Crystallization of bisphenol‐A polycarbonate induced by organic salts; physical aspects. I. Crystallization rate, melting behavior, and morphology

Abstract

SynopsisThe presence of organic acid salts in bisphenol-A polycarbonate (PC) completely modifies the crystallization mechanism, the melting behavior, and the morphology of the polymer. Organic salts are not ordinary nucleating agents for PC since they react with the polymer, producing metal phenoxide chain ends. On reaction, abundant instaneous nucleation is induced. The seeds are likely to be polymer crystalline fragments preexisting in the melt. The phenoxide chain ends significantly increase the growth rate of the crystalline phase. Melting points and enthalpies of fusion are unusually high, suggesting a high degree of crystalline perfection. Thick multilamellar crystals, which are likely to contain chains in extended configuration, are observed by electron microscopy. No trace of spherulitic morphology is found. The chemical instability of PC containing ionic chain ends is also shown to seriously affect the crystallization rate, the maximum degree of crystallinity, and the melting point.

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

“…Crystallinities over 50% were reached but unfortunately, with a reduction in the molecular weight. The authors stated that the PC crystals created with this nucleating agent did not have much interconnectivity (few tie molecules). We repeated this method, compounding PC with sodium o‐chlorobenzoate, to make highly crystalline PC for powder compaction, but found it made the PC extremely weak and brittle.…”

“…While this showed that PC could potentially crystallize from the melt, the molding did not possess uniformity, with crystallinity appearing only in a thin skin‐layer, and not in the core of the article. Bailly et al showed the crystallization kinetics of PC can be accelerated by organic salts like sodium o‐chlorobenzoate which act as “chemical nucleating agents” and reduce the crystallization half time of PC from 12.5 days to minutes. Crystallinities over 50% were reached but unfortunately, with a reduction in the molecular weight.…”

“…Bailly et al showed the crystallization kinetics of PC can be accelerated by organic salts like sodium o‐chlorobenzoate which act as “chemical nucleating agents” and reduce the crystallization half time of PC from 12.5 days to minutes. Crystallinities over 50% were reached but unfortunately, with a reduction in the molecular weight. The authors stated that the PC crystals created with this nucleating agent did not have much interconnectivity (few tie molecules).…”

Growth of Spatial Dendrites in Bisphenol-A Polycarbonate Induced by Dioctyl Phthalate at High Pressure

“…Many studies on the crystallization behaviors of BAPC have been reported, including bulk crystallization [3], solvent-induced and vapor-induced crystallization [2,4], effects of nucleating agents [5][6][7][8] and supercritical carbon dioxide [9,10] on crystallinity and crystallizability in polymer blends [11]. However, to the best of our knowledge, no investigation was performed on the morphology of high-pressure crystallized BAPC samples.…”

Transitions of morphological patterns of crystallizing polycarbonate in thin films

“…The thermal annealing is a very slow crystallization process (>100 h at 170–205°C) because of the rigidity of polymer backbone that hinders the rearrangement of the polymer molecules to an ordered crystalline structure 1, 2. BAPC can be rapidly crystallized by SINC using plasticizing solvents,3 nuclear agents,4 organic liquids,5 organic vapors,6 and super critical carbon dioxide 7. The other methods such as the wet‐drawn process8 and high‐pressure molding9 are also often used to crystallize polycarbonates.…”