PEG-150 Pentaerythrityl Tetrastearate is a chemical compound that, by weight, has 90 percent stearic acid.

The name defines the structure of the molecule

• PEG-150 refers to polyethylene glycol with an average molecular weight of 150, used as an emulsifier and thickener.
• Pentaerythrityl is the central structure derived from pentaerythritol.
• Tetrastearate indicates the presence of four esters of stearic acid, giving emollient properties.

Description of the Raw Materials

Pentaerythritol. A tetrafunctional alcohol used as the backbone.

Stearic Acid. Fatty acid used to impart emollient properties.

Ethylene Oxide. Used in the polyethylenation process.

Industrial Chemical Synthesis Process

• Reaction with Ethylene Oxide. Pentaerythritol reacts with ethylene oxide to form a polyethylene glycol (PEG) derivative.
• Esterification with Stearic Acid. The reaction of the PEG intermediate with stearic acid forms four esters, creating PEG-150 Pentaerythrityl Tetrastearate.

PEG-150 Pentaerythrityl Tetrastearate appears as a white powder or yellowish liquid.

What it is used for and where

Cosmetics

Surfactant - Emulsifying agent. Emulsions are thermodynamically unstable. Emulsifiers have the property to reduce the oil/water or water/oil interfacial tension, improve emulsion stability and also directly influence the stability, sensory properties and surface tension of sunscreens by modulating their filmometric performance.

It is used in doses up to 7 percent in leave-on products.

Commercial applications  

Hair Care Products: Used in shampoos and conditioners as a thickener and emulsifier.

Skin Care Products: Found in creams, lotions, and cleansers as an emulsion stabilizer.

Makeup Products: May be used in foundations and other cosmetic items.

Safety

The CIR Expert Panel concluded that Pentaerythrityl Tetrastearate is safe in current use practices and at the concentrations described in this safety assessment (1), and as far as PEG is concerned, given its high molecular weight, I believe there is no problem (allergies or specific intolerances aside, of course).

It has a low degree of skin irritability.

Food

Pentaerythrityl Tetrastearate is an indirect food additive that can be used for manufacturing food packaging.

• Molecular Formula: C₇₇H₁₄₈O₈
• Molecular Weight: 1201.99
• CAS: 115-83-3
• UNII  W9Q3DZS0EG
• EC Number: 204-110-1
• DSSTox Substance ID: DTXSID7026944

• Density/specific gravity at 20°C 0.915 +/- 0.06 
• Vapor pressure, mm Hg at 25°C 1.5 x 10^-27 
• Boiling point, °C 998.5 + 60.0 
• Melting point, °C 66-77 40
• Water solubility, g/L at 25°C and pH 1-10 6.3x10^-11

Synonyms: 

• [3-octadecanoyloxy-2,2-bis(octadecanoyloxymethyl)propyl] octadecanoate
• Octadecanoic acid, 2,2-bis(((1-oxooctadecyl)oxy)methyl)-1,3-propanediyl ester
• SCHEMBL158508
• Stearic acid, neopentanetetrayl ester

References________________________________________________________________

(1) Becker LC, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Liebler DC, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW, Andersen FA. Safety Assessment of Pentaerythrityl Tetraesters as Used in Cosmetics. Int J Toxicol. 2015 Sep;34(2 Suppl):99S-112S. doi: 10.1177/1091581815596731.

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And a premise on PEG.

Since the PEG (1) family is numerous and is found in many cosmetic, cleaning and medicinal products and others, we need a cognitive premise on the subject that is rather complex from the point of view of safety because these products not only come into contact with the skin but, as in the case of medicine, they are also ingested.

PEG or polyethylene glycols polymerise the condensed ethylene oxide and water and are called polyethylene glycols, but in reality, they are complex chemical components, polymers bound together. For example,  plastic is polyethylene and has a hard consistency, while  polyethylene aggregated to the glycol forms a liquid.

The number that appears after the initials PEG represents the molecular weight and the higher this number is, the less it penetrates  the skin. 

Here below are some studies in Medicine that refer to the use of PEG Polyethylene glycol in various fields.

Intestine

Polyethylene glycol with or without electrolytes is effective for the treatment of functional constipation, both in adults and in paediatric patients, with great safety and tolerability. These preparations are the most effective osmotic laxatives (more than lactulose) and are the first-line treatment for functional constipation in the short- and long-term. They are as effective as enemas in faecalomas, avoid the need for hospitalisation and are well tolerated by patients (especially when given without electrolytes) (2).

In the preparation  for colonoscopy,  polyethylene glycol tablets confirmed efficacy, acceptability, tolerance and safety similar to those of sodium phosphate (3).

For peripheral nerve repair (4).

Eyes

Dry eye syndrome is a disorder that affects 5-34% of the world's adult population with reduced quality of life. Artificial or lubricating tears are the most used therapy for treating this condition due to their low side effects profile, which attempt to modify the properties of the tear film. Polyethylene glycol has demonstrated clinical efficacy in the treatment of this condition (5).

Brain

Polyethylene glycol facilitates the neuroprotective effects of magnesium in head injuries (6).

Tumors

For transarterial chemoembolization, Polyethylene glycol is effective and safe for the treatment of liver cancer, as indicated by good tolerability, quality of life and high tumour response (7). 

Cosmetics

Many types of PEG are hydrophilic and are used as creams, topical dermatological preparations and in cosmetic products such as surfactants, emulsifiers, detergents, humectants and skin conditioners.

Safety varies from type to type given the structural complexity (8).

References___________________________________________________________________

(1) Fruijtier-Pölloth C. Safety assessment on polyethylene glycols (PEGs) and their derivatives as used in cosmetic products. Toxicology. 2005 Oct 15;214(1-2):1-38. doi: 10.1016/j.tox.2005.06.001.

(2) Mínguez M, López Higueras A, Júdez J. Use of polyethylene glycol in functional constipation and fecal impaction. Rev Esp Enferm Dig. 2016 Dec;108(12):790-806. doi: 10.17235/reed.2016.4571/2016.

Santos-Jasso KA, Arredondo-García JL, Maza-Vallejos J, Lezama-Del Valle P. Effectiveness of senna vs polyethylene glycol as laxative therapy in children with constipation related to anorectal malformation. J Pediatr Surg. 2017 Jan;52(1):84-88. doi: 10.1016/j.jpedsurg.2016.10.021.

(3) Chaussade S, Schmöcker C, Toulemonde P, Muñoz-Navas M, O'Mahony V, Henri F. Phosphate tablets or polyethylene glycol for preparation to colonoscopy? A multicentre non-inferiority randomized controlled trial. Surg Endosc. 2017 May;31(5):2166-2173. doi: 10.1007/s00464-016-5214-1.
Tsunoda T, Sogo T, Iwasawa K, Umetsu S, Oikawa-Kawamoto M, Inui A, Fujisawa T. Feasibility and safety of bowel cleansing using low-volume polyethylene glycol with ascorbic acid before pediatric colonoscopy: A pilot study. Dig Endosc. 2017 Mar;29(2):160-167. doi: 10.1111/den.12756.

(4) Hoffman AN, Bamba R, Pollins AC, Thayer WP. Analysis of polyethylene glycol (PEG) fusion in cultured neuroblastoma cells via flow cytometry: Techniques & optimization. J Clin Neurosci. 2017 Feb;36:125-128. doi: 10.1016/j.jocn.2016.10.032.

(5) Pérez-Balbuena AL, Ochoa-Tabares JC, Belalcazar-Rey S, Urzúa-Salinas C, Saucedo-Rodríguez LR, Velasco-Ramos R, Suárez-Sánchez RG, Rodríguez-Carrizalez AD, Oregón-Miranda AA. Efficacy of a fixed combination of 0.09 % xanthan gum/0.1 % chondroitin sulfate preservative free vs polyethylene glycol/propylene glycol in subjects with dry eye disease: a multicenter randomized controlled trial. BMC Ophthalmol. 2016 Sep 20;16(1):164. doi: 10.1186/s12886-016-0343-9.

Labetoulle M, Messmer EM, Pisella PJ, Ogundele A, Baudouin C. Safety and efficacy of a hydroxypropyl guar/polyethylene glycol/propylene glycol-based lubricant eye-drop in patients with dry eye. Br J Ophthalmol. 2017 Apr;101(4):487-492. doi: 10.1136/bjophthalmol-2016-308608.

(6) Busingye DS, Turner RJ, Vink R. Combined Magnesium/Polyethylene Glycol Facilitates the Neuroprotective Effects of Magnesium in Traumatic Brain Injury at a Reduced Magnesium Dose. CNS Neurosci Ther. 2016 Oct;22(10):854-9. doi: 10.1111/cns.12591.

(7) Aliberti C, Carandina R, Sarti D, Mulazzani L, Catalano V, Felicioli A, Coschiera P, Fiorentini G. Hepatic Arterial Infusion of Polyethylene Glycol Drug-eluting Beads for Primary and Metastatic Liver Cancer Therapy. Anticancer Res. 2016 Jul;36(7):3515-21.

(8) Jang HJ, Shin CY, Kim KB. Safety Evaluation of Polyethylene Glycol (PEG) Compounds for Cosmetic Use. Toxicol Res. 2015 Jun;31(2):105-36. doi: 10.5487/TR.2015.31.2.105.