Obtenção e uso de gradientes de densidade

AUTOR(ES)
DATA DE PUBLICAÇÃO

1987

RESUMO

Osmocentrifugation and contrifugal ultrafiltration were applied to the obtention of solfgeneratod gradients of macromolecular solute. Centrifugal ultrafiltration provides greater gradents in shorter times than in longer times. The range and shape of the density gradients can be varied, by using different centrifugation times and rotor speeds. Fractionation and characterization of particulate matter found in commercial paints and adhesives, formulated using polymer latexen, were achieved by centrifugation in density gradients. The results obtained are: Polyvinylace- tate (PVA) latex fractions with different tacticity and composition (related to plasticizers and/or impuritons)were obtained. Characterization of lates fractions was done by HNMR spectroscopy. Acrylic latex (copolymer or terpolymer of styrene and one or more acrylic monomers) fractions with different composition were obtained. The proportion of styrene inthe latex decreases with the increase of latex fraction density; the fraction of lower density shows the greater amount of metal carboxylate. These informatios were obtaincd by lnfrared spectrofotomtry of latex fractions. The polymeric and mineral fractions of two paints and two adhesives were also separated. The components of the mineral fractions were Identified by Infrered spectrofotometry. Theve experioments allowed the identification of PVA associated to calcium carbonate, perhaps as a stabilizer. Tho obtention of synthetic of cellulose acetado adequate to use in organic solvents was investigated, through transfor to liquids that are no solvents of cellulose acetato or through chemical modification of the acetate. By treating the membranes with uroa formaldohide they were renderod insoluble in common soIvents of cellulose acetate, but. their mecanical properties were unsuitable to furthor use. Membranes transferred from water to methanol and toluene were utilized in contrifugal ultrafiltration of polystyrene and PVA solutions. The results obtained follow the same pattern of behavior obtained proviously in aqueous solutions, and show that contrifugal ultrafiltratlon is an appropiate technique to concentrate polymeric solutos in non "aqueous systems.

ASSUNTO(S)

polimeros latex espectrofotometria

ACESSO AO ARTIGO

Documentos Relacionados