Settling in shampoo formulation

Hi there!

I've been doing test batches of a shampoo formula using two kinds of guar (hydroxypropyl and cationic) for both thickening and conditioning properties. While the shampoo has nice performance and leaves hair feeling clean and somewhat conditioned, it is changing in appearance over time. After about 7 days if left un-shaken, it appears that some of the ingredients settle in a bottom layer. There isn't complete separation, just a more opaque, viscous layer in the bottom 2/3 of the bottle. It looks to me like it's one of the guars, but I'm not sure.

Please see below the formula and process I'm following:

Phase I:
Water                                                                                37.82%
Aloe juice                                                                          21.05%
Glycerin                                                                             2.00%
Hydroxypropyl guar                                                           0.50%
Cationic guar                                                                     0.30%

Phase II:
Sodium cocoyl isethionate (Jordapon SCI)                           5.00%
Cocamidopropyl betaine                                                    15.00%
Coco glucoside (Ecosense 919)                                          10.00%

Phase III:
Agave extract                                                                     2.00%
dl-Panthenol 50% liquid                                                     1.80%
Hydrolyzed wheat protein                                                  2.00%
Propylene Glycol/Diazolidinyl Urea/Iodopropynyl Butylcarbamate (liquid Germall Plus)                                                                      0.50%
Fragrance (blend of essential oils)                                      0.80-1.00%

Process:
Combine both guars with glycerin. Add to water/aloe juice while using immersion blender to create a vortex. Heat to 150 F.
Combine surfactants in double boiler and heat to melt (170 F).
Add essential oil blend to melted surfactants and mix. Then add Phase II mix to Phase I and mix. Allow to cool to 115 F before adding remaining ingredients. Adjust pH to 5.6-5.7 using citric acid 50% solution.

I've retested the pH on samples from 1 month ago and there appears to be a drift up (alkaline) to about 5.9. I should also note the goal is to create a sulfate-free formula without the use of PEG thickeners.

I'd greatly appreciate any input, insights or advice. Thank you!

Comments

  • Kate, looks like you need another hydrotrope - or more of the one you have: CAPB. Neither SCI nor the glucoside is very hydrotropic and could use more help from the amphoteric, so raise that and lower the glucoside.  The gel phase is likely either the hydroxypropyl guar, the glucoside, or a coacervate complex with the anionic, so drop the nonionic guar, keep the cationic guar and change your order of addition.  Always add the amphotheric to your mixture after a cationic is added (HPGTC in this case), then the nonionic then anionic, so sequence: CAPB/glucoside/SCI. Also keep your pH above 7.0 since glucosides are less hydrophilic in the acid range and play well with others in the near alkaline range. Finally, drop the glycerine to an insignificant level and you will appreciate the higher viscosity and foaming. In surfactant systems such as yours, glycerine does absolutely nothing but kill viscosity, kill foam and rinse away to feed fishes.
  • Thanks so much for the reply @chemicalmatt. I had come across the recommendation to add the surfactants in the order you mention when using cationic guar, however, I also have a tough time melting the SCI without the help of the CAPB. Maybe I'll try just adding the surfactants to the water phase (in the correct order) and heat the entire mix to melt the SCI.

    Interesting about the pH - wondering if leaving the pH at around 7 will impact viscosity? Lowering the pH has helped with thickening in this formula. I'd not come across the information regarding glycerin affecting viscosity/foam before, but will try lowering the amount.

    Will report back on the next experiment!
  • One more thing - could using an immersion blender instead of an overhead mixer affect formula stability?
  • could using an immersion blender instead of an overhead mixer affect formula stability?
    Possible but unlikely since I see no ingredients such as carbomers.
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • Interesting
    @chemicalmatt , what would happen with SCI/glucoside/CAPB/cationic addition order?
    Is cationic/CAPB/glucoside/SCI order advised just because of solubility issues, or because nonionics (glucoside) somehow modify the cationic/CAPB mixture micelles?

    Sorry if this sounds like a totally newbie question
    but I'm just at the 'anionics+cationic coacervates can be compatible and beneficial' stage.


    Review on Anionic/Cationic Surfactant Mixtures

    Abstract
    It is commonly known that cationic and anionic surfactants cannot be mixed without the risk of precipitation or instability. However, many studies have shown that not only is it possible to combine cationic and anionic surfactants, but also that this combination can present synergic properties. Mixtures of anionic and cationic surfactants have many unique properties that can be very useful when used properly. The aim of this report is to present relevant information concerning the interaction between anionic and cationic surfactants. A bibliographic review on anionic/cationic mixtures is presented here in order to better understand their properties and possible synergic effects, as this is of practical importance for the chemical industry.
    https://link.springer.com/article/10.1007/s11743-007-1047-1
  • Thanks for the follow up @Belassi - I'm trying to better equip my lab and was considering an overhead mixer and homogenizer for both emulsions and surfactant-based products. Any other suggestions? So far, still making pretty small batches, up to 2 gallons.
  • I had the same issue in the past and tried many pieces of advice from different experts locally (too many actually). 
    I know it sounds simple but it well worked for me - try to include Ultrez 20. Pay attention to pH level during the production.

    Again, I am not a professional chemist and I can't professionally advice by reviewing a formula but this is a personal experience talking, make a sample and see how it goes.
  • edited June 23
    I really don't think you should use a homogeniser for surfactant products. I use slow paddle stirring but longer time. Don't need foam to be generated
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
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