PORON®

PORON® Microcellular Urethane, PORON® Foam Material

PORON® microcellular urethanes have been a major portion of Stockwell Elastomerics’ product line since Rogers Corporation developed this microcellular urethane foam for industrial and electronics applications in the 1980s. Stockwell Elastomerics inventories and fabricates PORON polyurethane in thicknesses from .012″ to .500″ thick and compressibility ranging from extra soft / slow rebound formulas to very firm formulas.

Rogers Corporation manufactures PORON industrial polyurethanes and Stockwell Elastomerics is a Preferred Converter for Rogers Corp and a leading authorized PORON supplier / PORON distributor. On the basis of total material laminated and fabricated in production, Stockwell Elastomerics fabricates more PORON into gaskets than any other material family.

Stockwell Elastomerics’ PORON Foam Options

In addition to being a Rogers Corporation Preferred Converter, Stockwell Elastomerics maintains inventory of the 4701 and 4790 PORON foam families. As a preferred PORON supplier and manufacturer of PORON gaskets and pads, Stockwell Elastomerics helps engineers select the best PORON for their specific application.

• Thin PORON Foam – PORON urethane foam is available in very thin grades often used for dust and splash seals for electronic devices.
• Thick PORON Foam – The standard, maximum thickness for PORON is 0.5″ (12.7mm). Stockwell Elastomerics regularly laminates layers of PORON for designs that require thicker materials.
• PORON Laminations – Stockwell Elastomerics laminates PORON to a custom thickness but can also laminated different grades of PORON to achieve a unique compression / deflection rate. In addition to laminating PORON layers, Stockwell Elastomerics laminates UHMW films, Formex, solid urethane and other material to enhance the toughness and wear resistance of a pad or gasket.
• Adhesive Backed PORON – As a Select 3M converter, Stockwell Elastomerics inventories and laminates a wide range of adhesive, peel and stick backings to PORON. Adhesives commonly specified are 3M 467, 3M 9485, 3M 9490LE, and 3M 9415.

Key Benefits of PORON Microcellular Urethane

• Low compression set – PORON cellular urethane has superior resistance to taking a compression set as compared to neoprene sponge or polyethylene foam. Less than 2% at 73°F and less than 10% at 158°F makes PORON an ideal gasketing material for many indoor enclosure applications where dust, light and incidental splash sealing are required.
• Energy absorbing – PORON’s ability to absorb mechanical shock vibration combined with its low compression set make it an ideal material for shock isolation of battery compartments and sensitive electronics in hand-held devices.
• Consistent microcellular structure – Fine and consistent open cells make PORON microcellular urethane an ideal dust gasket material, suitable for many cleanroom applications.
• Adhesive backings – PORON readily accepts most of Stockwell Elastomerics’ pressure sensitive adhesive offerings. Since PORON does not contain any plasticizers, it does not reduce adhesive shelf-life. The integral skin surface provides a clean, readily bonded surface.
• Thickness options – PORON is available in a wide range of thicknesses. Stockwell Elastomerics also offers bonded layers to achieve non-standard thicknesses and stacked/bonded assemblies.
• Smooth skin – Most grades of PORON foam are manufactured with a smooth skin on both sides. The supported products have a 1 mil PET film bonded permanently to one side.

PORON Foam Naming Convention and Offerings

PORON has a unique naming convention for identifying each specific grade. Below is an explanation of the Rogers PORON naming convention and how to callout PORON microcellular urethane foam on a drawing.

• PORON Market Prefix – the family of products, for industrial grades the market prefix is usually 4701 or 4790.
• PORON Formulation – generally relates to the hardness or firmness of PORON, while the numbers look like durometer values and track like durometer (low number is softer and high number is firmer), they are in actuality just a reference number for the formulation.
• PORON Density – the density of PORON is indicated after the second dash an is a two digit number, this value represents the density in lb/ft³. With a few exceptions, thickness and density are tied together, a selected thickness will have a designated density.
• PORON Color – the two digit number after the third dash represents the color. For industrial markets with prefix numbers 4701 and 4790, the color is black: 04. Special runs are available for other colors but large minimums are typically required.

How Much to Compress PORON Foam?

The answer to “how much to compress PORON foam” is – it depends. If PORON is being used for a dust seal, minimal compression is needed (assuming standard pressure). Usually for light water sealing such as splashing, 50 – 60% compression is a general range. While PORON is not typically Stockwell Elastomerics’ first choice for outdoor or heavy water exposure, it can be used when the compression range would be 60 – 70% to collapse the open cells (see images). Outdoor sealing is usually better served using a more UV and temperature stable material with a closed cell structure, so quite often Roger’s HT-800 silicone foam is specified.

The amount of pressure required to compress a PORON pad or PORON gasket can be estimated using compression force deflection curves such as the one below. The area (in²) is the area of the gasket or pad under compression. Click here for PORON compression curves.

PORON® AquaPro™ – Enhanced Sealing PORON Foam

PORON AquaPro is low outgassing, low compression set microcellular polyurethane foam with enhanced water sealing. Made in two formulations, 4701-37 very soft and 4701-41 soft, the AquaPro family of PORON foam offers better water sealing properties that the standard Poron foam grades. PORON AquaPro 4701-41 has been Stockwell Elastomerics’ recommended grade of PORON for applications requiring extra protection from water ingress. As with all open cell and modified closed cell foams, Stockwell Elastomerics recommends proper compression on the gasket to ensure a good seal, this is particularly important for wash-down or heavy water exposures. As will all PORON urethane foams, the AquaPro family shares the same excellent compression set resistance (rebounds very well) as the standard grades.

For more information on these materials, view the PORON AquaPro product information sheet.

When Would PORON NOT Be Recommended?

Despite the microcellular structure which appears to be closed cell, PORON is an open cell foam. Outdoor enclosures that are subjected to rain and temperature extremes may not be sealed properly with PORON gaskets. Conditions where PORON may be flexed or repeatedly compressed and relaxed in standing water may cause water to be wicked into the gasket. Temperatures below -20°F will cause PORON to stiffen noticably, and PORON is not recommended for constant temperatures above 158°F. Outdoor conditions may be better served with silicone sponge or high grade neoprene or EPDM sponge materials.

How To Order PORON Microcellular Urethane Foam

Stockwell Elastomerics sells PORON polyurethane foam as pre-cut parts or uncut sheets / rolls; 3M and Adchem adhesive backings are readily available. Most PORON parts manufactured by Stockwell Elastomerics have peel and stick backings to aid in processing and reduce assembly time. For assistance with selecting which PORON product to use, contact Stockwell Elastomerics’ Applications Engineers.

PORON® is a registered trademark of Rogers Corporation.