Context

Incorporating mineral fillers into polymers is a commonly used process to improve their mechanical, chemical or optical properties. Silica nanoparticles are the most used in polymers reinforcing. Due to their hydrophilic surface, these particles are modified with bifunctional silane to form a chemical bond between the nanoparticles (using the ethoxysilane moieties) and the polymer matrix (using the sulfur group). The composite material is obtained by a reaction triggered by heat (for example 170 °C in the case of vulcanization). For the fabrication of materials incompatible with heat or sulfur, the process relies more and more on photopolymerization. Incorporation of silica to improve mechanical properties of the materials is possible, but up to now the silica/polymer coupling remains low.

This invention reveals a new generation of photoinitiators combining a grafting group and a photoinitiator, contrary to current coupling agents comprising only the grafting group.

Technical description

The photoinitiators of the invention are made of a bifunctional silane (type SPI-1, Silane-based photoinitiator) grafted on the silica nanoparticles used as mineral filler in the to-be-formed polymer.

The surface of the modified silica nanoparticles becomes hydrophobic, allowing a better dispersion of the filler in the polymer matrix. After photopolymerization, the bond between the silica nanoparticles and the polymers is strong, leading to durable composite materials.

Development stage

Several chemical structures obtained, to adapt the molecules to the wavelength of the UV-visible light source used in the photopolymerization process.

Gram-scale production.

Benefits

• Better silica dispersion
• Improved stability / durability of the composite materials

Industrial applications

Photopolymerizable resins and polymers

Materials for dental applications

Photopolymerizable inks

Additive manufacturing / 3D printing

Medical devices