What is the Difference Between PIR and PUR?

When you’re planning to build a cold room and consulting with professional technicians for cold room solutions, you often face a common question: should you opt for PUR sandwich panels or PIR sandwich panels to construct the body structure of the cold room? In such instances, it’s essential to understand the differences between PUR and PIR. This article will compare PUR and PIR, providing a detailed explanation of their distinctions and advantages, allowing you to gain a deeper understanding of PUR and PIR.

PIR

What are PUR and PIR?

Polyurethane (PUR) and Polyisocyanurate (PIR) are two common types of polymer materials widely used in the construction industry, particularly in the cold room construction sector, where they are often utilized as the insulation core of sandwich panels.

 

Differences between PUR and PIR

 

PIR and PUR

While PUR and PIR share similar names and belong to the polyurethane family, they exhibit differences in structure, performance, and advantages.

Chemical Structure

PUR is primarily produced from the reaction between isocyanates and polyols, forming a polymer with repeating urethane linkages. It contains a higher proportion of linear structures and fewer cyclic structures in its molecular structure.

PIR is a variant of PUR, where the ratio of isocyanates to polyols is adjusted, resulting in a molecular structure with more cyclic structures. This modification enhances the thermal stability and structural integrity of PIR compared to PUR.

Thermal Insulation Performance

Both PUR and PIR exhibit good thermal insulation performance, but do they differ in their insulation capabilities? The answer is yes. The parameters commonly used to evaluate the insulation performance of materials include R-value, U-value, and K-value. Below, we will compare the R-value, U-value, and K-value of PUR and PIR to further illustrate the differences in their thermal insulation performance.

R-Value

The R-value, also known as the thermal resistance, is an important indicator used to measure the thermal insulation performance of materials. It represents the difficulty of heat flow through a material, or in other words, the material’s ability to resist heat flow. Simply put, the higher the R-value of a material, the better its thermal insulation performance.

The R-value of PIR is typically higher than that of PUR, which means that for the same thickness, PIR offers better thermal insulation performance than PUR.

U-Value

U Value

The U-value, also known as the thermal transmittance, is used to measure the heat conductivity of materials. It represents the amount of heat transmitted through a material per square meter, per second, per degree of temperature difference, indicating the material’s ability to allow heat to pass through. The U-value is the reciprocal of the R-value. In other words, the lower the U-value of a material, the better its thermal insulation performance, indicating less heat loss.

The U-value of PIR is typically lower than that of PUR, meaning that under the same conditions, PIR provides better insulation.

K-Value

The K-value, also known as thermal conductivity, is used to measure the heat conductivity of materials. It represents the amount of heat passing through a unit area of a material with a unit thickness under a unit temperature gradient per unit time. The K-value reflects the strength of the heat transfer process. Similar to the U-value, a lower K-value indicates better thermal insulation performance of the material.

The K-value of PIR is typically lower than that of PUR, indicating better insulation performance under similar conditions.

Fire Retardant Performance

Both PUR and PIR have good fire retardant properties, but their fire retardant effects differ due to differences in their chemical structures and production processes. Generally, PIR has better fire retardant performance than PUR.

As mentioned earlier, PUR molecules have more open-chain structures, which are prone to decomposition and release of combustible gases when exposed to flames, further exacerbating the fire. Therefore, additional flame retardants are usually added during production to improve the fire resistance of PUR. These fire retardants can cause PUR to form a char layer on the surface when exposed to flames, slowing down the spread of fire.

In contrast, PIR molecules have more ring structures, which improve the thermal stability of PIR. Without the addition of additional fire retardants, PIR can also form a char layer on the surface when exposed to flames, slowing down the spread of fire. By adjusting the reaction components and formulation technology reasonably during production, the fire resistance of PIR can be further improved.

Smoke Resistance

Smoke Resistance

Compared to PUR, PIR not only has better fire retardant performance but also better smoke resistance.Burning can produce smoke and certain toxic gases from both PUR and PIR, but due to the more stable chemical structure of PIR, the amount of smoke and toxic gases generated by burning is usually lower than that of PUR.

Price

Price is often one of the factors we consider when choosing a product. Compared to PUR, PIR has superior thermal insulation and fire retardant properties, which means that under the same conditions, the price of PIR is usually higher than that of PUR. Using sandwich panels of the same thickness, the cost of building a cold room with PIR sandwich panels will be higher.

Conclusion

Both PUR and PIR are excellent insulation materials for construction. Due to slight differences in their insulation and fire retardant properties, it is important to consider specific requirements when choosing between them, including insulation needs, fire resistance requirements, budget, and environmental factors. Although PIR tends to be more expensive, it offers better insulation and fire resistance properties. Therefore, when higher insulation and fire resistance requirements are necessary for a building, PIR may be more suitable than PUR. On the other hand, PUR is relatively cheaper and suitable for situations with limited budgets and less stringent insulation and fire resistance requirements in construction.

 

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