N.S. Yenikolopyan

A statistical model of crosslinked polymer structure

Abstract The kinetic and the topological aspects of the formation and structure of highly crosslinked polymers are considered. A statistical model has been developed to describe the correlations between the chemical composition of the original substances and the production and topology of the network. It is based on imagining the network to be a collection of rigns connected to each other at random and having some size distribution. The model has been analysed by the Monte Carlo method. The structural topology is described by introducing a size distribution function for the rings. The topology has been studied as a function of the vitrification conditions. A topologically critical yield and a drop in the rate constant for the reaction has been found to exist in the network at near stoichiometric reagent ratios.

The Macroscopic Kinetics of Rapid Processes of Polymerization in Turbulent Flows

Abstract The peculiarities of the macrokinetics of rapid polymerization processes in turbulent flows (when the times of the chemical reaction are less than or compatible with those of the reagent mixing) have been discussed. The characteristic specific phenomena have been elucidated, namely: dependence of the molecular characteristics output (MW and MWD) of the polymer formed on the geometry of the reaction volume and on the parameters of the processes of mixing and heat transfer (flow rates, turbulization, boiling, etc.). Such reactions require special methods of investigation and control including those in industries with principally new material-, resource-, and power-saving technology, in particular, for the production of the isobutylene polymers. It is expedient to distinguish the rapid processes of polymerization as a separate class.

Calculation and simulation of the polymerization of isobutylene as a fast reaction

A mathematical analysis of the kinetics of the rapid polymerization of isobutylene has been made; this has been done with a continuous scheme in which the special features of the properties of the reaction medium and the technological parameters of the reaction behaviour are taken into account. It has been shown that rapid reaction with local introduction of the catalyst occur in separate zones as a “flame” with different temperatures and kinetic parameters: this is accompanied by the formation of a polymer with enhanced molecular non-uniformity. The calculated data have been compared with experimental data and they have been found to agree.

Kinetics of radical polymerization of 1-vinyl-1,2,4-triazole☆

Abstract Studies were made of kinetic features of radical polymerization of 1-vinyl-1,2,4-triazole and the molecular weight variation of poly-1-vinyl-1,2,4-triazole in water, in DMF and in DMAA. The rate of polymerization of the monomer in water and MW of the polymer obtained is higher than in other solvents. MW of poly-1-vinyl-1,2,4-triazole is proportional to the concentration of the monomer. It was shown that a typical feature of polymerization, which is general for all the solvents studied, is the existence of a reaction rate for the initiator with a reaction order higher than 0·5. The mechanism of monomolecular decay of macroradicals is discussed. The effective activation energy of polymerization was found.

Macroscopic kinetics of fast polymerization processes. Review

Abstract Aspects of the macrokinetics of fast polymerization processes in turbulent flows are considered. The dependences of the yield and molecular characteristics (MM and MMD) of the polymer formed on the geometry of the reaction volume and the parameters of mixing and heat transfer processes (rates of flows, turbulization, boiling, etc.) have been established. It is shown that such reactions call for special methods of investigation and control. A fundamentally new material-, resource- and energy-saving technology has been devised for obtaining isobutylene polymers based on the developed model of fast flow polymerization.

The structural organization of a filler in dispersion-filled thermoplastics. Method of description and modelling

Abstract A method of quantitatively describing the fluctuations in the distribution of a filler in dispersion-filled thermoplastics by analysing the microphotographs of low-temperature fractures of the composites has been developed. A mathematical model for the structural organization of the dispersion-filled system is proposed. The nature of the fluctuations in the filler distribution and the effect on them of the volume fraction of the filler and the fillers particle-size composition have been analysed.

The structure of gel and sol fractions of epoxy compositions

Abstract A study was made of the chemical structure of gel and sol fractions of solidified epoxy compositions based on 4,4′-diaminodiphenylsulphone and resorcin diglycidyl and boiling acetone. The amount of unreacted epoxy groups was determined in gel and the proportion of free diepoxide, in sol. It was shown that up to 50% diepoxide excess of the sol fraction consists mainly of free diepoxide. Results of experiments were compared with data concerning the statistical model of crosslinked polymer structure.

Effect of mixing methods on the character of ultrafast polymerization processes

Abstract The effect of various methods of feeding reagents in ultrafast low temperature polymerization of isobutylene on the MM and MMD of the products is studied theoretically. It is established that the temperature distribution in the polymerization reaction and the molecular mass characteristics are connected with the system used for feeding the catalyst into the turbulent monomer stream. It is shown that, assuming identical conditions, it is possible to increase the mean number average degree of polymerization only by changing the catalyst supply.

Effect of temperature on the strength and deformation characteristics of crosslinked polymers based on epoxide oligomers

Abstract The deformation of epoxide polymers over a wide temperature range has been studied in the present work. The polymers investigated were synthesized from the diglycidyl ether of resorcinol and 4,4′-diaminodiphenylsulphone, taken in various molar proportions. It is shown that strain hardening is observed in the region of the glass transition temperature during deformation. At temperatures above the glass transition temperature, the equation σ = G ∞ ( γ −1/ γ 2 ), where γ =1+ e and G ∞ is the equilibrium high elastic modulus, satisfactorily describes the experimental results. A correlation dependence has been obtained between the tensile strength in the high elastic condition and the distribution of overstresses in the network structure.

Optimization of polyisobutylene molar mass characteristics

Abstract An analytical method has been developed and used to study the variation in polymer molar mass and molar mass distribution due to changes in the mode of polymerization. The potential of the method, which enables one to influence within certain limits the molecular weight distribution of a polymer prepared in a throughflow tubular reactor, is illustrated using the example of polyisobutylene.