Ronaldo Gonçalves dos Santos

Medidas de tensão superficial pelo método de contagem de gotas: descrição do método e experimentos com tensoativos não-iônicos etoxilados

Surface tension knowledge of surfactants aqueous solutions is important during amphiphilic molecule manufacturing and new product development, as feedback information to handle synthesis parameters to target performance. Drop counting method is an interesting simplification of drop weight method for surface tension measurements. A simple laboratory measurement device, with capability for temperature control, was assembled to allow investigation of ethoxylated surfactants. The implementation of the method was preceded by a detailed investigation of two factors that may affect the measured surface tension: drop formation velocity and surfactant ethoxylation degree. The limitations of the method are discussed on this basis.

Gelation Behavior of N-Decane Organogels with Gelators C28 and C40

Organogel formation during paraffin crystallization is one of the causes of oilfield problems. We investigated the formation of n-alkane organogels having C10 as liquid phase and n-octacosane (C28) and n-tetracontane (C40) as solid gelators. It was seen that C10/C28 and C10/C40 form organogels with onset gelation temperatures of 33°C and 48°C respectively, while C10/C28/C40, gelify at 52°C. Replacement of C28 by n-heneicosane (C21) reduced the crystallization rate of C40. This result indicates that the onset temperatures and crystallization rates of organogels with gelators in the range of C28 to C40 could be modulated through the introduction of shorter chain n-alkanes.