Ts.M. Frenkel

The properties of polyisocyanurates produced by the polycyclotrimerization of aromatic with aliphatic diisocyanates

Abstract The thermal stability, heat resistance and the physico-mechanical properties have been studied on homo- and copolymers produced by a polycyclotrimerization (PCTM) of various aromatic with aliphatic diisocyanates (DIC). The effect of the DIC type and also of the ratio of aromatic to aliphatic components have been examined. The polyisocyanurates (PICU) produced by a selective PCTM have been found to possess improved physico-mechanical properties and thermal stabilities due mostly to the polar interactions of the C = O groups situated at the joints of the polymeric network.

Polycyclotrimerization of aryldicyanates in the presence of Cr3+ acetylacetonate☆

Abstract A kinetic scheme for the polycyclotrimerization of an aryldicyanate has been proposed on the basis of the kinetic features governing the polycyclotrimerization of 2,2-bis-(4-cyanotophenyl) propane in the presence of (AcAc) 3 Cr as catalyst: this scheme has been analysed and compared with the experimentally established facts and with results that follow from the scheme. It has been shown that all the kinetic features may be quite satisfactorily described by the scheme proposed.

Effect of the nature of solvent on the polycyclotrimerization rate of 2,2-bis-(4-Cyanatophenyl) propane☆

The solvent nature was found to have a marked effect on the reaction rate and the thermal effect in the polycyclotrimerization of 2,2-bis-(4-cyanatophenyl) propane in the presence of chromium acetylacetonate. Placing the solvents in order according to the polycyclotrimerization rate we have: ditolylmethane > nitrobenzene > anisole > diglyme. The thermal effect for the polycyclotrimerization in nitrobenzene anisole and diglyme is 5–10 kcal/mole lower than in ditolymethane.

Rheological properties of the gels obtained by solution polycyclotrimerization of diisocyanates

Abstract The elastic properties and swelling of gels obtained by plycyclotrimetrization of diisocyanates in various solvents have been investigated, along with those of dry networks obtained from the gels after elimination of solvents, in relation to the conditions of their synthesis governing the mechanism of network formation. For the dry networks it was found that the degree of swelling increases and the elastic modulus is reduced when the initial gel concentration decreases. Anomalous elastic properties of the gels, and irreversibility of network swelling before and after elimination of the solvent are accounted for by the role of solution macrocyclization leading to a more complex network topology compared with the polycyclotrimerization in bulk.

The kinetics and the heat of cyclotrimerization of aryl- and alkylisocyanates☆

Kinetic features have been investigated and reaction heats measured by a calorimetric method for the cyclotrimerization of mono- and diisocyanates in diglyme solution and in bulk in the presence of triethylenediamine, and using the catalytic system triethylenediamine-phenylglycidyl ether. It was found that curves of the reaction rate vs. time go through a maximum. Enthalpies of the process for phenylisocyanate and 4,4′-diphenylmethane diisocyanate in diglyme are −51·8 and −91·2 kJ/mole, while the values for 1,6-hexamethyl-enediisocyanate in diglyme and in bulk are −150·2 and −156·4 kJ/mole respectively.

The polycyclotrimerization of isocyanates

Abstract A simultaneous polycyclotrimerization (PCTM) of aromatic with aliphatic components has been shown to be feasible with the catalytic system of triethylene diamine and phenylglycidyl ether. In bulk PCTM of diisocyanates, the functional groups conversion was quantitative. The effects of the triethylene diamine concentration and of the ratio of 4,4′-diisocyanodiphenylmethane to hexamethylene diisocyanate on the rate and the kinetics of the simultaneous PCTM have been examined.

The formation, structure and properties of network polymers synthesized by polycyclotrimerization of carbo-functional organosilicon macrodiisocyanates in solution☆

The structure and properties of network polymers, synthesized in solution and based on organosilicon oligomers with terminal hydroxyl groups (prepared by polycondensation) and isocyanate groups (formed by polycyclotrimerization) have been compared. The study of conversion, gel: sol ratio, elastic modulus and equilibrium swelling both of the initial gels, synthesized in solution and the dry networks obtained from them, demonstrated the significant role of the chemical process which formed the crosslinks. The features of the formation and properties of these networks essentially depend on the Mn of the oligomers and their concentration in solution. The character of the change in critical parameters for gel formation was analyzed.

Kinetic study of reactions of carbodiimides with α-oxides, and structure of the resulting compounds☆

Abstract The influence of various factors affecting features of reactions of carbodiimides with α-oxides has been investigated. The main product of the interaction of diphenyl carbodiimide with phenylglycidyl ether is 3-phenyl-5-phenoxymethyl-2N-phenyliminooxazolidine; the formation of diphenylcarbodiimide dimer and 3-phenyl-5-phenoxymethyl-2-oxazolidone is also possible. When oligomeric initial products are used the resulting unit-type heterogeneous polymers contain iminooxazolidine, oxazolidone and other chain fragments. The chain structure may be modified by altering the reaction conditions.

A calorimetric study of 1,6-hexamethylene diisocyanate, its polycyclotrimerizatinn and the resulting polycyclotrimer in the 13·8–370 K region☆

The following thermodynamic properties of 1,6-hexamethylene diisocyanate and its polycyclotrimer have been studied by precision adiabatic and isothermal calorimetry and by differential scanning microcalorimetry: isobaric heat capacity C°d thermodynamic parameters for monomer melting and for the glass transition and glassy states of the polymer, in the 13·8–370 K temperature range. The enthalpy, entropy and Gibbs energy of polycyclotrimerization have been calculated and the upper temperature limit of this process evaluated.

Mechanical properties of polymer glasses with various moduli

The possibility of preparing polymer glasses with a wide range of elastic moduli has been predicted by theoretical calculations. The properties of such glasses prepared by a polycyclotrimerization reaction of carbofunctional silicon-organic macrodiisocyanates were investigated. These polymers contain bulky crosslink points, formed by an isocyanurate ring with attached hydrocarbon fragments, connected by silicon-organic chains. Such glasses may exhibit the most varied elastic moduli as controlled by the length of the silicon-organic inter-crosslink segments.