of 81-820 C (Figure 6)is therefore in excellent agreement with the published value. The temper-

ature range over which Tg occurred is shown in Table I.

DISCUSSION

15. It has previously bee-n no.ed that most polymers show an increasein Cp with temperature, and those polymers studied in this investigation

ai !;.how this increase ith temqxratire. This increase in Cp with temper-ature is however, of little" s, ni cance when compared with the factthat n -imany of ue therm.,setting .polymers studied there were rather

abrupt increases in Cp over relatively narrow tcmperatuire ranges. These

abr-pt increases were usually followed by temperature ranges over which

tne increise in Cp was small and the rate apprrximrately constant,, These

incrc %ses in Cp can be explained as due to second order transitions which

arp -e t CC ijr-rincy w ti fjn th c jrp 0 ( fp~r : nc 7). T~~~; r ~ If, rr

are show, in Table 1.

16. In an amorphous thermosetting. polymer, Tg will usually takeplace over a temperature ran ge. Ar example of this is shoim in F"igFurewhen Tr for Epocast R-155 occurs over a 2 FcC range. Tt is possible that.limited transitions cain occur a' lower te, q+eratures due

to the acquisition of limited mobility by portions of the mair. chain orby side groups (Reference 13). Eowever, T is catastrophic and unambiguous,the other limited transitions occur at lower temperatures and the 7%gritudeof sch transitions when compared to Tg on Cp versus ttimperature plotswill be very small (Reference 13).

17. The magnitude and the sharpness of the change of Co at Tg inthermosetting resins are Z'teresting. For example, in Figure 5 EpocastR-155 shows an increase in Cp from O.LO cal/gmC at 5i°C to 0.58 cal/gm'Cat 1050C. The other extreme is shown by Paraplex P-L3 polyester resinshown in Figure 1. This resin shows an increase in Cp at T, but theincrease is very small and sharp. At 1270C Cp is 0.*7 cal/gmC andincreases to a value of O.L9 cal/gmC at 1300C.

18. The observed Tg points for epoxide polymer systems can becorrelated with heat distortion temperatures, Dh. The exact relationshipbetween 7g and Dh is obscure, but usually Dh occurs at a slightly highertemperature than Tg. It appears likely that the two points are closelyrelated, Tg being characteristic of the micro properties of a materialand being a more fundamental measurement, while Ph is characteristic ofthe macro properties. Homer, Cohen and Kohn (Reference lL) havedetermined Dh for a number of epoxide polymer-catalyst systems. In thecase of 7pon 828 and m-phenylene diamine, D, was found to be in tne rangeof 150-159'C for an extensively postcuredpolyer. o Tg was found upto 160'C which is the limit of the calorimeter. Tn the case of Epon626 with tris(dimethyl ainomethyl)phrnol tri(2-ethyl hexoate), Dh wasfound to be at 930C. The results of this study indicate that Tg wascomplete at 70C. In the two systems compared above, neither the curingcycles nor the amounts of curinp ; gent used by Homer and co-workerswere exactly the same as for the polymers used in the C.- determinationsso that an exact comparison cannot be made. Weiss (Reference 15) hasfoimd Dh for Epon 828 cured with 56.5% of dodecenyi succinic anhydrideto be 780C. This is in agreement with the results presented here whereTg occurred at about 60C. The effect of plasticizers is to lower thetripcrature at which Tg and Dh occur (Reference 10).

19. Those polymers that do not show indications of a second trxisitionover the temperature range stltdied are of c(,nsidprable interest. The factthat a transition is not observed suggests that Tg occurs at a temperatureeither below 250C or above the riixxiu mI tenierature attained by the calori-meter during the Cp determination. The latter case is probable with Epon828 cured with m-phenylene diamine. With polyethylene, diallyl phthalateand polywnide-FRL 2795 the problem is more complex. It appears that inthese polymer- large numbers of structural Croupr do not suddenly become

5

rA'flRT, Report 6255

activated as the te erature is raised. These three polymers hvt Dh-of 75% (Reference 16), 121'r (Reference 17) and 60'C, respectively(,eference 18). It is sugfested that polymers in which Tg is not ob-served by Cp masurements, and in which it can be established that Tgdoes not occur below 25'C or above li)C, can be considered to have abroad Tg which occurs over a very wide temperature range and is ofrelatively small magnitude.

20. Two polymers containing an SiO2 filler were studied. The amountof filler present was determined by chemical analysis. The Cp of duPont820-001 which contains 15 of SiO,, is shown in Figure 5 and the Cp ofHysol 6020-105 which contains 31.8' of Si02 is shown in Figure 2. Ttappears that this calorimeter cam. be used to determine Cp as a fuctionof temperature for any polymer containing a filler, the only renuirementsbeing that the percentage of filler be not too high so as to make theviscosity of the liquid unpolymerized polymer too great for satisfactorypouring into the calorimeter vessel.

21. in the case of polystyrene a previous determination of the Cpas a function of temperature had been made by Ueberreiter and Otto-Laupenmuhlen (Tqeference L) Their results showed that in the regionbelow Tg the Cp of polystyrene was not a function of the molecular weight.samples having an average molecular weight of b60, 2300 and 3650 werestudied and between -16'C ad +lL'C the results of three separate Cpdetermination on the three samples yielded results that were almostsuperimposable. However, upon increasing the temperature the samplehaving an average molecular weight of 860 showed a Tg starting at about25'C while the szaples having an average molecular weA.ght of 2300 and3650 began txj show a Tg at 65'C and 75°C, respectively. This iilustratesthe dependence of Tfg on the chain lengtn of the polymer. After Tg wascomplete the Cp values increased -it a rconstant rate, bMt the sample havinpthe highest molecular weight showed somewhat nigher values of Cp.

22. The data shoz- in Figure 6 for polystyrene in the range of 50' -

800C are almost identical with those of Ueberreiter and Otto-Laupenmuhlen.

This is an excellent check on the calorimeter used here. However, afterTg occurs at 81 - 82'C the results in Figure 6 show a progressive increasein Cp and the values were somewhat hipher than those found in the rev ousstudy. No information was available as to the average molecular weightof the polystyrene used in this investigation. From the fact that Tgoccurred at 81 - 82C it can be estimated to be high (> 10,000). Theprevious work has shown that after Tg had been reached the Cp was some-what dependeni on the average molecular weight and since the resultsihere for Cp were somewhat higher2 it can be concluded that the averagemolecular weight was high. The po:lystyrene used in this investigationhad a Dn of b,5 (Refere e. 1).

23. Epon 828 resin was cured with three different amine curingagents and a comparison of the results of the Cp deterrinations for

6

NAVA)RD eport 6255

the three rystems is of interest. In the first s'ztcm (Firurc i)m-phenylene diamine -s the curing agent, and as mentioned previously,this sytem shoved a progressi.e increase in Cp from about 0.33 cal/gmCat L00C to about 0.51 caligmC at 160'C. This increase is almost linearand no Tg was observed. Li the second s'stem (Figure 3) diethylamino-propylamine was the curing agent, and this system showed both an increasein Cp and a Tg occurring over a wide temperature rar.Fe, Teninating atabout 1150 C. Generally, the values of Cp were somewhat lower than whenm-phenylene diamine was used as a curing agent. In the third system(Figure 1) tris(dimethylayi-nomettiyl)phenol tri(2-ethyl hexoate) was thecuring agent and this system differed from the proceeding two in severalrespects. First, Cp was higher by about 10-15% over the temperaturerange of LO*C - 150C, Tz occurred rather sharply and was complete at70'C and Cp progressively increased to about 0.56 cal/gm°C at 150*0.

2L. On .e basis of these results, it would appear that the systemTpon 82 8 -tris(dimethylamincmethyl)pherol tri(2-ethyl hexoate) was lesscrosslinked than the other two systers on the assumption that Cp valuesare an index of the derree of crosslinkinF. The fact that Tg occurredsharply at a relatively low temperature reinforce.= this conclusion. Also,these results indicate the extent to which the physical properties of aresin system are dependent upon the curing agent used. Tn Pach case thestoichiometric amount of curing agent was used.

25. The systematic error in a typical deten'ination of Cp ascalculated in Equation I is estimated to be as foll T0

Quantity Frror

1 2 1.5%

R 0.Lh

M 0.2%

t

T 0o-5

Go 2.6%

From these -stimated errors and fnm an analysis of the scatter of pointson the Cp vs. temperature plots, the overall error is estimated to bewithin 5%. in addition, the accuracy of these Op determira+ticnn h_- keen

chpcked by repeating the work of 1wunderlich and DolP (Ref~rncP 3) onlow pressure po.Lyethylene. These iit-3tigitors used an elaborate calori-meter capable of high accuracy and precision. The results of both setsof data are shown in Figure 6 and show excellent agreement. The values ofCp for polystyrene also show excellent agreement with the work ofUeberreiter and Otto-Laupenmuhlen (Pefnrence L).

7

'AW)RP Report 6255

1N CLUSIONS

26. The Cp results have led to the folowong nclusions:

a. The Cp of thermosetting polymers is in the rpnge 0.20cal/gmrnC to 0.60 cal/gmoC in the temperature range 30"C to 1W'uc andis temperature dependent.

b. The Cp values obtained as a function of temperature bythe adiabatic calorimeter are sensitive to second order transitionsoccurring within the polymer.

c. The second order transition in thermosetting polymersgene-ally occurs at a higher temperature'than in thermoplastic polymers.

d. A correlation exists between the second order transitionand the heat distortion Dc-nt.

e. The Cp v-alues are real functions of the structure of thepolymer.

RECO1RhDATO'S

27. It is recommended that the Cp of polymers of known chemicaland physical structure be determined. W4ith data of this type it r.ybe possible to relate the Cp values to the structure of the polymer.On the same polymers, the effects of varying amounts of curing agentand plasticizers on Tg should be established. Suph information couldbe used to establish the nature of Tg. Finally, the change in Cp whichoccurs upon polymerization should be studied. This could be determinedby measuring the Cp of both the monomer and polymer.

8

NAVXI) Report 6255

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1.20 -I1,V ADIABATIC CALORIMETER

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NAWnR ;'?eport 6255

TA1RL I

'IPRAVJRE WOE(~ OF SEC.NP ORD7ER TA?%STTIC)"IS, T9

M ate ri al Figure Number Lae

Polyethylene 6 Not present

Epon 828 + DEAPA (43 600-115 0C

Epon 62 +M !PrJA 2)1Not present

Epon 828 +D4i0 0 0-

Epon 82B + I]'P-30 ()3 4j0 -650C

Dow 26 33 + 1~3. 6301b"

Polyamide-ERL 2795 2 Not,, presentL

DuPont 82U-001 5 1*9*

Hysol 6020-105 2 0, 0-85 0C

Paraplex P-03 31250-1280C

Dia.ll phthalate 'Not presont

Polystyrene 61 81 0-82 0C

(1) Diethylamiopropyain~e;.2) m-phenylene diamine(3) Dodecenyl succiriic anhydride

(W) Trsdi~:! -riToehlpe tri( 2-ethyl hexoate)

N~ixf!fl Report 625

DISTRIgiTIONCopies

Chief, Bureau of Ordnance

ReW 1ReU 1ReS 1ReO 3Rep-3 (M. E. Countryman) 3ReS6a (S. J. Matesky) 1Rep-3 (I.nurtcu-ski.)1

Director, Special Projects OfficeSP27 (W. Cohen) 1

(L. Liccini) i(R. H. Wertheim) i

Chief, Bureau of ShipsCode 3h6 (J. Alfers) 1

(w. C, ran ') 1

Chief, Briaa 4f .?'onauticsAttn: N. E. 1-omisell, Materials Branch 1

P. Goodwtn, Materials Branch 1Chief, Office of Naval Research 1

Navy DepartmentWashington 25, Do C.

DirectorNaval Research LaboratoryWashington 25s D. C.

Attn: J. Keyes I

CowmanderU. S. Naval Ordnance Test StationChina Lake, California

Commander if Sz Naval Ondnce Test Station3203 E. Foothill BoulevardPasadena, California

CommanderU. S. Taval Ordnance LaboratoryCorona, California

Attn: Dr. Charles P. Haber 1

NAIRD Report 6255

niSTrRI iTLoHCopies

DirectorForest Products LaboratoryMadison, Wisconsin

Chief, Armed Forces Special Weapons ProjectThe PentagonWashington 25, D. C.

DirectorAdvanced Research Projects AgencyDepartment of DefenseThe PentagonWashington 25, D. C.

CommanderOffice of Scientific ResearchTemporary Building TWashington 25, D. C.

Comanding OfficerAir Force Ballistic Missile DivisionHeadquarters, Air Research and Development Co-mdP. o. Rox 262Inglewood, California

Franklin InstitutePhiladelphia 3, Pennsylvania

Attn: Mr. Gunther Cohn

Armed Services Technical Informat'on AgencyArlinvton Hall StationArlington 12, Virginia

Attn: TIPDR 5

Nimm~ Report 625

DISTRIJ TIt4Copies

Comwanding GeneralAberdeem Proving GroxndAbe rdeen# Maryland 1

DirectorDiamond Ordnance Fuie LaboratoriefConnecticut Avenue and Van Ness St., N. If.WBshingten 25; D. C.

ComeanderAir Force Armament CenterEglin Air Force Base, Florida

Attin ACR

CosmnderWright Air Development CenterWright-Patterson Air Force BaseDayton, Ohio

Attn: R. TomashottHe rbert Scnwartz

DirectorSquier Signal Laboratories?CEL, Materials SectionFort Monmuth, Neu Jersey

Engineering Research & Development LaboratoriesMaterials BranchThe Engineering CenterFort Belvoir, Virginia

Attnt S. Goldfein

U, S. Coast Guard1300 E Street, N. W.Washington, D. C.

Attn: CDR J. W. Naab

Transportation Research & Development StationMarine DivisionFort Eustis, Virginia

Attn: N. T. 'arshall1

National Bureau of StandardsCo-ecticut Avenue and Van Ness St. N .W.Washington, D. C.

Attn: F. . Reinhart

'irectorN ati1al Advisory Cc ittee for Aeronautics512 H Street, N. W.Washington 25, D.C.

NA' RD Report 6295

DTISTRT 7JTIONCopie-s

Com-xz dinp OfficerU. S. P vaI 9ropellant PlantTndiar. Hcad, Mary and

Commanding Officer and DirectorNaval Electronics LaboratorySan Dierov ralifornia

ComanderU. S. Naval Underwater Ordnance StationNe.rport, Rhode Island

Materials LaboratoryF'ew York Naval ShipyardFrooklyn 1, New York

Attn: R. Fi. .inans 1

CrommanderU. S*. Naval Proving GrundDah!-re n, Virginia

Corrrander,U. S. Naval Air Development CenterjoLisville, Pennsylvania

Attn: Dr. H. Moore 1

CMfice of the Chief of OrdnanceDepa,~tment of the ArmyPentascn. Puilding14ashinpton 25, D. C.

Attn: T. P. Blevins 10 1Th'A 1

Commanding OfficerPicatinny k rsenalDover, New Jersey

Attn: Piastics Re~carc.h roup

Commanding GeneralFrankford ArsenalPhiladelphia, Pennsy!vania

Attn: D. J. Donnelly 1

Comman ding Genera.Watertown ArsenalWatertown, Massachusetts 1