Fluid Absorption & Cobb Testing Solutions for Paper, Board, and Textiles

In the manufacturing of paper, cardboard, tissue, non-wovens, and technical textiles, understanding how a substrate interacts with liquids is a critical quality metric. Liquid absorption refers to a material's capacity to take up and retain fluids within its porous matrix through capillary action and surface wetting.

Depending on the final application, manufacturers need to either maximize absorption (e.g., for hygienic tissue and paper towels) or strictly inhibit it (e.g., for water-resistant sizing in corrugated shipping boxes, liquid packaging boards, and outdoor textiles). Rycobel offers a complete portfolio of high-precision Cobb testers, fluid absorption instruments, and contact angle analyzers to transform subjective liquid interaction into precise, standardized laboratory data.

Critical Absorption Test Methods & Industrial Applications

Liquid absorption cannot be measured using a single universal method because the underlying physical mechanism varies between materials. Our testing solutions are categorized by three primary physical properties:

1. The Cobb Water Absorption Method (ISO 535)

The Cobb Test is the globally accepted standard for determining the water absorptiveness of sized paper, paperboard, and corrugated cardboard. It measures the mass of water absorbed by a specific surface area of a material over a predefined period.

Significance: It ensures that shipping boxes maintain structural integrity under humid conditions and prevents water-based inks from bleeding during high-speed printing.

2. Sorpitivity and Capillary Absorption for Hygienic Products

For high-loft materials like toilet paper, kitchen rolls, facial tissue, and non-woven hygiene substrates, absorption capacity and absorption rate are paramount.

Significance: Testing quantifies exactly how much liquid a fiber matrix can hold per gram of material and how fast it pulls liquid away from a surface. It helps R&D teams mathematically verify whether adding layers or changing the embossing pattern genuinely improves absorption or merely increases material thickness.

3. Dynamic Wetting and Contact Angle Analysers

Before absorption can even occur, a liquid droplet must wet the surface of the material. A Pocket Goniometer (PGX+) analyzes the precise contact angle / wetting angle of a fluid droplet the exact millisecond it hits the substrate.

Significance: If the contact angle is high ($>90^\circ$), the surface is hydrophobic (liquid-resistant); if it approaches $0^\circ$, the surface is completely hydrophilic, leading to near-instantaneous fluid absorption.