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Metecno-Aluma Shield is committed to delivering environmentally friendly insulated metal panels that deliver the highest R-values the industry has to offer:

USGBC, LEED™, and Polyiso

Pentane Press Kit

Pentane as a Blowing Agent in Metal Wall and Roof Polyisocyanurate Insulated Foam Panels

On July 22nd 2002 the U.S. Environmental Protection Agency (EPA) published its ruling on acceptable substitutes for ozone-depleting substances (ODSs) in the foam blowing sector under the Significant New Alternatives Policy (SNAP) program [1,2]. The action mandated that the production of HCFC 141b cease from January 1st 2003 but also stated that users may continue with 141b as long as stockpiles last. The EPA also withdrew its proposed decision to list HCFC 22 as an unacceptable substitute for CFCs but for “existing users” only. This means that specifiers need to be aware that ozone depleting metal insulated panels are still available which requires greater scrutiny during product selection evaluation.

It should be noted that the EPA intends to review the use of HCFC 22 in metal insulated panels to determine the progress of non-ozone-depleting alternatives and reserves the right to introduce new HCFC rulings at a future date. It is also important to remember that the 35% reduction step in the overall HCFC cap as required by the Montreal Protocol on Substances that Deplete the Ozone Layer will enter into force in both Canada and the USA on January 1, 2004 [3]. Careful review of insulated panel product data and chemical composition is advised when striving for environmentally friendly solutions.

In order to comply with the terms of the SNAP program as well as section 606 of the Clean Air Act [4] and the Montreal Protocol, Aluma Shield Industries (ASI) elected to switch from 141b to pentane as a blowing agent. Full compliance with the new regulations has meant significant investment in foam processing equipment by ASI but does mean that the company will be able to continue with its new pentane blown (HCFC FREE) polyisocyanurate (PIR) foam system into the future with no restriction on use.

Hydrocarbons (HCs) from the family of pentane isomers have already been successfully introduced and operated in the USA by rigid insulation, appliance, and spray foam manufacturers. Pentane has also been for several years the blowing agent of choice for metal insulated panel manufacturers and other insulation providers throughout Europe and China.

Pentane as a Blowing Agent

The most common pentane blowing agents used in the manufacture of PIR systems and their respective chemical formulations are listed below.

• N-pentane C5H12
• Iso-pentane (CH3) 2CHC2H5
• C-pentane (C5H10)

These pentane isomers all have different physical properties and it is important to note that the blowing agent used by ASI is a highly efficient blend of the aforementioned pentane isomers developed, with the new generation of polyols, to meet the needs of the market from a performance standpoint. Exact pentane formulation by each manufacturer varies within the industry. Substantiated performance data such as thermal conductivity values, physical properties, compliance standards, functional characteristics, and warranties are typically the basis for product comparison not the three accepted pentane formulations.

Performance Characteristics of Pentane

Environmental Compliance:

All three pentane isomers have zero Ozone Depleting Potential (ODP) and either a zero or very low Global Warming Potential (GWP) potential (less than .00044) as compared to HCFC 22, which has an ODP rating of 0.055, and a GWP of 1700. For this reason, the EPA lists pentane, as a suitable replacement for HCFC’s which are viewed as harmful to the stratosphere [2. HCFC’s are considered to be ozone-depleting substances (ODSs) as over time cells break down in the presence of strong ultraviolet (UV) radiation and release chlorine or bromine atoms, which destroy ozone molecules. In fact, one chlorine or bromine molecule can reportedly destroy 100,000 ozone molecules. The change from CFC-11 to HCFC-141 reduced the ozone depleting power by 90%. The pentane based chemistry provides 100 percent reduction of ozone depletion. The added benefit of either zero or low global warming potential is an indirect advantage of pentane formulation

Thermal Efficiency:

The PIR chemical bond has good thermal stability and tests have proved that the pentane-blowing agent used by ASI contributes to excellent panel insulation performance. The pentane PIR system used by ASI has, in fact, a low K-factor as a result of the very fine cell structure achieved in the PIR foam system. The thermal conductivity values achieved from tests on an actual panel samples carried out by a ISO certified laboratory are stated below [5]:

The blowing agent used in the manufacture of rigid PIR foam plays an important part in the insulating performance of the metal insulated panel. It is not however the sole determinant of thermal efficiency and much depends on the formulation of the polyol, catalyst choice, reactivity and density of the foam system. Exclusive test data reported on the thermal efficiency of only the blowing agent should be treated with an element of caution because such information does not take into account the performance of the metal cladding wall systems. A more valid method for measuring thermal efficiency, especially for comparative purposes, is the performance of the entire panel assembly, including the design of the metal insulated panel, the joint detail and the air tightness of the seals, which collectively have a significant bearing on the total panel thermal performance. ASTM Standard Test Method C-1363 offers this approach.

Interestingly, the Long Term Thermal Resistance (LTTR) of pentane blown polyisocyanurate has also proven to be excellent with the results predicting an LTTR well within 1 percent of the actual R-value after 4.5 years of ambient aging [7]. This testing by S.N. Singh, et al, supports other findings on long-term sustainability performance using the LTTR measurement method.

The new soon to be adopted standard for the insulated panel industry is C1363-97 Standard Test Method for the Thermal Performance of Building Assemblies by Means of a Hot Box Apparatus. This test method covers the laboratory measurement of heat transfer through a specimen under controlled air temperature, air velocity, and thermal radiation conditions established in a metering chamber on one side and in a climatic chamber on the other side. This method of testing thermal performance should bring more uniform industry reporting of Rvalues.

Fire Performance:

Foams that incorporate PIR technology into the polymer blend have enhanced flammability performance in comparison with conventional polyurethane (PUR) foams when tested to the established industry standards [8]. ASI pentane blown panels have been tested in accordance with the UL 723/ASTM E84 Tunnel Test and the FM 4880 Full-Scale Corner Test standards and achieved a Class 1 rating.

The insulated foam panel system is tested for Class 1 FM 4880 fire rating. Flame-retardants are added to all Class 1, two-component urethane systems. Pentane-blown insulated panels are fire tested to the same standard as HCFC chemistry and report equal performance.

Other pentane considerations include workplace safety as related to precautions in mitigating flammability risks of HC blowing agents during the production process, which is not related to end user application.

VOC Issues:

The pentane blowing agent, as used by ASI, is considered a VOC reportable per EPA requirements on pollution equipment control during manufacturing. However, the amount of VOC generated is very small and does not require any particular treatment or special processing before discharge.

Freeze Stability and Dimensional Stability:

Freezer tests and analysis of results from tests on panels manufactured on ASI’s continuous lines have shown that the tight processing parameters employed by ASI and the small, fine cells of the foam system give rise to both excellent freeze stability and all round dimensional stability even at relatively low density. With regards to the claim that HCs tend to act as an aggressive solvent in contact with the polyol, the reality is quite the contrary, - the lower polarity of pentane compared to other conventional blowing agents results in a reduced solubility of pentane in polyols [8].

Summary

The accelerated EPA requirements to abandon HCFC 141b as a blowing agent led ASI, over several years, to review the various new technologies available as blowing agents and fully developed PIR systems. ASI’s desire to comply with our own internal environmental responsibilities and achieve the best possible balance between product performance and economic value was a great opportunity for the adoption of a pentane blown PIR chemistry solution.

HCFC 141b Metal Insulated Panels are still on the market either because of stockpiles of the chemistry, purchased before the 2003 EPA compliance date or panels containing HCFC’s are being imported. HCFC 22 is allowable by the EPA in panel manufacturing for a few more years but does not offer the environmental advantages that HC’s (Pentane) do in Ozone Depletion Potential or the indirect benefits of low or zero Global warming potential. Additionally, the development and subsequent testing of Polyiso HCFC Free pentane based Insulated Panels has helped to prove required performance characteristics.

References

1. Federal Register/Vol. 67, No. 140/Monday, July 22,2002/Rules and Regulations.
2. EPA’s Ozone Depletion World Wide Web site “http://www.epa.gov/ozone/snap/index.html”
3. I.H. Rowlands. The Fourth Meeting of The Parties to The Montreal Protocol: Report and reflection.
4. American Regulation Title VI; Clean Air Act, 40 C.F.R. Part 82: Federal Register, Final Rule, December 10, 1993.
5. The Dow Chemical Company.
6. 7. F. Xinghe, X. Xiaofeng. “Pentane Blown Rigid Polyurethane Foams for Refrigerators” Polyurethanes Expo 1996.
7. S. N. Singh, M. Ntiru and K. Dedecker. “ Long Term Thermal Resistance of Pentane Blown Polyisocyanurate Laminate Boards” Polyurethanes Expo 2002.
8. M. Skowronski, F. Pignagnoli 2002. “ Hydrocarbon Blown Polyisocyanurate Systems for Continuous Laminate Metal Faced Panels” Polyurethanes Expo 2002, U.S.A.