Fluorocarbons & Sulphur Hexafluoride and Insulation Foams: Technical and Safety Aspects

These structural insulated panels provide high R-value and require less labor to install than stud-framed walls and ceilings.

Several HFCs have excellent thermal insulating characteristics. These specific properties have made them good candidates as foam-blowing agents for the replacement of HCFC-141b and HCFC-142b in the production of insulating foam.

This is particularly the case in those applications where there is limited space available for insulation, e.g. appliances such as freezers and refrigerators. The use of HFCs enables appliance manufacturers to meet stricter energy-consumption standards while offering their customers the same storage capacity.

Because of their favourable toxicity and flamability properties, these HFCs are also the foam blowing agent of choice in in-situ insulation. They help the owners of many older buildings to achieve lower heating and cooling expenses.

At the same time, the use of these HFCs in providing superior insulation is reducing CO2 -emissions associated with the energy required for the heating and cooling.

Technical

Fluorocarbons used for insulation foams : See the Related Links

Note : Most HCFCs are now banned in developed countries. They are still used in developing countries.

In a foam, it is the cell gas, not the solid polymer which is the insulating agent. There are various ways of producing a foam. The key characteristic is that all foams have a cell structure. HFCs are used to create and fill out the cells during the foam blowing process. There are essentially two types of cell structures. In open cell foam, air can move into and out of the cells. In closed cell foam, the blowing agent such as HFCs is trapped in the cell structure. This second type of foam is used in thermal insulation. Several HFCs have been developed for their low thermal conductivity, and their ability to remain captured in the cell structure. Emissions during production and their use are minimal. Other HFCs are used to improve the uniformity and consistency of the cell structure (especially for construction foam).

Safety aspects

The HFCs used in foam blowing applications are either non-flammable or mildly flammable compared to the most commonly used foam blowing agent family, pentanes. Pentanes are relatively inexpensive compared to HFCs, but they require significant investment in explosion proof production and storage facilities. Moreover, pentanes tend to migrate faster through the cells walls, reducing the insulation properties. Since pentanes have photochemical oxidising properties, they can cause smog when emitted, whereas HFCs do not contribute to smog.

Recovery and recycling

Since HFCs are predominantly used in closed cell foams, and since they generally have low migration rates, it is possible to recover the majority of the HFCs used in the production of foam. Several countries have developed technologies to recover blowing agents from used appliances (predominantly to prevent the emission of CFC-11). This trend is expected to continue as more countries introduce end-of-life recovery schemes, often funded through compulsory consumer purchase fees.