Many household and industrial cleaners are strongly alkaline, highly acidic or contain oxidizing agents. This creates challenges when one would like thicken them or to have a gel formulation instead of the corresponding thin liquid version. In many cases, viscous, gel or foam formulations are preferred, as they ensure longer residence time on the vertical surfaces and are also safer to use as they are good at preventing any unwanted splashing. Today we will look at how MFC allows you to manufacture stable gel formulations at low to high pH as well as with oxidizing compounds, such as hydrogen peroxide.
The biggest challenge regarding the thickening of highly acidic or alkaline products, as well as oxidizing compounds such as bleach, is to find a stable rheology modifier. Most of the common rheology modifiers have a narrow pH working range and are often vulnerable to oxidizing agents. The chemical instability of the compounds leads to a short shelf life of the end product. In addition to the chemical stability, the rheology modifier should also provide a drip resistant profile for the formulation.
Many toilet bowl and bathroom cleaners, that are tailored to remove scale and rust, have a pH below 3 and are often based on hydrochloric acid. On the other hand, several cleaning products are based on sodium hypochlorite, typically stabilized with sodium hydroxide to pH 10-13. As can be seen from the list below, the amount of suitable thickeners is low (Table 1.), especially when you are targeting high pH formulations with oxidizing agents.
|Compound||pH range||Oxidizing agents|
|Cellulose ethers||3–11||Not stable|
|Magnesium aluminium silicate||2–13||Stable|
Table 1. Stability ranges of common thickeners used in cleaning products.
Want to learn more on the storage stability of Exilva under a wide pH range? We have previously written about the subject.
Thickening with MFC
Due to its insoluble nature, MFC shows considerably higher stability against chemical reactions than water soluble polymers. Figure 1 shows the complex viscosities of 1% Exilva in 5% sodium hydroxide (NaOH), 10% hydrochloric acid (HCl) and in hydrogen peroxide (H2O2), after 24 hours as well as after 1 month storage. As can be seen from the figure, MFC effectively thickens these media as well as shows good storage stability.
Figure 1. Complex viscosities (Pas) of 1 wt% MFC (Borregaard’s Exilva MFC) suspensions after 24 hour and 1 month storage at room temperature.
The high stability of MFC allows it to be used to thicken various home care and industrial cleaning products such as, toilet bowl cleaners, bathroom cleaner, degreasers, metal cleaners, rust removers and car cleaners. The high chemical stability is also important in various other application fields such as coatings and adhesives.
In addition to the chemical stability, MFC provides exceptional rheological properties and outstanding compatibility with various compounds such as surfactants. Due to the high viscosity at rest as well as high shear thinning, one is able to design formulations that are easy to spray as well as non-dripping (Figure 2).
Figure 2. Anti-sag and spray properties of sprayed MFC formulation. The emulsion on the left hand side is a reference without MFC. The right hand side formulation contains 0.3% MFC (Borregaard’s Exilva MFC) which effectively prevents dripping on non-horizontal surfaces.
MFC offers a solution for those who are looking to simplify their formulations or have fewer additives on their shelf. In addition to the high performance and stability, MFC is a renewable choice for your challenging formulations, taking you one step closer to sustainable products.
Otto Soidinsalo works as a technical application manager at Borregaard. He has a Ph.D. in organic synthesis from the University of Helsinki and his working experience ranges from organic synthesis, cellulose ethers and its applications to nanocrystalline cellulose and microfibrillated cellulose.
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