Static Mixers vs. Dynamic Mixers for Two-Component Reactive Adhesives

When selecting a mixer type, it is important to consider the following factors:

• Viscosity/rheological behavior of the adhesive
• Application type (manual cartridge or dispensing machine)
• Cleaning
• Output rate
• Portability
• Pumping pressure

Source: Huntsman Advanced Materials

Image Credit: Huntsman Advanced Materials

Two-component reactive adhesives necessitate thorough mixing of their components to attain their full final properties. Hence, cartridges and dispensing machines typically come equipped with a mixer to ensure proper blending of the components.

Static Mixers for Light Weight and Simplicity

A static mixer is composed of a series of spiral or square elements aligned in a tube. As the two adhesive components are pumped together past each element, they undergo separation, resulting in the formation of layers. The number of layers doubles as the mixture passes each element, indicating that 20 elements in series produce over 1 million layers. This process effectively ensures a homogeneous mix of the two components.

Static mixers are typically disposable, which means they are lightweight, maintenance-free, and do not require cleaning between applications. They are available in various sizes and can be mounted on either manual cartridges or automated dispensing machines. Static mixers are effective with low-to-medium viscosity products. However, they may not achieve a sufficiently homogeneous mix under certain conditions:

1. When the viscosity of the different adhesive components varies significantly.
2. When the viscosity is very high or the components are strongly thixotropic.

Static mixers often generate back pressure as the material flow is restricted through them. This back pressure can result in very high pumping pressures or low output rates, especially when dealing with high-viscosity adhesives.

Advantages

• Well-suited to cartridges and meter-mix equipment
• Exceptionally simple and reliable operation
• Cleaning is not required
• Cost-effective

Disadvantages

• Low output with high-viscosity products
• Can create high back-pressure on metering pumps
• May not mix all product types

Dynamic Mixers for Hard-to-Mix Products

A dynamic mixer typically consists of a shaped, often spiral, rotor that rotates inside a tube or chamber mounted on a mixing head.

The two adhesive components are pumped through holes at the inlet and blend as the rotor turns. The rotor requires independent driving, such as electrically or pneumatically, which makes it unsuitable for manual cartridge application. Additionally, the mixing head is heavier and less portable compared to a static mixer.

Dynamic mixers are able to overcome some of the limitations of static mixers, as they are able to effectively mix components with very different viscosities or materials with very high viscosity.

Dynamic mixers typically necessitate a cleaning operation between applications, such as solvent flushing or disassembly and cleaning. These mixers generate low back pressure, allowing them to be used with lower-pressure pumps or to achieve high output rates.

A combination of dynamic and static mixers is used in some automated dispensing machines to optimize mix quality versus the size of the mixing head.

Image Credit: Huntsman Advanced Materials

Advantages

• Able to mix highly thixotropic or high-viscosity products
• Generates low back pressure for metering machines

Disadvantages

• Only suited to meter-mix equipment
• Less mobile due to increased size
• Cleaning or flushing is required between applications
• Higher expenditure

This information has been sourced, reviewed and adapted from materials provided by Huntsman Advanced Materials.

For more information on this source, please visit Huntsman Advanced Materials.