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The problem of shelf-life of polymerizable compounds is dealt with in conjunction with the problem of their processing. Kinetic parameters that characterize the polymerization of such compounds under storage conditions and the monomer processing have been analysed. Feasibility of a complex approach to the problem of shelf-life and processing of polymerizable compounds is shown using the example of the application of weak antioxidants. By increasing the antioxidant concentration the stability of the monomer is raised and the use of weak antioxidants facilitates monomer processing. The possibility to optimize the solution of problems connected with shelf-life of monomers and their processing has been shown. Values of parameters that characterize oxidative polymerization of methyl methacrylate, inhibited by several weak antioxidants have been determined along with the corresponding stoichiometric constants. The stoichiometric coefficient of an antioxidant has been found to depend on its concentration and on the rate of initiation.

Using a model system chain transfer to an oligomer unit was studied during polymerization of dimethacrylic esters of oligotetramethylene glycols. It was found that chain transfer has a very slight, negligible effect on the overall reaction system. The constant of the reaction of chain transfer to the elementary unit of oligotetramethylene oxide was evaluated.

The kinetics of the polymerization of methyl methacrylate (MMA) and dimethyltriethylene glycol (TGM-3) have been studied in the presence of oxygen and of an anti-oxidant (AO). The induction period depends on the monomer concentration in a closed system and increases with the AO content only in a relatively narrow range of concentration. A method is suggested for estimating the initiation rate of the polymerization. The ratio of the rate constant of the phenol inhibited reaction to that of a peroxide radical reaction with the monomer has been evaluated. The solubility of oxygen in MMA and TGM-3 has been determined.

A study was made of polymerization of the dimethacrylic ester of oligotetramethylene glycol with M = 600 at 50° in the presence of AID and benzoquinone. By simply comparing rates of inhibited and uninhibited polymerization rate constants of chain extension and rupture were determined. It was found that ke ≅ 400, kr ≅ 7 × 104 1./mole·sec, which indicates diffusion control of chain rupture from the very beginning of the reaction up to the moment of gel formation. Results were compared with kr for other oligoester acrylates.

The rate of initiation was determined for the polymerization of the oligo(tetramethyleneglycol dimethacrylate), mol.wt. 700, in the presence of azo-iso-butyronitrile and benzoyl peroxide in the temperature interval 10–90°. The initiation efficiencies were calculated for both the initiators at different temperatures. The initiation efficiency is considerably reduced by a fall in temperature, and this is the result of increased viscosity of the oligomer inhibiting liberation of the initiating radical from a “cage”.

The kinetic theory of gel formation and the boundaries of formation of gel are discussed. The beginning and end of gel formation are taken as those degrees of conversion at which the maximal and minimal concentrations of polymer chains respectively are attained. In differing from Flory's theory in its definition of the gel point and consequently also in the mathematical expression of the criterion (dN/dt = 0 instead of Pw/Pn→∞ according to Flory), the theory outlined here enables the laborious and sometimes complex calculation of the MWD to be avoided. At the same time it is essentially an adequate statistical theory. Equations are obtained for determining the gel point and gel time and on the basis of these together with gel point measurements, it is shown that the reactivity of the double bonds in side blocks on the polymer chains from the dimethacrylates of ethylene glycol (at 60°) and triethylene glycol (at 40°) is substantially greater (by a factor of then the reactivity 1432 0688 V 3 of the double bonds in a polyfunctional monomer.

The kinetics of polymerization in the presence of oxygen and inhibitors of the anti-oxidant type is considered. Equations for the rates of polymerization and oxidation of the monomer and for the consumption of the inhibitor are obtained for conditions of effective inhibition. Equations are obtained that determine the length of the induction period for the reaction occurring in enclosed or in open systems.

Equations have been obtained for the rate of oxidation and polymerization of a monomer, the induction period and other parameters of the reaction of polymerization occurring at any concentration of the antioxidant. The conditions in which the antioxidant acts as an oxygen co-inhibitor are defined. The values of the lower and upper limits of the concentration of antioxidant, the critical rate of initiation and the critical concentration of the monomer are established.

Equations are given for the estimation of the efficiency and time limits of gelling in the presence of kinetic chain transfer agents. The study results are reported of the gel formation by polyhydroxytetramethylene-α,ω-methacrylate of M = 700 (MTMH-700). The validity of the kinetics of gel formation for the experimental findings is analysed. The rate constant of the individual polymerization stages have been estimated.

The kinetics of gel formation have been examined and a quantitative analysis carried out of the dependence of polymer chain concentration on time and on the degree of conversion of polyfunctional vinyl compounds. At low conversions, the polymerizate has been found to consist only of monomer molecules, and virtually only a single growing super-macromolecule. The validity of the mathematical criterion d N/ dt , d N/ d M)=0, which had been earlier used to determine the limits of gel formation has been proved.

A study was made of certain features of the polymerization of triallylcyanurate. It is shown that the order of the reaction with respect to monomer, initiator, and the overall energy of activation are strictly constant values, as in the case of ordinary vinyl polymerization, and depend on initiator and monomer concentration, and consequently on the degree of conversion. A mechanism accounting for peculiarities of the polymerization reaction is discussed from a quantitative standpoint.

A MAJOR difficulty in studying the mechanism of three-dimensional polymerization is the problem of determining the rate of photochemical initiation (w~), which is more complex than determination of w i under linear polymerization conditions t. The formation of a crosslillked insoluble polymer makes it quite impossible to find w~ by measuring the average coefficient of polymerization. The impossibility of completely extracting monomer from a three-dimensional crosslinked product of polymerization also precludes use of the other classical methods of determining the rate of photoinitiation such as, for instance, chemical and radiochemical methods of determining fragments of initiators in polymers. In the same way it would be hard to obtain satisfactory results using the inhibitor method of determining the rate of photoinitiation using the well-known equation

IF [1, 2] IT was reported tha t the polymerization kinetics of oligoesteracrylates t (OEA) is a diffusion-controlled process even at low degrees of conversion (G< 1%). At these G the influence of the physical properties (viscosity) of the reaction system on the apparent reactivity of OEA consists mainly in the recombination of polymer radicals, the reaction which has the smallest true activation energy. This was confirmed in [3] where the growth rate and chain termination constants of OEA were studied as functions of G. I t is very interesting to s tudy the relation between the apparent reactivity and structure of OEA at high G, where the polymerization product reaches the consistency of a solid (viscosity above 10 la poise). Under these conditions not only the chain termination but also the growth is a diffusion-controlled process. Even for small molecules in media approximating the consistency of a solid, D, the diffusion coefficient is 10 -11 cm2/sec [4]. This means tha t any bimolecular process will be restricted by diffusion if the rate constant of this process exceeds 10 -3 1./mole. sec. For methacrylates at G 0 (3,5-7), kp~--2-7×10 2 1./mole.sec and ko~_10v 1./mole.sec. Of course, these processes are completely controlled by diffusion at high G. Under these conditions the apparent reactivity of an oligomer will depend, not on the chemical features of the structure, but on the mobility and steric accessibility of the reaction eentres (radicals and double bonds). Thus the -C-C-chain is identical in all OEA. I t can be assumed that the mobility and steric accessibility of the reaction centres of different OEA will be determined by the structure of the transverse (oligomeric) block. The aim of the present work was to establish the relation between the OEA structure and kinetic features of the polymerization process at high G. The experiments used the thermometric procedure already described in [8,14].

Polymerization processes in solid and highly viscous media are considered. It is supposed that many processes in solids are ratelimited by rotational diffusion related to conformational transitions of structure elements containing reaction centers. This supposition agrees well with data on radical combination kinetics and the overall kinetics of polymerization in solids.