摘要:

Thin polymer films solidified from solutions can display a broad range of barrier and mechanical properties, depending on the quality of the solvent and the initial polymer concentration. These findings apply specifically to polymers containing polar groups, exemplified in this work by polymethyl methacrylate and a styrene-butyl acrylate copolymer, but not to polymers like polystyrene. In the former two cases it has also been shown that very different surface tensions exist at the air and the substrate interface, provided the films were solidified against high surface energy solids. These observations have been attributed to the ability of polar-group-containing polymers to adopt various chain conformations at and near interfaces, these conformations reflecting interactions between polymer and solvents and between polymer and substrate. An additional contribution is attributed to the degree of chain entanglement persisting in solutions. The measured properties often pertain to metastable states of the films, and the findings thus indicate the existence of a thermodynamic driving force for the time-dependent change (aging) in properties of protective films.

ISSN:0022-233X    

DOI:10.1080/00222338608063372

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The diglycidyl ether of Bisphenol-A (DGEBA), suitable for the manufacture of epoxy-glass fiber laminates, has been cured with bis(m-aminophenyl)methylphosphine oxide (BAPO), and the results have been compared with a commercially available 4,4′-diaminodiphenyl sulfone (DDS). DSC studies indicated that an increase in the concentration of diamine resulted in an increase in the extent of the curing reaction even above the optimum level of diamine. Cured resins were stable up to 300°C and started losing weight above this temperature. Glass fabric-reinforced laminates based on DGEBA:BAPO exhibited a higher limiting oxygen index (LOI), as well as higher shear and flexural strength than those based on the DGEBA:DDS system. Thermal aging at 185°C for 100 h did not affect the mechanical properties of laminates. However, a significant decrease was observed in interlaminar shear strength by boiling in water for 100 and 200 h.

ISSN:0022-233X    

DOI:10.1080/00222338608063373

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Expressions for the molecular size distribution, the average degree of polymerization, etc. are derived by means of the nonsteady-state method for addition polymerization with instantaneous initiation, termination by disproportionation, and combination. Furthermore, a theoretical method is established with which the curves of the differential molecular weight distribution and the values of other molecular parameters can be calculated from the initial conditions of polymerization and the monomer conversion or reaction time. This theory is suited to such types of polymerization as that of vinyl monomers radiated by60Co under deep-freezing conditions, the resultant not very reactive free radical accumulating, then stopping the radiation, and letting the polymerization begin at a higher temperature.

ISSN:0022-233X    

DOI:10.1080/00222338608063374

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The set of kinetic differential equations for star-coupling of polymers have been solved rigorously both with and without the effect of steric hindrance. The relations between the molecular parameters of star-branched polymers and those of prepolymers are derived. When the star-coupling reaction goes quantitatively to completion, the same theoretical result was obtained, no matter whether there is steric hindrance or not. In this case, the more arms in the star-branched polymer, the more homogeneous is the molecular weight distribution; if the number of arms is large enough, the molecular weight distribution will become very narrow and almost be independent of the polydispersity of the arms.

ISSN:0022-233X    

DOI:10.1080/00222338608063375

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A new theory is proposed involving a short-range interaction parameter, N0, which allows for finite chain effects. The parameter z, which was originally suggested by Yamakawa, is redefined to make it applicable to finite chains. The dependence of intrinsic viscosity on molecular mass as predicted by most of the acknowledged theories of polymer solution seem to be incompatible with the Mark-Houwink-Sakurada relation. This makes the evaluation of interaction parameters from viscosity data difficult. Therefore, an attempt is made here to show that these theories contain some basic assumptions (and/or mathematical simplifications) which may lead to erroneous conclusions.

ISSN:0022-233X    

DOI:10.1080/00222338608063376

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Arylsulfonyl chlorides have been found to react quantitatively with polystyrene in the presence of Friedel-Crafts catalysts at room temperature. Polymers having the general structure I, where R = H, CH3, Cl, Br, F and OCH3, were prepared and characterized by NMR and IR spectroscopy, differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA).

ISSN:0022-233X    

DOI:10.1080/00222338608063377

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The Cr(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) polychelates of 4,4′-(4,4′-biphenylylenebisazo) salicylaldehyde-salicylic acid were prepared. The analytical data are found to be consistent with 1:1 (metal:ligand) stoichiometry. The polychelates were further characterized by conductivities, magnetic moment, as well as electronic and infrared spectral properties. All polychelates are found to have an octahedral stereochemistry.

ISSN:0022-233X    

DOI:10.1080/00222338608063378

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

It was found that the cationic ring-opening polymerization of tetrahydrofuran (THF) was initiated by carbon black containing CO+ClO4-groups, which had been introduced by the reaction of COCl groups with AgClO4, in the presence of promoters such as epichlorohydrin (ECH) and diketene. It was confirmed that formation of poly(oxytetramethylene), i.e., poly-THF, was propagated from CO+ClO4-groups on carbon black surfaces and effectively grafted onto it. The grafting ratio with ECH as promoter increased to 66.8% as conversion increased. The activation energy of the polymerization initiated by CO+ClO4- groups in the presence of ECH was determined to be 8.1 kcal/mol. Furthermore, poly-ECH, poly(styrene oxide), and poly(propylene oxide) can be grafted onto carbon black surfaces by the ring-opening polymerization of the corresponding alkylene oxides with CO+ClO4- groups on the carbon black as initiator. The polyether-grafted carbon black obtained from the above polymerization produced a stable colloidal dispersion in a good solvent for polyether.

ISSN:0022-233X    

DOI:10.1080/00222338608063379

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The kinetics of cyclopolymerization of N,N' -methylenebisacrylamide (MBA) was carried out using peroxydisulfate ion as initiator. The rate of polymerization, Rp, was found to be proportional to [M] and [S2O82-]1/2for the uncatalyzed system. A cyclopolymerization mechanism was found to fit the experimental results. The k21/kt1/2value for MBA polymerization was evaluated. Evidence in favor of the cyclopolymerization mechanism is provided. The addition of Ag ion enhances Rp.

ISSN:0022-233X    

DOI:10.1080/00222338608063380

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This work deals with the kinetics of multifunctional polymerization with instantaneous initiation and monomer transfer. The set of very complicated kinetic differential equations is rigorously solved by a graphical method. Then, the expressions of the molecular weight distribution function, the number- and weight-average degree of polymerization, the distribution of functionality, the average functionality, etc. are obtained. Furthermore, a procedure is proposed for calculating the molecular weight distribution curve and the values of the other molecular parameters mentioned from the initial conditions of the polymerization.

ISSN:0022-233X    

DOI:10.1080/00222338608063381

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor