Document BmQDx3kkbM8wRyEzRLbE17Ko

B. F. Goodrich Chemical Company A CHVISOM OF TH6 S. F. GOOOfftCH COMPANY DEVELOPMENT CENTER Degradation and Combustion Products From Poly(vinyl chloride) II - Description of Pyrolysis Unit and Initial Pyrolysis of PVC Date Completed: by M.M. O'Hara December 2, 1968 Date Issued: Dcceofcer 6, 1968 Distribution: Akron General Chemical Plant P.T. Whitmire - R.S. Reynolds Akron Legal Dept. E.K. Bean Avon Lake Genera I Chemical Plant R.N. Rylands-R.W. HcKay-J.M. Whitney Breckavllle Research Center R.J. Fawcett *C.F. Clbbs Calvert City *C.L. Woods - D.B. Schrock Cleveland W.F. Blxby W .E. Brodine C.H. Hetzfer P.H. Lawrence E.W. Harrington M.W. Larson 0 C.D. Segner (7) R.D. Scott - J.L. Nelson B.M. Zwicker - J. Valentine Development Center *L.F. Arnold *L.A. Bennecc *R.R. Bloor *L.H. Conklin B.A. DlLlddo C.E. Fleming C.H. Kotheimer R.M. Kroager *C.H. Lufter D.P. Knechtges Development Center continued.... R.J. Meyer B K. Mikofalvy C.E. Parks N.H. Sherwood J.A. TePas G.L. Wheelock Technical Council R.J. Wolf C.T.F. (3) C.B. Cooper - J.P. Piers Long Beach L.C. Crunkleton - S.S. Michels Niagara Falls *T.R. Llnak - J.A. Klupar BFG04366 Modified Report -- r\ *** a T00SS90Z I - MAJOR OBJECTIVE: the major objective In chi* work i the development of the nece**ary analytical tools for the rapid determination of the degradation and confcusclon products from PVC. In addition to studies of PVC, the developed analycleal-pyroLysis tool will be used in the following areas: 1. toxicity, 2. flammability, 3. polymer structure and stability, 4. efficiency of PVC stabilizers, 5. polymer identification (fingerprinting). II - LIMITED OBJECTIVES A pyrolysis unit that afforded the following capabilities was desired: 1. che temperature of pyrolysis accurately known, 2. wide range of pyrolysis temperatures possible, 3. all volatile pyrolysis products be admitted to Che gas chromatograph for analysis, 4. capabilities for pyrolysis In an oxygen rich and oxygen poor atmosphere, 5. reproducibility. Ill - SUMMARY OF CONCLUSIONS: 1. A radiant heat pyrolyzer having the necessary capabilities for degradation, toxicity, flammability and polymer characterization studies has been constructed. 2. Initial pyrolyaes of PVC (Geon 103EP F-7) In both a nitrogen and helium atmosphere have been carried out. The result of these studies showed that at 600*C., PVC degrades to 21 major (identifiable) and 25 minor components. 3. The major degradation products have been identified by mass spectromecr1c techniques. These products are: l. HCl 2. C02 (and N2) 3. e thane 4. ethylene 5. propane 6. propylene 7. butane b. butene 9. butadiene 10. dlacecylene 11 K*. n r/* n.* b?go^61 20855002 Pa gc 2 12 . t o l ue ne 13. 14. 3 xylenes 15. 16. chlorobenzene 17. ethyl toluene 18. indane 19. naphthalene ?:>20 2 2 isomers of mothylnaphthalene 4 . A quantitative analysis encompassing volatiles and non-volatiles has been completed. The results of that determination are contained in the following table. X Weight ~58 (Theoretical) -10 --32 Composition of Fraction HC1 Carbonaceous Ash(non-volatile) Volatile Aliphatic and Aromatic Hydrocarbon Fraction IV - FUTURE ACTION: The next phase of this research problem is: 1. carry out the pyrolysis of PVC in varying levels of oxygen and compare and correlate the results with those pyrolysis results obtained under inert conditions. 2. pyrolyze copolymers of PVC and other polymers in order to obtain a catalog of reference pyrograms (polymer characterization) 3. a study of the flamabll 1 ty character 1stics of PVC-AcrylatePVDC-Phosphonate-Polymers has been Initiated. (Preliminary results are very encouraging.) 4. initiate a program in the thermo-oxidative degradation of Hydrin 100 and 200. This work will be in support of current studies on the Hydrin process. 20855003 BFG04368 Page 3 V - INTRODUCTION AND DISCUSSION' In a recent outline of objectives,^ it was stated that a pyrolysisgas chrocu tograph-mass s pec t romo te r tandem system was being developed for purposes of carrying out polymer degradation studies. The gas chrov:o;r . phic technology required for separating the typical degradation products fro-. ?YC has been developed and detailed in a status report. (2) The present paper dv.-,l< with the pyrolysis apparatus that has been constructed for these studies, with initiat pyrolysis of PVC ar.d with the identification of the major pyrolysis products from PVC. It was deemed necessary that the pyrolysis unit have a number of capabil it ies. These were: 1. that the temperature of pyrolysis be accurately known, 2. that a wide range of pyrolysis temperatures be possible, 3. that all pyrolysis products be admitted to the gas chromatograph for analysis, 4. that pyrolysis could be carried out under an oxygen rich and oxygen poor atmosphere, and 5. that some degree of reproducibility exist. In an of the areas in which this pyroly s-gas chromatographicaass spectrometrie tool will be used (See I, Major Objectives), it will be Important that all volatile degradation products be analyzed. For studies in which polymer structure is to be correlated with degradation products, the temperature of pyrolysis must both be accurately controlled and known. Similarly, the capability of a wide range of pyrolysis temperatures is Important. The need for being able to control pyrolysis atmosphere is important with respect to simulating usual combustion conditions. Finally without some degree of reproducibility, correlations of degradation products sod toxicity, or flammability, for example, would be impossible. It is felt that the pyrolysis unit constructed and described in detail below meets the above requirements. A. Description of the Pyrolysis Unit The unit basically consists of a quartz chamber which is heated by an external furnace. The furnice is that which is provided with the P and E commercial unit and temperatures of up to 1000'C. are possible. The quartz chamber contains an inlet lire through which carrier gas (He) can be admitted to the pyrolysis chamber and an effluent (exit) line through which the degradation products (ar.d carrier gas) are carried. These two lines have been connected to an F ar.d M Cas Sampling Valve in such a way so as to replace the nocovil "tempiina loop". A carrier gas line from the chromatograph leading to the valve and 'n effluent line leading from the valve to the injection p*rt of the chromitograph have also been constructed. BFG04369 20655004 20655005 01iff** v) a?qjpu3 stsXiojXj c-'--i sun 3an qdp^?o;pcoj^o s*p 03 auT'j 3usni5^3 *0*3 tkMj so jTjjro ?M'A U9AQ AIA jt9qtupi3 sysXxojiQ oorujnj rrsXjo.iX<j (0 <i (3 (a (D (3 (V I t I I I I ir i i t i i f i i i i i j- an Page 4 With the vjIvo in the "in" position, carrier gas by-passes Che pyrolysis chamber (l.e., the "sample locp") enrough the valve and travels directly to the injection port of the gas chromatograph. With Che valve in this position, the pyrolysis ur.it Is then loaded with a porcelin boat containing sample, the ho: zone of the chamber is brought to temperature and che encire unit is purged with N2 or .'>2/02 The boat is then moved into the hoc zone where degradition is carried out. Once the degradation period his been completed, the gas sampling valve is switched to the "out" position. Carrier gas is than admitted to the pyrolysis uric and the degradation products are carried from the unit, through the heated sampling valve to the injection port of che chroma cograph. (See accompanying block dla gram). All effluent lines through which the pyrolysis products pass, as well as the gas sampling valve itself, are heated. Provisions were made during che construction of che effluent line Co the Injection port of the chromatograph for "on-column" injection. A calibration was made between che temperature read-out on che pyrolysis unit and the actual temperature inside che hoc zone of che pyrolysis chamber so Chat Che crue temperature of pyrolysis could be known. B. Volatilization of an Analytical Sample In the Pyrolysis Chamber. An analytical sample of benzene, toluene and naphthalene was prepared and analyzed on the gas chromatograph by two methods. The first was che usual direct injection procedure (Method A) while che second Involved placing che mixture in a sample boat, volatilizing the sample in che hot zone of the pyrolyzer and sweeping the vapor from the pyrolyzer to the chromatograph (Method B) for analysis. The results of these two runs are 'contained in Table I. It is believed that the 31 difference in analysis Isa result of the differences in che two methods and not due to a "selective extraction" of one of the products while in transit from che pyrolysis chamber to the gas chromatograph.^ If this were happening, one would expect che naphthalene content to be low in the analysis obtained by Method B. However, che opposite of this results: Naphthalene is 31 higher when the analysis Is carried out by Method B. TABLE I - C.C. Analysis of Analytical Mixture. Method A: Direct Injection; Method B: Sample Volatilized in Pyrolysis Chamber. Benzene Toluene Naphthalene Jt__ 41 48 11 Method B JL 38 48 14 20655006 Page 5 It should bo noted that while in Method A the chromatographic peak due to benzene Is sharp with no tailing, the same peak by Method B is broad and tails considerably. This factor is the most probable source of error in this analytical determination. C. Initial Pyrolysis of PVC. Identification of Major Degradation Products Preliminary degradations of PVC were carried out at 600*C. for 5 minutes in an inert atmosphere (X2 or H). Initially, sample sizes in the S to 10 mg. range were used but due to the preponderance of products (other than HCl), amounts in the 20-30 mg. range were necessary. Since HC1 has an adverse effect on the chromatographic column used for separating the degradation products fSE52 on ABS), it was removed through reaction with copper powder. In a typical pyrolysis run, a 25 mg sample of PVC (Geon 103EP F-7) produced, upon thermal decomposition, 21 major and 25 minor products. The identification of the major products has been completed and the results of these identifications are contained in Table II. ^BLEM^ii^J|rodkjCj^Frocn_the^hennal^eradaion=jyMPV^iat!j600J|i HCl CO2 Ethane Ethylene Propane Propylene Butane Butene Butadiene Olacetylene Benzene Toluene Xylene ( 3 Isomers) Chlorobenzene Ethyl toluene Indane Naphtha lene- 0-Methylnaphthalene a-Me thylnaphthalene 'cG 20655007 Page 6 A typical pyrogram of PVC can be divided Inco three- regions: volatile gases (CO2 C2H4, C2H6, etc.), low boiling saturated and unsaturated hydrocarbons (C^-Cfc) and high boiling aromatics (benzene, toluene, naphtha lee,.-). In order to ciore fully Investigate the volatile gas products (the low end of the pyrogram), gas chroma tographl c separation of these particular pyrolysis products or. a Porapak QS column was necessary. Thus, In order to Identify all degradation products, analysis on a Porapak and on an SE-52 column had to be carried out. The minor degradation products from PVC could not bo Identified due to sensitivity limitations In the ova ss spectrometer. However, the majority (18 of 25) of these minor products appear In the "aromatic region" of the PVC pyrogram while the remaining minors (7) are In the light hydrocarbon region. Boettner and Weiss^^ have reported that both aliphatic and aromatic products are evolved when PVC is degraded In the presence of air (TABLE III). A more recent report(^) by Noffz Indicates that the only degradation products from PVC (aside from HC1) are aromatic type compounds (TABLE IV). WBLEIII-WeizhtLossvs^DeeradationProductsfromPVClnAirjO) 1555 Aromatic (401) CO HCI (97%), Benzene (3X) Aliphatic (30V CO and CO, (?0Z) CO2 Zox 201 weight loss 0Z 20655008 I. Benzene 2. Toluene 3. Ethylbenzene 4. Xylene 5. Chlorobenzene 6. Xylene 7. Styrene 8. n-Propylbeozene 9. Allylbenzene 10. 2-Methyl styrene 11. Azulenc 12. Indane 13. Me thylindane 14. Indonc 15. Te tral in 16. Ml: thyl Indar.e 17. Naphthalene 18. Me thylnaphthalene 19. 0i-Me thy Inaph tha le 20. Diphenyl me thane 21. CJ2H12 BFG04373 Pge 7 The results from the u-orjc described in the present paper correspond fairly closely to the findings of Boettner and Weiss. Although Koffz has reported th.it the only products arising from the thermal degradation of PVC are various aromatics, the actual state of affairs appears to be that both aliphatic, olefinie hydrocarbons and aromatics are formed. One of the more interesting aspects of the degradation products coming from PVC is the Large amount of CO2. Direct probe experiments involving the degradation of PVC in the heated inlet system of the mass spectrometer have verified that a large amount of CO2 is released during degradation in vacuum. This result reflects one of two situations: a considerable amount of absorbed oxygen on the PVC resin or oxygen chemically bonded to the backbone of the polymer. In order to further investigate this, a sample of the resin was placed In the cold zone of the mass spectrometer Inlet system ar.d evacuated overnight (10*6 am Hg). The sample was then moved to the hot zone of the inlet system where degradation proceeded. The amount of CO2 released from the degassed sample of PVC was identical to that released from a sample that had not undergone overnight degassing. The results, however, cannot be construed as evidence for oxygen bonded Into the PVC polymer. It may well be that the released CO2 results from absorbed oxygen that is not effectively removed durLng the vacuum treatment. This phenoomon of CO2 generation during the pyrolysis of PVC in an inert atmosphere is being further investigated. Another factor that requires limited Investigation is the effect of secondary reactions on the types of degradation products. Since the pyrolysis products from PVC reside in the hot zone of the pyroiyzer for relatively long periods (5 minutes) of time, secondary degradations of primary products are quite possible. This important factor will be further investigated by varying the temperature and time of degradation. D. Quantitative Analysis Sumirv: A quantitative analysia of the degradation products from PVC at 600*C. reveals that approximately 58X (by weight) of the polymer is converted to HCl, 321 to aliphatic and aromatic hydrocarbons and 101 remaining as a carbonaceous ash. It has previously been stated that the large amount of CO2 generated during the pyrolysis of PVC cannot be explained In the absence of further data. 20555003 BFG04374 M . '; r.<# The anoun: -cf CO2 gc-r.c rated' during ,a typical pyrolys is'-r^Sc^^^^^dr^^cr h-ilf of the vola t lie fraction b,f 'the degradat Jon produc t'f^.'.^tx^'view of this discre psney, a, preciiS; quantitative analysis is not possible at this tine. However, a-"faiFiy ;good approximation of the quantity of volatile products ir. relaticr: to the quantity of starting polymer can be rode. Since only-30". of The poTyner is covertqd into a hydrocarbon and Ct^C?) fraction, uncertainty in the origin of the CC>2 does not result in too large of an error. In order to determine the amount to residue that results from the 600"C. degradation of PVC in an inert afnosphere, a 21.7 mg. sample of the-' pc'ym.r was pyrol.y.jed at 600*C. for 5 minutes in the absence of copper ptvfrder. The residue (2.10 pj) chiis accounts for approximately 107. of the ssraple, Sycw-c.; weight. Since 58'. by weight of the polymer is HC1, this Waves 'approximately 327, of the original- polymer that is converted into the hydrocarbon snd-C02 (?) fraction,.-" [3oett,ner and Weiss have reported that;, (TABLE 111) of' PVC Is converted Intof- aromat id and a 1 ipha tie hydrocarbonsT The following anal-yjSis .(TABLE Vc) is of- this 32*', volatile fraction that is produced during the pyrolysis of ?VC In^Ash of the two quantitative ;analyses' that were carried .put, two exac c- we ighS-samples . of .PVC- wete''degraded'-(for- each ';ahaly's'i s) under thfe same fpnd fed ions. The prodpe ts fros? one of. the deTgfaditions were analyzed j<Sti the -Pnrepals QS r.ciyh vhWe the.products' frbm Ttvi? "second degradation were *naTy'secL<i*/--.icVii SE57 column. In this way, both the volatile gases and the hi-gher:>W%cvIar,weight aromatics could he precisely analyzed. ' This dyal rabysis procedure was carried out twice and the results of these two' analyses afetpresenCe'd in Table V. The resuj; ts; deaonstrate-^the excel lent reproducibility that is ohc-sitiad in these pyrolys is'`experiments. For example, in only one instance do the' two analyses differ by more than 2% absolute. In that case (butane, butadiene butene, diacetylene), the calculation of the gas chromatographic peak area was difficult due to the dlssysnetry of the peak (See Appendix). Approximately half of the volatile fraction consists of saturated and unsaturated hydrocarbons while the remaining products are the aromatics. Of these, 667. Is benzene. It should be noted that the CO2 content that results in each analysis is not Included In the calculations. Thus, the quantitative analysis Involves only the hydrocarbon fraction. This analysis can be adjusted if it is found that the large amount of COj does indeed result from the degradation of PVC. BFG04375 TABLE V - Quantitative Analysis of the- Volatile Fraction (32% bv u'cirht) fr.m PVC.* Component Analysis I C.C. Peak Area 7. N2 127.1 - ch4 58.2 18 co2 367.4 - C2H4 21.7 7 C2H6 30.2 9 c3h6 25.7 8 c3h8 Butane Butadlene Butene Dlacetylene (?) ) 9.5 23.2 3 7 Benzene 109.4 34 Toluene Xylenes ( 3 Isomers) 14.8 7.7 5 2 Chlorobenzene 7.4 2 Indane 1.3 -l Ethyl toluene 1.7 -l Napththalene 7.7 2 Methyl naphthalene (a-?) \ Methyl naphthalene (*-?> 3-2 l z 321.7 100 Analysis II C.C.P.A. 7. 31.2 38.2 232.0 20 - 12.6 7 17.2 9 11.4 6 3.6 2 8.0 4 67.2 9.5 4.7 5.3 1.5 1.4 5.6 3.1 189.3 35 5 2 3 -1 -***1 3 2 100 BfG0^6 Page 10 1. L.B. Crider, M.M. O'Hara - "A Study of the Degradation and Combustion Products from Polymers. Objectives and Problem Description" Inter-Organitacion Correspondence. B.F.C. Chemical Company, August 2, 1968. 2. M.M. O'Hara, "Degradation and Combustion Products From Poly(vinyl chloride) : Part I. September, 1968. 3. Boettner and Weiss, American Industrial Hygiene Assoc. Journal 28, November-December, 1967. 4. Noffz, Benz, Pfag, Z. Anal. Chem. 235 #1 p. 121-37 (1968). 20655012