F. Tüdös

Analysis of the Linear Methods for Determining Copolymerization Reactivity Ratios. V. Planning of Experiments

Abstract A method for planning of experiments has been elaborated which makes it possible to decide the adequacy of the two-parameter model of binary copolymerization. At the same time, the procedure provides equal and reasonably low relative errors of r1 and r2. In the approximate knowledge of the parameters and of the value of analytical error, the procedure furnishes the number of measurements and the monomer feed values necessary for the desired accuracy. It was obtained as a “rule of thumb” that, in spite of the erroneous practice, the points should be arranged uniformly within the range of copolymer composition instead of monomer composition. For the objective performance of retrospective evaluations, an “efficiency factor” has been introduced.

Correlation between Oxygen Uptake and Carbonyl Formation in Polyethylene Oxidation

Abstract The ratio of absorbed O2 and carboxyl groups formed was studied in LDPE oxidation. It was found that this ratio is independent of the reaction conditions in a wide range (20–100 kPa O2 pressure, 90–160°C, and thickness of 20–1170 μm). If the pressure of O2 was 2.7 kPa, less - COOH formed. A semiempirical mathematic equation was constructed to describe the relation between the acid content and oxygen consumption.

Degradation of HDPE and LLDPE in closed mixing chamber: a comparison

SummaryHDPE and LLDPE (containing n-butyl branches) were degraded in a closed mixing chamber. After degradation some physical and mechanical properties were investigated as a function of the chemical structure of the polymers. The effect of degradation was found different for the two materials.Physical and mechanical properties of HDPE depend strongly on crystallization conditions and chemical irregularities of the polymer chain. The most pronounced change in physical properties was found as an effect of oxygen incorporation into the polymer at the beginning of the process. Tensile properties of the samples have shown rapid destruction after the yield point.Physical and mechanical properties of LLDPE reveal much less dependence on crystallization conditions and changes of the chemical structure. Chemical changes caused by degradation of the polymer do not essentially change the degree of crystallinity under the conditions investigated. Chain breaking of the polymer results in a slight decrease in the tensile properties, which can be attributed to the decrease in the number of tie-chains.

Physico-chemical studies of polymeric carriers

SummaryDensitometric conformational studies were made on poly(1-vinyl-2-pyrrolidone-co-maleic acid) in the presence of LiCl, NaCl, KCl, CaCl2, and MgCl2, in order to control ion-binding of the polyanion in dilute aqueous solution. Experimental verification of principal role of deprotonation in the conformational transition of the polyacid chains during titration is given. Correlation was found between the apparent molar volume of the copolymer and the ionic radius of the bound cation.

Effect of an inert solvent on the copolymerization of styrene/diethylmaleate

We studied the effect of an inert solvent (benzene) on the overall rate of copolymerization in the system styrene/diethylmaleate (ST/DEM), initiated with azo-bis-iso-butyro-nitrile (AIBN) at 50°C. The experimental results can be interpreted on the hot radical theory.

Kinetics of Radical Polymerization. XLI. Kinetic Investigation of the Radical Polymerization of Methyl Methacrylate in Benzene and Bromobenzene

Abstract The present paper deals with the radical polymerization kinetics of the systems MU-AIBN-Bz-50°C and MMA-AIBN-BrBz-50°C. The rate of initiation and the k2/√k4 value were determined in a broad range of monomer concentrations. The initiation rate constant was found to be independent of the concentration of solvent and monomer. In the system MMA-Bz the k2/√K4 value does not change with dilution, while in the system MMA-BrBz it depends on the viscosity of the initial monomer-solvent mixture.

Kinetics of Radical Polymerization at High Conversion I. GPC Measurements of Molecular Mass Distribution

Abstract A series of poly(methyl methacrylate) (PMMA) samples was prepared with different monomer concentrations and to different degree of conversion in benzene, at 50°C. Average molecular weights and intrinsic viscosity values in the eluent (THF) measured by GPC using an online viscometer are reported. At monomer concentrations up to 50 mol %, no gel effect is observed even in the case of very high conversions (∼90%); both molecular weights and kinetic parameters which determine the length of the polymer chain remain practically unchanged independent of conversion. From monomer concentrations of 75 mol %, significant increase of both of these values is observed depending on conversion. The average branching numbers of polymer chains for all samples remain close to zero. The polydispersity values are generally near 1.7. These results denote that there is no significant chain transfer to polymer and the disproportionation probability in chain termination reactions agree with earlier results described in t...

Kinetics of radical polymerization. XLVI: Kinetic investigation of the polymerization of styrene in solution by gel permeation chromatography

Abstract Molecular mass distribution was investigated for the polymerization of styrene initiated by AIBN at 50° in the presence of various solvents. Two types of solvents were chosen; in one, there is no chain transfer to solvent (Bz, DMF) whereas in CCl 4 the chain transfer should be considered. The molecular mass distributions of the systems were determined by GPC and they were also calculated from kinetic data in terms of the hot radical theory. The agreement of MMD curves obtained by both methods (GPC and kinetic) are within experimental error, sufficient.