ABSTRACT
Small particles are used for reinforcing fillers in elastomers and thermoplastics.1-7 These include synthetically prepared carbon black, silica and zinc oxide, as well as naturally occurring calcite, clay, and talc. These particles are commercially available in various sizes. Many particles are quite small, on the order of 0.01 µm (or 10 nm) but others are on order of 0.1 µm. The tire industry, in its early years, used primarily zinc oxide as a reinforcing filler. The industry then began using carbon black.8 Recently, attention has been given to silica as particle reinforcement because it lowers rolling resistance, thus causing lower fuel consumption.9 Carbon blacks have been traditionally used in tire manufacturing industry because of their reinforcing effect when mixed into elastomers. Today, small amounts of zinc oxide are retained in rubber compounds for their ability to enhance vulcanization/
CONTENTS 7.1 Introduction ........................................................................................................................ 123
7.1.1 Nanoparticles ......................................................................................................... 124 7.1.1.1 Carbon Black1, 3, 6, 7, 10 ................................................................................ 124 7.1.1.2 Silica4, 5, 10-18 ............................................................................................... 125 7.1.1.3 Zinc Oxide (ZnO) .................................................................................... 129 7.1.1.4 Titanium Dioxide .................................................................................... 130 7.1.1.5 Talc ............................................................................................................ 130
7.1.2 Processing Equipment ........................................................................................... 130 7.1.3 Dispersion Problems with Small Particles ......................................................... 131
7.2 Rubber-Nanoparticle Compounds .................................................................................. 132 7.2.1 Particle Dispersion and Agglomerate Characteristics upon Processing ....... 132 7.2.2 Processability ......................................................................................................... 138 7.2.3 Extrusion Characteristics ..................................................................................... 140
7.3 Further Comments on Processing ................................................................................... 143 7.3.1 Intermeshing vs. Banbury Mixer40 ...................................................................... 143 7.3.2 Ultrasound Extruder Processing ......................................................................... 144 7.3.3 Particle Effects on Mechanical Properties of Elastomer Vulcanizates ........... 144
7.4 Conclusions ......................................................................................................................... 146 References ..................................................................................................................................... 147
cross-linking processes involving sulfur. Titanium dioxide has also been used for white tire sidewalls.
