Al.Al. Berlin

The synthesis and some properties of oligo (oxyethylene-urethane methacrylates)☆

THE synthesis of high polymers from reactive oligomers has become widespread in recent years. From the technological point of view the most interesting are polymerizable oligomers with unsaturated end groups, which are convertible without elimination of side products to crosslinked substances of high molecular weight, in which the length of the chains between network points is dependent on the molecular weight of the original oligomers. In this connection one of the pressing problems of the physical chemistry of these polymers is to find the dependence of the properties of the high polymers on the nature and size of the oligomers. Here the first task is to study the dependence of the properties of the oligomers on their molecular weight. The materials used in this investigation were the polymerizable oligomers, a,w-bis(4-methacryloxyethylcarbamatotoluylene-2-carbaminic) esters of oligo(ethylene) glycols (oligo(oxyethyleneurethane methacrylates)) of molecular weight 670-15,600.

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.

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.

Rapid method for determining molecular characteristics of polyisobutylene

Abstract Results are given of determining molecular characteristics of polyisobutylene using a combination of a liquid chromatograph and a double bond analyser (ADS-4). The possibilities offered by the method are compared with those well known for determining MW and MWD of polyisobutylene.

High temperature pyrolysis of polymers

Abstract Heat transfer at the gas-solid interface in degradation of polymers underconditions simulating the action of a flame has been investigated, and the heat of evaporation and temperature of the surface layers of the polymers (PMMA, PS, PE, PP and POM) were determined in the course of the work. Problems relating to the effect of the characteristics of the external medium (the composition and temperature of the gas) on these quantities are discussed. The energies of activation for pyrolysis of PMMA, PS and PE were determined.

The elasticity of diepoxide molecular chain conformations

Abstract The Monte Carlo method has been used to analyze the set of real diepoxide molecular conformations. As a result it was found that the entropic elasticity of the short diepoxide chains as a function of stretching is a stepwise process; its configurational behaviour greatly differs from that assumed in the Langeven and Gaussian approximations.

The relative reactivity of primary and secondary amino groups in aromatic amines

The reaction of aromatic amines (aniline and m-phenylenediamine (MPDA)) with epoxide compounds (phenyl glycidyl ether (PGE) and resorcinyl diglycidyl ether (RDGE)) is studied. The ratio of the rate constants of addition of the NH2 groups of primary and secondary aromatic amines to the epoxide group has been found. The concentrations of intermediate products of the reaction of RDGE with aniline, PGE and MPDA are calculated. The molecular weight of the product of reaction of RDGE with MPDA was determined.

The mechanism and kinetics of dehydrochlorination of polyvinylchloride

Several chemical reactions are involved in dehydrochlorination of PVC. These are: 1) random elimination of HCl from normal PVC units; 2) growth of polyene sequences initiated by COCH = CH structures; 3) slow growth of polyene sequences initiated by isolated CH=CH linkages; 4) growth of polyene systems initiated by conjugated CH=CH linkages. The relatively high rate of the over-all process of dehydrochlorination of PVC is attributable mainly to the conjugated ∼ rmCO−(CH= =CH)n∼ structures (n⩾1) originally present in the polymer molecules.

Influence of flameproof viscose fabrics on the burning of epoxyorganoplastics

A study has been made of the fireproofness of composites containing ED-20 epoxy resin and flameproof viscose fabric. It is shown that if a phosphorus-containing flam-retardant is included in the composition of viscose fabric, there is a change in the degradation pathway of the epoxy resin, and the temperature of the material and the ignition temperature are lowered. In this way the composite is rendered flameproof.

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.