Research Seminar #5, Jul 11, 2012, 14h30-16h
1. Solubilidade de hidrofluorocarbonetos em solventes aromáticos e álcoois: valores experimentais e modelização com a equação de estado de CPA
José M. de Sousa
CIEPQPF, DEQ-FCTUC, Thermodynamics & Thermophysical Properties of fluids Group
Hydrofluorocarbons (HFCs) are anthropogenic substances that have exceptional and unique physical and chemical properties. They have found widespread use in practical applications such as refrigerants, aerosol propellants, plastics, pharmaceuticals, oils, pesticides and others.
In the last decades, the HFCs have been used to replace the stratospheric ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) due to the substitution of the chloride atom by fluorine, which originates “green refrigerants”, with low ozone depletion potential, less inflammables and lower toxicity.
In this study new experimental data of gas solubility of hydrofluorocarbons (CH3F, CH2F2, CHF3 and CF4) in aromatic solvents (benzene, toluene, m-xylene, mesitylene) have been determined in the temperature range [288, 308] K and at atmospheric pressure.
The gas solubility data of the hydrofluorocarbons in aromatic solvents and in lower alcohols obtained in previous work were correlated with the CPA EoS, a cubic equation which incorporates an association term. The hydrofluorocarbons and aromatic solvents were treated as non-associated compounds and the alcohols as self-associated compounds.
2. New Modifeid Fillers for Papermaking
Ana F. Lourenço
CIEPQPF, DEQ-FCTUC, Particles, Polymers and Biomaterials Technology Group
Precipitated calcium carbonate (PCC) is the most common filler for the papermaking. The use of this compound allows the substitution of fibres by a less expensive material that improves the optical properties of paper. However, there are disadvantages in the incorporation of PCC in the papermaking process, namely the decrease in the fibre-to-fibre bonding which leads to a reduction of the paper strength.
It is possible to modify the fillers surface in order to increase the filler content without sacrificing the paper mechanical resistances. Recently, we published an in situ synthesis of silica at the surface of PCC by sol-gel method. The present work reports the application of this silica-coated PCC as a filler to produce paper.