Jiri E. Kresta

Comparative Studies of Isocyanurate and Isocyanurate-Urethane Foams

The problem of flame resistance and smoke evolution of urethane foams has attracted increasing attention within the last few years, not only by material suppliers, foam applicators and users, but also by local, state and federal agencies. Although it is readily recognized that the currently available flammability methods leave something to be desired with regard to correlation with actual fire condi-

A Comparative Study of the Effect of Phosphorus and Chlorine in Urethane and Isocyanurate-Urethane Foams

I n recent years there has been a growing tendency of increasing the thermal stability of many polymer systems and, whenever possible, to impart flame resistance with low smoke evolution. For urethanes, this tendency has become of vital importance, especially in the manufacture of cellular, rigid urethanes for applications in construction, transportation and insulation of equipment requiring maintenance at elevated temperatures. Conventional methods for improving flame resistance of rigid urethane foams include the addition of a phosphorus and/or halogen containing compounds either in the form of an additive, a reactive component, or, to a lesser degree, in the form of a protective coating. Major research emphasis has shifted to flame-resistant compositions which are integral parts of the urethane chemical structure. These, of course, can be utilized by either the one-shot or prepolymer methods in the preparation of foams. Disadvantages of these types of cellular urethanes are relatively high smoke evolution, limited heat resistance, and in many cases, reduced hydrolytic stability. Hence, recent trends in the development of low flammability urethane foams have been based on copolymers containing heat-resistant groups, such as isocyanurates, oxazolidones, carbodiimides, and cyclic imides (1-22). The isocyanurate ring is thermally more stable than the urethane group, due to the absence of labile hydrogen. Isocyanurates, free of basic or

Thermostability of Urethane Elastomers Based on p-Phenylene Diisocyanate

Polyurethane (PU) elastomers based on p-phenylene diisocyanate (PPDI), poly(oxytetramethylene) glycol or poly(1,6 hexamethylene adipate) gly col and 1,4-butanediol were prepared at different NCO/OH ratios, and the mechanical property changes of these elastomers after heat aging at 150 °C were examined in the presence and absence of various antioxidants. It was found that the highest retention of mechanical properties of the polyether based PU elastomers were achieved with Irganox 1010 followed by Irganox 1024. There was no synergism observed in the combinations of antioxidants. The thermal oxidation stability of PUs based on polyester polyol was better than one based on polyether polyol. Both NCO/OH ratio and the methods of ad dition of antioxidants to PU elastomers affect the final thermostability of the elastomers.

New Heat Resistant Isocyanate Based Foams for Structural Applications

This paper describes unique types of isotropic urethane-isocyanurate and urethane-urea isocyanurate foams based on a combination of an aromatic polyester polyol and an amine-containing tetrol as the only polyols with a low functionality polymeric isocyanate

Technical Session XX: Chemical New Heat Resistant Isocyanate Based Foams for Structural Applications

formance to RIM moldings, the conventional glass fibers affect the surface quality of moldings causing declined DOI (distinction of image) due to the surface roughness remaining even after coating. Needless to say the shorter the fiber length is, the better the surface quality is. However, shorter fillers must be added in larger amounts to give comparable stiffness to moldings since the reinforcement efficiency depends mostly on aspect ratio. So, shorter fillers are not always the best solution. In consideration of the situation, we have carried out the study on Bayflex 110 RIM systems with various new and well known fillers such as milled glass fibers with different diameters, sieved processed mineral fibers and inorganic whiskers to find a filler giving both enough reinforcement and excellent DOI. We found that length and diameter of fillers affect surface roughness of molding very much and that fibers giving outstanding surface quality as well as sufficient reinforcement have fiber length under eighty microns and diameter under five microns. Fillers with these dimensions have been successfully applied to RRIM exterior parts in the industries.