TechnologIES

Porous Fiber

Manage fluids with increased flow speed and control

Porous Fibers Innovation Expert

Porous fiber consists of bonded fibrous strands which create two-dimensional cross-sections that can be extruded to create three-dimensional shapes. Between the directionally aligned fibrous strands are voids, or pores, which can be independently controlled for fluid management applications that require faster flow or greater absorption of liquids.

These bicomponent fiber materials have an inner core and outer sheath that provide an ideal capillary structure for liquid transfer, filtration, and diffusion applications where wicking speed, wicking distance, filtration efficiency, and flow resistance are key drivers of the device’s performance.

Made from a variety of thermoplastic materials with varying properties, our materials are moldable for high-volume applications and customizable for easy fabrication and conversions. We provide large sheets, rolls, or other material formats specific to your needs.

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Manufacturing process

Porous fiber uses heat and pressure in the bonding process similar to sintered porous plastics. Instead of bonding particles, though, it bonds fibrous strands. A sheath is wrapped around customized fibers and the fibers are bonded in various configurations. This does not involve knitting or weaving, but rather forming fibrous components such as sheets, rods, tubes, blocks, and 3D geometrics.

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Options for customizing porous fiber

Physical properties

When designing a porous fiber component, it’s critical to understand the three key physical properties that impact materials and functionality of the part:

Pore size: the size of the voids in the porous media. Depending on the material, pore size can be large or small to align with the customer’s needs. Porex can control the diameter of the directional fibers and the density of the materials to provide greater control over wicking speed, wicking distance, and filtration efficiency.
Pore volume: the percentage of air in the part compared with the total volume of the part. In porous fiber materials, density is more commonly referenced, and it is inversely proportional to pore volume. Porous fiber components are available in very low to high densities depending on the desired capabilities. A higher pore density (the heavier the part), the lower the pore volume and vice versa. For higher density parts, greater absorption and flow resistance of liquid materials can be achieved and for lower density parts, increased speed and overall flow can be achieved.
Operating temperature: the temperature range at which the final porous fiber part will be required to operate.

Understanding typical material properties will guide you in selecting the right polymer for your device’s function and operating conditions. Below is a chart that shows common materials with their physical properties; however, this is not an exhaustive list.

Polymer	Pore Sizes (microns)	Pore Volume (%)	Operating Temperature (F)
Polyolefins (PE, PP)	10 to >100	50 to >95	150-250
Polyesters (PET, PBT)	5 to >100	30 to >90	300-350
Polyamides (N6, N6,6)	5 to >100	30 to >90	300-400
Cellulose Acetate (CA)	10 to >100	50 to >80	100-300

Chemical properties

Choosing the right polymer material is important to ensure lasting functionality for your end product or device. One of the key questions to consider is with what – if any – chemicals the porous fiber component will come into contact with. Below is a table that shows chemical compatibility of the common polymers mentioned above:

Chemicals	PE, PP	PET, PEB	N6, N6,6	CA
Acids (non oxidizing)	Good	Good	Poor	Poor
Bases	Good	Poor	Good	Poor
Oil	Good	Good	Good	Good
Aromatic solvents	Good	Good	Good	Good
Non-polar aliphatic solvent	Fair	Good	Good	Good
Polar-aprotic solvents	Fair	Good	Fair	Fair
Polar-Protic solvents	Fair-Good	Fair-Good	Good	Good
Halogenated solvent	Good	Good	Good	Poor
Oxidizing agents	Poor	Poor	Good	Good

Material options

The material used in bonded fibers is thoroughly evaluated based on the product or applicational requirements. Four of these main materials include:

Polyolefins (LDPE, LLDPE, HDPE, PP)
This is the most commonly used material with the simplest molecular structure. There are limitations on temperatures for many applications though.

Polyesters (PET, PTT, PBT)
This material is a versatile option that is available with almost all fiber technology platforms.

Polyamides (Nylon 6, Nylon 6,6)
If heat resistance and chemical compatibility is a concern, polyamides are a good option. They are used in hydroscopic to hydrophilic applications.

Other Suitable Materials:

Cellulose acetate (CA) when you are wanting biodegradable materials
Polylactic acid (PLA) which is a renewable raw material
Polyphenylene Sulphide (PPS) for high temperature resistance applications
Co-polymers in many configurations

While these are the most common materials used to design porous fiber components, there are many other options available. Work closely with your application engineer to define your specifications, and they can help select the best material(s).

Additive Options

Additives and treatments open the door to many possibilities for your porous fiber component. Below are some additives and treatments used with the common polymers listed above:

Hydrophobic treatments
Self-sealing, liquid barrier
Hydrophilic treatments
Colorants
Color change
Bactericidal / bacterial static
Carbon, potable water, odor elimination
Oleophobic treatment
Laminated support structure

Geometric Options

Porous fiber can be manufactured into a variety of geometries. Our engineers work with you to better understand your manufacturing process to determine the best size, shape, and dimension you need. Typical geometric options include:

Sheets and Rolls
Rods and Tubes
2D Plugs and Vents
Nibs
3D Simple Structures

Assembly Options

Customizable assembly and converting options are endless. Typical options for sintered plastics include:

Thermal & ultrasonic welding
Overmolding
Die-cutting
Press fit
Pressure-sensitive adhesive (PSA)

It’s important to understand how the final product or device will be assembled. Our team works with you to develop a porous fiber solution that can decrease assembly time and complexity by combining multiple parts into a single custom-engineered part.

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Intro to Porous Fiber

Common applications for porous fiber

Wick

Wicking works extremely well with porous fiber, as capillary forces are able to promote ease of fluid transfer in applications such as point-of-care diagnostic sample testing, dialysis treatments, and commercial applications such as inkjet printing cartridges.

Filter

Porous fibers can help to separate a solid or liquid from a mixture. Some of these applications include automotive oil & fuel water separation filters, injectable and applicator glass shard filters for life science applications, as well as liquid contaminant removal filters for consumer and industrial segments.

Diffuse

Porous fiber solutions can offer precision control over the diffusion rate in applications such as bioprocessing spargers, plug-in air fresheners, as well as insecticides.

Apply

Application products such as whiteboard marketers work great with porous fiber nibs. The material allows the ink to apply evenly and completely onto a surface or substrate.

Why do pore size and flow matter?

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