What is pir duct?

Answer 1

What is PIR / PUR?

Rigid polyurethane (PUR) and polyisocyanurate (PIR) insulation products are highly effective and lightweight. When they are manufactured they have the ability to bond to most materials. Their excellent thermal conductivity,high strength to weight ratio, combined with great manufacturing versatility provides a large variety of products which makes PIR/PUR insulation products the optimum choice for most construction insulation applications.

The first commercial applications for polyurethanes were developed in the middle of the 20th century. Since then they have been finding use in an ever-increasing number of applications in industries such as construction, automotive, refrigeration, furniture and footwear. Polyurethanes are extremely versatile and are found all around us in many every day items.

Rigid PUR insulation products are made by reacting a liquid polyol component with a liquid polymeric isocyanate, Methylene Diphenyl di-Isocyanate (MDI), component in the presence of a blowing agent and other additives. The mixed components then react exothermally to form a rigid thermosetting polymer and since the blowing agent evaporates during this exothermic reaction a rigid closed cell low density insulation product is created. Excellent insulation is achieved because the gas trapped within the closed cell structure has a very low thermal conductivity and there is minimal heat conduction through the solid cell walls due to the low density, where approximately 97% of the volume of the foam is trapped gas.

Rigid PIR differs from PUR in that it is produced using an excess of the MDI component. In the presence of an appropriate catalyst the excess MDI reacts with itself to form isocyanurate which is characterised by greater heat stability. The resultant PIR insulation products exhibit increased fire performance and reduced combustibility and higher working temperature limits compared to PUR and when incorporated into building products, can meet some of the most demanding fire performance requirements such as those currently stipulated for some applications by the insurance industry.

Details of approvals for specific products are available from BRUFMA members.