engleski

Influence of colloidal silica particle size and surface modification on the properties of polyacrylate

With modification of the filler surface, different morphologies of composite particles could be achieved. The aim was to obtain good dispersion of the filler in polymer matrix. In this work polyacrylate (PA) systems with 10% mass of colloidal silica with particle sizes 12, 25 and 50 nm were prepared. Surface of the filler was modified nonionic emulsifier, cationic initiator AIBA and silane MPS. Particle sizes of PA+silica systems were investigated with laser diffraction, rheological properties with rotational rheometer and particle morphology with scanning electron microscope (SEM). Thermal properties of films prepared from synthesized emulsions were investigated with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Mechanical properties of the films were determined by tensile test on a mechanical testing machine. PA systems in which silica surface is unmodified and modified with nonionic emulsifier and cationic initiator AIBA have particles in micrometer sizes, while system in which silica surface is modified with silane MPS has particles in nanometer sizes. SEM analysis showed that composite particles in which silica surface is modified have irregular shapes with homogeneous surface regardless of composite particles in which silica surface is unmodified. Lowering the particle size causes increase in polyacrylate emulsion viscosity regardless of silica surface modification. In systems with the same particle size of silica but different surface modification, systems with unmodified silica surface have the lowest viscosity. Thermal analysis results showed that the addition of 10% of colloidal silica with different particle sizes and surface modification have no influence on polyacrylate Tg, reduces T95, but at higher temperature increases PA thermal stability. Addition of 10% of colloidal silica increased polyacrylate strength at break and elongation at break for all silica particle sizes and surface modifications.

in situ, emulsion polymerization, polyacrylate, silica nanofiller, particle size

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