Palm Stearic Acid — Frequently Asked Questions

Most rubber compounders use a single-pressed or rubber grade, often traded as 1801. In rubber, stearic acid mainly activates zinc oxide in sulphur vulcanisation and helps disperse fillers, and a little residual unsaturation has little effect on the cure. Light-coloured or high-specification compounds may need a double- or triple-pressed grade. Whichever grade you choose, run a rheometer cure-curve comparison before switching source, because differences in moisture and in the C16/C18 ratio can shift scorch and cure times.

No. Palm stearin is the solid fraction of palm oil and is still a triglyceride, with the fatty acids bound to glycerol. Stearic acid is the free fatty acid obtained after the fat has been split, hydrogenated and distilled. The candle trade sometimes calls stearic acid stearin, which causes confusion. The acid value tells them apart: around 205–212 mg KOH/g for stearic acid, but very low for refined palm stearin.

Less than it seems. 1842 is a trade convention that is usually offered as a triple-pressed grade, and the last two digits are often read as an approximate C18 content of around 42%. Grade codes are not standardised, though, and different producers use the same code for slightly different products. Compare the iodine value, colour, titre and C16/C18 composition on the specification rather than relying on the code alone.

Palmitic and stearic acids crystallise together, and their ratio controls how the blend solidifies. Two triple-pressed lots with the same iodine value can therefore behave differently. In vanishing creams the ratio affects pearlescence and texture. In candles it affects crystal structure, hardness and surface finish. In rubber it slightly changes the melting behaviour and bloom. Where texture or crystallisation matters, specify a C16/C18 range as well as the grade.

Beads flow freely and suit automatic weighing and dosing systems. Flakes are the most common form, economical and easy to melt. Powder disperses fastest in dry blends and cold processes, but it is dusty and needs dust control, because fine fatty-acid dust can form combustible clouds. Large continuous users with heated storage can take molten product in tankers, which avoids melting on site. The chemistry is the same in every form, so choose on handling and dosing.

Cosmetic formulators normally use a triple-pressed grade with low colour and odour, listed under the INCI name Stearic Acid. Pharmaceutical grades must meet a pharmacopoeia monograph, such as the Ph. Eur. types 50, 70 and 95 or the USP-NF monograph, and food use falls under E 570. These grades need documents that cover the specific product and manufacturing site. State the intended use in your enquiry so that the specification, certificate of analysis and certificate scope can be checked against it.