[chemicalmatt]

Any material that has a significant polar charge may be considered an electrolyte. Those having ionic bonds (salts) are the most highly charged given their high polarity in relation to their mass. Those with higher molecular mass (organic materials), or covalently shared ionic functional groups have lower charge-mass ratios and are therefore less electrolytic. Amino acids and proteins are mildly charged whereas quaternary ammonium compounds are more strongly charged with ionic strength inversely proportional to their mass: i.e. cetrimonium chloride is more electrolytic than behentrimonium chloride. The ionic nature (mono-, di-, tri-valent), structure and molar mass of the anion and cation also factor into this. This is the short answer, there is much more. There will not be a test however.

[chemicalmatt]

@Abdullah It’s been a while since I worked with it but isn’t STPP more soluble in cold water than in hot?

[chemicalmatt]

@cocoblue the correct logical order is stability > PET USP51 > HRIPT. If the formula is not thermodynamically stable then sterility testing and safety testing is no longer important. When you have (favorable) results documented for all three then you are free to choose any CDMO you want to; no need to run these again. After >35 years in that sector I can tell you the client who comes into play with formula ownership and integrity fully vetted like this gets instant “street cred” and the deference that goes with that. You will have a distinct advantage in the price quote too, the CDMO knowing you can move elsewhere at any time.

[chemicalmatt]

Yup, I’ll be working at our booth #803. Stop by and say hello or just to talk about your work, beauty industry goings-on and formula chemistry. The educational agenda there is packed with content and @Perry44 will be all over that.

[chemicalmatt]

Propylene glycol is not the “wet” problem, decyl glucoside is. DEL that surfactant (why add it in first place?) and fix the PG: water ratio at 2.0 to 2.5: 1, it will work fine. You don’t say which grade sodium stearate is used, but 8.0% seems high to me. Most of these start at 6.0% with little increase from there.

[chemicalmatt]

@EricT Those potassium soaps start losing their solubility the lower the pH difference. That is your haze factor. I’ll also mention piroctone doesn’t care for lower pH either, even as it is mainly insoluble to begin with. Switch those out with a standard anionic such as SLES or SLS (I know: sulfates - EEEK!) and you will feel better. Better yet use ALS and drop pH < 7.5. ALS is a better hydrotrope for piroctone olamine.

[chemicalmatt]

So simple: get a sample of nearly any silicone crosspolymer gum blend from Dowsil, Momentive, Wacker, BRB, ShinEtsu. Add a small amount of phenyltrimethicone or C12-15 alkyl benzoate, then get busy shinin’ then tyres. Another approach: start out with Versagel (Calumet) then add those shiny components.

[chemicalmatt]

@Camel The level 0.50% menthol will sting my eyes in a hot shower, so keep that in mind. Most of the scalp-cooling shampoos use 1.0%, so you can increase to that and find success. I could not handle it but most folks can. And, yes, you are correct to dissolve into the surfactant blend. Menthol is more oil soluble than water soluble.

[chemicalmatt]

That low level of urea will not change pH significantly over time, even as it decomposes into biuret, ammonia and nitrates. The lactate buffer does work best however, so you are on right track. (Rice starch is the other.) A more cogent question is why have it in a shampoo in the first place? As a keratolytic it is not applied to hair long enough or in high enough concentration to perform any valuable function in a cleansing product. Applied as a leave-on product it will swell the cuticle allowing conditioner elements to absorb faster/deeper, but in rinse-offs?

[chemicalmatt]

@Onur the SPF 50 is chiefly - but not entirely - built by nano zinc oxide, and as you surmised: likely uncoated. The other elements in an anhydrous formula such as this one also boost SPF as these are occlusives, though not UV absorbers. They function in synergy with ZnO, which deflects sunrays while the lipids block them.

[chemicalmatt]

PEG-12 Dimethicone comes to mind as does butylene glycol. Both are superior plasticizers to glycerin.

[chemicalmatt]

@Abdullah I recommend substituting 0.8:1 if that lauramidopropyl hydroxysultaine is the standard 50% solution and they are comping it to the standard 30% CAPB solution. A little extra sultaine helps.

[chemicalmatt]

@garima this will not be stable without an alkali agent to saponify the stearic acid, not with that oil load anyhow. Stearic acid is your primary emulsifier there when used with an alkali such as triethanolamine, AMP or tromethamine, otherwise it is only a weak builder since cetyl alcohol is already in there. As for “mouldy”…what @Paprik said: find and add a good preservative and do it soon!

[chemicalmatt]

@Abdullah here is an interesting note to add to the excellent summation by @ketchito . The boron x-link of guar gum is used in petroleum fracking operations worldwide. When the price of crude oil rises above ~$100/barrel the fracking operation becomes financially viable and the price of ALL guars goes through the roof. I’ve seen that price increase by 5X and the MOQ go to 10,000 kg when the frackers are using it fulltime. One more reason to watch those feedstock prices! Same goes for palm oil and castor oil.

[chemicalmatt]

HI there @Graillotion Polyquaternium-37 is your best bet for rheology enhancement, i.e. my personal fave Synthalen CR from 3V Sigma USA, or the Kleasol line from Rheolab (UK). There are others, most having similar viscosity outcomes, similar sensorial haptics but differing in clarity of the gel. If a clear product is no issue then the world is your oyster. Polyquaternium-32 is second banana here, the precursor to PQ-37.

[chemicalmatt]

I agree with @PhilGeis here, EDTA is very stable. I’ve used 7 year old material before, no problem. That BHT on the other hand? It was white originally and may form nitrosamines with certain amino-functionals when decomposing like that. Toss it.

[chemicalmatt]

@LabGuy You are 100% correct, so I guess this means this post is self-correcting? You need to rebalance that polyol-water ratio closer to 3:2 of glycol: water and cut that glycerin with propylene, butylene or dipropylene glycol. That last one DPG being the best choice.

[chemicalmatt]

We’ve been through this many times before. Measure mass in a 100ml graduate cylinder to the line precisely at 60C both (liquid) product and water. Although the expansion coefficients are not same, this will NOT affect the SpG value significantly. Clean-up? Just pour out your lipstick and chase the cylinder with chloroform or methylene chloride (in a fume hood preferably.)

[chemicalmatt]

What’s with all those hyaluronate species? Must be one helluva’ hyaluronic salesperson calling on you there. You need to be more specific in your composition. Is that “PGA” polyglutamic acid? If so it is redundant with those many HA’s. What is meant by “betaine”? If it is true betaine (trimethylglycine) that may be your problem as it may be complexing with that HA crosspolymer. Remember “less is more” as Buckminster Fuller said.

[chemicalmatt]

Rapidgel EZ1 at 1.0% would do the trick and you might reduce the Olivem 300 at same time. Final viscosity would be a thin lotion more like what you are looking for.

[chemicalmatt]

There would be three intersects in that Venn diagram. E.g. PEG-40 hydrogenated castor oil is an emulsifier, surfactant and solubilizer. MOST emulsifiers are also surfactants, but not so much the reverse.

[chemicalmatt]

We use a Memmert HPC150 chamber and it works like a charm. How “economical” would be your call but Memmert makes many sizes to suit different folks. As for tests to conduct, standard accelerated stability conditions for pharma are 45C at 55% RH success over 90 days for prelim approval of a given formulation depending on its constitution (some formulations require lower temp/longer time.) Besides assay of your API - the most important test - you will also record pH, viscosity and any signs of discoloration or decomposition over the course of the shelf life and one year beyond. Testing labs? Too many to list, depends on your location.

[chemicalmatt]

This is pushing the solubility limit for azelaic acid unless you raise the pH closer to neutral with a metal hydroxide. With a little more Polawax this should work. Xanthan gum will be dispersed into water first (NOT in the oil phase) then add AZA into water at temperature, adjust pH to 5.5 - 6.5, then proceed as planned and see what you get. I would add a little cetyl alcohol to mitigate the “soaping” from the PEG ester and improve stability at same time. Kudos to you for employing Germall as preservative.

[chemicalmatt]

I think you need to more clearly define what exactly is “liquid carbomer”. There are many acrylate liquid rheology modifiers, most are 30% activity, and some are geared towards thickening surfactant systems. Others are not. If you are using one of the 30% acrylics suitable for your shampoo formula, then 1.0% w/w (0.30% solid) is far too short. Start with 3.50% and go from there. I would not adjust the pH below pH5.0 either. None of these build well below that pH and without the acid salt preservatives (as Perry remarked) you won’t need to.

[chemicalmatt]

This should work just fine. I think you may be applying too much mixing there. Slow cool while slow mix and this should build, assuming your starting temp is > 75C. Finally, adding NaCl solution while at 25 - 35 C can build viscosity here too. A little bit o’ salt goes a long way and most formulators don’t know this works with cationic systems not just anionics.