tion equation,.: for this group was not as great as for all other classes. However. it mas considered necessary to inclucle this group. because of the scarcity of data for fused-ring aromatic compounds. The average accuracy for all API hydrocarbons analyzed nas considerably less than one carbon group for each type. This was considered adequate as a first approximation for determining the average number of the various structural groups. It was realized. initially. that the. molar volume and the molar refraction were very intimately related properties and that the equations devrlopcd in terms of the fire structural groups might not be independent. However. this investigation reveald that these two equations were in fnct independent, and that the difference- between them \$ere of such a mGignitude that the solutions obtained \$-ere in substantial agrec,mcnt with the known values of the groups prrwmt. Consequently, it was established that n considerable amount of structural information could he dedured from thcsc ti\-o cloq~ly related properties. The results of the application of this nirthod indicatd the merits and some of the deficimcies of this t r p e of qtructiiral a d y a i s . 4 s physical propwtieq 1)ecome availahlc on new tvpes of structures. the scope of thi. method may be extended. This approach could be applied to types of structures not already covcred, by developing analogous equations for other physical properties and also by considering additional interaction effects. One of the nim-itq of this system lay in the manncr in uhich the coefficients in the molar
volume and molar refractMn equations were determined. This method should give confidence in extrapolating beyond the molecular \$-eightrange of the known compounds that were uscd to establish the system. Definition of symbols: CI = No. per molecule of CH,, CH,, CH, and C groups in linear and branched chains D, = CI (calcd.) - C, (obsd.) C, = S o . per molecule of CH, groups in saturated rings, including case where hydrogen atoms may be replaced by branched or linear chains D1 = Ct(ca1cd.) - C2(obsd.) C3 = No. per molecule of CH groups which are junctions hetween fused saturated rings, as well as similarly situated groups where hydrogen is replaced hv linear or branched chains D3 = C,?(calcd.) - C, (ohsd.) C, = 10. per molecule of CH arouns in aromatic rings, inclu&ng case where hydrogen may be replaced by branched or linear chains Dd = Cl(ca1cd.) - Ca(obsd.) I
C, = KO. per molecule -C-
Dj’=
I
groups
which are junctions bitween fused aromatic rings, as well as common junctions between saturated and aromatic rings C5(calcd.) - C5(0bsd.i LITERATURE CITED
1 ) AI-Mahdi, A. .4.K., Ublielohde, A R , Compt. rend. rkunion ann U L P C c o m n
thermodynam., Cnion intern. phys (Parzs), 1952, Changenients de phases. 360-5. 2) Al-RIahdi, A. A. K., Ubhelohde, .4. R . , Proc. Roy. Soc. (London), 220‘4, 143-56 (1953). (3) Burdett, R ; Taylor, L. W., Jones, L. C., ,Jr., Molecular Spectroscopy,” p. 36, Report of Conference Organized by Spectroscopic Panel, Hydiocnrhoii
Research Group, Institute of Petroleum, London, Oct. 28-9,1954. (4) Eccleston, B. H., Coleman, H. J., Adams, N. G., J . Am. Chem. SOC.72, 3866-70 i1950’1. (5) Egloff, G., “Physical Constants of Hydrocarbons,” Vol. 111, p. 25, ACS Monograph, Reinhold, Sew York, 1946. (6) Krevelen, D. W. van, BrennstgfChena. 33, 260-8 (1952). ( 7 ) Ibtd., 34, 167-82 (1953). (8) Krevelen, D. W.van, Blom, L., Chermin, H. A. G.,Sature 171,1075-6 (1953). (9) Krevelen, D. W.van, Chermin, H . A G., Fuel 33, 79-87 (1954). (10) Krevelen, D. W. van, Schuyer, J., ‘Coal Science, aspects of Coal Constitution,” Chap. VI and VII, Elsevier, New York, 1957. (11) Kurtz, S. S., J r , Sankin, Albert, Ind. En9. Chem. 46, 2186-91 (1954). (12) Lorentz, H. A . , Ann. Physik 9, 641 (1880). (13) Xes, K. van, Resten, H. &4.van, “Aspects of the Conqtitution of hIineral Oils,” pp. 299-314, Elsevier, Sew York, 1951. (14) Ibid., pp. 318-49, 445-53. (15) Ibid., Chap. IV. (16) Schicssler, R. W., Whitmore, F. C., Ind. Eng. Chem. 47, 1660-5 (1955); - h i . Doc. Inst., Doc. 4597. (17) Schuyer, J., Blom, L., Krevelen, D. W.van, Trans. Faraday Soc. 49, 1391401 (1953). (18) Schuyer, J., Krevelen, D. W. van, Fuel 33, 176-83 (1954). (19) Smith, E. E., Analysis of Lubricating Oils. Part 1. Correlation of Phvsical Properties and Structural Composition of Lubricating Oils, Engineering Experiment Station, Ohio State Cniversity, 1953, Bull. 152, pp. 1-31. (20) Vlugter, J. C., Waterman, H. I., Westen, H. A. van, J . Inst. Petrol. Technologists 18, 735-50 (1932). (21) Ibid., 21, 661-76 (1935). (22) Ward, A I,., Kurtz, S. S., Jr., IXD. E Y G . CHEM., . k Y 4 L . ED. 10, 559-76 (1938,.
RECEIVED for review June 9, 1958. Acreptrti April l5] 1959. Division of Gas and Fiiel Chemistry, 134th lIeeting, .iCS, Chicago, I l l , Septemhrr 1958.
identification and Analysis of Polyurethane Rubbers by Infrared Spectroscopy P. J. CORISH Chemical Research Department, Dunlop Research Centre, Fort Dunlop, Birmingham, England The identification and analysis of polyurethane rubbers by the infrared spectra of microtomed sections are described. The use of crystallinity bands to characterize the acid portion of the polyester in polyester-urethanes is discussed as well as the characterization of the diisocyanates by their absorptions in the skeletal region. A hydrolytic method of degradation of polyurethanes into portions which can b e identified by their infrared spectra is outlined.
1298
ANALYTICAL CHEMISTRY
P
are elastomcric and plastic materials resulting from the condensation-polymerization of diisocyanates and polyols. They derive thcir name from the chemical linkage formed when the isocyanate. radical reacts with an active hydrogen atom. Depending on the nature of the diisocyanate-polyol reaction, the resulting product can take one of several forms: synthetic rubbers, flexible foams, rigid foams, adhesives, coatings, fibers, paints, and molding compounds. All come OLYURETHAXCS
under the general heading of polyurethanes. The application of analytical procedures to polyurethane rubbers which arc based on polymeric glycols (whereas plastics are bawd on lo^ molecular weight glycols) is described. These methods. howevcr, may be applicable over a wider range of materials. JIany polyurethanes have been described (I, 9, 10, I S , 16, 16) and the materials are of commercial importance. Basically, a block polymer with
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