Fabrication of crystalline articles of aromatic polycarbonate by hot powder-compaction

Polycarbonate is well known for forming amorphous, transparent, and exceptionally tough articles by conventional methods such as injection molding and extrusion. It is not possible to extrude polycarbonate from the melt into crystalline, shaped articles. A novel method to fabricate crystalline polycarbonate articles from acetone-crystallized powder was devised. The method was adapted from powder metallurgy and it involved compacting acetone-crystallized polycarbonate powder above the glass transition temperature (Tg) and below the melting peak temperature (Tm). The hot powder-compaction process yielded shaped articles, which retained the crystallinity of the original polycarbonate powder. Although the crystallinity of the powder and the articles was less than 20%, surprisingly the articles were non-sticking above the Tg and so could be released from the mold at the compaction temperature. Furthermore, the crystalline polycarbonate articles had a Vicat softening temperature above 180°C, excellent shape and dimension retention above Tg, increased hardness, as well as resistance to acetone and other solvents. That is, the properties were different from those of conventional amorphous polycarbonate articles. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers