B.A. Komarov

Epoxy-amine composites with ultralow concentrations of single-layer carbon nanotubes

The physical and mechanical properties of composite materials based on epoxy-amine systems—diglycidyl ether of diphenylolpropane-eutectic mixture of aromatic amines (40 wt % m-phenylenediamine-60 wt % 4,4′-diaminodiphenylmethane) and epoxy-diane resin ED-20-eutectic mixture of aromatic diamines with ultralow contents (≤0.1 wt %) of single-layer carbon nanotubes—are studied. It is shown that, for the concentration dependence of the modulus of elasticity during tension, the additivity rule is obeyed only at the lowest concentrations of carbon nanotubes. In this case, the presence of near-surface layers of a matrix with an increased elastic modulus should be considered.

The role of proton donors in initiation of polymerization of epoxide compounds by tertiary amines

The effect of the proton donors water, n-pentanol and isopropanol, on polymerization of phenyl glycidyl ether catalysed by dimethylbenzylamine at 70° has been investigated. The residual quantity of the proton donors in the system was determined by the kinetic method. The kinetics of formation of hydroxyl groups in the reaction system was studied. Experimental evidence is provided to support the assertion that tertiary amines cannot induce polymerization of epoxide compounds of the glycidyl ether type, in the absence of a proton donor. A scheme illustrating the formation of the growing active centre, a tetra-alkylammonium alcoholate, and its reaction is proposed.

The molecular weight and functionality distributions in the phenylglycidyl ether polymerizate in the presence of tertiary amines

Abstract Column- and gel-chromatography have been used to study the phenylglycidyl ether (PGE) oligomers produced in the presence of dimethylbenzylamine with or without alcohol as additive. The oligomers have been found to possess a trimodal terminal OH-group distribution and to contain also non-hydroxyl molecules or those with only a single OH-end group, or with 2 OH-groups. The mol. wt. distribution (MWD) of the oligomers is independent of the polymerization conditions in the 1·01–1·10 range. The mechanism of the process is discussed.

Conversions of the reactive polymerization centres in glycidyl ethers by tertiary amines

A detailed investigation was carried out of the reactive polymerization centres in phenylglycidyl ether in the presence of dimethylbenzylamine, pyridine and β-picoline. The main contribution in the reactive centres conversion to tetraalkyl ammonium alcoholates is made at elevated temperatures by the Hofmann decomposition reaction. In the event of polymerization below 40°C the main route of the reactive centres conversion will be their decomposition which is accompanied by an alkyl radical dissociation from the tetraalkyl ammonium cation.

The mechanism of initiation of polymerization of trioxan in the presence of tritylium salts

A study has been made of the mechanism of initiation of the polymerization of trioxan in benzene, catalysed by tritylium salts. Polymerization of trioxan in the presence of Ph3C+SbF6− (in the absence of water) is initiated by abstraction of a hydride ion from the monomer molecule. When Ph3C+SbCl6− is used SbCl5, formed by decomposition of the trytilium salt in solution, plays an important part in initiation. Efficient hydride ion donors (1,3-dioxolane, tetrahydrofuran) and also linear acetals and epoxides, substantially increase the rate of initiation in polymerization of trioxan in the presence of trityl salts. Compounds containing hydroxyl groups (water, alcohols), cycloheptatiene and triethylsilane inhibit the initiation reaction.

Mutual influence of polymerization and polycondensation reactions in the curing of epoxide oligomers by amines

Abstract A study has been made of the mechanism of reactions of phenylglycidyl ether with aniline and n-butylamine in the presence of dimethylbenzylamine and diethylaniline. The mutual influence of polymerization and polycondensation processes during reactions of epoxide oligomers with mixtures of primary and tertiary amines was observed. It was found that depending on the reactivity ratio of primary and tertiary amines leading respectively to polycondensation or polymerization of epoxides, the total process could accordingly be accelerated or inhibited. Reasons for the kinetic effects observed are discussed.

Kinetics and mechanism of polymerization of 1,3-dioxolane in various media under the action of methoxymethylhexachlorantimonate☆

The polymerization of 1,3-dioxolane under the action of CH3OCH2SbCl6 and PhCSbF6 has been investigated in various media. The effective constants for the dissociation of active propagating sites with a hexachlorantimonate counter ion, to molecular forms, have been determined and the dependence of these constants on the dielectric permeability of the medium has been discussed. It is shown that the rate constants for chain propagation at the free ion and at an ion pair differ by a factor of 3. It has been establishedthat an increase in the ionic strength of the polymerization solution leads to an increase in the concentration of active site having a hexachlorantimonate counter ion and to a decrease in the polymerization rate constant.

Kinetics and Mechanism of the Late Stage of Cure Reaction-induced Microphase Separation

Abstract Reaction-induced phase separation in oligomer modified epoxy resin cured by tertiary amine as a catalyst was studied. Evolution of the reaction system morphology was observed in situ by optical microscopy technique. Intensity of the coalescence that proceeds at the late stage of phase separation depends on conditions of the cure, i., formulation and temperature. The final morphology of the reaction system was shown to depend on a chemical mechanism of the cure process, first of all, polycondensation or polymerization reaction paths.

Kinetic features of phenylglycidyl ether polymerization under the action of tertiary amines

Abstract A study has been made of kinetic features of phenylglycidyl ether polymerization under the action of dimethylbenzylamine in the presence of alcohol additions. The temperature dependence of the rate constant of the side isomerization reaction has been determined. The rate constant of transfer of the growing active centre to propargyl, allyl and isopropyl alcohols have been determined, as well as the ratio of the active centre decay rate constant and the initiation rate constant, and the dependence of this ratio on the initial concentrations of components of the system.

The participation of macromolecules in generation of active centres in polymerization of cyclic acetals

Abstract The polymerization of 1,3-dioxolane in solution in methylene chloride, catalysed by antimony pentafluoride, fluorosulphonic and perchloric acids, azonenzene perchlorate or a mixture of antimony pentafluoride and fluorosulphonic acid, has been found to be an autocatalytic process. A kinetic analysis of the autocatalytic polymerization of 1,3-dioxolane under the influence of boron trifluoride etherate has been made. The ratio of the rate constants of reaction of the catalyst with a polymer chain unit and with a monomer molecule was determined. The rate constant for the formation of active centres by reaction of Et 2 O·BF 3 with the polymer has been determined by the method of degradation of the polydioxolane. The mechanism of reaction of Lewis acids with the monomer and with the polymer molecule is discussed.