Effect of Recycling on the Rheological, Mechanical and Optical Properties of Polycarbonate
The research was aimed at analyzing the polycarbonate scrap arising during production and its possible secondary utilization. The analysis of morphological, rheological and thermal data revealed significant differences between the original pellets and the reground material obtained from injection molded parts. Test specimens were injection molded from various mixtures of the virgin and the reground material, and their mechanical and physical properties were analyzed. Based on the results the reground material may be used in less than 20% proportion, as the mechanical properties of the products do not deviate significantly from those of the products made from virgin polycarbonate.
Effects of moisture exposure on the mechanical behavior of polycarbonate materials used in electronic packaging
The mechanical properties of polymer materials are often a key concern of the microelectronic packaging industry. The theoretical analysis of stress, strain, and deformation induced in electronic assemblies due to environmental exposures such as moisture adsorption, isothermal aging, and thermal cycling require the complete characterization of mechanical properties and constitutive behavior of the constituent materials. In this work, an experimental investigation has been performed on the effects of moisture adsorption on the stress-strain behavior of polycarbonate materials used in electronic packaging. Uniaxial test specimens were exposed in a controlled temperature and humidity chamber to combined hygrothermal exposures at 60 C and 90% RH, 60 C and 50% RH, and 40 C and 50% RH for various durations. After moisture preconditioning, a microscale tension-torsion testing machine was used to evaluate the complete stress-strain behavior of the material at several temperatures (T = 20 C, 40 C, and 60 C). It was found that moisture exposure strongly affected the mechanical properties of the tested polycarbonate, especially ultimate strain limit. Reversibility tests were also conducted to evaluate whether the degradations in the mechanical properties were recoverable. Upon fully redrying, the material was found to recover most of its original mechanical properties. In addition, optical microscopy was utilized to examine the fracture surfaces of the failed specimens, and observe the influence of moisture exposure.
Self-assembly of pyridinium-tailored anthracene amphiphiles into supramolecular hydrogels.
The mixing of a polyacid cross-linker with a pyridinium-functionalized anthracene amphiphile afforded a supramolecular hydrogel through a self-assembly process that was primarily driven by π-stacking and electrostatic interactions.