What is the main uses of stearic acid ?

Stearic acid is a common fatty acid. At room temperature, it appears as a white waxy solid with a slight luster and an animal fat odor. This substance is widely present in nature and can be found in animal fats and vegetable oils. In industrial production, it is mainly extracted from butter and palm oil. Due to its stable chemical properties and unique physical characteristics, it plays an important role in multiple fields.

It is the most widely used in the industrial manufacturing field. In plastic products workshops, stearic acid is a commonly used lubricant and mold release agent. It is sprayed on the surface of the mold during injection molding, which not only helps the plastic flow smoothly but also enables the finished product to easily dette from the mold. Rubber tire factories often use it as an active agent, which can better cross-link rubber molecules and enhance the anti-aging performance of tires. When the foundry workers prepare the sand molds, they will add an appropriate amount of stearic acid to improve the air permeability of the molding sand, making the metal liquid flow more smoothly during casting and the surface of the castings smoother.

Stearic acid is indispensable in daily chemical products. In the cosmetics laboratory, technicians use it to make ice cream and cold cream. When the stearic acid content in the formula table reaches 15%, the cream will present a beautiful pearlescent effect. On the production line of a soap factory, workers mix stearic acid and sodium hydroxide for saponification. The resulting sodium stearate can produce rich foam. All the experienced workers in candle workshops know that adding 5% to 10% stearic acid can prolong the burning time of paraffin candles and prevent the candle tears from dripping.

The food processing industry has strict usage standards. In the chewing gum production workshop, it serves as a gum base component to keep the product with an appropriate chewiness. During the temperature adjustment process in a chocolate factory, stearic acid helps cocoa butter form a stable crystal structure, and a crisp sound can be heard when it is broken open. According to the national standard GB2760, the maximum usage of stearic acid in food shall not exceed 15 grams per kilogram. Quality inspectors will conduct regular spot checks to ensure compliance.

The application in the medical field emphasizes purity. In the sustained-release capsules, the outer layer of the drug is wrapped with a stearic acid film. This protective film does not dissolve when exposed to gastric acid and only gradually releases its efficacy in the intestines. Magnesium stearate is a commonly used lubricant in the tablet workshop during tablet pressing, which enables the powder to pass smoothly through the tablet press mold. In the base of medical ointments, the soap base formed by its reaction with sodium hydroxide not only ensures the stability of the ointment but also promotes skin absorption.

Agricultural production also has special uses. When making powder in the pesticide workshop, adding a trace amount of stearic acid can enhance the adhesion of the powder on the plant leaves. When a fertilizer factory produces granular fertilizer, spraying stearic acid solution can form a waterproof film on the surface of the fertilizer granules, preventing them from caking. Agricultural technicians guided fruit farmers to spray stearic acid water solution on the surface of citrus fruits, which can form a protective film on the fruit skin and extend the freshness period by about 20 days.

The application in emerging fields is constantly expanding. On the lithium battery production line, the surface of the cathode material is coated with a stearic acid film, effectively suppressing capacity attenuation during the battery’s cycling process. In the 3D printing material research and development laboratory, engineers discovered that adding stearic acid could improve the flow performance of PLA material, making the interlayer bonding of printed parts tighter. Environmental-friendly coating enterprises are conducting experiments on water-based resins modified with stearic acid. Preliminary data shows that the number of times they can withstand scrubbing has increased by three times.

In the quality control stage, inspectors determine the purity through acid value measurement. The acid value range of qualified products is between 196 and 210mgKOH/g. Ash content testing can reflect the content of metal ions. For pharmaceutical-grade products, the ash content should not exceed 0.05%. The melting point is detected by the capillary method. The pure product should be completely melted at 69.6℃. These strict tests ensure that users in different industries receive products that meet the standards.