Blowing Agents for Polyurethane Foams

By Dr. S. N. Singh, Huntsman Polyurethanes Polyurethane foams are used in many applications including household and commercial refrigerators and freezers, building insulation and roofing, doors, cushioning, packaging, sprays and marine flotation, etc. The polyurethane foam industry was radically shaken up by the discovery, in the mid 1980s, that certain chlorofluorocarbons (CFCs) used as blowing agents can damage the environment. Hydrochlorofluorocarbons (HCFCs) were developed as replacements, but they are now scheduled to be phased out as they also have ozone depleting potential. Global agreements have been introduced such as the Montreal Protocol and the Kyoto Protocol, which severely limit the use of many blowing agents. Global warming, ozone depleting potential, atmospheric lifetime and volatile organic compounds are the primary environmental issues with any blowing agent, and there are other factors to consider such as long-term breakdown products, halogen-free nature and acidification potential. Blowing agents must also satisfy the requirements of the marketplace including cost, flammability, compatibility with materials of construction, and safe and economic manufacturing processes. Each application for foams has its own specifications, for example, low flammability, low toxicity, load bearing capability and cushioning effects. The long-term stability of the foam structure and the insulating properties of the foam are also key. The blowing agent used in polyurethane has a critical effect on these attributes. Insulation is affected by the gas phase thermal conductivity of the blowing agent. Stability is affected by several properties, such as the solubility of the agent in the polymer and the diffusion rate compared with air. This review discusses the legal requirements and property specifications for blowing agents in different applications. It highlights the effects of changing blowing agents including the need for reformulation. Many new polyols, isocyanates and surfactants are being developed to overcome problems. Similarly, new equipment is being produced, for example, to cope with the flammability issues surrounding the use of hydrocarbon blowing agents, such as pentane. Each type of blowing agent is described. Key environmental and physical properties are listed, together with advantages and limitations. Foams are described by types and by applications. The review also describes, briefly, the current state of the market and which new blowing agents are likely to be used in each sector. The developments by many different companies are outlined. Key Features

• Clearly written, easily accessible overview of:
• Types of blowing agents
• Types of foam
• Environmental issues
• Feasability issues
• Property requirements
• Polyurethane foam formulation
• Technological developments
• Exceptionally well referenced.

Contents

• Introduction
• Blowing Agents - Considerations Since the mid 1980s
• Alternative Blowing Agents
• Blowing Agents for Low Density Rigid Foam
• Blowing Agents for Low Density Flexible Foam
• High Density Foams and Elastomers

• About the author Dr Singh is a leading expert on blowing agents, formulation and long-term stability of polyurethane foams, and has a collection of publications including patents. He is currently a Development Associate with Huntsman Polyurethanes (formerly ICI Polyurethanes).

  The current price for this Rapra Technology Ltd. book may differ from the listed price. Please ask for an up-to-date non-binding offer under  Rapra Review Reports, Vol. 12, No. 10, Report 142, 2002