Blowing Agent Phase-Out Schedule
Government regulation drives a significant amount of technology innovation for companies involved with rigid polyurethanes. As will be discussed in Section 8.4, insulation efficiency requirements and blowing agent restrictions are inextricable.
TABLE 8.10 Promulgation of regulations for blowing agents previously used for polyurethane rigid foams
Approximately 75% of the insulative potential of a foam depends on the foam structure and the properties of the gas within the closed cells, both of which the blowing agent has strongly causative relationships to. Regulations governing industrial use of blowing agents are particularly relevant to polyurethane technology because they not only govern current use but also future use, since whole classes are designated for banning in future years . Table 8.10 is a compendium of relevant historical and future restrictions. Future restrictions will provoke a significant amount of reformulation of polyurethane systems along with development of new classes
TABLE 8.11 Restricted blowing agents and potential substitutes for polyurethane rigid foam production
of blowing agent. Along with insulation potential, a blowing agent must also possess sufficient solubility in foam formulations to result in low-density foam, must be acceptable from an environmental health and safety standpoint, must have acceptable flammability characteristics, and must be compatible with equipment and other formulation additives. The dates listed are not universally implemented on the same time schedule, but given the commercial importance of the US and European markets for polyurethane rigid foams, they certainly are milestones for industrial use of blowing agents. In fact, some countries have implemented restrictions on accelerated time schedules.
An alternative view is to look at what blowing agents are allowed and the typical regulated blowing agent it can replace (Table 8.11).