polyurethane foam spraying - PROPERTIES

Globally recognized as the number-one polymer, polyurethane foam belongs to the class of gas-expanded or foamed plastics. Any thermal insulation material contains 85 to 90 per cent of air, so manufacturing insulants on the construction site is much more convenient and profitable than “carrying the air” by railway or truck from afar.

Polyurethane foam is the result of a reaction between two liquid components - polyol and polyisocyanate – which produces air-filled microcapsules.

Inclusive of possible losses, one metric ton of feed can produce 20 cubic meters of PUF with a density of 50 kg/m3. A ton is four 200-liter drums. The production effectiveness, economic feasibility and convenience are obvious. Instead of delivering 20 cubic meters of insulant by truck to the construction site, one will merely need a minivan to transport the plant, a compressor, and the materials to the required place. Besides, if you bring prefabricated insulant to the site, you will have to store it and add certain process steps (such as fixing and covering) during its installation on the structure. All this is not required if the building is heat-insulated with PUF on the site.

In all parts of the world, prefabricated PUF has no problems with toxicity tests. Russian sanitary requirements are even more stringent than in other countries, however, all regional Sanitary Supervision Centers issue health certificates stating that PUF is “safe for heat-insulating application”.

If the PUF manufacturing components contain fire-retardants, the foamed plastic will only burn where and as long as there is flame from an external source. When the flame is extinguished, PUF will stop burning and will not smolder or smoke. If you need to insulate a pipe that will be buried underground, you obviously don’t have to care about ignitability. But when you are placing an insulant between two walls of a residential house, you should use non-combustible grades of polyurethane foam. Self-ignition of PUF is hard to imagine; it may happen when the wall temperature reaches several hundred degrees centigrade, so PUF will be the last to burn.

PUF manufacturing equipment can be divided into two classes. Expensive and complicated high-pressure casting equipment is designed for manufacturing Flexible, Integral Skin and Rigid PUF products, which are widely used in automotive industry, mechanical engineering, furniture manufacturing, light industry, aircraft industry, and railway car building. Polyurethane foam pipe covering, plates, and sandwich panels are all manufactured with high-pressure casting machines.
The second type is low-pressure equipment, which is a more popular polyurethane foam spraying technology. One of the most popular domestic plants of this type is PENA-98, which has a 40% market share in Russia. Its latest modification – P20UM – enables a stepless production rate (raw material consumption) control. In addition, PENA-98 is the only Russian-made low-pressure unit equipped with a real POURING HEAD (see more details).

One of the typical applications of a Pouring Head-furnished PENA-98 P20UM is manufacture of small-size molded articles, sectional thermal insulation covering for pipes. You can see the equipment operation in the PRODUCTION PROCESS ANIMATION (click here).

Polyurethane foam spraying is the most promising technique of creating heat insulation and waterproof coatings. PUF’s ability to cover complex-shape surfaces with excellent adhesion allows architects to design and implement thermal insulation for various types of buildings that have complicated forms such as barges, arches, columns, etc.
Polyurethane foam is ideal for repair of damaged roofing (with any slope angles) of old, insufficiently heat-insulated buildings. Practice shows that, for instance, PUF spray roof covering saves up to 80% of time and up to 50% of money in comparison with traditional methods.

According to this process chart, a roof is first covered with a 40-50 mm polyurethane foam thermal insulation coating with a density of 60 to 80 kg/m3, and then a protective waterproof layer of high-density PUF. The thickness of the protective layer can be chosen within the range from 10 to3 mm (depending on the material density, which can vary between 120 and 600 kg/m3).

PUF is excellent for thermal insulation for pipes and heating mains. Sprayed insulation provides a monolithic, fully waterproofing pipe covering. No additional coating is required, except painting to protect the pipes from direct sunlight.
Due to its specific handling abilities, polyurethane foam is ideal for winterization of attics, interior sides of roofs (it has superb adhesion even to ceiling surfaces), as well as vertical structural units such as walls and frontispieces. Besides, PUF can be a perfect nonputrescible insulation for floors, foundations, and underground floors.

PUF has an estimated durability of 25 to 30 years, but this is not the limit. Technicians in Germany, USA, Sweden, and Japan have dismantled wall, roof and foundation structures, take samples of PUF pipe coating made in the 1970s, and reported “no change in properties”. Correctly manufactured PUF has no chemical reasons for degradation. More than 90% of its cells are closed, i.e. constitute plastic capsules filled with carbon dioxide.

PUF is unrivalled for its low heat conductivity. Widely used domestic PUF’s maintain a stable thermal conductivity factor of 0.028 W/(m·deg), which will probably reduce to 0.02 W/(m·deg) in the near term. The thermal conductivity factor of extruded cellular polystyrene, which has nearly the same quality but ranks lower in workability, is 0.03 W/(m·deg) and is not expected to decrease.
In contrast with most heat insulating materials, the thermal conductivity of PUF does not depend on ambient humidity (this is not the case with other insulants), so it can be well preserved under rain or snow. To calculate the comparative heat-protective efficiency of different building materials, it is enough to divide the conductivity factors? E.g., for polystyrene foam and PUF the result will be 0.04 / 0.028 = 1.43, which means that the heat-protection performance of 10 cm PUF is equivalent to 14.3 cm of dry polystyrene foam.

Using PUF offers inarguable benefits.
• Thermal insulation coating can be sprayed on any surface with any geometry. PUF can be cast into any cavity whose volume corresponds to the batched weights of the components.
• The perfect manufacturing process minimizes the work time;
• The sprayed layer is integral and jointless, which ensures the high durability. In a casting process, the whole volume of the cavity is filled with homogeneous material.
• Provided there are no mechanical damages, the product life will be at least 25 years;
• Can be used in a wide range of temperatures (from -250°Ñ through +180°Ñ);
• Low thermal conductivity factor (0.023 to 0.032 W/(m·K);
• The material is non-biodegradable, resistant to microbes, mold, and decay;
• PUF is a nonflammable, self-extinguishing material;
• The water absorption of the surface-filmed material for 24 hours at a 98 % RH is 0.04% or 2g/m2.

The portable, compact and reliable equipment offered by NST will allow spraying or casting polyurethane foam in both in-field or on-site conditions and fixed installations.

This thermal insulation material is highly efficient, extremely workable, top quality, inexpensive, and has unrivalled properties. The manufacture of various types of PUF in Russia is constantly increasing, but unfortunately, this material is still not as widely used as in Western Europe and the USA, where PUF has been providing successful solutions for over 50 years.

The most important applications of PUF are:

1. Refrigeration engineering (heat and cold insulation for household and commercial refrigerators, coolers and freezers, food and agricultural product storages);
2. In-transit refrigerating units (heat and cold insulation for refrigerated trucks and railroad cars);
3. Construction of fast-to-erect industrial and civilian projects (owing to the heat-insulating and load-carrying ability of rigid PUF’s integrated in sandwich structures);
4. Construction and overhaul maintenance of residential buildings, detached houses, and weekend houses (thermal insulation for outside walls, internal covering for roofs, insulation for window openings, doors, etc.);
5. Industrial and civil engineering (outer waterproofing and thermal insulation of roofs by sprayed rigid PUF);
6. Pipeline transportation (thermal insulation for crude and fuel oil lines, high-performance insulation of low-temperature pipelines at chemical facilities by casting PUF into preassembled covering shells);
7. Local heating systems (rigid PUF thermal insulation for newly laid or overhauled hot water supply pipelines using various process techniques of casting and spraying);
8. Radio and electrical engineering (improving the vibration resistance of a wide range of electrical devices, waterproof covering of contact couplings using the good electrically insulating and non-conducting properties of structural-type rigid PUF’s);
9. Automotive industry (molded parts of motor vehicle interiors based on flexible, semi-rigid, integral skin, and thermoformable PUF’s);
10. Furniture industry (manufacture of upholstered furniture using flexible polyurethane foam; cabinet parts and features from rigid PUF; lacquers, adhesives, finishes, etc.);
11. Light industry (manufacture of polyurethane imitation leather and products, PUF-based double fabrics. etc.);
12. Railway car building and aircraft industry (extra-fire resistant flexible PUF molded products, special PUF grades based heat and noise insulation);
13. Mechanical engineering (thermoplastic PU / special PU and PUF grades based products).