Glycols for humectancy, texture enhancers, and hurdle microbe approach.

Formulating

Glycols for humectancy, texture enhancers, and hurdle microbe approach.

Posted by Graillotion on December 16, 2020 at 6:47 am

As I formulate with more skill, I have acquired a new appreciation for the ‘glycols’. I have been using propanediol as a multi functional and humectant, and butylene glycol as a co-humectant. As I have decided to add some bug food (colloidal oatmeal) to an upcoming formula, I have become more interested in adding additional hurdles to my preservation system, including maximizing what I can get from the glycols.
For the sake of what I can easily acquire, I would like to keep the conversation focused on Propanediol, Butylene Glycol, Pentylene Glycol, and Caprylyl Glycol. (Sorry, just haven’t been able to find small quantities of Hexylene Glycol from a re-packer in the US.)

1) As far as humectant properties….are some of these better than others, or can they be considered interchangeable?

2) I am a nut…when it comes to textures. At low percentages…1-5% will any of these have a sensory advantage over the others? Or texturally speaking they will have imperceptible differences?

3) Ok….the MOST important aspect. Regarding hurdle technology, can anyone link me something that goes into detail about the differences between these glycols? I will paste a snippet from @Bill_Toge I found in an old thread….this is some of they kind of information I am looking for:

linear 1,2-glycols are antimicrobial - the efficacy increases as the chain length increases, so caprylyl glycol (C8) works better than 1,2-hexanediol (C6; ‘hexylene glycol’ is a branched 3,5-diol), which works better than butylene glycol (C4)

unless they’re included at 30% +, they’ll not have a significant effect on the water activity

Thank you Bill.

Any information on which would be redundancies, and which would be synergies…would be greatly appreciated, as well as inclusion rates to make them functional hurdles.

Always learning …. thanks to this awesome forum.

Pharma replied 3 years, 12 months ago 6 Members · 14 Replies
14 Replies

Pharma

Member
December 16, 2020 at 7:43 pm

If used at, say, 5%, they will contribute to a lower water activity. Together with other dissolved stuff, it might bring it so far down that microbes will start to starve which allows other preservation hurdles to work bether .

3) Correct. Linear C8 chains, no matter whether it’s caprylyl glycol, caprylic acid, glycerol monocaprylate, or similar, are often antimicrobial and perform better than C6 or C10 analogues. This is thought to have something to do with water-lipid distribution causing microbial membrane disturbances.

BTW there are many more hexanediols of which the 1,2-, 2,3-, and 3,4- are glycols in the proper sense. However, INCI doesn’t know proper sense :smiley: . 3,5-hexanediol is a misnomer and would be the same as 2,4-hexanediol. Cosmetics usually uses 1,2-hexylene glycol whilst the 1,6-isomer is a common synthetic intermediate. Having both hydroxy-groups at one end of the carbon chain turns all these glycols into co-emulsifiers which allows for membrane interactions whereas hydroxy-moieties distributed somewhere greatly reduce this antimicrobial effect. Moisturising wise, this is probably less of an effect though too long carbon chains reduce water solubility and hygroscopy = the longer the chains, the less moisturising the molecule will be.

There’s a thread from this year about the sensory and humectancy profile of several such ingredients somewhere hidden on this board .
jemolian

Member
December 17, 2020 at 1:41 am
Regarding the skin feel wise, they do have some differences, so you can pick which you prefer. I have the following on hand, so if you need to me patch test for a description do let me know:
- 1,2-Hexanediol
- Pentylene Glycol
- Propylene glycol
- Propanediol
- Butylene Glycol
- SymDiol 68 (1,2-Hexanediol (and) Caprylyl Glycol)
User experience wise, 1,2-Hexanediol, Pentylene Glycol, Propylene glycol makes my face tingle, Caprylyl Glycol makes my face warm. I use Propanediol, Butylene Glycol in my hand wash so i’ve not tested it on my face at the moment.
helenhelen

Member
December 17, 2020 at 10:45 am

@jemolian I’d love to know what you think Propanediol feels like compared to pentylene glycol. I use both glycerin and pentylene glycol at the moment in a cream but I’ve always wondered if propanediol would add much in terms of moisturisation or skin feel.
jemolian

Member
December 17, 2020 at 1:18 pm

@helenhelen testing at 3% in 15% Aristoflex Avc, i think it’s hard to tell the difference between the two. Testing at 100% as is, they just feel about equally wet or slightly greasy, so not too much difference there as well.

I’d say the difference would largely be perhaps the cost and what kind of use rate you’d like to have, besides from the potential irritation that each glycol or diol might cause for the user. Some people do look for Butylene Glycol free products while some people break out from Propanediol due to the high concentration from product range from The Ordinary.
helenhelen

Member
December 17, 2020 at 2:06 pm

@jemolian Thanks for that!
Graillotion

Member
December 17, 2020 at 8:01 pm

jemolian said:

@helenhelen testing at 3% in 15% Aristoflex Avc, i think it’s hard to tell the difference between the two. Testing at 100% as is, they just feel about equally wet or slightly greasy, so not too much difference there as well.

I’d say the difference would largely be perhaps the cost and what kind of use rate you’d like to have, besides from the potential irritation that each glycol or diol might cause for the user. Some people do look for Butylene Glycol free products while some people break out from Propanediol due to the high concentration from product range from The Ordinary.

So what I hear you saying, from a possible marketing approach: If I am using propanediol and Butylene glycol (which I am), that if I sub them out for hexanediol, Pentylene Glycol, and Caprylyl Glycol, it will be unlikely to change any of the sensories? However it will enhance hurdles and possibly be more palatable to those scanning an INCI for Butylene and Propanediol?

(I was able to secure SymDiol 68, so hexanediol is back in play!)
jemolian

Member
December 18, 2020 at 12:34 am
Yes, that was what i was thinking as well previously. From what i’ve seen, the recommended use rates for 1,2-Hexanediol & Pentylene Glycol don’t need to be very high, but in terms of cost wise, is it cheaper compared to the combo you are using?

For the Symdiol 68, in the marketing brochure, they did mention some moisturizing functionality at about 0.5%. Though Caprylyl Glycol might cause some emulsion instability? I see people having these issues sometimes in the facebook groups when the use Optiphen
https://www.dropbox.com/s/3pfb8r222arkjyj/PB_SymDiol-68.pdf?dl=0

If you are using the Euxyl PE 9010, you can consider adding up to 3% of Pentylene Glycol. You can take a look at the pdf for some info for consideration if you haven’t before:
- dermosoft® Pentiol eco - https://www.dropbox.com/s/qmlt3ucxt3lhatk/PI_dermosoft_Pentiol%20eco_052019.pdf?dl=0
- Hydrolite 5 - https://www.dropbox.com/s/dwuqpcyvowokqa7/616751%20Hydrolite%205%20QS%20cn.pdf?dl=0
- Hydrolite 5 - https://www.dropbox.com/s/8vw6uvbvcsuxoia/Hydrolite%205_Green_pb.pdf?dl=0
For the 1,2-Hexanediol:
Graillotion

Member
December 18, 2020 at 1:53 am

Thank you for all the links @jeremien, I am digging into them now.

Do you know the ratio in the Symdiol 68? From what I could see….it looks like it was pretty close to 50/50?
jemolian

Member
December 18, 2020 at 1:58 am

I would believe so. I only have the MSDS for Symdiol 68T, which has Tropolone, so here’s the pdf for reference: https://www.dropbox.com/s/71cgja7seopt2ty/SymDiol68T12HexanediolCaprylylGlycolTroploneAllDocuments.pdf?dl=0

Though you can also refer to the Making Cosmetics version’s SDS https://www.makingcosmetics.com/msds/sds-hexanediol-caprylyl-glycol.pdf
PhilGeis

Member
December 21, 2020 at 2:35 pm

In my exprience, longer chain glycols exert an antimicrobial effect beyond any modification of product Aw.
jemolian

Member
December 21, 2020 at 2:57 pm

@PhilGeis in terms of longer chain, would it be from pentylene glycol and higher？I’ve been wondering about that.
PhilGeis

Member
December 21, 2020 at 5:34 pm

jemolian said:

@PhilGeis in terms of longer chain, would it be from pentylene glycol and higher？I’ve been wondering about that.

yes
zetein

Member
December 22, 2020 at 1:55 am

@Pharma Hello.

Does hygroscopicity equal its moisturising effect? Would erythritol, mannitol, glucose etc. have almost no humectancy since they have low hygroscopicity?
Pharma

Member
December 22, 2020 at 5:48 am

No, hygroscopy doesn’t equal moisturising effect but it helps a lot. Like worms don’t catch fish but hooks do. And yet, I wouldn’t go out fishing without worms :smiley: .

Hygroscopy is like bait, it attracts water whereas moisturising is the hook which binds water to your skin. Sure, most hygroscopic substances are actually doing both.