4-Methylbenzophenone

Updated: 2026-07-15

Overview

4-Methylbenzophenone is an aromatic ketone derivative primarily valued for its role as a Type II photoinitiator in UV-curing applications. As a member of the benzophenone family, it exhibits strong absorption in the 250-350 nm UV range, making it effective for initiating polymerization reactions when exposed to UV light sources. The compound was first synthesized in the early 20th century but gained industrial significance with the development of UV-curable technologies in the 1970s. Today, it accounts for approximately 15-20% of the photoinitiator market share in Asia-Pacific regions, particularly for cost-sensitive applications where its balance of performance and economics is advantageous.

Physical and Chemical Properties

The crystalline structure of 4-methylbenzophenone gives it moderate melting characteristics (57-60°C), which facilitates handling in industrial processes. Its conjugated aromatic system provides excellent UV absorption properties, with a molar extinction coefficient of ~15,000 L·mol⁻¹·cm⁻¹ at 280 nm. Chemically, it demonstrates typical ketone reactivity including participation in Grignard reactions and nucleophilic additions. The methyl group at the para position enhances its solubility in common organic solvents compared to unsubstituted benzophenone, while maintaining sufficient thermal stability (decomposition >250°C). This makes it suitable for formulations requiring moderate curing speeds and good shelf stability.

Main Applications

In UV-curable coatings, 4-methylbenzophenone serves as a surface-curing agent, particularly effective for clear coats and thin film applications. It synergizes well with tertiary amine co-initiators to achieve complete curing within seconds under medium-pressure mercury lamps (output 300-400 nm). The printing industry utilizes it in offset and flexographic UV inks, where its balanced reactivity prevents excessive crosslinking that could compromise ink flexibility. Emerging applications include dental composites and 3D printing resins, where its ability to initiate polymerization at relatively low UV intensities (50-100 mW/cm²) proves advantageous for precision curing processes.

Safety and Storage

As a Category 2 skin irritant (GHS classification), handling requires nitrile gloves and protective eyewear. The powder form presents inhalation risks (PEL 5 mg/m³), necessitating local exhaust ventilation during bulk handling. Spills should be contained with inert absorbents rather than water, due to hydrophobic properties. For long-term storage, maintain temperatures below 30°C in amber glass or HDPE containers with nitrogen blanket when possible. Shelf life typically exceeds 24 months when protected from moisture and UV exposure. Incompatibilities include strong oxidizing agents and concentrated mineral acids, which may cause exothermic decomposition reactions.

B2B Procurement Guide

Industrial buyers should specify technical grade (≥98% purity) with maximum limits for residual solvents (<0.5%) and heavy metals (<10 ppm). Batch certificates should include HPLC purity analysis and UV absorbance spectra for quality verification. Bulk shipments (500kg+ drums) typically offer 10-15% cost savings versus small packaging. Leading manufacturers are concentrated in China (60% global capacity), Germany and India. For regulatory-sensitive applications, request REACH/ECHA compliance documentation. Just-in-time procurement is recommended due to price volatility in benzene derivative markets.