Hydroxyethyl cellulose (HEC) Shampoo Stability

JennycatJennycat Member
in Formulating
We are formulating with HEC as a thickener in the formula, and the pH is between 6-7. The initial viscosity was well above 4000 cps, but after 30 and 60 days in the chamber (40C), the viscosity dropped significantly, however the entire shampoo is still clear without any phase separation.

I am wondering if anyone has similar experience with viscosity change of HEC thickened shampoo or other cellulose thickened systems?

Much appreciated!

General formula:
Surfactant blend (40% active) 16%
HEC (Tylose 100000) 1%
Cationic conditioner 0.5%
PE82 1%
Sodium Benzoate 0.5%
Citric acid q.s. to pH 6-7
Humectant ~1%
Water q.s

Comments

  • chemicalmattchemicalmatt Member, Professional Chemist
    Did you activate it with a tiny bit of alkali? Try it after wetting out at high-speed for at least 30 minutes and you'll see it gel. You are dispersing the HEC into the RT water at the start, before adding anything else, correct? If not, that would be the problem too. Also, what is PE82???  
  • JennycatJennycat Member
    edited July 2020

    Thank you for your response!

    Yes I did disperse HEC in cold water then activate it with alkali ingredients, and the viscosity was achieved to 4000 cps after batching, which is desirable for our product (the surfactant blend does not thicken much). However when it sits in chamber it's slowly losing its viscosity, therefore I am wondering if some sort of hydrolysis would happen at pH 6-7.

    PE82 is 80% phenoxyethanol and 20% ethylhexylglycerin.

    chemicalmatt said:
    Did you activate it with a tiny bit of alkali? Try it after wetting out at high-speed for at least 30 minutes and you'll see it gel. You are dispersing the HEC into the RT water at the start, before adding anything else, correct? If not, that would be the problem too. Also, what is PE82???  

  • chemicalmattchemicalmatt Member, Professional Chemist
    Depending on what's in that surfactant blend, Jenny, it does not appear obvious what would do that. I've had viscosity drops with HEC and proteins, enzymes and other amino acid derivs but HEC is generally pretty robust as you know. Leucidal once dropped a cleanser formula built with HEC; that has enzyme qualities is all I could figure. 
  • JennycatJennycat Member
    chemicalmatt said:
    Depending on what's in that surfactant blend, Jenny, it does not appear obvious what would do that. I've had viscosity drops with HEC and proteins, enzymes and other amino acid derivs but HEC is generally pretty robust as you know. Leucidal once dropped a cleanser formula built with HEC; that has enzyme qualities is all I could figure. 

    Thank you Matt! We do have some amino acid derivatives for claim purposes. This is very interesting and I'll need to keep that in mind when I formulate.
  • EVchemEVchem Member
    You don't really need the Sodium Benzoate do you? It's activity diminishes drastically as pH rises, I think above 5.5 it is functionally useless. I don't know if that's interacting with HEC but might as well take it out.
  • JennycatJennycat Member
    EVchem said:
    You don't really need the Sodium Benzoate do you? It's activity diminishes drastically as pH rises, I think above 5.5 it is functionally useless. I don't know if that's interacting with HEC but might as well take it out.
    Thank you @EVchem! That's a great point. I have the impression that even at neutral pH Sodium Benzoate would provide some anti-fungal and anti-mold effect. I made a batch without Sodium Benzoate and I will see if that would help.
  • letsalcidoletsalcido Member
    @chemicalmatt I have not been able to formulate a surfactant with HEC.

    At first I noticed I wasn’t letting it hydrate long enough. Then I thought I did (was heating it up to 75C and a couple drops of 10% NaOH, stir for 10min), and in a few occasions adding an amphoteric surfactant would kill the viscosity.

    I let it sit overnight once, then added surfactants and it seemed stable, until a couple days latter where my wash separated into two phases. I did adjust the pH to 5.5, so I’m wondering if that can be destabilizing it (in this shampoo as well, being a slightly acidic pH).

    But then... I’ve read HEC is used to thicken acidic toilet bowl cleaner.

  • chemicalmattchemicalmatt Member, Professional Chemist
    @letsalcido ; HEC won't do well with high levels of surfactants unless they are cationic, even then it has limited rheology, and why you may see HEC on a hair conditioner label (like @Jennycat) not a shampoo. HydroxyMETHYLcellulose is advised for shampoo, body wash, surfactant systems. See METHOCEL (Dow). It's so safe you can eat it too. Use Methocel F4 in milk shakes to prop up foam.

  • letsalcidoletsalcido Member
    @chemicalmatt thank you for that info. I’ll try HMC and see how that goes! 

    Didn’t mean to hijack the topic, I thought it could be related. 
  • amitvedakaramitvedakar Member
    chemicalmatt said:
    @letsalcido ; HEC won't do well with high levels of surfactants unless they are cationic, even then it has limited rheology, and why you may see HEC on a hair conditioner label
    well can I  use HEC with SLES, CocodineDEA, CAPB system + GHTC.
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