General Design

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Ticona offers a range of thermoplastics materials for engineering applications. Our product range includes semi-crystalline, amorphous and liquid crystal polymers. In semi-crystalline polymers, the nature of the polymer chain is such that it can fold up into ordered structures such that a crystalline, i.e., relatively sharp, melting point is seen.  Since amorphous polymers do not manifest a melting point, from the engineering point of view their most important temperature parameter is the glass transition temperature, Tg. Above this temperature, amorphous polymers become more or less soft and rubbery, while below Tg, they are hard and glassy. Liquid crystal polymers have the distinctive property of maintaining a degree of crystalline organization even in the melt.  As many of the mechanical, physical and chemical property differences between plastics can be attributed to their strictures, it is important for designers to know what kind of material they are designing for.

In general, semi-crystalline and liquid crystal thermoplastics are stiffer, stronger, and have better chemical and temperature resistance than their amorphous counterparts. Their time-dependent properties, such as creep and fatigue behavior, are usually better than those of amorphous materials, but they usually require higher melt temperatures for processing, tend to shrink and warp more, and have lower impact resistance.

There are many considerations to take into account when selecting a plastic material for an application.  To help make this choice a systematic process, we recommend using our Design Checklist when choosing a thermoplastic material for your application. After having narrowed down the choice of material, there are two very basic rules to consider in the actual part design – avoid sharp corners and keep wall thickness as uniform as possible. Properly radiusing corners, the roots of threads, and other angles avoids the creation of notches that act as stress concentrators from which failures can originate.  Uniform wall thickness helps to prevent problems with differential shrinkage and warpage.