A set of aromatic copolyimides was obtained by reaction of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and mixtures of the diamines 1,4-bis(4-amino-2-trifluoromethylphenoxy)-2,5-di-tert-butylbenzene (CF3TBAPB) and 3,5-diamino benzoic acid (DABA). These polymers were characterized and compared with the homopolymer derived from 6FDA and CF3TBAPB. All copolyimides showed high molecular weight values and good mechanical properties. The presence of carboxylic groups in these copolymers allowed their cross-linking by reaction with 1,4-butanediol. The crosslinked polymer films were extensively characterized and it was observed that the degree of crosslinking was low in the copolyimides possessing a small number of carboxyl groups. The degradation temperature of these crosslinked copolyimides was lower than their corresponding non-crosslinked ones. Glass transition temperatures were higher than 260 oC, showing the non-crosslinked copolyimides the highest values. Young moduli of these crosslinked showed values higher than 1.9 GPa, and slightly lower elongation at break when compared with the precursor copolyimides. All copolyimides (precursor, and crosslinked ones) films could be tested as gas separation membranes. It was seen that CO2 permeability values were around 100 barrer, having better selectivity than that of the homopolymer. Moreover, the plasticization resistance of the crosslinked material having a large number of carboxylic groups was excellent.

High porosity and mass transport properties of microfiltration polymeric membranes benefits nutrients supply to cells when used as scaffolds in interstitial perfusion bioreactors for tissue engineering. High nutrients transport is assumed when pore size and porosity of the membrane are in the micrometric range. The present work demonstrates that the study of membrane fouling by proteins present in the culture medium, though not done usually, should be included in the routine testing of new polymer membranes for this intended application. Two poly(ε-caprolactone) microfiltration membranes presenting similar average pore size (~0.7µm) and porosity (>80%) but different external surface porosity and pore size have been selected as case study. The present work demonstrates that a membrane with lower surface pore abundance and smaller external pore size (~0.67 µm), combined with adequate hydrodynamics and tangential flow filtration mode is usually more convenient to guarantee high flux of nutrients. On the contrary, having large external pore size (~1.70µm) and surface porosity would incur in important internal protein fouling that could not been prevented with the operation mode and hydrodynamics of the perfusion system. Additionally, the use of glycerol in the drying protocols of the membranes might cause plasticization and a consequent reduction of mass transport properties due to membrane compaction by the pressure exerted to force perfusion. Therefore, preferentially, drying protocols that omit the use of plasticizing agents are recommended.

In this paper, ground tire rubber (GTR) was mechano-chemically modified with road bitumen 160/220 and subsequently treated using a microwave radiation. The combined impact of bitumen 160/220 content and microwave treatment on short-term devulcanization of GTR were studied by thermal camera, wavelength dispersive X-ray fluorescence spectrometry (WD-XRF), static headspace and gas chromatography-mass spectrometry (SHS-GC-MS), thermogravimetric analysis combined with Fourier transform infrared spectroscopy (TGA-FTIR), oscillating disc rheometer and static mechanical properties measurements. The obtained results showed that bitumen plasticizer prevent oxidation of GTR during microwave treatment and simultaneously improves processing and thermal stability of obtained reclaimed rubber.