Page 33 - Curriculum Visions Dynamic Book

Nylon “thread” is pulled through the upper liquid.
Branched chain polymers will not soften or melt at all without decomposing (They are the ones that char when too hot an iron is applied to them.) Acrylics are an example. In this case the polymer cannot be melted in order to spin it. Instead, it must be dissolved and then spun from a solution.
Both kinds of polymer can be made into liquids that can be extruded through fine holes to form filaments. This makes them very suitable for mass production.
Furthermore, these long chains have great strength, so that they will not break easily even when formed into thin fibres.
Not all long-chain polymers make useful fibres. That is because the fibres have to have quite high melting points; otherwise they will melt when they are ironed. At the other end of the scale, if the melting point is too high, it will be hard to melt the polymer in the factory in order to spin it.
The differences in temperature can be quite critical, as anyone who has ironed a synthetic fabric at too high an iron setting will know to their cost. Polypropylene,
for example, has a melting temperature
of 176°C. It is used as fibres in clothing, upholstery, and carpet fabrics. A closely related polymer, polyethene, however, has a lower melting temperature at 137°C, too low for use in most domestic fabrics.
Polyesters are a group of easily made and cheap synthetic fibres. Terylene® is
an example. It has a higher melting point (265°C) than polypropylene but is still easy to work with. Nylon also has a melting point of 265°C, again, making it easy to work with and spin from molten form.
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