pu foam

Additional advantages of polyurethane foam plastic sealants

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Polyurethane foam sealants can not only prevent air and water intrusion, but also offer myriad related advantages. These sealants offer the potential for energy savings, improved comfort, weather resistance, sound mitigation, and reduced exterior noxious gas infiltration.

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Structural and adhesion advantages

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In certain cases, structural enhancements for building assemblies can be increased with polyurethane foam plastic sealants. Most foam plastic sealants adhere well to nearly all substrates, adding structural strength in some sealing applications. Windows are one example where a polyurethane foam plastic sealant can prevent side jamb rotation, raise window design pressure ratings, and help increase the anchorage of the window or door during high wind events.

 

Certain foam plastic sealant products can perform these structural functions better than others; when these functions are critical, evaluations should be run using independent, third-party testing.

Adhesion and the attachment between building materials is another developing use for polyurethane foam plastic adhesives. In the aftermath of recent hurricanes, plastic foam roof tile adhesives were noted to perform well.

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A formal Notice of Acceptance (NOA) for these products also exists from Miami-Dade county. Roof insulation foam plastic adhesives have also excelled in uplift tests for application on flat and low-slope roofs. Additionally, using polyurethane foam plastic adhesive sealants for the attachment of drywall and subfloor panels is becoming popular—application can be fast, easy, and conform to the required codes, while usually reducing the mechanical fastener count and the associated thermal bridging.

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Sound transmission

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Plastic polyurethane foam sealants can be good for reducing sound transmission through gaps in wall, floor, or roof assemblies, helping minimize noise pollution. ASTM International C 919, Standard Practice for Use of Sealants in Acoustical Applications, quantifies sound reduction when gaps are sealed in building enclosure assemblies.

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Testing objectives and standards

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Early plastic polyurethane foam sealant testing focused on plastic product material properties borrowed from standard ASTM D 20 Committee on Plastics, tests intended for preformed cellular products. Current testing of foam sealants now focuses on building assemblies or subassemblies mirroring the actual end-use. Therefore, sample preparation for testing should be specific and simulate the foam plastic sealant geometry evident in the final application.

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ASTM International

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In 1997, the ASTM Committee on Aerosol Foam Sealants (C 24.61) began the task of developing germane standards for foam plastic sealants. So far, one test method, ASTM C 1536, Standard Test Method for Measuring the Yield for Aerosol Foam Sealants, and one specification, ASTM C 1620, Standard Specification for Aerosol Polyurethane and Aerosol Latex Foam Sealants, have been published. Two more tests are in ballot process and three more standards are in draft stage. ASTM C 1620 provides:

• a maximum leakage limit per ASTM E 283, Standard Test Method for Determining Rate of Air Leakage through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the Specimen;

• a maximum allowed flame-spread index and smoke-developed index requirements per ASTM E 84, Standard Test Method for Surface Burning Characteristics of Building Materials;

• a minimum requirement for R-value; and

• mandates the reporting of several additional foam plastic sealant properties (including a reporting requirement for foam plastic sealant yield measured exclusively by ASTM C 1536).

The foam plastic sealant industry has also participated in developing ASTM E 2112, Standard Practice for Installation of Exterior Windows, Doors and Skylights, which includes Annex A for foam plastic sealants and foam plastic tapes. A new standard for air leakage assembly testing has also received plastic industry input, while standards for water intrusion are being reviewed. This author chairs a new ASTM task group in Committee E 06 for building performance (Standard Practice for Measuring Air Leakage Rates for Air Barrier Components Used for Sealing Discontinuities in Air Barrier Materials).

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Building codes

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Since the International Building Code (IBC) does not specifically reference foam plastic sealants (or other sealants and most adhesives), local codes are often left to various interpretations. Unlike the denser tube sealants or adhesives they resemble in use, some code officials treat foam plastic sealants as if they were cellular plastic insulation. This can place excessive thermal barrier protection requirements on products for many sealant applications. Some manufacturers have employed Underwriters Laboratories (UL) 1715, Fire Test of Interior Finish Material, to obtain acceptance when this issue is in doubt. As such, diversified testing and International Code Council Evaluation Service (ICC ES) reports are used to confirm the fire safety of existing applications or help gain acceptance for new ones.

North of the border, the National Building Code of Canada (NBC) specifically references foam plastic sealants. The Canadian National Standard, Underwriters Laboratories of Canada (CAN/ULC) S 710.1, Thermal Insulation—Bead: Applied One-component Polyurethane Air Sealant Foam, Part One: Material Specification, is a foam plastic sealant material requirement published in January 2005. Few construction products meet such rigid demands; CAN/ULC S 710.1 includes an air barrier assembly durability test using a full wall section with rapid thermal cycling from –20 to 66 C (–4 to 150 F) for 60 cycles. Pressure cycling is simultaneously employed from –1000 to 1000 Pa (–21 to 21 psf). However, the standard is still too new to be referenced by the Canadian code at this time.