Reactive Flame Retardants for Polyurethane Foams

Abstract

This article presents an up-to-date review of chemical compositions, particularly those bearing the elements of halogen and phosphorus, and structural features of flame retardants which have been chemically incorporated in polyurethane foams. Particular Anthony J. Papa is project scientist with the Chemicals and Plastics Division, Union Carbide Corp., South Charleston, W. Va. He received his Pk.D. degree from Washington State University in 1960, and did postdoctoral work at Purdue University in 1961 and exploratory research on polyurethanes as leather substitutes at Du Pont from 1962 to 1966. He has had experience in the areas of urethane, isocyanurate, and phenolic foams, and since 1966 has worked in the fields of rigid and flexible foams.directed toward the construction marketplace, but at the present time the biggest outlet for flame-retardant rigid polyurethanes is still as insulation for the transportation industry. Test MethodsA review of all flammability test methods applicable to polyurethane foams is beyond the intent of this article. The most commonly employed small and medium scale tests for rigid foams include the ASTM D 1692 test, the Butler chimney test, the Bureau of Mines flame penetration test, the ASTM E 162 radiant panel test, and the ASTM D 568 vertical bar test. The ASTM E 84

Trichlorobutylene Oxide Based Flame Retardant Rigid Polyurethane Foam

“…The resulting polyols, RF-14 (from pure TCBO) and RF-19 (from modified TCBO) contain 19-20% Cl but ideally have viscosities under 100,000 cps at 25°C. Similar properties are exhibited by several of the reactive flame retardant polyols on the market today (7). For example, Pluracolg 463 has an OH No.…”

“…The tendency has been recognized before as the major fault in using this type of reactive flame retardant (7). The compressive strength, thermal conductivity K-factors and low MVT values for the TCBO-polyols in Table 6 are considered to be quite in line with today's desired standards (27).…”

“…Today, the list of major commercial and developmental reactive flame retardants for rigid urethane foam is comprised mostly of polyols featuring phosphorus alone as the flame retarding moiety (7). Indeed, the systems containing phosphorus in the +5 oxidation state, as the sole fire retardant specie, are especially significant because potentially they represent the least expensive solution to flame retarding urethane foam (19).…”

“…It is now recognized (in the literature) that rigid urethane foam made from aromatic polymeric isocyanates, having a functionality of 2.3 to 3.2, and polyols with an average functionality of 4 or more, shows little tendency toward melting when subjected to a flame (7). Instead, the thermal degradation leads to the formation of tarry distillate products and, more importantly, to carbonaceous char residues.…”

“…As such, they show greater permanence, particularly after accelerated aging of foam, as compared to the more fugitive additive-type retardants. The most commonly used reactive-type flame retardants are polyols containing phosphorus or halogens or combinations of these elements (7). Each candidate has its advantages or disadvantages in terms of its relative efficiency as a flame retardant versus price and its effect on the physical properties and stability of the flammable substrate in which it is incorporated.…”