What are the key differences between viscose and pulp in flushable fabric?

The demand for sustainable and flushable hygiene products has led to the development of innovative materials like viscose/pulp flushable fabric for toilet paper. Both viscose and pulp are widely used in flushable fabrics, but they differ in composition, manufacturing processes, performance, and environmental impact. Understanding these differences is crucial for manufacturers, buyers, and environmentally conscious consumers.

1. Material composition and sourcing

Viscose in flushable fabric

Viscose, also known as rayon, is a semi-synthetic fiber derived from regenerated cellulose, typically sourced from wood pulp or bamboo. The manufacturing process involves dissolving cellulose in chemicals to create a viscous solution, which is then extruded into fibers.

Key characteristics of viscose in flushable fabric:

• Smooth, silk-like texture, enhancing softness.
• High absorbency due to its hydrophilic nature.
• Can be engineered for faster disintegration in water.

Pulp in flushable fabric

Pulp, often referred to as wood pulp or cellulose pulp, is a natural fiber obtained directly from trees (e.g., eucalyptus, spruce) or recycled paper. It undergoes mechanical or chemical processing to break down raw wood into fibrous material.

Key characteristics of pulp in flushable fabric:

• Naturally biodegradable and compostable.
• Less processed than viscose, retaining more of its original fibrous structure.
• Typically coarser than viscose but can be refined for softness.

Comparison table:

2. Manufacturing processes

Viscose production for flushable fabric

The production of viscose involves multiple chemical stages:

1. Alkali treatment – Wood pulp is soaked in sodium hydroxide.
2. Xanthation – The pulp reacts with carbon disulfide to form cellulose xanthate.
3. Dissolution – The xanthate is dissolved in a weak alkali to create viscose solution.
4. Extrusion & spinning – The solution is forced through spinnerets into an acid bath, solidifying into fibers.

This process allows for precise control over fiber thickness and strength, making viscose adaptable for flushable fabrics.

Pulp production for flushable fabric

Pulp manufacturing is generally simpler:

1. Mechanical pulping – Wood chips are ground into fibers (retains lignin, making it less ideal for flushable fabrics).
2. Chemical pulping – Lignin is removed (kraft or sulfite processes), producing purer cellulose fibers.

Pulp fibers are shorter and less uniform than viscose, which can affect flushability and softness.

3. Flushability and disintegration

A critical requirement for viscose/pulp flushable fabric for toilet paper is the ability to break down quickly in water to prevent plumbing issues.

• Viscose fibers can be engineered to disintegrate rapidly due to their fine structure, but excessive chemical processing may slow biodegradation.
• Pulp fibers naturally disperse well in water but may require additional refining to meet flushability standards.

Industry standards (e.g., INDA/EDANA flushability guidelines) assess:

• Dispersibility – Time to break apart in moving water.
• Biodegradability – Rate of decomposition in wastewater systems.

4. Softness and strength

• Viscose is inherently softer, making it preferable for premium flushable fabric for toilet paper.
• Pulp is more rigid but can be softened through refining processes.

Wet strength is another key factor:

• Viscose loses strength faster when wet, aiding flushability.
• Pulp retains more structure when wet, which may require additives to improve disintegration.

5. Environmental and cost considerations

Biodegradability and sustainability

• Pulp is naturally biodegradable with minimal processing.
• Viscose requires chemical treatment, raising concerns about wastewater pollution.

Cost differences

• Pulp is generally cheaper due to simpler processing.
• Viscose is more expensive but offers superior softness and customization.

The choice between viscose and pulp in flushable fabric depends on:

• Softness requirements (viscose is superior).
• Flushability performance (both can be optimized, but pulp is naturally dispersible).
• Cost and sustainability goals (pulp is more eco-friendly and economical).

As the demand for viscose/pulp flushable fabric for toilet paper grows, advancements in fiber engineering will continue to refine these materials for better performance and environmental compatibility.