Rubber & Plastics
Material selection for rubber & plastics
In rubber and plastics processing, oleochemicals are used at low dosages but with large effects. They activate vulcanisation, help fillers disperse, reduce melt viscosity and friction, stabilise PVC, and give films antistatic and antifog properties. Because dosages are small, lot-to-lot consistency is what compounders value most.
What the process needs. In sulphur-cured rubber, stearic acid works with zinc oxide as the activator system. It forms zinc soaps in the compound that make zinc available to the accelerator, which speeds up and improves the cure. It also acts as a processing aid and helps disperse carbon black and mineral fillers. Typical additions are around 1–3 phr (parts per hundred rubber). In plastics, stearic acid and its derivatives serve as internal and external lubricants, release agents and dispersing aids. Calcium and zinc stearates are core components of calcium-zinc PVC stabiliser systems and act as acid scavengers in polyolefins. Glycerol monostearate is used as an antistatic and antifog additive, while epoxidised soybean oil (ESBO) acts as a secondary plasticiser and heat co-stabiliser in PVC.
Key specification parameters. For rubber-grade stearic acid, compounders usually look at acid value, iodine value, titre, the C16/C18 ratio, moisture and ash. Higher unsaturation (iodine value) and excess moisture can affect cure behaviour and blooming. Metallic stearates are specified by metal content, free fatty acid, moisture, particle size and melting point. For ESBO, oxirane oxygen and iodine value show how completely the oil has been epoxidised. For dioctyl sebacate, check ester content, acid value and colour.
Recommended product types. Stearic acid in single-pressed rubber grades, commonly traded under codes such as 1801, and in double- and triple-pressed grades for plastics, masterbatches and light-coloured compounds. Zinc stearate and calcium stearate. Glycerol monostearate. Epoxidised soybean oil. Dioctyl sebacate as a low-temperature plasticiser. Hydrogenated castor oil for rheology control.
Documentation. Ask for a specification and a certificate of analysis for each lot, the safety data sheet, and, for food-contact or toy applications, the regulatory statements your market requires, such as compliance with EU food-contact plastics rules. Compliance depends on the grade and the producing site, so ask for the certificate scope with your quotation.
Handling and shipping. Stearic acid is supplied as beads, flakes or powder in 25 kg bags. Beads flow better in automatic weighing systems, while powder disperses faster. Store bags cool and dry, away from heat that causes caking. Metallic stearates are fine powders that can form combustible dust clouds, so control dust, earth handling equipment and follow the safety data sheet. ESBO and dioctyl sebacate are liquids shipped in drums, IBCs or tank containers; keep them sealed to limit moisture pick-up.
Qualifying a new source. Because an additive's effect only shows up in the compound, run a cure-curve (rheometer) comparison or a processing trial alongside the certificate of analysis before switching a stearic acid or stearate source in production.
Products for Rubber & Plastics
Palm Stearic Acid
Palm stearic acid is not pure stearic acid but a graded blend of palmitic and stearic chains, sold by titre. Common grades are 40:60, 50:50 and triple-pressed, and the titre determines hardness, melting point and downstream behaviour.
Hydrogenated Castor Oil (Castor Wax)
Hydrogenated castor oil, supplied as flake or micronised powder, is the direct precursor to 12-hydroxystearic acid, the thickener in most lithium greases. Splitting the wax releases the hydroxy acid that gives grease its structure.
Cardanol (Bio‑Based Phenol)
Cardanol (CAS 37330-39-5) is a renewable phenol distilled from cashew nut shell liquid. It carries a fifteen-carbon unsaturated side chain on the benzene ring, which gives phenolic resins built from it a natural internal flexibility.
Zinc Stearate
Zinc stearate is the zinc salt of stearic acid, a water-insoluble and hydrophobic metallic soap made from palm-derived fatty acid. It is supplied at 10.5-11.1% zinc as powder, beads, flakes or granules.
Calcium Stearate
Calcium stearate is the calcium salt of stearic acid, a water-insoluble metallic soap made from palm-derived fatty acid. It is supplied as white powder at 125, 200 or 325 mesh, and as beads and granules.
Glycerol Monostearate
Glycerol monostearate is a non-ionic emulsifier produced by esterifying glycerol with stearic acid. It is a milky white to pale yellow waxy or powdery solid, odourless and tasteless, freezing point 60-70C.
Epoxidised Soybean Oil (ESBO)
An epoxidised vegetable triglyceride (CAS 8013-07-8) bought on oxirane oxygen content. One of the highest-volume bio-based functional chemicals, and a route into polyols without petrochemical feedstock.
Dioctyl Sebacate (DOS)
A diester of sebacic acid (CAS 122-62-3), the ten-carbon diacid obtained from castor oil. A castor-derived ester used as a synthetic lubricant base stock as well as a low-temperature plasticiser.
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Start with the process and specification
- End use and required material or feedstock
- Critical analytical limits and physical form
- Handling temperature, storage and pack format
- Volume, documentation needs and delivery destination
Confirm the evidence before ordering
Grade, origin and certification are confirmed for each proposed source. A vegetable-derived feedstock is not automatically certified sustainable, pharmaceutical grade or suitable for every application; request the evidence needed for your intended use.
Product illustrations show representative material and packaging. The quotation confirms the actual source, grade, pack size and labelling.
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