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  • Writer's pictureBona House Materials

PUR or PIR sandwich panel?

Updated: Apr 30, 2023

PIR, full name Polyisocyanate Foam, also known as "polyisocyanurate", "polyisocyanurate foam PIR" or "tri polyester PIR". PIR is a foaming material made by reacting isocyanate with polyether under the action of a catalyst, which has better physical and fire resistance than ordinary polyurethane. It is an ideal organic low-temperature thermal insulation material with small thermal conductivity, lightweight, shockproof, and strong adaptability. It is widely used in oil refineries, chemical plants, ethylene, fertilizer, cold storage, and construction industries for thermal insulation.


PUR, full name Polyurethane (polyurethane), is a polymer with carbamate segment repeating structural units, which is made by the reaction of isocyanate and polyol. It has excellent material performance, wide applications and a wide range of products, and PUR foam is the one most widely used. PUR products are divided into foam injected products and rigid polyurethane foam products. Injected foam products include soft, hard and semi hard PUR foam plastics, rigid foaming products include coatings, adhesives, synthetic leather, elastomers, and elastic fibers.



Difference between PIR and PUR sandwich panel


1. The fire resistance of PIR is superior to that of PUR;


PUR and PIR are two foam systems. Polyols are divided into polyester polyols and polyether polyols. PUR is a foam system formed by the reaction of polyether polyols and isocyanates. PIR is formed by the reaction of polyester polyols and isocyanates. The isocyanate index of PUR board is usually between 110 and 120, and the crosslinking degree of PUR foam system mainly depends on the functionality of polyether polyol. However, with the increasingly strict requirements for fire rating, PUR foam is facing a huge challenge in the fire prevention specification. Usually, in order to meet the requirements of fire prevention specifications, a large number of flame retardants will be added to the formula system, which will affect the compression strength, dimensional stability and other physical properties of the foam, and increase the cost of the product.


The degree of crosslinking of PIR system depends on the trimerization of excessive isocyanate. Generally, the isocyanate index reaches 200~300. Under the action of the corresponding catalyst, the excessive isocyanate can self-react to form six membered rings, provide crosslinking for the foam collective, and at the same time promote the combustion and coking to form carbon through its own six membered ring molecular structure, so as to improve the fire resistance of the foam system.


2. The PIR reaction is simple and can use low-cost raw materials;


3. PIR can give the product better dimensional stability at high and low temperatures, lower thermal decomposition rate, and form a protective carbon layer during the combustion process;


4. The mechanical strength of PIR is superior to that of PUR;


5. PIR has high production efficiency;


Deficiencies of PIR compared to PUR sandwich panel


1. High brittleness and lower fluidity than PUR;


2. Poor adhesion, with a bonding force of only 1/2 of PUR to the metal skin of sandwich panel;


3. PIR has a rapid secondary foaming property that can affect the performance of the plate surface;


4. Poor surface ripening and late post ripening;


The process range is relatively narrow (production temperature is higher than 60 ℃), making production difficult to control.


In the continuous PIR sheet production, the control of equipment and external environment is crucial to the quality of the final product. It is necessary to conduct good temperature control for various chemical raw materials, because it has a huge impact on the stability of the entire chemical reaction process and the entire foam forming process.

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