Measuring Thermal Crystallinity in PET
The mechanical properties of poly (ethylene terephthalate) (PET) depend on the degree of crystallinity. PET crystallizes from both thermal and strain-induced process paths. Strain-induced crystallization occurs under uniaxial or biaxial stretching, the latter is common in stretch blow molding. Thermal crystallization takes place when cooling from the melt or under sustained elevated temperature which are both common during injection and blow molding. The current work focuses on comparing methods used to quantify the percent thermal crystallinity in injection molded water bottle preforms. An injection molded preform with a gradient of induced thermal crystallinity was examined using Differential Scanning Calorimetry (DSC), Micro X-ray Diffraction (μXRD), and Raman Spectroscopy. Correlating these three techniques for percent thermal crystallinity, helps with the development of nondestructive crystallinity measurement methods to aid with process optimization and part quality.
Determination of phthalate acid esters plasticizers in polyethylene terephthalate bottles and its correlation with some physicochemical properties
Abstract A method for the analysis of phthalic acid esters or phthalates (PAEs) in polyethylene terephthalate (PET) bottles based on the use of microwave-assisted extraction (MAE) and liquid chromatography with UV detection (LC-UV) was developed. The microwave-assisted extraction procedure was optimized by a three factors Box–Behnken response surface design. High PAEs recoveries were obtained by microwave-assisted extraction using 70% of acetonitrile at 140 °C during 30 min. Moreover, some physical properties of PET samples as thickness, and crystallization and melting temperatures were determined by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. Those parameters were correlated, through Pearson correlation coefficient, with the content of PAEs determined in PET containers (dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP)) and with the content of PAEs in water obtained from a migration test in PET. The migration procedure was based on a standardized procedure (EU 82/711/EEC and 85/572/EEC directives) stipulated by the European Union (EU). The concentrations of PAEs found in PET bottles were between 1.1 and 14.8 mg kg−1 for DMP, 9.3 and 63.6 mg kg−1 for DBP and DEP was only detected in one of the 10 analyzed samples at a concentration of 3.1 mg kg−1. The analysis of the samples obtained by applying the migration test showed that DBP was found in five of the ten analyzed samples reaching concentrations from 14.5 up to 25.6 μg L−1. DMP was found in five of the ten analyzed samples, with concentrations from 4.1 to 50.6 μg L−1, whereas DEP was not detected in any of the analyzed samples. The results of the Pearson correlation coefficient indicated that there was a significant correlation between the thickness and the total concentration of PAEs in the PET samples (95% confidence interval), as well as the DBP content in PET samples and the concentration of DBP migrated from bottles to the water (90% confidence interval), indicating that the content of PAEs in the samples and the migration rate of these compounds was related to the physical characteristics of PET bottles.
Solidarity. Reflections on an Emerging Concept in Bioethics. Summary
1. References to solidarity are currently on the increase in public discourse. In the UK and beyond, during economic crises and in a political climate where many feel that mutual assistance has lost currency, calls for a new and forceful emphasis on the meaning of solidarity are increasingly heard. Such appeals to solidarity are inevitably linked to ideas about how societies function, and about how and where the boundary between individual, familial, communal and societal spheres of responsibilities should be drawn.