Polyisocyanurate - Wikipedia

Polyisocyanurate ( ), also referred to as PIR, polyol, or ISO, is a thermoset plastic[1] typically produced as a foam and used as rigid thermal insulation. The starting materials are similar to those used in polyurethane (PUR) except that the proportion of methylene diphenyl diisocyanate (MDI) is higher and a polyester-derived polyol is used in the reaction instead of a polyether polyol. The resulting chemical structure is significantly different, with the isocyanate groups on the MDI trimerising to form isocyanurate groups which the polyols link together, giving a complex polymeric structure.[2]

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Manufacturing

The reaction of (MDI) and polyol takes place at higher temperatures compared with the reaction temperature for the manufacture of PUR. At these elevated temperatures and in the presence of specific catalysts, MDI will first react with itself, producing a stiff, ring molecule, which is a reactive intermediate (a tri-isocyanate isocyanurate compound). Remaining MDI and the tri-isocyanate react with polyol to form a complex poly(urethane-isocyanurate) polymer (hence the use of the abbreviation PUI as an alternative to PIR), which is foamed in the presence of a suitable blowing agent. This isocyanurate polymer has a relatively strong molecular structure, because of the combination of strong chemical bonds, the ring structure of isocyanurate and high cross link density, each contributing to the greater stiffness than found in comparable polyurethanes. The greater bond strength also means these are more difficult to break, and as a result a PIR foam is chemically and thermally more stable: breakdown of isocyanurate bonds is reported to start above 200 °C, compared with urethane at 100 to 110 °C.

PIR typically has an MDI/polyol ratio, also called its index (based on isocyanate/polyol stoichiometry to produce urethane alone), higher than 180. By comparison PUR indices are normally around 100. As the index increases material stiffness the brittleness also increases, although the correlation is not linear. Depending on the product application greater stiffness, chemical and/or thermal stability may be desirable. As such PIR manufacturers can offer multiple products with identical densities but different indices in an attempt to achieve optimal end use performance.

Uses

PIR is typically produced as a foam and used as rigid thermal insulation. Its thermal conductivity has a typical value of 0.023 W/(m·K) (0.16 BTU·in/(hr·ft2·°F)) depending on the perimeter:area ratio.[3] PIR foam panels laminated with pure embossed aluminium foil are used for fabrication of pre-insulated duct that is used for heating, ventilation and air conditioning systems. Prefabricated PIR sandwich panels are manufactured with corrosion-protected, corrugated steel facings bonded to a core of PIR foam and used extensively as roofing insulation and vertical walls (e.g. for warehousing, factories, office buildings etc.). Other typical uses for PIR foams include industrial and commercial pipe insulation, and carving/machining media (competing with expanded polystyrene and rigid polyurethane foams).[citation needed]

Effectiveness of the insulation of a building envelope can be compromised by gaps resulting from shrinkage of individual panels. Manufacturing criteria require that shrinkage be limited to less than 1%[citation needed] (previously 2%[citation needed]).[4] Even when shrinkage is limited to substantially less than this limit, the resulting gaps around the perimeter of each panel can reduce insulation effectiveness, especially if the panels are assumed to provide a vapor/infiltration barrier. Multiple layers with staggered joints, ship lapped or tongue & groove joints greatly reduce these problems.[citation needed]

Polyisocyanurates of isophorone diisocyanate are also used in the preparation of polyurethane coatings based on acrylic polyols[5] and polyether polyols.[6]

Health hazards

PIR insulation can be a mechanical irritant to skin, eyes, and upper respiratory system during fabrication (such as dust).[7] No statistically significant increased risks of respiratory diseases have been found in studies.[8][better source needed]

Fire risk

PIR is at times stated to be fire retardant, or contain fire retardants, but these describe the results of "small scale tests" and "do not reflect [all] hazards under real fire conditions";[9][better source needed] the extent of hazards from fire include not just resistance to fire but the scope for toxic byproducts from different fire scenarios.

A study of fire toxicity of insulating materials at the University of Central Lancashire's Centre for Fire and Hazard Science studied PIR and other commonly used materials under more realistic and wide-ranging conditions representative of a wider range of fire hazard, observing that most fire deaths resulted from toxic product inhalation. The study evaluated the degree to which toxic products were released, looking at toxicity, time-release profiles, and lethality of doses released, in a range of flaming, non-flaming, and poorly ventilated fires, and concluded that PIR generally released a considerably higher level of toxic products than the other insulating materials studied (PIR > PUR > EPS > PHF; glass and stone wools also studied).[10] In particular, hydrogen cyanide is recognised as a significant contributor to the fire toxicity of PIR (and PUR) foams.[11]

PIR insulation board (cited as the FR and the FR products of Celotex, a Saint-Gobain company)[12] was proposed to be used externally in the refurbishment of Grenfell Tower, London, with vertical and horizontal runs of 100 mm and 150 mm thickness respectively;[13] subsequently "Ipswich firm Celotex confirmed it provided insulation materials for the refurbishment."[14] On 14 June the block of flats, within 15 minutes, was enveloped in flames from the fourth floor to the top 24th floor. The public inquiry into the fire determined that the Celotex cladding material was one of the primary causes of the rapid spread of the fire, as they were much more flammable than permitted by building regulations. Celotex deceived regulators about the fire performance of the cladding by secretly adding fire retardant materials to the cladding panels that were used during safety testing.[15]

References

What Is PIR?

PIR or polyisocyanurate is one of the most thermally efficient insulation materials available in the industry. PIR is often described as combustible insulation, a term used for many other insulating materials. However, these materials (polyurethane/PU/PUR/EPS/XPS) do not have the properties that PIR possesses.

PIR is a thermoset polymeric material, combining isocyanates and polyols. This means it does not melt on heating. Depending on the process of manufacturing and the standard followed, the quality and performance of PIR may vary. That is why, it is important to check for the required certifications when making a choice.

What Is a PIR Panel?

PIR sandwich panels or polyisocyanurate sandwich panels comprise three layers—high-density, rigid polyisocyanurate foam covered with coated galvanised or aluminum plates on both sides.

Are you interested in learning more about PIR Core Panels? Contact us today to secure an expert consultation!

These PIR panels have superior heat insulation properties as well as mechanical load and and high wind speed load-bearing capacity and, thus, find application in the construction of building materials that require high fire resistance. In fact, its thermal conductivity is below 0.023 W/(m·K).

In modern construction, PIR sandwich panels are also the most effective acoustic materials.

Where Are PIR Panels Used?

PIR panels have unique properties.

• Ability to reduce the heat transmission caused due to the difference between the internal and external temperature. This helps achieve maximum freezing efficiency when used in refrigeration or cold storage.
• Heat and sound insulation
• Better chemical-resistance and water-resistance properties
• Anti-corrosive and insect-free
• Easy installation
• Lightweight
• Environment-friendly

Because of the abovementioned properties, PIR sandwich panels find extensive applications in chemical industry, petroleum industry, construction of clean rooms, cold storages, warehouses, prefab buildings, and ripening chambers, packaging, cold chain and refrigeration industry, military and space industry, transportation, aviation, and others.

What Is the Difference Between PU and PIR Panels?

Rigid Polyurethane (PU) foam has been used in construction since the s as a high-performance insulation material. Over the years, PIR has become the preferred choice due to its exceptional thermal insulation properties.

One of the  major difference between PU and PIR sandwich panels is the fire/flame resistance property. PU foam is known has limited fire resistance and PU sandwich panel is normally produced with B2 and B3 fire classification. Whereas, PIR not only slows down the spreading of flames but also lowers smoke emission. When compared to PU, PIR panels have better fire resistance, lower combustibility, and higher working temperature range. Usually, PIR panels are produced in accordance with the B1 or B2 fire rating.

What Is the Difference Between PIR and XPS?

Both EPS (expanded polystyrene) and XPS (extruded polystyrene) are manufactured from the petroleum-based resin which is a thermoplastic based on non-cross-linked polymers. Such polymers when exposed to high temperatures melt and also get degraded in certain solvents.

PIR, on the hand hand, is a thermoset plastic which is based on cross-linked polymers that can tolerate higher temperatures and have better heat resistance. They do not melt but char at high temperatures and are also more resistance to solvents and chemicals than polystyrene.

Is PIR Panel Fire Rated?

Rinac’s PIR panles are B2-grade fire-rated and certified as CLASS ‘O’ building material in accordance with BS 476 part 6 & 7 standard.

How Can Rinac Support Your Construction Needs

Rinac offers clean modular construction options with three different types of core materials.

PUF sandwich panels

• Metal laminates made from pre-painted galvanised steel
• Low density of up to 35—40 kg/m3
• Customised finishes of aluminum, plastisol, and stainless steel
• CFC-free and high-temperature insulation

PIR sandwich panels

• Certified by ISO, OHSAS, EMS [IMS-ISO & of and OHSAS /]
• B2-grade fire-rated PIR material
• Certified as CLASS ‘O’ building material in accordance with BS 476 part 6 & 7 standard
• Quick and easy-to-install with self-mating interlocking
• Excellent insulation as R/U values drastically reduce radiant heat transfer and condensation

FM approved sandwich panels

For more information, please visit Insulated Cold Room Doors.

• In accordance with the European standard EN and ISO standards
• CFC-free high-quality polyisocyanurate (PIR) foaming material with an average density of 42 kg/m3, firmly sandwiched between the metal surfaces
• Factory-made and self-supporting
• Double skin metal faced insulated
• Exceptional fire-resistant and thermal properties