How Wetlaid Nonwovens Are Made: From Fiber Suspension to Finished Fabric

Wetlaid nonwovens play a critical role in demanding applications, such as filtration and medical materials, wipes, and specialty papers. While the end uses vary widely, success in wetlaid production always depends on precise control of fibers, water, and process conditions throughout the manufacturing line.

In this article, we walk through the wetlaid nonwovens manufacturing process step by step, highlighting the technical principles that transform a dilute fiber suspension into a high‑value finished fabric.

Step 1: Fiber Selection and Preparation

The wetlaid nonwovens process begins with fiber choice. Unlike drylaid technologies, wetlaid nonwovens can accommodate very short fibers, typically ranging from 3 to 12 mm, as well as fine diameters that are difficult to process by other methods.

Common fiber types include:

• Cellulosic fibers (wood pulp, specialty pulps)
• Synthetic fibers (polyester, polypropylene, polyamide)
• Glass, carbon, or mineral fibers
• Blends engineered for specific functional properties

Before forming, fibers must be fully dispersed to prevent clumping, also known as flocculation. This requires careful control of:

• Fiber length and flexibility
• Surface chemistry
• Water quality and chemistry
• Mechanical energy input during pulping and mixing

Effective fiber preparation establishes the foundation for uniform formation and consistent end‑product properties.

Step 2: Creating a Stable Fiber Suspension

Once prepared, fibers are diluted in water to form a low‑consistency suspension, often below 1% solids. This extreme dilution is essential; it allows fibers to move freely, align randomly, and distribute evenly during sheet formation.

Key objectives at this stage include:

• Maintaining fiber dispersion without entanglement
• Preventing agglomeration or settling
• Ensuring consistent suspension flow to the forming section

Process stability here is critical. Variations in consistency or chemistry can quickly translate into formation defects, or strength variability downstream.

Step 3: Sheet Formation on the Wire

The diluted fiber suspension is delivered to the forming section, where it is deposited onto a moving forming wire. As water drains through the wire, fibers begin to interlock, creating a continuous wet web.

Unlike traditional papermaking, wetlaid nonwovens often demand:

• Extremely uniform fiber distribution
• Controlled orientation or uniform properties
• Accommodation of synthetic or non‑bonding fibers

Drainage control is central to achieving these goals. Too rapid drainage can lock fibers in place prematurely, while insufficient drainage can destabilize the web. Forming elements, vacuum systems, and water removal strategies must be carefully balanced to support formation quality and productivity.

Step 4: Web Consolidation and Dewatering

After initial formation, the fragile wet web requires gentle yet effective consolidation. At this stage, the web contains a high percentage of water and minimal inherent strength.

Mechanical dewatering, often assisted by a vacuum, removes additional water while preserving formation. The challenge is to:

• Increase solids content without web damage
• Maintain fiber distribution and thickness uniformity
• Prepare the web for bonding or drying operations

Process control during consolidation directly affects downstream runnability and final product uniformity.

KADANT'S ROLE

Wetlaid nonwovens form the foundation of many essential products including fiberglass mat or glass veil, tea bags, hygiene and medical components, and filtration media, which are areas Kadant provides substantial value with improved efficiency and product quality through roll cleaner assemblies, wire belt cleaning, filtration, and showering technologies.

Proven Kadant technologies such as the VeriLite™ roll cleaner assembly, the M-clean™ system, and the RotoFlex™ resource recovery strainer help wetlaid operations achieve cleaner processes, reduce energy and water costs, and meet increasingly rigorous performance and sustainability goals.

For a real‑world example, see the case study: Nonwoven Fiberglass Mat Dryer Wire Cleaning with the M-clean PRO.

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Step 5: Bonding and Creating Functional Strength

Many wetlaid fibers do not naturally bond. Therefore, additional bonding mechanisms are typically required. The bonding strategy depends on the application and fiber blend and may include:

• Latex or chemical bonding, applied via saturation or spraying
• Thermal bonding, using thermoplastic fibers activated by heat
• Hydroentanglement, for selected specialty structures

Each bonding method introduces its own process considerations, including add‑on control, penetration uniformity, and energy consumption. Precise application is essential to achieve target strength, porosity, and flexibility without compromising formation.

Step 6: Drying and Moisture Control

Drying removes remaining water and stabilizes the bonded structure. This is a critical step, as drying conditions influence:

• Dimensional stability
• Mechanical strength
• Surface characteristics
• Final moisture content

Uniform drying prevents internal stresses, curl, and variability across the web. Energy efficiency and thermal control are also key, particularly for high‑throughput wetlaid operations.

Step 7: Finishing and Converting

The final stage of wetlaid nonwoven production includes finishing processes such as:

• Calendering for thickness and surface control
• Coating or treatment for functional performance
• Slitting, rewinding, or sheet cutting

Finished fabric properties, such as basis weight, porosity, tensile strength, and absorbency, are the cumulative result of every upstream decision. Consistency at this point reflects disciplined process control from fiber preparation through drying.

The Importance of Integrated Process Expertise

Wetlaid nonwoven manufacturing is inherently a combination of papermaking elements, polymer science, fluid dynamics, and mechanical engineering. Small variations at any stage can have outsized effects on product performance and operational efficiency.

Successful nonwovens producers focus on the interaction between fibers, water, and machinery across the entire process. Equipment design, wear management, stock preparation, and forming control all contribute to long‑term reliability and product quality.