RESUMO
Nowadays, development of new biobased/biodegradable polymers from biological resources is of great interest from a sustainability standpoint. Polyhydroxybutyrate (PHB) and polylactic acid (PLA) are two biopolymers obtained from renewable resources. In this study, the flame-retardant effect of a newly developed flame retardant (FR) based on melamine in a PLA/PHB blend was studied. Several combinations containing this new FR combined with ammonium polyphosphate (APP) and sepiolite were introduced in a PLA/PHB blend. 20 wt% of FR were introduced into a matrix containing 75 wt% PLA and 25 wt% PHB blended with a microcompounder. According to pyrolysis combustion flow calorimeter (PCFC) analyses, all the FR formulations exhibited reduced flammability. The results revealed a considerable decrease in the peak of heat release rate (pHRR) by 33 % in the presence of the new FR while a reduction of about 60 % for combinations with APP and sepiolite. The new FR system significantly enhanced the fire behaviour of PLA/PHB blend. The work presents the first cone calorimeter analyses of PLA/PHB composites. The fire behaviour evolved from thin sample to a thick charring behaviour highlighted by an increase of the residue after cone calorimeter from 0 to 14.7 % with this FR system.
RESUMO
Rod-like polyelectrolytes are an interesting model system because their persistence length is independent of the ionic strength and pH of the surrounding medium and they permit the investigation of polyelectrolytes in the absence of conformational degrees of freedom. In this work, rigid-rod poly(aramide) polyelectrolytes were synthesized by the Higashi method. Electrophoresis NMR spectroscopy in conjunction with diffusion NMR spectroscopy has been applied to determine the effective charge of the polymer. The charge was determined from the balance between the force in the electric field and the hydrodynamic friction in the steady-state electrophoretic motion. Because only organic counterions were present, and were identified in the proton NMR spectra, the counterions were investigated as well, and the fraction of condensed counterions was determined directly. From the effective charge per molecule and the knowledge of the fraction of condensed counterions, the total charge per molecule was determined. Finally, from the total charge, the number of repeat units and thus the molecular weight were inferred.
RESUMO
A novel surface-modified polypropylene microfiltration membrane is investigated for its potential use in drinking water treatment. The flux decline rate of the modified membrane is substantially lower than the original polypropylene membrane for filtration of a soft, high-natural organic matter (NOM) surface water because a progressive adjustment in membrane permeability counteracts the flux decline due to fouling. In general, the prospects for reduced flux decline by membrane modification depend upon the characteristics of raw water such as hardness, particulate and NOM properties and concentration, and pretreatment strategies.
