Industrial-grade polyethylene glycol (PEG)

01

Choose the molecular-weight grade and physical form

21 CFR 172.820 identifies polyethylene glycol as an addition polymer of ethylene oxide and water with a mean molecular weight of 200 to 9,500, and permits it in food tablets as a coating, binder, plasticizing agent and/or lubricant. [1] Acme-Hardesty's PEG data sheet lists PEG 200, 300, 400 and 600 as clear, colourless liquids at 25 °C with average molecular weights of 190–210, 288–311, 380–420 and 570–630. [2] PCC lists POLIkol 800 (molecular weight 750–850 g/mol) as a paste or solid at 20–25 °C with a solidification point of about 30 °C, [3] and POLIkol 4000 (about 4000 g/mol) as a white to pale yellow solid with a solidification point of about 55 °C. [4] BASF's Pluriol E 8000 bulletin gives an average molecular weight of 8000–9500 g/mol, a melt point of 61 °C, and supply as cast solid, prill or pastille. [5]

The grade also sets the use. BASF lists polyethylene glycols as thickeners, lubricants, mold release agents, defoaming agents, softeners, conditioners, antistats, sizing agents and dispersants, and as feedstock for fatty acid esters. [5] PCC describes POLIkol 800 as having softening, lubricating, wetting and antistatic properties, [3] and POLIkol 4000 as a softening and antielectrostatic agent for household chemicals, ceramics, paper and metal sectors, a binder in dishwasher bars and washing tablets, and a component of water-soluble synthetic machining fluids and heat transfer fluids. [4]

Viscosity is quoted at 99 °C in these sheets, not at 40 °C: 4.0–4.2 cSt for PEG 200, 7.0–8.0 cSt for PEG 400 and 10.8–11.0 cSt for PEG 600, [2] and 750 cSt for Pluriol E 8000. [5] State the temperature with any viscosity limit.

Give the supplier the grade (nominal molecular weight) and the acceptable average molecular-weight range, physical form (liquid, paste, prill, pastille or cast solid), the end use (plasticizer, softener, lubricant, binder, dispersant or intermediate), hydroxyl-value, water, pH and colour limits with test methods, any ethylene glycol, diethylene glycol or 1,4-dioxane limits, regulatory or pharmacopoeia grade needed, packaging, and quantity.

02

Fix the hydroxyl value, water, pH and purity limits

The hydroxyl value tracks molecular weight: Acme-Hardesty lists 550–570 mg KOH/g for PEG 200, 360–390 for PEG 300, 265–295 for PEG 400 and 180–195 for PEG 600; [2] PCC lists 132–148 mg KOH/g for POLIkol 800 [3] and 25–30 mg KOH/g for POLIkol 4000. [4] Water limits differ by form: 0.20% max for the liquid grades, [2] 0.5% m/m max for POLIkol 800, [3] 1.0% m/m max for POLIkol 4000, [4] and 0.1% max for cast solid versus 0.75% max for prill or pastille Pluriol E 8000. [5]

pH is 4.5–7.5 in 5% aqueous solution for the Acme liquid grades and for Pluriol E 8000, [2] [5] 5.0–7.5 in 5% solution for POLIkol 4000 and 5.0–7.5 in 10% solution for POLIkol 800, so the solution strength must be stated. [4] [3] Colour limits are 20–25 APHA max for the liquid grades, [2] 30 Hazen max (25% solution) for POLIkol 800 [3] and 50 APHA max (25% solution) for Pluriol E 8000. [5] For purity, 21 CFR 172.820 limits total ethylene and diethylene glycols to 0.2% by weight, [1] and Acme-Hardesty sets 1,4-dioxane at 10 ppm max. [2]

Editorial calculation: a linear PEG has two terminal hydroxyl groups, so its hydroxyl value is about 2 × 56,100 ÷ Mn mg KOH/g (KOH 56.1 g/mol). For the PEG 400 range of 380–420 g/mol this gives about 295–267 mg KOH/g, for POLIkol 800 at 750–850 g/mol about 150–132 mg KOH/g, and for POLIkol 4000 at 4000 g/mol about 28 mg KOH/g — each close to the listed hydroxyl range, which is why the hydroxyl value is the practical check on the molecular-weight grade. [2] [3] [4]

03

Grade list, certificate, test methods and forms to ask each PEG supplier for

When requesting quotations, ask each supplier for its grade list with molecular-weight and hydroxyl-value ranges, a certificate of analysis, the test methods used, the physical forms and packaging available, and samples.

04

Polyethylene glycol chains, terminal hydroxyls, water, glycols and 1,4-dioxane

The first two rows are linked by arithmetic: a linear PEG carries two terminal hydroxyls, so the hydroxyl value falls as molecular weight rises, from 550–570 mg KOH/g for PEG 200 to 25–30 for PEG 4000. [2] [4]

05

Molecular weight, hydroxyl value, solidification point, water, pH and colour for a PEG order

Three limits only mean something with their test condition: viscosity in these data sheets is quoted at 99 °C, pH in a 5% or 10% solution, and density at 40 °C or 70 °C, so write the condition beside each value. [2] [3] [4]

06

Send the grade, limits and use together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Grade: [PEG 200–8000; Mn range]
Form: [liquid; paste; prill; pastille; cast solid]
Limits: [hydroxyl value; water; pH and solution %; colour]
Purity: [EG + DEG; 1,4-dioxane; regulatory grade]
Use: [plasticizer; softener; lubricant; binder; dispersant]
Supply: [packaging; quantity; CoA]

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