Chemical nucleation, a new concept applied to the mechanism of action of organic acid salts on the crystallization of polyethylene terephthalate and bisphenol—A polycarbonate

In this paper, we report differential scanning calorimetry studies of the temperature and molar mass dependences for the primary and secondary crystallization behavior of bisphenol A polycarbonate ...

Influence of structural and topological constraints on the crystallization and melting behavior of polymers: 3. Bisphenol a polycarbonate

In this work, we prepared blends of bisphenol A polycarbonate (PC) and poly(∈-caprolactone) (PCL) in a wide composition range by melt mixing and solution mixing. Two different molecular weights of PCL were used (nominally, 10.000 g/mol, PCL10, and 80.000 g/mol, PCL80). The thermal behavior of both systems was studied via differential scanning calorimetry under dynamic and isothermal conditions. The blends were miscible in the entire composition range in the liquid and amorphous states, as indicated by the single glass-transition temperature (T g ) exhibited by both the PC/PCL10 and PC/PCL80 blends. The compositional variation of the T g was accurately described by the Fox equation for the PC/PCL80 blends, whereas slight deviations from this equation were exhibited by the PC/PCL10 blends. For blend compositions containing 40% or more PCL, either one or both blend components crystallized. Crystallization occurred during cooling from the melt or during subsequent heating in the form of cold crystallization. Although PCL crystallization was reduced and its crystallization rate decreased with the addition of PC, PCL was a very effective macromolecular plasticizer for PC, to the extent that crystallization during the scan was detected for some blend compositions. Isothermal crystallization experiments allowed the determination of equilibrium melting points (T o m ) by the Hoffman-Weeks extrapolation method. A T o m depression was found for both PCL and PC components as the content of the other blend component was increased. The Avrami equation was closely obeyed by both blend components during the isothermal overall crystallization kinetics up to crystalline conversion degrees of 60-70% and with values of Avrami indices ranging from 3 to 4, depending on the crystallization temperature employed.

Thermal characterization of polycarbonate/polycaprolactone blends

The crystallization and melting behavior of bisphenol A polycarbonate treated with supercritical carbon dioxide (CO2) has been investigated with differential scanning calorimetry Supercritical CO2 depresses the crystallization temperature (Tc) of polycarbonate (PC) The lower melting point of PC crystals increase nonlinearly with increasing treatment temperature This indicates that the depression of Tc is not a constant at the same pressure Tc decreases faster at a higher treatment temperature than at a lower temperature The leveling off of the depression in Tc at higher pressures is due to the antiplasticization effect of the hydrostatic pressure of CO2 The melting curves of PC show two melting endotherms The lower melting peak moves to a higher temperature with increasing treatment temperature, pressure, and time The higher temperature peak moves toward a higher temperature as the treatment temperature is increased, whereas this peak is independent of the treatment pressure, time, and heating rate The double melting peaks observed for PC can be attributed to the melting of crystals with different stability mechanisms © 2003 Wiley Periodicals, Inc J Polym Sci Part B: Polym Phys 42: 280–285, 2004

Effect of supercritical carbon dioxide on the crystallization and melting behavior of linear bisphenol A polycarbonate

Concentration dependence of crystallinity of polycarbonate by shock-cooling and subsequent freeze-drying of its various solutions

This paper concerns the action of plasticizers and nucleating agents on the crystallization of bisphenol-A polycarbonate. The influence of plasticizers is to increase the rate of crystallization to a great extent using 10 percent of a plasticizer such as trimellitic acid, tridecyloctyl ester. The influence of nucleating substances on plasticized and undiluted polycarbonate is investigated. A large number of substances have been found capable of nucleating polycarbonate crystallization. The un-plasticized semi-crystalline polycarbonate is characterized by a much higher melting point (300°C) than the plasticized semi-crystalline systems (210–245°C). The stability of bisphenol-A polycarbonate in the presence of nucleating salts is also examined. We observe a substantial decrease in the molecular weight in the presence of a great number of nucleating substances. The modulus-temperature curves of two semi-crystalline polymers are reported in the last series of experiments.

R. Legras

Papers

Some new aspects of the crystallization of bisphenol-A polycarbonate