Elemental composition – CH 2 Polyethylene Polypropylene Polyisobutilene

1. On the Universal Behaviour of Some Organic Compoundsunder CompressionB.A. Nadykto RFNC-VNIIEF, Sarov, N.Novgorod region, 607190, RussiaPresentation for the Joint U.S. – Russia Conference on Advances in Material Science, August 30 – September 04, 2009, Prague, Czech Republic

2. A number of widely used hydrocarbon materials transfer into solid state due to the formation of additional inter-molecular bonds during polymerization. Such materials are polyethylene, polypropylene, polyisobutylene. These materials have about the same initial density and the same elemental composition (СH2), only the structures of the initial molecules differ. At normal pressure and temperature these materials have strongly differing properties. For example, polyisobutylene, in contrast to polyethylene, is an elastomer, like caoutchouc. At the same time, as the analysis conducted shows, the behaviours of polyethylene and polypropylene under compression are similar and are described with one and the same equation of state (with the same parameters).

3. Elemental composition – CH2Polyethylene Polypropylene Polyisobutilene Polystyrene. Elemental composition - CH

4. Computational Technique E=EC+ET ; P=PC+PT . σ = ρ/ρn, ρn is the equilibrium density at P=0, T=0. In Mie-Grueneisen form PT=ΓρET. In Dugdale-MacDonald approximation, Γ = (2σ1/3 – 1)/(3 σ1/3 – 2). EH = (PH+P0)(1/ρ00-1/ρ)/2; U = [PH(δ-1)/(ρ00δ)]1/2 ; D = U δ/(δ-1); δ = ρ/ρ00 1. Nadykto B.A., Physics-Uspekhi, 36(9) 1993, 794-827.

5. (a) (b)Figure 1. The P(ρ) curves for (а) HP polyethylene (ρoo = 0.92 g/cm3); (b) polypropylene (ρoo = 0.90 g/cm3). Experimental data:  - from ref. [7], x – from ref. [6]. The curves were calculated by us for two different polyethylene phases.

6. Another type of hydrocarbons has chemical composition CH or close to it (C14H12). Polystyrene exhibits complex behavior under compression, which is indicative of the presence of phase transformations followed by the change of the material electron structure. EOS parameters for different polystyrene phases describe well the stilbene (C14H12) behavior under compression. Benzene (C6H6) and toluene (C7H8) hydrocarbons that are liquid under normal conditions, under compression display the behavior similar to that of polystyrene. The electron configuration of nitrogen-like carbon ion can be expected in these compounds.

7. (a) (b)Figure 2. Dependence P(ρ): a) for polystyrene, experimental data: squares – from [7], crosses – from [6]; b) for stilbene, experimental data: squares – from [7]. The curves are our calculations for different phases of polystyrene.

8. The correlation behavior of compressibility of hydrocarbon and fluorocarbon compounds of CF2 type is shown. It can be connected with the possibility of identical electron configuration of oxygen-like carbon ion.

9. (a) (b)Figure 3. The dependence of parameters on the Hugoniot for polytetrafluoroethylene: a) P(ρ); b) D(u). Experimental data:  – from Ref.[16], ∆ – from Ref.[15], x - from Ref.[6], ◊ – from Ref.[7]. The curves are the results of our calculations for different polytetrafluoroethylene’s phases.

10. (a) (b)Figure 4. The curves for polychlorotrifluoroethylene: a) P(ρ), b) D(u). Experimental data: x – from Ref. [6]. The curves are the results of our calculations for different polychlorotrifluoroethylene’s phases.

11. a) (b)Figure 5. a) Comparison between the P(ρ) curves for polytetrafluoroethylene (curves and experimental data on the right) and polychlorotrifluoroethylene (curves and experimental data on the left). It is evident that these materials demonstrate similar behaviour in compression. b) The P(ρ) curve for polytetrafluoroethylene. Triangles (∆) show the pressure points [7] on the Hugoniot for liquid (carbogal) of the same elemental composition (CF2) as Teflon.

12. a) (b)Figure 6. Curves a) P(ρ), b) D(u) for polyvinylidene fluoride (PVDF). Experimental data: ∆– form Ref.[6],  – from Ref.[17]. The curves are the result of our calculations for different PVDF phases.

13. Organometallic compounds ferrocene (Fe(C5H5)2) and uranocene (U(C8H8)2) are sandwich-type compounds with the metal ion in the center and two cyclic hydrocarbon groups, located in parallel planes. The ferrocene density under normal conditions is 1.49 g/cm3 [19], the uranocene density is 2.29 g/cm3 [20]. The electron structures of the compounds are, evidently, determined by the external electron shell of the CH group, which should be similar to that of pure hydrocarbons of similar compositions. The partial density of hydrocarbons is 1.042 g/cm3 in ferrocene, 1.068 g/cm3 in uranocene, which within 1-2% equals the polystyrene density under normal conditions. Therefore the density of these metalloorganic compounds grows if compared with the corresponding hydrocarbons, mainly due to the mass of the metal ion, which does not essentially contribute to the specific volume compared to the CH group. In this case compressibility of a organometallic compound must be determined by the bulk modulus close to that of the corresponding hydrocarbon at equilibrium density of the organometallic compound. Close results have been obtained for compounds of element composition С24H24Hf and С22H20Hf (data from [21]).

14. Table. 1. Properties of organometallic compounds • [19] Chemistry encyclopaedia. Moscow. BRE. 1999. Vol..5. p. 87. • [20] Chemistry of actinides. Edited by J.Katz, G.Seaborg, L.Morss. Moscow: Mir. 1991. P. 398. • [21] K.C. Juntunen, B.L. Scott, J.L. Kiplinger. J. Alloys and Compounds. Vol. 444-445 (2007). P. 363-368. • [22] Chemistry encyclopaedia. Moscow. BRE. 1999. Vol..4. p.559.

15. In literature [23], we have found density values for ten salts of acetic acid for bivalent metals M(C2H3O2)2. In nine cases, the deviation from the average partial density of the hydrocarbon complex M(C2H3O2)2. ranges 1–2%, and in one case – 4 %. Along with this, densities of the compounds differ by a factor of two and more. This means that the metal ion has almost no contribution to the compound volume and is likely to be located in one of the interstitial voids of the hydrocarbon complex.

16. Table 2. Properties of acetic acid salts

17. Conclusions It has been shown that hydrocarbons of the same elemental composition, CH2, demonstrate the same behaviour under compression. Apparently, the volume and compressibility of a compound is determined by a carbon ion and hydrogen makes no contribution to its volume. It is noted that fluorocarbons of different elemental compositions have almost the same slopes of the P(ρ) curves in sections with appropriate pressures (close values of bulk modulus). This can be attributed to the fact of the same compressibility of the electron shell of a carbon atom (ion) in various fluorocarbons. The calculated D(u) curves clearly demonstrate non-linear and non-monotone behaviour within a wide range of parameters. Such non-monotone behaviour is demonstrated to the highest extent by the P(ρ) curves. The non-monotone behaviour is proved by comparison with available experimental data. The density of metalloorganic compounds grows if compared with the corresponding hydrocarbons, mainly due to the mass of the metal ion, which does not essentially contribute to the specific volume compared to the CH group.

18. References 1. Bridgman P.W. Collected Experimental Papers. Harvard University Press. Cambridge. MA. 1964. 2. Walsh J.M. //Bull. Am. Phys. Soc. 1954. Vol. 29. P. 28. 3. Bancroft D., Peterson E.L., Minshall S. //J. Appl. Phys. 1956. Vol. 27. P. 291. 4. Altshuler L.V. // Physics-Uspekhi, 1965. V. 85. N 2. P. 197. 5. Lawson A.W., Tang T.Y. //Phys. Rev. Vol. 76. P. 301. 6. Marsh S. P.(ed.) LASL Shock Hugoniot Data. University of California, Berkley, 1980 7. Trunin R.F.(ed.). Experimental data on shock-wave compression and adiabatic expansion of condensed matters. RFNC-VNIIEF, Sarov. 2006. 8. Nadykto B.A. //Doklady AN SSSR. 1991. V. 316. N 6. P. 1389. 9. Nadykto B.A. // Physics-Uspekhi, 1993. V. 36, P. 794. 10. Nadykto B.A. //VANT. Ser.:Theor. i Prikl. Fizika. 1996. Issue 3. P. 58. 11. Nadykto B.A.//In New Models and Numerical Codes for Shock Wave Processes in Condensed Media, edited by I.G. Cameron. Oxford: AWE Hunting BRAE, 1998. P. 205. 12. Nadykto B.A. //Khimicheskaya Fizika. 1999.V. 18, N 11.P. 87.

19. 13. Kennedy G.C., LaMori P.N. // J. Geophys. Res., 1962, Vol. 67, P. 851. 14. Weir C.E. // J. Res. Natl. Bur. Std., 1953. Vol. 50, P. 95. 15. Champion A.R. //J. Appl. Phys. 1971, V. 42, N13, p. 5546-5550. 16. Robbins D L, Sheffild S A, Alcon R R. Shock Compression of Condensed Matter 2003. Edit. by M D Furnish, Y M Gupta, J W Forbes. AIP. Melville. New York 2004. P. 675-678. 17. Millett J C F, Bourne N K. J. Phys. IV France. (2006). Vol. 134. P. 719-724. 18. Dattelbaum D.M., Robbins D.L., Sheffield S.A. at all. Shock Compression of Condensed Matter 2005. Edit. by M D Furnish, M. Elert, T. P. Russell, C.T. White. AIP. Melville. New York 2006. P. 69-72. 19. Chemistry encyclopaedia. Moscow. BRE. 1999. Vol..5. p. 87. 20. Chemistry of actinides. Edited by J.Katz, G.Seaborg, L.Morss. Moscow: Mir. 1991. P. 398. 21. K.C. Juntunen, B.L. Scott, J.L. Kiplinger. J. Alloys and Compounds. Vol. 444-445 (2007). P. 363-368. 22. Chemistry encyclopaedia. Moscow. BRE. 1999. Vol..4. p.559. 23. Chemists Handbook. V. 2. М.: Khimia. 1964.