The appliance industry is a major user of rigid urethane foams, which includes household refrigerators, household freezers, and residential water heaters. The development of physical blowing agents revolutionized the rigid urethane foam industry. At this time, the most viable physical blowing agents are HCFCs (for, example, HCFC 141B), hydrocarbons (for e.g. Cyclopentane) and etc.
This process involves pouring foaming ingredients into a closed void space to form an integral part of the foam and substrates. Commercial products that use this process include household refrigerators and deep freezers.
Rigid urethane foams are applied in many thermal insulation products such as refrigerators, freezers, refrigerated trucks, refrigerated containers, refrigerated warehouses, building and construction, chemical and petrochemical plants, water heaters, portable ice boxes, and thermos bottles. It should be noted that rigid urethane foam contributes considerably to energy savings on the earth.
Because of the energy conservation regulations in the United States hydrocarbons cannot be used as blowing agents in the U.S. appliance industry. However, European and Asian countries employ hydrocarbons such as cyclopentane as blowing agents because hydrocarbons are economical, have zero ODP and nearly zero global warming potential (GWP), and allow for thicker insulation wall thickness. Hydrocarbons have some disadvantages such as higher K-factor, flammability, and high investment costs.
In principle, the required physical properties of appliance foam include low foam density, high dimensional stability, low K-factor, good adhesion to plastic door liners, zero ODP, and low GWP.
Another important application area of appliances is residential deep freezers. In the past, residential water heaters were insulated with glass fibers, but they now are insulated with rigid urethane or urethane-modified isocyanurate foam. The insulation foam requires higher heat stability than conventional rigid foam.
Rigid polyurethane insulating foam makes a major contribution to sustainability and eco-design by reducing the energy required to keep refrigerators and freezers cold. The insulation efficiency of polyurethane foams is a key property for the low temperature preservation of food during processing, storage and distribution to the consumer. Without polyurethane insulated refrigeration, approximately 50% percent of the world’s food would rot, heavily influencing our daily life and food related business.
Polyurethanes are ideal for the insulation of refrigerating appliances and have major advantages as they are:
- excellent insulators
- structurally strong thanks to the rigidity of the foam and adhesion of external skins (plastic and metal)
- the most cost-effective manufacturing solution, with multiple operations combined into one
- effective in confined spaces, allowing the maximum amount of food to be stored
- robust and strong
- very light, thus reducing transportation costs
- affordable, keeping the costs of refrigerators and freezers down
This means that ever more stringent energy standards can be met, with benefits to the consumer through lower energy bills and a reduction in energy used. As shown below, EU energy efficiency initiatives have resulted in considerable energy savings since 1990.
Even when using small amounts of the material, the low thermal conductivity of polyurethanes results in excellent insulation, leaving a large useful space for the consumer. In addition, polyurethane rigid foams have a long service life. Fridges can consume up to 30% of total household electricity, so energy efficiency makes a real difference. Because of the introduction of polyurethanes into refrigerators, models designated A++ today are 60% more efficient than refrigerators 15 years ago.
According to the EU Waste Electrical and Electronic Equipment (WEEE), “white goods” such as refrigerators and freezers are subject to recovery and recycling targets across Europe. Foam from the appliances can be extracted and either recycled or used as fuel, depending on national infrastructures, further helping to conserve natural resources.
Polyurethanes thus play a crucial role in the energy-efficient transportation and preservation of our food, ensuring that it reaches our tables fit for consumption. More information on the use of polyurethanes in the cold food chain.