Surfactant Selection Guide: 4 Key Parameters for Industrial Cleaning

Abstract

Global industrial growth has increased the demand for advanced industrial cleaning. The success of these processes depends heavily on the choice of cleaning agents. With rising environmental standards, selecting the right raw materials is now a priority. This article explains how to select water-based surfactants by comparing key molecular parameters for high-efficiency and eco-friendly results.

Four Critical Parameters for Surfactant Selection

To select the right surfactant, we must analyze four molecular characteristics: Surface Tension, HLB Value, CMC, and Cloud Point (Krafft Point).

1. Surface Tension

Surfactants lower the surface tension of a cleaning agent. Common surfactants can reduce this to approximately 30 mN/m. Lower surface tension reduces the liquid's contraction force. This allows the cleaner to spread easily across the substrate, ensuring better wetting of the soil.

2. HLB Value (Hydrophilic-Lipophilic Balance)

The HLB value measures the balance between the hydrophilic and lipophilic parts of the molecule.

• HLB 1–6: Lipophilic (oil-loving). Used as defoamers or W/O emulsifiers.

• HLB 7–9: Balanced. Used as wetting and penetrating agents.

• HLB > 10: Hydrophilic (water-loving). Commonly used as emulsifiers in cleaning.

3. CMC (Critical Micelle Concentration)

The Critical Micelle Concentration is the lowest concentration at which surfactant molecules associate to form micelles.

• Below CMC: Molecules exist freely, and surface tension drops as concentration increases.

• At CMC: Surface tension reaches its minimum.

• Above CMC: Adding more surfactant only increases micelle density, which helps dissolve more oil.

4. Cloud Point and Krafft Point

• Krafft Point: For ionic surfactants, solubility rises sharply above this temperature. Selection must occur at temperatures above the Krafft point.

• : For non-ionic surfactants, solubility drops as temperature rises, causing the solution to become cloudy. For best results, choose a surfactant where the cleaning temperature is at or slightly below its cloud point.

Case Study: Aluminum Alloy Degreaser Formulation

System Requirements

Industrial degreasing is more effective in alkaline conditions due to the saponification of fats. Therefore, we use a Sodium Hydroxide (NaOH) system.

However, aluminum is an amphoteric metal, meaning it corrodes in both acidic and alkaline environments. To prevent damage, we must:

1. Strictly control the alkali content.

2. Select a robust corrosion inhibition system (e.g., Sodium Silicate).

Selecting the Surfactant

Applying our four parameters to an aluminum cleaner:

• Surface Tension: Target < 30 mN/m.

• HLB Value: Target > 10. If using Isomerized Alcohol Ethoxylates, the EO (Ethylene Oxide) count should be 5+.

• Temperature & Cloud Point: If cleaning at 50°C (ultrasonic), the cloud point must be above 50°C. This requires an EO count of 7+.

• Pour Point (Ease of Use): For room temperature efficiency, the surfactant should remain liquid (pour point < 30°C).

Conclusion: For the primary surfactant, an EO range of 7 to 12 is ideal for emulsification and detergency.

The Role of Penetrating Agents

While high-EO surfactants are great emulsifiers, their wetting power is weaker. We must add a penetrating agent (HLB 7–9, EO 4–6).

• Straight-chain: Stronger emulsification.

• Branched-chain: Superior penetration.
  For industrial use, surfactants with 8–10 carbon atoms in the lipophilic chain are generally preferred as penetrants.

Optimized Formulation Example

Cleaning Process: Dilute 10–20 times. Use for room temperature immersion cleaning (ultrasonic assistance is recommended for best results).