Polyglyceryl fatty acid esters — the "polyglycerol esters" of older literature — went from niche to mainstream in a decade, driven by one formulator demand: an emulsifier that works without ethoxylation. They are built from two renewable feedstocks, glycerol and a fatty acid, joined by an ester bond, and because the polyglycerol backbone is available at several degrees of polymerisation, the same chemistry spans the whole HLB range from W/O to strong O/W. One family can replace an armada of PEG-based emulsifiers, with none of the 1,4-dioxane or ethylene-oxide labelling questions attached.
The naming system, decoded
Every grade is described by three pieces of information, and reading them correctly is half the work of selecting one:
- Polyglyceryl-N — N is the average degree of polymerisation of the polyglycerol chain, i.e. how many glycerol units are condensed together. It is not the esterification degree. A higher N means more free hydroxyls, a more hydrophilic molecule and a higher HLB.
- The fatty acid — the suffix (Laurate, Myristate, Stearate, Isostearate, Oleate, Caprylate, Caprate, Ricinoleate, Hydroxystearate) sets the lipophilic character: chain length, branching and unsaturation. Stearate is the workhorse, isostearate the liquid and skin-feel option, caprylate/caprate the light, water-thin ones, ricinoleate the highly polar W/O choice.
- The esterification prefix — Mono (implied), Di, Tri or Sesqui tells you how many fatty acids are attached per polyglycerol. More esterification means more oil-soluble and a lower HLB. Polyglyceryl-10 Distearate (CAS 12764-60-2) and Polyglyceryl-10 Stearate (CAS 79777-30-3) share a backbone but are not interchangeable: the distearate is the more lipophilic of the two.
So Polyglyceryl-2 Diisostearate (CAS 67938-21-0) is a short, two-unit polyglycerol carrying two branched C18 acids — an oil-soluble W/O emulsifier — while Polyglyceryl-10 Laurate (CAS 34406-66-1 / 74504-64-6) is a long, ten-unit polyglycerol with a single C12 acid, a strongly hydrophilic solubiliser. Same chemistry, opposite ends of the HLB scale.
HLB is set by the polyglycerol chain
The practical rule for scanning a catalogue: low N for W/O, high N for O/W. Polyglyceryl-2 and -3 grades typically sit around HLB 3–7; Polyglyceryl-4 and -6 grades around 8–13; Polyglyceryl-10 grades around 12–16. Esterification pulls the number down within each group — a distearate is less hydrophilic than the corresponding monostearate.
Two caveats before you design a formula around a published number. First, HLB is an approximation for a molecule that is not a single compound but a distribution of oligomers and esters, so treat catalogue values as a starting point and confirm the required ratio at the bench. Second, the emulsifying system, not the emulsifier, is what works: polyglyceryl esters perform at their best in a blend, usually with a fatty alcohol such as cetearyl alcohol to build the lamellar gel network that gives a cream its structure.
Four functional families
| Role | Typical grades | Use level | Where it shines |
|---|---|---|---|
| W/O primary emulsifier | PG-3 Polyricinoleate (29894-35-7 / 235783-76-3), PG-2 Dipolyhydroxystearate (156531-21-4) | 1–4% | Water-resistant sun care, foundations, silicone-heavy systems; the polyricinoleate is one of the strongest W/O emulsifiers available |
| W/O co-emulsifier and pigment dispersant | PG-3 Diisostearate (66082-42-6), PG-2 Diisostearate (67938-21-0), PG-2 Triisostearate (120486-24-0), PG-2 Sesquioleate | 1–3% | Lipsticks, colour cosmetics, sunscreens; wetting pigments and improving spreadability |
| Solubiliser and O/W co-emulsifier | PG-4 Caprate (160391-93-5), PG-4 Isostearate (91824-88-3), PG-6 Caprylate (51033-35-3 / 108777-93-1 / 149175-64-4), PG-6 Dicaprate (74504-65-7), PG-6 Pentaoleate (104934-17-0) | 2–5% | Fragrance and essential-oil solubilisation as a PEG-40 hydrogenated castor oil replacement; light, water-thin micro-emulsions |
| O/W primary emulsifier | PG-10 Stearate (79777-30-3), PG-10 Isostearate (133738-23-5), PG-10 Oleate (79665-93-3), PG-10 Myristate (87390-32-7) | 2–4% | Facial creams and lotions with a PEG-free label; the isostearate and oleate are liquids, easier to process cold |
| Lamellar liquid-crystal emulsifier | PG-6 Stearate (and) PG-6 Behenate (95461-65-7 / 99149-24-3) | 3–5% | Biomimetic creams with a layered α-gel structure; slow-release actives and long-lasting hydration |
Where polyglyceryl esters beat PEG emulsifiers
| Dimension | Polyglyceryl esters | PEG / ethoxylated esters |
|---|---|---|
| Feedstock | Glycerol + vegetable fatty acid, both renewable | Requires ethylene oxide |
| Label | PEG-free, no EO, no ethoxylation statement needed | PEG-n nomenclature to declare |
| Residual risk | No 1,4-dioxane or ethylene-oxide route in the molecule | Trace 1,4-dioxane and EO residuals are a documented audit item |
| Mildness | High — several grades are food-grade (E475) | Generally good, molecular-weight dependent |
| Natural certification | Accepted under Ecocert / COSMOS frameworks | Restricted or excluded |
| Electrolyte tolerance | Good; polyglyceryl systems carry salts better than most nonionics | Moderate, degrades with salt load |
| pH window | Wide, roughly pH 3–10 for the nonionic/mildly anionic grades | Narrower, hydrolysis risk at extremes |
| Cost per kg | Higher | Lower |
| Odour | Can carry a faint glycerol/soap note in lower-purity lots — specify odour-controlled grades | Usually near-odourless |
The cost premium is real, and for a mass-market body lotion a PEG-based system still makes commercial sense. But for anything positioned around clean label, sensitive skin, PEG-free or natural certification, the polyglyceryl route is now the mainstream choice rather than a compromise — and the newer grades have closed most of the performance gap.
Three formulations that show the system logic
A light O/W day cream. PG-10 Stearate 3% as the primary emulsifier, cetearyl alcohol 2% as co-emulsifier and consistency factor, a C8–C10 triglyceride 8% and caprylic/capric triglyceride as the emollient phase, glycerin 5% as humectant, and 0.5% xanthan gum to control yield stress. The stearate forms a lamellar network with the fatty alcohol; the result is a white, cushiony cream with a PEG-free ingredient list.
A water-resistant mineral sunscreen. PG-3 Polyricinoleate 2% plus PG-2 Dipolyhydroxystearate 2% form the W/O interface, with a volatile silicone as the continuous phase and 15–20% treated zinc oxide dispersed in it. This is the classic architecture for high-SPF, water-resistant products, and both emulsifiers tolerate the high electrolyte load that a mineral pigment brings.
A fragrance solubilisate. PG-4 Caprate 4–8% will clear a 1% fragrance oil load into a water-based toner at room temperature, replacing PEG-40 hydrogenated castor oil one-for-one. It is also the mildest of the common solubilisers, which is why it is the usual pick for facial mists and micellar waters.
What to demand on the COA
- Esterification degree / monoester content — the primary identity parameter. A PG-10 Stearate that is mostly diester will not emulsify the way the specification implies.
- Free glycerol — usually specified ≤ 1%. High free glycerol makes the finished product tacky, can depress preservative efficacy and is the main driver of the "soapy" odour complaint.
- Acid value — free fatty acid; ≤ 5 mg KOH/g is a reasonable ceiling. A rising value signals hydrolysis in storage.
- Saponification value — confirms the ester content and catches dilution.
- HLB value — ask for the supplier's measured value, since HLB varies with the oligomer distribution.
- Heavy metals and microbiology — Pb ≤ 10 ppm and As ≤ 2 ppm for cosmetic use; tighter limits plus an E475 food-grade statement if the product is edible.
- Colour and clarity — Gardner or APHA; colour drift usually means an aged or oxidised fatty acid feedstock.
Selection checklist
Four questions settle most briefs. Which phase is continuous? W/O means PG-2 or PG-3; O/W means PG-10. How much electrolyte is in the water phase? Mineral pigments, salts and AHA buffers push you towards the more tolerant grades or a higher emulsifier loading. What is the label story? A PEG-free or COSMOS brief narrows the field immediately but the polyglyceryl family covers it end to end. What skin feel is wanted? The liquid isostearate and oleate grades leave a lighter finish than the solid stearates, and the esters contribute genuine emolliency rather than just structure.
Shanghai Better Chemical supplies a full polyglyceryl ester toolkit — PG-2 Diisostearate, PG-2 Dipolyhydroxystearate, PG-2 Isostearate, PG-2 Laurate, PG-2 Sesquicaprylate, PG-2 Sesquioleate, PG-2 Tetraoleate, PG-2 Triisostearate, PG-3 Diisostearate, PG-3 Polyricinoleate, PG-4 Caprate, PG-4 Isostearate, PG-6 Caprylate, PG-6 Dicaprate, PG-6 Pentaoleate, PG-6 Stearate (and) Behenate, PG-10 Diisostearate, PG-10 Distearate, PG-10 Dioleate, PG-10 Isostearate, PG-10 Laurate, PG-10 Myristate, PG-10 Oleate and PG-10 Stearate — plus ready-made blends such as PEG-30 Dipolyhydroxystearate (and) PG-3 Diisostearate and PEG-7 Glyceryl Cocoate (and) PG-2 Laurate. Per-lot COA with esterification, free glycerol and acid value data supplied as standard, along with TDS/MSDS and samples for bench evaluation. Tell us your emulsion type, target HLB and label requirements, and we will recommend the right grades and quote current pricing.