- ArtículoAcceso AbiertoRevisión sobre los aspectos biológicos del "fouling"(1996)The development of fouling communities is object of world-wide research since the last half of the century. Biological fouling of vessels has been known since the beginning of man ’s maritime activities. Biological corrosión became a problem of concern when steel replaced wood as the primary ship construction material. The purpose of the present paper is to present a guide about biological aspects of fouling for the non-specialist (the non-biologist). The scope ofthis guide is to give some historical references, development sequences of the fouling community, abiotic factors influence, fouling problems, study methodology and enough elements to recognize the most important taxa with some pictures. Also, in relation to freshwater fouling, a basic approach and comments about exotic species introduction by ships are presented. A glossary and a broad bibliography on this subject are ineluded.
- ArtículoAcceso AbiertoThermodynamics of solutions of hydrocarbons in low molecular weight poly(isobutylene): a gas chromatographic study(1996)The reduced chemical potentials (x*) of twenty normal and branched alkanes, cyclohexane and three aromatic hydrocarbons at infinite dilution in polyisobutylene (PIB) were measured by gas-liquid chromatography at five temperatures between 35 and 65°C. Reduced partial molar residual enthalpies (k*) were calculated from the temperature dependence of x*; they are positive for PIB+alkane systems, but smaller than those obtained in former chromatographic studies. Although uncertainties on k* are at least one order of magnitude larger than those on x*, binary X12 Flory parameters obtained from k* display a good correlation with the structural parameter 0ɵv defined as the ratio of the number of hydrogen atoms on methyl groups to the total number of hydrogen atoms in the alkane molecule. Very poor or nil correlation exists between X12 values obtained from x* and 0ɵ1. The evidence is by no means conclusive, but in principie the x* results obtained for PIB + alkane systems could be explained in terms offree volume contributions and of the antipathy between methyl groups on the alkanes molecules and the polymer side groups. Positive partial molar residual entropies were detected for the three aromatic hydrocarbons; their partial molar residual enthalpies are however highly positive, resulting in their poor solvent properties towards PIB.
- ArtículoAcceso AbiertoActivity coefficients of hydrocarbons at infinite dilution in di-n-octyltin dichloride: comparison with results obtained in other alkyltin solvents(1996)The gas chromatographic method was employed to measure the infinite dilution activity coefficients of twenty-eight hydrocarbons of different types in di-n-octyltin dichloride between 323.15 and 353.15 K, and ofseven branched alkanes in tri-n-octyltin chloride between 313.15 and 333.15 K. A comparison is made between the results obtained for all the solutes in both solvents and in tetra-n-octyltin.
- ArtículoAcceso AbiertoThermodynamic consideration of the retention mechanism in a poly(perfluoroalkyl ether) gas chromatographic stationary phase used in packed columns(1996)Retention voluntes of fifteen hydrocarbons were measured in columns containing several concentrations of a commercial poly(perfluoroalkyl ether), Fomblin Y HVAC 140/13, as the stationary phase. Two different type ofpacking were studied: one ofthem employed pre-silylated Chromosorb P AW DMCS as the solid support, and the other type wasprepared by coating the stationary phase on Chromosorb P AW and silylating on-column. On-column silylated columns showed unequivocal symptoms of partial deactivation; retention volumes changed regularly with the contení of stationary phase in pre-silylated columns. Analysis of retention in pre-silylated columns indicates that a mixed mechanism (partition and adsorption on the gas-liquid interface) is operative. Systems hydrocarbon + perfluorocompound show pronounced positive deviations from the ideal behaviour that can be attributed to repulsión between the hydrocarbon and the perfluorocompund segments.
- ArtículoAcceso AbiertoRecent developments in miniemulsion polymerization(1996)Some developments in miniemulsion polymerization aiming at taking advantage of its unique mechanisms minimizing the drawbacks of this technique are discussed. The discussion ineludes preparation of highly concentrated latexes, miniemulsion polymerization in continuous stirred tank reactors (CSTRs), and elimination of the low molecular weight hydrophobe.