Aqua Keep 10SH-NFC. How to Use Guide

Transcription

1 How to Use Guide Introduction Aqua Keep 10SH-NFC is an aqueous thickener with an interesting rheology. It forms hazy gels that are structured in bulk but the viscosity breaks on the skin to give a water thin product. The viscosity of Aqua Keep depends on percentage of Aqua Keep and ph according to the graph below which are in Kobo s brochure: Contact Us Applications@koboproducts inc.com Acknowledgement: Aston Chemicals Ltd. Author: Lorna Radford Technical Development Chemist Figure 1-Viscosity versus amount of Aqua Keep 10SH-NFC used in water, from Kobo s brochure Figure 2-Viscosity of a 0.5% mixture of Aqua Keep 10SH-NFC in water versus ph, from Kobo s brochure Kobo Products, Inc So. Clinton Ave. So. Plainfield, NJ USA tel +1 (908) fax +1 (908) Kobo Products, SAS 135 Rue Buissonniere Quartier Bouysset LABEGE France tel +33 (0) fax +33 (0) Kobo Brasil Ltda. Rua Bamboré n.41 Ipiranga - São Paulo/SP Brasil tel +55 (11) Kobo Dispatek Inc Nihombashi-bakurocho Chuoku, Tokyo, Japan tel +81 (3) January, 2015

2 How to Add Aqua Keep 10SH-NFC can be added directly to cold water. Upon addition, it immediately starts to swell and thicken the water. Stirring with a spatula and waiting for several minutes leads to a homogeneous gel; however, it is preferable to sprinkle over water while paddle stirring. This is because addition without stirring can lead to formation of clumps which wet at the surface and then the middle of the clump remains dry. These will eventually hydrate and swell, e.g. wait for 10 minutes. Figure 3-Adding the powder all at once and then stirring with a spatula leads to lumps of dry powder caught in the gel. Waiting 5-10 minutes allows hydration of these clumps to form a homogeneous gel. How Much to Add 0.20% Aqua Keep in water does not form a gel, it just thickens the water very slightly; 0.35%Aqua Keep in water forms a thick gel in bulk. The more Aqua Keep that is added, the hazier the gel becomes. Figure 4-0.2% Aqua Keep in water does not form a gel-this can be seen by the smooth surface (left) after stirring. 0.35% Aqua Keep in water does form a gel as shown by the uneven surface after stirring.

3 Viscosity Variation with ph in Water Deionised water has a ph of around 5. When Aqua Keep 10SH-NFC is added to water, the ph increases to around % and 0.35% Aqua Keep in water was tested. The ph was varied using Potassium Hydroxide (20% dilution in water) and Citric Acid (10% dilution in water). The viscosity at varying ph was investigated: % Aqua Keep ph Viscosity / cp (T-C spindle, 5.0 rpm) Comment No gel formed No gel formed This was the ph directly after added Aqua Keep to water (no ph adjuster used) Several drops of 20% Potassium Hydroxide were added, just to see what would happen at high ph No gel formed Reducing the ph broke the gel Gel formed 85,000 cp Gel formed 90,000 cp This was the ph directly after added Aqua Keep to water (no ph adjuster used) Increasing the ph slightly increased the viscosity slightly At 0.20%, no gel formed when the Aqua Keep was initially added to water. When the ph was increased further (even all the way to ph 10.67), there was no gel formed. This indicates that there is a critical amount of Aqua Keep required to get gel formation, regardless of the ph. At 0.35%, a gel formed when Aqua Keep was initially added to water. The viscosity of this gel was around 85,000 cp (Brookfield viscometer, T-C spindle, 5.0 rpm). The ph of the initial gel was When the ph was lowered, the gel broke. When the ph was increased slightly, the viscosity of the gel increased slightly. (N.B. I m not sure why 0.20% Aqua Keep in water gave an initial ph of 7.4 whereas 0.35% Aqua Keep gave ph 6.9. The ph meter was calibrated just before testing and the ph was tested several times with rinsing of the ph probe in between each test.) This is in agreement with Kobo s graph where they have used 0.5% Aqua Keep in water:

4 Figure 5 - Our viscosity testing using 0.35% Aqua Keep in water (in red text) is in agreement with the trend from Kobo's testing using 0.5% Aqua Keep in water (graph). Figure % Aqua Keep in water forms a gel with ph 6.9 (uneven surface shows gel). Increasing the ph to 7.5 increases the viscosity slightly (uneven surface). Lowering the ph breaks the gel (flat surface due to the reduction in structure). Figure 7-0.2% Aqua Keep in water does not form a gel at its initial ph of 7.3 or after adjustment to ph 10.7.

5 Viscosity Variation Combined with Viscolam AT100P LR107/16 Refreshing, Moisturising Gel uses a combination of 0.40% Aqua Keep 10SH-NFC and 2.00% Viscolam AT100P. Viscolam AT100P s viscosity does not vary with ph, as shown by the graph below found in Lamberti s brochure: Figure 8 - Viscosity variation of 3% Viscolam AT100P in water. The ph stability is very wide since the viscosity remains relatively constant across a broad ph range. As has already been discussed, the viscosity of Aqua Keep 10SH-NFC varies with ph. Considering these two facts, it is therefore not surprising that the following behaviour was observed when the ph of the Refreshing, Moisturising Gel was altered: At low ph (acidic conditions), the viscosity of the Refreshing, Moisturising Gel dropped; however, it still retained some viscosity. This can be explained by the viscosity from Aqua Keep breaking at low ph, but the viscosity from Viscolam remaining constant. At high ph (acidic conditions), the viscosity of the Refreshing, Moisturising Gel increased slightly. This can be explained by the viscosity from Aqua Keep increasing a little bit at increased ph, but the viscosity from Viscolam remaining constant. N.B. The testing on Refreshing, Moisturising Gel was qualitative not quantitative (the ph and viscosity weren t actually measured). Testing involved adding citric acid to one sample of the gel in a small beaker and adding potassium hydroxide to another sample in a different beaker. The beakers were stirred using a spatula and the viscosity was indicated by the resistance to stirring.

6 Considering Performance vs. ph of Skin Care Formulations From the testing above, it would make sense to use a higher ph so that the content of Aqua Keep 10SH-NFC can be minimised to reduce costs. However, other factors have to be taken into account when creating a skin care formulation: Aqua Keep is most effective at ph 7 or above. Below ph 6 it provides no viscosity. Neutral ph is 7. The ph of skin is around 5.5. Balancing the points above, it could be concluded that a formulation with high ph (such as above ph 7) might be too high to use on the skin and could cause irritancy. For this reason, lots of skin care products are formulated between ph However, for Aqua Keep to be effective, the ph should ideally not go below ph 6.5. Just under or around ph 7 would therefore be the optimum conditions for Aqua Keep 10SH-NFC. Since the addition of Aqua Keep to water immediately gives a mixture around ph 7, it might not be necessary to adjust the ph; however, if there are other ingredients in the formulation that could cause a difference in ph, it could be useful to use a ph adjuster (e.g. with TEA, KOH or NaOH).