摘要:

The thermal decomposition of polyoxypropylene glycols under a nitrogen atmosphere has been studied in the temperature range 320 to 700[ddot] K under dynamic operating conditions with a differential scanning calorimeter and a thermogravimetric scanning system. In the DSC studies, Ellerstein's suggestion to use stainless steel mesh was followed to minimize differential energy losses. Differential scanning calorimetry yields zero-order kinetics while the data obtained with the thermogravimetric system fits first-order kinetics. Various ways of decomposition, satisfying both zero- and first-order kinetics, are discussed. The heat of decomposition is found to change with temperature, and activation energies obtained by DTG increase with rate of heating. Differential enthalpic analyses provide activation energies applicable to chain ruptures as well as volatile product evaporation, whereas thermogravimetric analyses furnish activation energies only for the second stage.

ISSN:0022-233X    

DOI:10.1080/00222337408066404

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

A self-consistent set of bond energy terms permitting estimation of heats of formation of halogen compounds is evolved. The overall precision attained is ±0.7 kcal/mole, which is considerably better than that of the experimental data. Heats of formation of halogen containing monomers and polymers, and heats of polymerization are calculated.

ISSN:0022-233X    

DOI:10.1080/00222337408066405

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

A dynamic model of a nonisothermal continuous stirred tank polymerization reactor is developed to predict product molecular weight distribution parameters. Deliberate oscillations in operating variables were programmed into the model and the resulting time-averaged reactor performance indices compared with that for optimum steady-state operation. Results indicate that periodic operation does influence polymerization reactor performance, particularly with regard to time-averaged molecular weight polydispersity. Significant resonant behavior was encountered with molecular weight properties at low frequencies.

ISSN:0022-233X    

DOI:10.1080/00222337408066406

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Carboxymethyl amylose was fractionated and the fractions were characterized by light scattering and viscometry. The viscosity and the molecular weight data have been used to evaluate the Mark-Houwink's constant a, expansion factor α, Flory's universal constant Φo, and unperturbed dimension of the chain. The configurational parameters, e.g., effective bond length b, Kuhn-Kuhn chain segment length Am, and steric factor σ have also been determined and compared with those of similar cellulose derivatives obtained in our laboratory.

ISSN:0022-233X    

DOI:10.1080/00222337408066407

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Nauman defined in his review paper [1] that “the segregation number is… a ratio of characteristic times; a characteristic time for micromixing divided by a characteristic time for macromixing:” Nseg= τmicro/τmacroand has also selected as “a logical characteristic time for the macro-mixing is the mean residence time t.” The final result of his derivation for a spherical droplet is Nseg= 0.55r2/π2Dtfor a continuously stirred tank reactor (CSTR), where D is the diffusion coefficient and micromixing results from molecular diffusion between droplets (of packets or eddies) and the bulk of reactor fluid, and r is the radius of these droplets or eddies. It is supposed that an agitator dispersed the fluid down to the characteristic radius of r.

ISSN:0022-233X    

DOI:10.1080/00222337408066408

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The completely conjugated polymer, polyethynylferrocene, was prepared by heating ethynylferrocene with catalytic amounts of azobisisobutyronitrile to 180-240[ddot] under nitrogen in bulk. Cyclotrimerization competes with polymerization under these conditions. Pure low molecular weight polyethynylferrocene was isolated and characterized by IR and NMR spectroscopy and by a gel permeation chromatography. The pure polymer exhibits a conductivity of 2 × 10−14−1cm−1. Attempts to prepare polyethynylferrocene by heating acetylferrocene in molten zinc chloride were, contrary to literature reports, unsuccessful. A polymer containing hydroxyl and keto groups was obtained, and extensive degradation of the ferrocene groups occurred. The general reaction scheme is discussed. It includes cleavage of cyclopentadienyl rings from ferrocene and the incorporation of cyclopentane rings into the polymer structure.

ISSN:0022-233X    

DOI:10.1080/00222337408066409

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The polymerization of acrylonitrile initiated with the imidazole-copper (II) complexes was studied in dimethylsulfoxide solution. The ability of the complexes to initiate polymerization seems to depend on their anion. 2-Substituted imidazole-copper (II) complexes of the type, CuL4X2(L = imidazole as ligand and X = anion), were also found to initiate vinyl polymerization. From the data of electronic spectra in dimethylsulfoxide solution, the initiation mechanism is discussed in terms of the formation of the active species by the interaction of the complex with monomer molecules.

ISSN:0022-233X    

DOI:10.1080/00222337408066410

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The γ-radiation-initiated polymerization of acrylonitrile (AN) at 25[ddot] C has been studied, both in aqueous solution and in emulsion, at dose rates between 70 and 175 krad/hr. The effect of added emulsifier, sodium lauryl sulfate (SLS), on reaction rates, Rp, and on polymer molecular weight, Mn, has been investigated. G (monomer polymerized) values ranged from 7,500 in aqueous solution to 20,000 in bulk to 45,000 in emulsion, all based on the total energy absorbed. In the aqueous solution polymerization, where Rpis approximately first order in initial monomer concentration over the range 0.15 ± [AN]o± 1.06 moles/liter, addition of SLS increases Rpbut does not influence the order of the reaction with respect to [AN]o. In the emulsion system at 70 krad/hr and at a phase volume ratio AN/H2O of 1/2, (PR = 1/2), Rpvaries as [SLS]0.1over the concentration range 0.01 ± [SLS] ± 2.5± wt/vol of aqueous phase. At the same PR value, and at 80 krad/hr, Mnof the polymer (measured by viscometry in dimethylformamide solution) is effectively independent of [SLS] in the range of 0.01 ± [SLS] ± 10± wt/vol of aqueous phase. Initial Rpvalues are either independent of PR in the range 1/3 ± PR ± 1/1 or exhibit an insensitive and unsystematic dependence thereon. Based on measurements at 70 and at 175 krad/hr, the intensity exponent of Rpat PR = 1/2 is approximately 0.4.

ISSN:0022-233X    

DOI:10.1080/00222337408066411

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The rates and gel formation of the radiation-induced co-polymerization of a number of dimethacrylates and trimethylol propane trimethacrylate with methyl methacrylate has been studied in detail. The rates were found to be linked to the nature and amount of gel formed rather than to differences in the reactivities of the monomers.

ISSN:0022-233X    

DOI:10.1080/00222337408066412

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

An equimolar cyclopentadiene-maleic anhydride copolymer was formed by the addition of t-butyl hydroperoxide to the molten Diels-Alder adducts at 175 to 285[ddot] C. The same copolymer was formed by the high temperature copolymerization of maleic anhydride, in the presence of the hydroperoxide, with cyclopentadiene per se or as generated in situ from dicyclopentadiene. The copolymer resulted from the homopolymerization of the comonomer complex which underwent excitation under the influence of the catalyst. The copolymer, softening point 290 to 320[ddot] C, was saturated and had a proposed norbornane-2, 3-dicarboxylic anhydride repeating unit with 5, 7 linkage.

ISSN:0022-233X    

DOI:10.1080/00222337408066413

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor