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Untreated Precipitated Silica

Updated: 2026-08-22

Overview

Untreated precipitated silica is a synthetic, porous form of silicon dioxide produced through the reaction of sodium silicate with sulfuric or hydrochloric acid. Unlike fumed silica, it is manufactured via a wet process, resulting in a cost-effective material with high surface area and reinforcing properties. Primarily used as a performance additive, it enhances mechanical strength, viscosity, and durability in elastomers, plastics, and coatings. Its untreated form lacks surface modifications, making it suitable for applications where chemical inertness is critical.

Physical and Chemical Properties

Untreated precipitated silica exhibits a highly amorphous structure with a typical surface area of 50-400 m²/g, depending on production parameters. Its porosity and particle size distribution (5-100 nm aggregates) contribute to its effectiveness as a thickening and anti-settling agent. Chemically inert and thermally stable, it resists decomposition below 1,600°C. The material is hydrophilic due to surface silanol groups, which can be modified for specialized applications. Its refractive index (~1.46) allows for transparent formulations in coatings and adhesives.

Main Applications

In the rubber industry, untreated precipitated silica is a key reinforcing filler for tires, shoe soles, and industrial rubber goods, improving tensile strength and abrasion resistance. It reduces rolling resistance in 'green tires,' enhancing fuel efficiency. The plastics sector uses it to modify rheology and reduce shrinkage in thermosets. In coatings and inks, it acts as a matting agent and anti-settling aid. Personal care products like toothpaste leverage its mild abrasiveness, while food-grade variants serve as anti-caking agents.

Safety and Storage

While non-toxic, untreated precipitated silica requires handling precautions due to its fine particulate nature. Prolonged inhalation may cause respiratory irritation; NIOSH-approved dust masks are recommended during bulk processing. Store in sealed containers away from moisture to prevent clumping. Bulk bags should be kept on pallets in ventilated areas. Spills can be swept up mechanically—avoid water jets to prevent airborne dispersion. Disposal follows local regulations for inert materials.

B2B Procurement Guide

Industrial buyers should prioritize specifications like BET surface area (e.g., 150 m²/g for rubber vs. 50 m²/g for plastics), pH (typically 6-8), and loss on drying (<5%). Request certificates of analysis (CoA) for heavy metal content if used in food-contact applications. Suppliers in China (e.g., Fujian, Shandong provinces) dominate production, with capacities exceeding 1 million tons annually. MOQs for bulk purchases start at 1 ton, with discounts for 20+ ton orders. Sample testing is advised to verify compatibility with existing formulations.

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