What is Reticulated Polyether Foam?
Reticulated polyether foam is a lightweight, flexible and durable open cell polyurethane foam. The open cell structure enables air and water to pass through the foam while trapping and collecting dust particles. Reticulated foam is made with a very unusual process of “blowing the foam”, literally setting an explosion to open the cells within a controlled combustion chamber.
Reticulated polyurethane is measured in pores per inch (PPI), which is the measure of how many “cells” or openings the foam has and it's used to determine its filtration capacity. Low porosities (4 PPI - 20 PPI) have a very open cell structure that allow more fluid and air flow through the foam. In contrast, higher porosities (80 PPI - 100 PPI) have a very tight cell structure resulting in fluid and air flow reduction.
The cell count can vary in reticulated foams, typically +/- 5 PPI. The thickness of the foam will also impact the filtration capacity of the foam. The thicker the foam, the less air or fluid that is allowed to flow through the foam.
Reticulated foams are very compressible, the lower the cell count, the easier to compress (lower compression deflection force). As these are very open cell polyurethane foams, they have very low compression set, typically well under 5%, which is the amount of thickness lost after extended periods of high compression, or in other words, the amount the foam would be expected to recover (ex. 5% compression set = 95% recovery, etc.).
Polyether polyurethane foam has a higher moisture and mildew resistance than polyester reticulated foam. If your application calls for exposure to high humidity, or even act as a moisture filter/baffle, the polyether foam will be a better choice of material.
Some common uses of reticulated foams include:
- Cushioning and padding
- Sound absorption
- Air and fluid filtration
- Trapping dust particles and filtering out insects
Specialized Coatings for Reticulated Polyether Foams
It is important to evaluate the following coated foams when specifying reticulated foam for filtering and sealing applications:
- Acrylic Coated Reticulated Foam: It is more expensive than the uncoated foam. Typically used when the product will be exposed to UV light, but NOT directly to the elements such as wind, rain, excessive handling. This is often found on commercial windows and doors, and outdoor HVAC filters where there is a mesh/screen cover to protect the filter.
- PVC Coated Reticulated Foam: This is the most expensive foam. Typically used where the product requires maximum durability and longevity. PVC coating can also be used to make the product flame retardant, along with additives in the foam. This is typically used in curtainwall weep baffles, outdoor speaker covers, and power switch filters where flame retardant rating is required.
- Bacteriostatic Coated Reticulated Foam: This specialized type of coating may be used for fluid filters in wet environments such as fish ponds or aquariums. Bacteriostatic coated reticulated foam has anti-microbial qualities which minimize the growth of bacteria and mold on the foam, which is a key factor when animals such as fish or reptiles may be living in or around the water filtered by the foam.
Industry Standards for Reticulated Polyether Foam
In our experience, there are several “industry standards” that may help the user specify the best foam for their application. Here is a partial list of those industry standards:
- Weep Baffles for Residential Windows and Doors: The industry standard is 30 PPI. However, some designs require more drainage and more air flow. In these cases, 20 PPI or even 10 PPI can be specified. Uncoated reticulated foam is commonly used in the weep sump area, behind the weep holes where the foam will not be exposed to direct or indirect UV light or any potential flame source. PVC or acrylic coated reticulated foam should be used anywhere that the foam will be exposed to UV light, either directly or indirectly.
- Weep Baffles for Curtainwall and Commercial Windows: The industry standard is 30 PPI. In instances where the wind load is heavy, such as in high rise façades (over 40 stories), 40 PPI can be specified. For maximum longevity, air and weep baffles for curtainwall and commercial windows call for PVC coated reticulated foam.
- HVAC Filters: 20 PPI - 30 PPI is the standard. Some equipment, such as very large compressors or blowers may specify higher porosity, around 40 - 45 PPI if the air flow is higher. PVC coated reticulated foam should be used anywhere that the foam will be exposed to UV light, either directly or indirectly.
- Power Switches: Standard is 45 PPI. This is used to collect dust particles and preventing them from entering into the switch enclosure. This calls for a very specialized type of PVC coated reticulated foam, as it needs to be both UV resistant and UL-94 HF-1 compliant. If both of these specifications are needed, the foam requires a different coating process than “normal” PVC coatings.
We offer porosity ranging from 4 PPI to 100 PPI, in increments of 5 - 10 PPI. Most filters and baffles are simple rectangular shapes (ex. 1” x 2” x 5”). For more complex applications, H-O Products has the capability to cut many unusual shapes with our CNC water jet, digital cutter operations, slitters and die cutting equipment.
You can send along a print or drawing, we can cut any shape up to 5” thick, 60” wide x 118” long. Contact us if you need help designing or specifying any reticulated foam product, we will be glad to assist in the specification/design process in any way possible.