Polyisocyanurate or Polyiso or ISO owes its popularity to its excellent thermal insulation performance (determined by its R-value). This thermosetting polymer gets its hardened, irreversible, and thermally insulating molecular structure with the application of heat. This property of Polyisocyanurates is particularly useful for roofing insulation applications. But the advantages of these materials and their significance do not end with just one property. There is a significant amount of reasons why many constructors prefer to use these polymers over others as a viable insulation material for their roofing materials. This essay is an attempt to study the significance of Polyisocyanurate as an insulator and its relevance in modern roofing structures.
Usage
Thermally insulating roofing materials are not only used to protect the roofing structures from external temperature variations but they are also important in improving the energy efficiency of any equipment used to control the interior air conditions of a building (or home). And since better insulation made it possible to have thinner walls and roofing materials, engineers were able to save considerable amount of interior space and money . So it is apparent that thermal insulations cannot be neglected while laying the roofing structure of any building or house. But to fully understand the importance of polyiso or Polyisocynurates in thermal insulation, it is imperative that we analyze this polymer further.
Polyiso has a molecular structure similar to that of polyurethanes except for a few differences in the quantities of its ingredients and also the additives used to improve its insulation properties. And one of the most useful attributes of this polymer is its thermosetting property. Instead of melting to form a liquid (like other polyurethanes) upon exposure to extreme temperature conditions, they form a charred hardened structure that insulates the underlying structure from the outside temperature variations.
Their popularity in the roofing industry can also be attributed to their resistance to molten asphalt and many roofing adhesives. It makes them perfect for insulating sloping roof structures. But the advantages of Polyisocyanurates do not end with these few. They are also fire retardant and are not inflammable in ordinary conditions. And, even though the dust produced during their manufacture can cause respiratory problems, no instances of this polymer causing other health hazards have been noted in any stage of its usage (that is, during the synthesis, manufacture of insulator laminates, and its application). But more importantly, they have been recorded as having high moisture resistance. This is what makes them the favorite insulation tool for many manufacturers and constructors.
Construction and design
Ordinary Polyisocyanurate Laminate Foams are manufactured by mixing the liquid foam forming ingredients and depositing them on a moving lower facing . This chemical ingredient mixture undergoes an exothermic chemical reaction which expands and causes them to come in contact with the upper facing. And upon coming contact with the upper facing, they adhere strongly to them. This is how an ordinary insulation laminate is manufactured for use. The choice of facing materials is determined by the particular needs of a structure (such as walls or roofs). For instance, the waterproofing requirements of a roofing structure may demand the use of aluminum foils or fiberglass-reinforced cellulosic felts as facing materials since these two are compatible with almost all waterproofing membranes.
R-value of Polyisocyanurates
The thermal performance of any insulation material can be easily understood using its R-value. Long Term Thermal Resistance (LTTR) is the most recently accepted and scientifically proven method to measure the R-value of any insulation material . LTTR (ASTM C1289 Standard) can be used to calculate the 15 year, time weighted average R-value of any roofing insulation materials. This method uses an accelerated aging technique where thin slices of foam insulations are conditioned under a particular temperature for a set number of days to predict the performance of the insulation material in the future .
The typical R-values of polyurethane products range from R3.6 to R7.2 per inch where R5.6 per inch is the generally accepted R value standard by the NRCA (National Roofing Contractors Association) for insulation materials . But one advantage Polyisocyanurates have on their R value is that it increases with the insulator thickness. So it is possible to improve their thermal performance over the years by thickening the polymer layer inside the laminate envelope. The polyiso roofing insulation product from GAF, named Energy Guard, is significant to the roofing industry due to the high R-values that they boast (above the standard 5.6 per inch value). And since they use organic/glass facers, they are significantly more lightweight than most of the products available in the market today. Another important aspect of the Energy Guard from GAF is its relatively lower water permeability compared to other insulation boards available today.
Conclusion
Polyisocyanurate has been the most popular insulating material for a significant amount of time in the roofing industry. Some of the advantages that these polymers have over other insulation materials are 1.Improved energy efficiency 2.Better Performance 3.Versatility 4.Better Thermal and Mechanical Performance and 5.Environment friendliness . Their moisture resistance, compatibility with other roofing materials and adhesives, negligible health hazards, and thermosetting properties are only a few of the unique characteristics that make Polyisocyanurate the favorite among all the available insulation materials (such as Perlite, Polystyrene, Cellular glass insulation, etc). And, for this reason, it is highly likely to remain the favorite for a significant amount of years to come.
Bibliography
Center for the Polyurethanes Industry. (2016). Polyurethane and Polyisocyanurate Foams. Washington: American Chemistry Council.
PIMA. (2016). Polyisocyanurate. Retrieved April 15, 2016, from Polyisocyanurate Insulation Manufacturers Association: http://www.polyiso.org/
Roxul. (2010, February 15). R-Value claims of Polyisocyanurate Insulation. Roxul Technical Bulletin , pp. 1-2.
