摘要:

AbstractEnthalpies and free energies of formation of a group of aliphatic fluorocarbons and their radicals for 298.15°K. and the ideal gaseous condition are calculated from the available experimental heat and entropy data, extended by means of empirical series treatments. The polymerization of tetrafluoroethylene and the thermal breakdown of the resulting polymer are recognized as thermodynamically equivalent processes, differing only in the sign of the thermal quantities involved. Free energy changes attending various intermediate steps in the free radical‐initiated polymerization are calculated. The heat and free energy of polymerization are highly exothermal at 298.15°K., compared with those for other olefinic compounds. At high temperatures reversal of the synthesis steps is to be expected. Initiation of degradation need not occur merely by reversal of the termination process, although this possibility is not exclu

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616401

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY

摘要:

AbstractWhen propylene oxide is polymerized or when it is added onto an alcohol or phenol, the terminal hydroxyl groups can be of primary or secondary types, depending on how the epoxide ring opens. The nature of the terminal hydroxyl group becomes important if the polyglycol ether is reacted further, as in the case of polyurethane foams. The primary hydroxyl group reacts much more rapidly with isocyanates than the secondary hydroxyl group, and hence the performance of the polyglycol varies with the ratio of primary to secondary hydroxyl group content. An analytical method has been developed to differentiate the primary from the secondary hydroxyl groups on polypropylene glycol, and a study was made of the variation in the ratios of the two hydroxyl types versus molecular weight of the polyglycol and versus other chemical treatments to which the polyglycol was exposed.

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616402

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY

摘要:

AbstractPoly(n‐docosyl methacrylate) was prepared by emulsion polymerization. Since the weight‐average molecular weight of the unfractionated material appeared to be unusually large, light scattering measurements were made in three solvents and at several temperatures. No evidence of association in solution was found. Values of average molecular weight, dimensions, and second virial coefficients are repor

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616403

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY

摘要:

AbstractA modified isothermal distillation calorimeter is described in which an electronic weight recording device has been incorporated. Heats of polymerization of four vinyl monomers have been verified and −ΔHpvalues at 74.5°C. for six new monomers are reported. The values for acrylamide and methacrylamide furnish some evidence of association in the monomeric state in nonpolar solve

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616404

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY

摘要:

AbstractThe possibility of formulating a structure of cellulose I without postulating a twofold screw axis in the structure has been investigated. Although structures of this type can be found for which the agreement between observed and calculated intensities is similar to that obtained by Meyer and Misch, none of them is completely satisfactory. In this analysis it is shown that the original interpretation of the x‐ray fiber diagram is uncertain because of the overlap of reflections and that a new approach is required that uses the envelope of diffraction spectra rather than the individual reflection

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616405

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY

摘要:

AbstractThe chain decomposition oftert‐butyl hydroperoxide in the presence of copperoctoate producestert‐butoxide andtert‐butyl peroxy radicals which are both able to initiate the polymerization of styrene. Consequently, half the number of the endgroups of the polymer molecules will be present, as peroxybutyl group, which can initiate a second‐step polymerization. In the first part of this paper, the kinetics of polymerization of styrene witht‐butyl hydroperoxide (t‐BHP) and copper octoate have been studied. In the absence of monomer, the chain decomposition is relatively short on account of the reaction of the Cu1+ion withtert‐butyloxide radical and the precipitation of the copper salt; contrarily, in the presence of styrene the primary radicals add preferentially monomer, and no copper salt precipitation occurs. In both cases the overall energy of activation of decompositiont‐BHP/Cu2+octoate is equal to above 21 kcal/mole. At constant Cu(oct)2concentrations the square root law relationship between the rate of polymerization andt‐BHP concentration is only valid for the low concentrations; at higher values, it increases much slower up to an asymptotic value. Similar conclusions arise from the rate dependence on the copper octoate concentrations at constantt‐BHP and monomer concentrations.In the second part of this paper, the polystyrene carrying peroxy‐t‐butyl end‐groups has been used as initiator of the polymerization of a second monomer (methyl methacrylate and vinyl acetate) for the synthesis of block polymers at 97°C. This second step polymerization is a first order reaction with respect to the monomer concentration, and 0.5 order with respect to the initiator. Some thermal polymerization of methyl methacrylate must be taken into account for the evaluation of the amounts of second homopolymer. The relative reactivity of both radicals has been evaluated from their ability of further monomer addition; by measuring the amounts of homopolymerRHand block polymerRBby fractional precipitation and determination of their styrene content, it was possible to determine the efficiency of block polymerization.In the case of methyl methacrylate the ratioRB/RHis equal to 1.2 in agreement with the chain termination reaction; therefore the efficiency of both radicals is admitted to be equal, and consequently independent of their size.In the case of vinyl acetate the much lower value ofRB/RH(0.26) is not a measure of the relative efficiency but a consequence of chain transfer reactions on monomer and solvent, which increase

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616406

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY

摘要:

AbstractThe tacticity theory previously reported was generalized so it could be applied to the proton magnetic resonance data obtained for a variety of methyl methacrylate polymers. This system is the only one known for which sufficient data exist or may be obtained to provide a test of the theory. From the data available, parameters characterizing the distribution of iso‐ and syndiotactic sequence lengths in each sample were obtained These parameters, in turn, were used to predict melting behavior for each sample capable of crystallization. The tacticity theory not only is consistent with the data on free radical‐initiated (syndiotactic) polymers, about which there was no question of interpretation, it also provides an explanation for an uncertainty in the interpretation of the data on anionic‐initiated (isotactic) polymers. Thus, in this case at least, the theory appears to provide a connection between experimentation and polymer configur

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616407

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY

摘要:

AbstractThe thermal degradation of epoxy resins was studied in a static system over the temperature range 300–450°C. The reaction proceeds without an induction period, the initial rate being maximum. The rateWincreases with temperature according to the lawW=Ae–E/RT. The effective activation energy was 35 kcal./mole. The reaction products consist of gases, a resinous liquid, and a solid residue. The liquid has practically the same spectral characteristics in the infrared as the initial epoxy compound. In the infrared spectrum of the residue the bands characteristic of the epoxy group are absent. Water and formaldehyde were found among the liquid products. Methane and carbon monoxide were found in large amounts by means of a chromatographic method. In the thermal degradation of the unhardened epoxy resin the low molecular fraction volatilizes, and the high molecular fraction degrades liberating the radical which isomerizes and decomposes to CO and ĊH3. The methyl radical abstracts a hydrogen atom from the polymer and is converted to methane. The ROĊH2radical formed on liberation of the epoxy group yields formaldehyde. Among the gaseous products formed in the thermal degradation of the epoxy resin hardened by polyethylene polyamine (PEPA) were found H2, CO, CH4, C2H6, C2H4, C3H6, and C3H8. Ethane, ethylene, propylene, and propane are possibly produced by decomposition of the PEPA radical. The thermooxidative degradation of epoxy resins was investigated in a static system. The reaction was shown to be of the degenerate branching chain type. The dependence of the induction period on the oxygen pressure and on the temperature was de

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616408

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY

摘要:

AbstractCrystalline copolymers of styrene and 4‐methylpent‐1‐ene and styrene and 5‐methylhex‐1‐ene have been prepared with the catalytic system α‐TiCl3–AlEt3in toluene. The polymerizations were carried out in dilatometers with the use of a special stirring apparatus which is described. The copolymers produced were shown to be heterogeneous in composition. Fractions soluble in cold pentane are enriched in 5‐methylhex‐1‐ene and have x‐ray diffraction patterns similar to those of crystalline isotactic poly(5‐methylhex‐1‐ene). The fractions insoluble in cold pentane are enriched in styrene and on crystallization have x‐ray diffraction patterns similar to those of crystalline isotactic polystyrene. Infrared spectra were also examined. Determination of reactivity ratios gave the values: styrene (M)‐4‐methylpent‐1‐ene,r1= 0.89 ± 0.05,r2= 3.67 ± 0.22; styrene (M)‐5‐methylhex‐1‐ene,r1= 0.59 ± 0.057,r2= 4.00 ± 0.28. Statistical analysis shows that the copolymer is probably a mixture of block macromolecules, the chain backbones consisting mainl

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616409

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY

摘要:

AbstractThe unit cell dimensions of a linear polyethylene are reported as determined by x‐ray diffraction measurements at five‐degree intervals from −70°C. to +130°C. and at −196°C. The relative expansion coefficient of theadimension of the orthorhombic unit cell was found to increase from 1.1 × 10−5/°C. at −196°C. to 22 × 10−5/°C. at 30°C. to 58 × 10−5/°C. at 138°C., the melting point of the crystal. The coefficient of thebdimension was found to vary from −2.8 × 10−5/°C. at −196°C. (questionable) to +3.8 × 10−5/°C. at 30°C., and then to −7.3 × 10−5/°C. at 138°C. These values were obtained from series expansion analytical fits to the experimental points, and are less accurate at the ends of the temperature range; the 30

ISSN:0022-3832    

DOI:10.1002/pol.1962.1205616410

出版商:Interscience Publishers, Inc.    

年代:1962

数据来源: WILEY