By means of a combined thermal analysis technique,, the thermal behaviour of rigid polyurethane foams containing additive antipyrenes was studied. The presence of phosphorus-and phosphorus/chlorine-containing antipyrenes based on phosphate and phosphonate and a combination of them led to decreases in the rates of heat and weight loss during heating. More steps of decomposition were formed and the interval of decomposition was widened and shifted to higher temperatures. Some thermal characteristics make it possible to predict the optimum antipyrene compositions and concentrations with minimum time, labour and material consumption under laboratory conditions. Rigid polyurethane foam (RPUF) is an organic material with a high tendency to burn. Its combustibility depends essentially on the thermal stability of the structural chemical bonds and the products of decomposition. As with other types of polyurethanes, its flammability is reduced by the addition of antipyrenes. The problem of selecting optimum antipyrene compositions for polymers is becoming an urgent necessity. It requires the development of laboratory methods which are minimum time-, labour-and material-consuming and can provide maximum insight into the inhibiting effect of antipyrenes, thereby allowing a comparative evaluation of their efficiency. A major shortcoming of the available flammability tests is their failure to meet these requirements. Directly proportional relationships between polymer flammability tests and thermal analysis data have, recently been found [1][2][3][4][5]. Systematic studies [6][7][8][9] in this field, however, are still scarce.The aim of this work was to study the effect of additive antipyrenes with different compositions and structures on the mechanism and kinetics of the total thermal decomposition reactions of RPUF, and the possibility of evaluating their effectiveness as combustion inhibitors.

The effects of P-and Cl-containing reactive antipyrenes with different compositions and structures on the mechanism and kinetics of the total thermal decomposition of rigid polyurethane foams, together with the possibility of evaluating their effectiveness as combustion inhibitors, were studied by means of a combined thermal analysis technique. It is shown that dynamic thermal analysis can register the changes resulting in the mechanisms and kinetics of the thermal decompositions of the investigated polyurethanes from comparatively low concentrations and differences in the concentrations and from differences in the chemical compositions and structures of the antipyrenes. The most sensitive characteristics associated with the influence of antipyrenes in this case were the coke residue determined at 850 ~ in an inert medium and the areas of exothermic peaks I and II in the DTA curve in air medium.Because of the increased tendency to burning and the requirements for their combustion stability, the problem of selecting optimum antipyrene compositions [1] for polyurethanes is becoming an urgent necessity. This requires the development of laboratory methods which are minimum time-, labour-and material-consuming and can provide .the maximum insight into the mechanism of the inhibitory effect of antipyrenes [1][2][3][4].Additive antipyrenes are not always efficient enough. The tendency is to search for reactivity modifiers which are introduced into the polymer molecule during synthesis. In the case of polyurethanes, it is the most convenient to introduce them in the polyol component. Systematic investigations on the thermal behaviour of substances of this type are still scarce.The aim of the present work was to study the effects of reactive antipyrenes with different compositions and structures on the mechanism and kinetics of the total John Wiley & Sons, Limited, ChichesterAkad~miai Kiad6, Budapest

No abstract

Thermal analysis, IR and emission spectroscopy were used to study the influence of phosphorus and phosphorus/chlorine-containing antipyrenes on the thermal decomposition of polyurethane elastomers based on 4,4'-diphenylmethane diisocyanate and polytetraoxymethylene. The introduction of P-containing antipyrene into the structure of polyurethane elastomers induces changes in the mechanism and kinetics of thermal decomposition towards inactivation of the exothermal reactions of oxidative decomposition. It causes a shift of the first exothermal peak towards higher temperatures by 100 ~ and helps the formation of temporarily stabilized structures. P/CI-containing antipyrene has a smaller positive effect towards inactivation of the exothermal decomposition reactions and the formation of temporarily stabilized structures.The use of antipyrene is one of the most common methods of reducing polymer flammability. For most antipyrenes the flame-proofing mechanism has not yet been explained. It is probable that the thermal decomposition of modified polymers is affected in a specific way. Study of the thermal decomposition of similar systems in a sufficiently wide temperature range would clarify the nature of the reactions proceeding and would help in the choice of a suitable antipyrene.There have been quite a number of reports on the thermal analysis of various polyurethane polymers [1-5], including elastomers [6]. We have no information concerning thorough studies on the influence of flame-proofing additives on the thermal decomposition processes of polyurethanes. The directly proportional relations recently found between flammability tests and thermogravimetric and differential thermal analysis results [7] recommend a wider utilization of these methods for evaluation of the influence of antipyrene on different polymers.In an earlier work [8] on the same polyurethane elastomers (PUE) modified with phosphorus and phosphorus/chlorine, a connection was found between their thermal behaviour (shift and intensity reduction of the first thermal peak) and the value of the oxygen index. This correlation gives information on the optimum concentration of antipyrene as concerns its effectiveness for combustion retardation. The aim of this work is a more detailed study of the transformations these polymers undergo upon heating, and the influence of antipyrenes on the thermal decomposition mechanism.