Making a Rapid Completion of Crystallization for Bisphenol A Polycarbonate by a Double-Layer Film Method

Abstract

Bisphenol A polycarbonate (PC) is difficult to crystallize. In this study, it was found that PC could rapidly accomplish melt crystallization only within 8 min by laying poly(ethylene glycol) (PEG) film on it. Polarized optical microscope (POM) was applied to trace the growth of spherulites of PC in PEG/PC double-layer films during isothermal crystallization in a wide range of temperatures, which were above the melting temperature for PEG. The dependence of spherulitic growth rate (G) on isothermal crystallization temperature (T c ) followed a "bell-shape" curve, just like some other semicrystalline polymers did. A PEG film was laid on a PC film at 250 °C for 5 min to obtain a PEG/PC double-layer film, which was subsequently quenched to different T c 's for observation on its crystallization process by using POM. It was surprising to observe that the spherulitic growth rate of PC was significantly improved and the crystallization time was obviously shortened. The miscibility for PEG/PC blends was evaluated by applying differential scanning calorimetry (DSC), which played a crucial role in the crystallization accelerating effect. This method provides an operative way to surmount the particular disadvantages of PC, such as very slow crystallization rate and harsh conditions that PC needs to crystallize in the film processing.

Effective enhancement of poly(bisphenol-A carbonate) crystallinity with polyamide-66 ionized nucleation through ion-dipole interactions coupled with plasticization

“…For instance, common PC plasticizers include organic solvents such as acetone [20][21][22], carbon tetrachloride [23,24], tetrahydrofuran [24,25], ethyl acetate [26], chloroform [27], and supercritical CO 2 (SCCO 2 ) [28,29] can enhance the free volume and movement of PC molecular chains, and promote the ordering of molecular chanis into regular helica segments, which serve as crystal nuclie to initiate PC crystalization. Similarlly, flexible polymers such as polycaprolactone [30,31], polyethylene glycol [32], epoxy resins [33], esters such as diallyl phthalate [34], tributyl citrate [35,36], and small molecule liquid crystals such as cholesterol nonanoate (CN) [37,38] enhance the flexibility of PC to alevate the crystal growth. In addition, plasticizers are coupled with nucleating agents to achieve the modification in a greener, efficient, and environmentally friendly way.…”

Rapid Melt Crystallization of Bisphenol-A Polycarbonate Jointly Induced by Pressure and Flow

“…The topic of PC crystallization is interesting, and some efforts have been dedicated to inducing PC crystallization by improving its chain flexibility such as adding plasticizers and special chemical nucleating agents, − blending flexible polymers, , and employing the solvents with plasticization effects (e.g., supercritical CO 2 , and organic solvent vapors). However, it remains elusive to accelerate pure PC melt crystallization under the conditions analogous to actual polymer processing that involve pressure and flow. − Flow-induced crystallization has been overwhelmingly studied on flexible polymers, such as polyethylene and isotactic polypropylene (iPP). − Some consensus has been reached in understanding flow-induced crystallization.…”