Home Education Fillers for Polymer Applications
The PMMA referred to here is a lightly cross-linked form (hence thermoset). PMMA is a relatively expensive polymer and is mainly used for its clarity and transparency. Thus it is mainly used unfilled. Even so, the optical properties can be put to good effect in making highly filled products that simulate the appearance of polished minerals. This is made use of in solid surface applications. In Europe the main fillers used for this application are hard ones such as cristobalite, with relatively small amounts of soft ATH being used. North America and Japan both have a strong liking for what is known as synthetic or cultured marble and onyx for which ATH or calcium carbonate is widely used to obtain the required appearance.
The phenolic market is a specialized one and mainly uses natural calcium carbonates and hard fillers. Where fire retardancy is important, ATH is often used.
The main epoxy market making use of particulate fillers is in printed circuit boards, which require fillers that impart high thermal conductivity, while being electrically non-conductive. Alumina, magnesia, and specialized aluminosilicate fillers are used. There is also some use in flooring and solid surface applications which use hard fillers such as quartz.
While large total amounts of thermoset polyurethanes are used, much of this is for foam production where fillers are little used. There is some use of fillers in polyurethanes in footwear, but these are mainly elastomeric types of polyurethane. The main filler use in thermoset polyurethanes is for fire retardance, and this can be achieved by addition of fillers such as ATH or expandable graphite.
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