Effect of filler content on morphology and physical-chemical characteristics of poly(vinylidene fluoride)/NaY-zeolite filled membranes

Poly(vinylidene fluoride) electrospun membranes have been prepared with different NaY zeolite contents up to 32%wt. Inclusion of zeolites induces an increase of average fiber size from ~200 nm in the pure polymer up to ~500 nm in the composite with 16%wt zeolite content. For higher filler contents, a wider distribution of fibers occurs leading to a broader size distributions between the previous fiber size values. Hydrophobicity of the membranes increases from ~115º water contact angle to ~128º with the addition of the filler and is independent on filler content, indicating a wrapping of the zeolite by the polymer. The water contact angle further increases with fiber alignment up to ~137º. Electrospun membranes are formed with ~80 % of the polymer crystalline phase in the electroactive  phase, independently on the electrospinning processing conditions or filler content. Viability of MC3T3-E1 cells on the composite membranes after 72 h of cell culture indicates the suitability of the membranes for tissue engineering applications.

Certificação da qualidade e desempenho empresarial: evidência empírica para Portugal

This paper it is investigated the effect that quality certification has on Portuguese companies` performance, controlling simultaneously for the effect of a set of variables specific to the company and to the industry. Results suggest that quality certification does not have an instantaneous impact on companies’ performance. A positive and significant impact increasing function of the number of years that a company is certified. It is also highlighted a significant impact of company specific characteristics on its performance. In industries with a large number of companies with quality certification it is revealed a stronger effect of the years of certification on companies’ performance, as well as a significant effect of both company and industry specific characteristics on performance.