Correctly dosing and mixing 2K: cartridge, static mixer and mixing ratio
Two-component adhesives and potting compounds only cure fully when both components are mixed in the correct ratio and homogeneously. The cartridge, dispensing device, and static mixer form a coordinated system for this purpose. This guide shows what is important regarding ratio, equipment selection, and application.
To the point: precise dosing in six steps
- Check the mixing ratio from the data sheet (for example 1:1, 2:1, 4:1 or 10:1).
- Choose a cartridge and static mixer that match this ratio.
- Choose the dispensing device according to quantity and frequency: manual or compressed air.
- Discard the initial run until the material emerges evenly and thoroughly mixed.
- Dose evenly and adhere to the pot life.
- After use, leave the filled mixer in place as a seal or replace it in good time.
Why the mixing ratio determines the quality
In two-component (2K) systems, two components react with each other in a defined ratio, such as resin and hardener or base and catalyst. If the ratio is incorrect, part of the system remains uncured. This results in incomplete curing and reduced strength, temperature resistance, and resistance to various media. Too much hardener can be just as detrimental as too little. Therefore, the ratio is not a recommendation but a requirement. The information on the container and in the technical data sheet is always authoritative.
Common mixing ratios and what they mean
The ratio determines the cartridge geometry and the appropriate mixer. A 10:1 cartridge cannot be dispensed correctly with a 1:1 device. The following overview serves as a guide; the specific ratio can be found in the data sheet.
| Relationship | Typical use (orientation) | Notice |
|---|---|---|
| 1:1 | many methacrylates, individual epoxides and PU | simplest dosage |
| 2:1 | many epoxides | most common ratio in epoxides |
| 4:1 | certain epoxides and PU | Adjust mixer to the ratio |
| 10:1 | many silicones, individual PU | small hardener content, mixer particularly important |
Cartridge systems: Double cartridge, F-system and A-system
SILITECH carries the most common 2K cartridge systems. Dual cartridges keep both components separate until processing; the F-system (approximately 210 ml and 400 ml) and the A-system are commonly used. The cartridge type, volume, and ratio must be compatible with the material, dispensing device, and mixer. Matching the system and device correctly prevents leaks and material waste.
Manual or compressed air: the right dispensing device
- Handheld devices such as the Sulzer Mixpac DM2X series (DM 200-01 for 1:1 and 2:1, DM 200-10 for 10:1) or the Mixpac DP 400 series for 400 ml cartridges: for individual pieces and small series, full control, no compressed air connection required.
- Pneumatic tools such as the LOCTITE 97002 pneumatic cartridge gun: consistent dispensing at higher frequencies and less fatigue, suitable for serial production.
- Syringe and pump dosing systems such as the digital LOCTITE syringe dosing system 98866 or a pneumatically operated feed pump: for small, precisely reproducible quantities, for example in electronics manufacturing.
The selection depends on the ratio, cartridge volume, and quantity.
The static mixer: without it, no homogeneous material
A static mixer is a mixing tube with fixed elements. It mixes both components solely through the pressure exerted by the dispensing mechanism, without any moving parts. Crucial factors are the design (helix or quadrilateral), the number of mixing elements, and the correct ratio. A mixer that is too short or unsuitable will not produce a homogeneous material, even if the ratio is correct. Mixer selection is covered in a separate article.
Plan lead time and waste correctly
At the beginning, the material often comes out not completely mixed. This initial run is discarded. A residue also remains in the mixer after dispensing, which hardens. Both of these factors must be included in the quantity calculation. If work is interrupted during the pot life, the filled mixer can seal the cartridge. Once the pot life has expired, the mixer is replaced.
Typical mistakes when dosing and mixing
- Mixer too short or of incorrect design: the material remains partially mixed in and does not harden completely.
- The device or mixer is not suitable for the ratio of the material.
- The initial batch was not discarded: the first quantity is not completely mixed.
- Pot life exceeded: the material thickens in the mixer.
- Slanted or jerky squeezing results in uneven material flow.
Checklist for practical use
- Ratio taken from the data sheet.
- Cartridge, device and mixer are matched to this ratio.
- Preliminary run discarded, potting time in focus.
- Clean, even pressing.
- Leave the mixer in place after use or replace it in a timely manner.
We will gladly advise you on selecting the right system consisting of cartridge, device and mixer, based on your material and quantity.
