The structure of a polymer – trying to imagine it – is similar to a skein: in semi-crystalline materials, there are organized domains that are repeated within the structure. Considering that they are made up of two phases, semi-crystalline are characterized by two temperatures: the Tg (glass transition temperature), concerning the amorphous part, and the Tm, that is the melting temperature concerning the crystalline part.
Properties of crystalline polymers compared to amorphous materials:
- better chemical resistance;
- better abrasion and wear resistance;
- better stress resistance;
- generally higher continuous operating temperature (they can be used at temperatures that are higher the Tg);
- more elastic return after deformation;
- more resistance against atmospheric agents.
However semi-crystalline polymers, because of the presence of two phases, are characterized by:
- absence of transparency;
- higher coefficient of linear thermal expansion and less dimensional stability;
- more shrinkage during the cooling phase (because of the difference in density between the crystalline phase and the polymer at molten state);
- greater dependence of the elastic modulus on temperature.
PEEK is a semi-crystalline thermoplastic polymer with great performances, the most advanced among semi-cristalline materials, thanks to its mechanical properties and the amazing chemical resistance, even in high temperature conditions (up tp 200°C) and in corrosive environments. The Roboze 3D printers with FFF technology take advantage of this technical material with high performance in terms of mechanical, thermal and chemical resistance on extrusion additive manufacturing systems, managing to meet every kind of market’s need, even the most extreme one.
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