Luis M. Gugliotta

EMULSION COPOLYMERIZATION OF ACRYLONITRILE AND BUTADIENE. SEMIBATCH STRATEGIES FOR CONTROLLING MOLECULAR STRUCTURE ON THE BASIS OF CALORIMETRIC MEASUREMENTS

A semibatch emulsion copolymerization of acrylonitrile and butadiene is theoretically investigated, with the aim of controlling the molecular structure of the produced NBR. An open-loop estimator based on calorimetric measurements is proposed for monitoring the chemical composition, the average molecular weights, and the average degree of branching. With little effect on the other quality variables, the intermediate addition of acrylonitrile allows to produce a polymer with a constant chemical composition. Similarly, the intermediate addition of the chain transfer agent produces a polymer with either a fixed or with a prespecified linear variation of the average branching. The required feed profiles are obtained from a numerical inversion of a discrete process model. By increasing the initiator loads, the semibatch strategies also allow to increase the final conversion between 3% and 6%, without altering the reaction time nor deteriorating the polymer quality with respect to the batch. The numerical procedures were tested by inputing (relatively noisy) heat measurements from an industrial batch reactor.

Particle Size Distribution of SBR and NBR Latexes by UV-VIS Turbidimetry near the Rayleigh Region

Abstract This paper deals with data treatment problems that arise when turbidimetry is employed to estimate the particle size distribution (PSD) of soft polymer latexes with low diameter limits around 40 nm. Scanning electron microscopy and dynamic light scattering were used as comparison techniques. Industrial latexes of styrene-butadiene rubber (SBR) and of acrylonitrile-butadiene rubber (NBR) were investigated. The data treatment involved the use of Mies Model to obtain an average diameter and/or the complete PSD. For estimating the complete PSD, a least squares optimization (with an imposed distribution shape) and a numerical deconvolution procedure (without assumptions on the distribution shape) were attempted. A synthetic example was solved to investigate the limits of the applied numerical methods. For the polymer refractive index functions, Cauchys Law was used — and its adequate adjustment proved essential for good turbidimetric estimations. A reasonable agreement between the turbidity measurem...

Emulsion polymerization of styrene. Use of n -nonyl mercaptan for molecular weight control

Abstract The unseeded emulsion polymerization of styrene with n-nonyl mercaptan (nNM) as chain transfer agent (CTA) was investigated, with the aim of producing a PS latex of a low molecular weight polydispersity at high conversion and in short reaction times. To this effect, starved and minimum time semibatch reactions were investigated and compared to equivalent batch polymerizations. The high reactivity of nNM with respect to the monomer makes it feasible to implement a minimum time policy with intermediate addition of CTA only. The MWDs of the minimum time runs were intermediate between the broader distributions of the batch reactions and the narrower distributions of the starved experiments. The conversion profiles of minimum time experiments almost coincided with those of equivalent batch polymerizations. For controlling MWDs through semibatch operations, it seems preferable to use nNM instead of other (less reactive and more common) CTAs like tert-dodecyl mercaptan or CCl4.

Emulsion Copolymerization of Acrylonitrile and Butadiene in an Industrial Batch Reactor. Estimation of Conversion and Polymer Quality from On-line Energy Measurements

ABSTRACTA method for monitoring an industrial emulsion copolymerization of acrylonitrile and butadiene for the production of two NBR grades is presented. From an on-line calculation of the reaction heat (proportional to the mass flow rate of evaporated refrigerant), three open-loop estimators of increasing complexity were developed for monitoring conversion, copolymer composition, and average molecular weights. A good agreement between on-line estimates and off-line measurements was obtained.

EMULSION COPOLYMERIZATION OF ACRYLONITRILE AND BUTADIENE. CALCULATION OF THE DETAILED MACROMOLECULAR STRUCTURE

A novel mathematical model is developed that predicts the detailed macromolecular structure of an acrylonitrile-butadiene rubber (NBR) produced in an industrial emulsion polymerization. The model consists of: (i) a basic module that calculates the monomer conversion and the copolymer composition; (ii) a particle size distribution module; and (iii) a macromolecular structure module that calculates the bivariate chain length distributions of the linear fraction and of each branched topology (characterized by the number of branching points per molecule). From the bivariate distributions, the univariate distributions of molecular weights, copolymer composition, and degrees of branching are obtained. The model was validated from global measurements of conversion, average molecular weights, average composition, and average degrees of branching.

Immunodiagnosis of Chagas disease: Synthesis of three latex-protein complexes containing different antigens of Trypanosoma cruzi

This article describes the physical adsorption and the chemical coupling of 3 antigenic proteins of Trypanosoma cruzi onto polystyrene (PS) based latexes to be used as novel immunodiagnosis reagents for detecting the Chagas disease. The coupled proteins were a homogenate of T. cruzi, or a recombinant protein (either Ag36 or CP1). With the homogenate, between 30 and 60% of the total-linked protein was chemically coupled, showing a small dependence with the pH. For Ag36 and CP1, around 90% of the total-linked protein was chemically coupled, with a maximum coupling at pH 5 (i.e., close to the isoelectric point). The chemical coupling of CP1 was less affected by the pH than the coupling of Ag36.

Synthesis of latex-antigen complexes from single and multiepitope recombinant proteins. Application in immunoagglutination assays for the diagnosis of Trypanosoma cruzi infection.

The physical adsorption and the chemical coupling of recombinant proteins of Trypanosoma cruzi onto polystyrene and core-shell carboxylated particles were respectively investigated with the ultimate aim of producing latex-protein complexes to be used in an immunoagglutination assay able to detect the Chagas disease. To this effect, two single proteins (RP1 and RP5) and a multiepitope protein derived from three antigenic peptides (CP2) were evaluated, and sensitizations were carried out at different pHs. The maximum physical adsorption was produced at pHs close to the protein isoelectric point (i.e., pH 6 for RP5 and pH 5 for RP1 and CP2). High fractions of antigens were chemically bound to the carboxyl groups, and the highest surface density of linked protein was also observed at pHs close to the protein isoelectric point. The three latex-protein complexes obtained by covalent coupling at such pHs were tested with sera from a panel of 16 infected and 16 non-infected patients. In the immunoagglutination assays, the latex-CP2 complex produced the best discrimination between positive and negative sera.

Optimisation and standardisation of an immunoagglutination assay for the diagnosis of Trypanosoma cruzi infection based on latex-(recombinant antigen) complexes.

To determine the conditions under which the immunoagglutination assay to detect Chagas disease, obtained from a novel latex‐(chimeric recombinant antigen) complex, shows greater discrimination between the responses of a positive control serum and a negative control serum.

Synthesis and characterization of latex-protein complexes from different antigens of Toxoplasma gondii for immunoagglutination assays

ABSTRACT The acute phase recombinant protein of Toxoplasma gondii P22Ag was expressed and purified and the homogenate of the parasite was obtained from an infected mouse. These antigens were used to produce latex-protein complexes (LPC) through physical adsorption and chemical coupling onto different latexes, with the aim of producing immunoagglutination (IA) reagents able to detect recently acquired toxoplasmosis. Polystyrene and “core-shell” latexes where employed, exhibiting varied particle size, functionality (carboxyl or epoxy), and charge density. In sensitization experiments for producing LPC, the recombinant protein showed better coupling efficiency onto the particles surface than the homogenate and this could be explained by the complex mixture of the homogenate, which includes a large number of proteins of different molecular mass, isoelectric points, and hydrophobicity. The synthesized LPC were employed in IA assays. To this effect, the agglutination reaction was followed by measuring the changes in the optical absorbance by turbidimetry. Experiments against control sera were performed to evaluate the performance of various LPC and it was observed that the IA test based on P22Ag and the carboxylated latex of 350 nm of particle diameter allowed a good discrimination between acute sera and chronic/negative ones. The proposed test is cheap, rapid, and easy to implement. GRAPHICAL ABSTRACT

Immunoagglutination test to diagnose Chagas disease: comparison of different latex-antigen complexes.

To evaluate the diagnostic performance of novel latex–protein complexes obtained from different antigens of Trypanosoma cruzi through immunoagglutination test using a panel of T. cruzi‐positive sera, leishmaniasis‐positive sera and negative sera for both parasites.