Pyrolysis Kinetics and Flammability Evaluation of Rigid Polyurethane with Different Isocyanate Content

Abstract

Polyurethane (PU) is a typical product of the reaction between isocyanate and polyol, whose ratio would greatly influence material properties. In this paper, to investigate the influence of isocyanate on PU thermal stability and flammability, three kinds of rigid polyurethanes (RPUs) with different isocyanate ratio (1.05, 1.1, and 2.0) were manufactured in a laboratory and employed to have a series of TG (thermogravimetry), DSC (differential scanning calorimetry), and cone calorimetry tests. Kissinger's method was used to calculate the activation energy and judge their stabilities. However, for such a complex degradation which consists of five reactions, it does not make sense by Kissinger method to obtain only two peak active energies. Considering complexity of PU degradation in air, genetic algorithm (GA) was employed to calculate kinetic triplets of five sub-reactions. The effects of isocyanate contents on each sub-reaction stability were obtained and then analyzed. By cone calorimeter testing, we found that great differences in heat release rate data. However, DSC analysis showed a complete opposite changed trend. Such difference is caused by DSC and calorimeter’s sample morphology, the former using grinded polyurethane powders but the latter polyurethane foam block.

Special structures and thermal stabilities of polyurethanes derived from diol and triol having oxazolidone moieties

“…On the other hand, the T d10 values of PU‐3 and PU‐4 were lower than PU‐1 , although the T g values of PU‐3 and PU‐4 increased with increasing M n values and M w /M n values. Generally, the thermal decomposition of the branched polyesters and polyurethanes synthesized by a chain‐growth polymerization readily starts from the chain terminal 41–45 . In particular, such branched polymers are extremely prone to thermal decomposition from the chain terminals because the hydroxyl groups of the terminals cause depolymerization, although the thermal decomposition temperature depends on the branched degree and molecular weight 42,43 .…”

“…Generally, the thermal decomposition of the branched polyesters and polyurethanes synthesized by a chain-growth polymerization readily starts from the chain terminal. [41][42][43][44][45] In particular, such branched polymers are extremely prone to thermal decomposition from the chain terminals because the hydroxyl groups of the terminals cause depolymerization, although the thermal decomposition temperature depends on the branched degree and molecular weight. 42,43 Since the 1 H NMR spectra of PU-3 and PU-4 clearly showed the hydroxy groups of the terminal (Figures S16 and S17), the T d10 values of the multi-branched polyurethanes were lower than that of PU-1 stabilized by the intermolecular hydrogen bonds.…”

Clays as Inhibitors of Polyurethane Foams’ Flammability

“…As mentioned above, polyurethane foams function among plastics as materials with versatile properties and a wide range of industrial applications [52]. Nowadays, more and more attention is being paid to improving the flammability properties of polyurethanes, which in turn determine their use in automotive applications, mattresses, and insulation boards in construction [53,54]. Environmental factors also drive such an approach to reduce plastics' environmental impacts [55].…”