Viscosimetry Methods Research Articles

Equilibrium Rigidity of Polyorganophosphazene Molecules

The optical anisotropy and orientation angles of polyorganophosphazene (PPhPh) molecules with different lengths and side-chain structures have been investigated by flow birefringence and viscosimetry methods. Quantum-chemical calculations of the optical anisotropy per monomer unit within the polymer fragments with different conformations were carried out. It was shown that both short-range and long-range interactions (i. e. the structure of the polymer backbone and steric interactions between side chains) influenced the conformation of the PPhPh molecules and should be taken into account for the determination of the thermodynamic rigidity value A. The experimental value of A, (50 ± 5)·10–8 cm, obtained by different methods, adequately corresponds to the structure and observed physical parameters of the PPhPh molecules. Molecules of this class of polymers are not rigid chains in a common way (A > 150·10–8 cm), but alternating double bonds of their backbones bring about some increase in the equilibrium rigidity. It can be assumed that, for this class of polymers, the mesogeneity on a molecular level is defined by the strong interactions of fluorine-containing side chains rather than by the rigidity of their backbones.

Alterations of molecular characteristics of polyethylene under the influence of UV-radiation

The influence of UV-radiation on the molecular characteristics of low-density polyethylene in dependence of samples' thickness and the dose has been investigated by methods of viscosimetry, light scattering, turbidimetry and gelation measuring. It was established that the destruction and crosslinking processes of macromolecules proceed simultaneously with the irradiation. In a range of doses previous to gelation increase of mass-average molecular mass and degree of branching of macromolecules accompany the irradiation. The intensity of change of the molecular characteristics is lowered along with the increase of samples’ thickness, as soon as the basic molecular transformations occur in a thin film layer of the samples’ surface. For the same reason the gelation point dose decreases along with the decrease of samples’ thickness and the destruction-to-crosslinking speeds ratio rises up to a constant value, but lowers with decrease of samples’ thickness. It has been assumed that the degree of change of molecular characteristics is independent of samples’ thickness and mechanisms of influence of UV- and γ-irradiation on polyethylene is similar.

Effect of γ-radiation on the molecular characteristics of low-density polyethylene

The influence of γ-radiation on the molecular characteristics of low-density polyethylene dependant on the samples’ thickness, the intensity and the dose has been investigated by methods of viscosimetry and light scattering. A remarkable increase of molecular mass by the increase in radiation doses was established. It is linear for the mass-average molecular mass while for the viscosity average molecular mass it is minimum at the initial doses. The origin of this minimum is explained by the change of macromolecular hydrodynamic volume, as it has also been established that the growth of molecular mass at the initial doses is mainly due to the increase of the degree of macromolecular branching. A dependence of the rate of change of polyethylene molecular characteristics on the samples’ thickness, irradiation intensity and dose was established.

Prediction of creep of cured expoxy resin filled with marble flour

1. We discovered that the principles of TTA, CTA, TCTA are applicable to the description of series of diagrams of short-time creep of epoxy resin filled with marble flour, at different temperatures (20–60 °C) and with different concentrations of filler (c < 0.45). 2. It was experimentally established that the function of temperature-time reduction of filled resin does not depend on the degree of filling and coincides with the function of temperature-time reduction of unfilled binder; the function of concentration-time reduction does not depend on the temperature. 3. The applicability of the principles of analogy to the prediction of long-time creep of the filled polymer under consideration was experimentally established. 4. Modeling and calculation of the deformation properties of a composite on the basis of its structural components showed that near particles of filler there can be an interphase layer whose rigidity is greater than the rigidity of the matrix, and the pliability for all the time sections is proportional to the pliability of the matrix. 5. The results of evaluating the extension of the interphase layer correspond qualitatively to the results of the experiment for determining the thickness of the interphase layer by the method of viscosimetry.

Réticulation dgeba-copolymères acide acrylique-styrène et anhydride maléique-styrène

A kinetic study of the epoxy resin curing reaction with anhydrid maleique-styrene and acid acrylic-styrene copolymers carried out through viscosimetry method. Different compositions of acid in the copolymers are used. For each one the medium's viscosity vs the time is studied at different temperatures and catalyst's composition. The constant rates and the limit values of time and viscosity are calculated. The results show that the curing depends upon the structure and the copolymer's composition.

Thermal stability of solutions of cellulose in methylmorpholine-N-oxide and systems based on it

The thermal stability of MMO and of cellulose solutions in MMO has been investigated by the methods of viscosimetry, thermogravimetric analysis, and mass-spectrometric analysis.

Change in molecular parameters of aromatic polyamides on heating

Changes in the molecular parameters of aromatic polyamides on heating have been evaluated by the methods of viscosimetry and light-scattering.

Molecular parameters and conformational conversions of poly(N-vinyl-2-pyrrolidone) on complex formation with cobalt ions

The hydrodynamic properties of dilute solutions of poly(N-viny1-2-pyrrolidone) (PVP) and its Co(II) complexes were studied by high-speed sedimentation and viscosimetry methods. Unperturbed dimensions of PVP in two solvents (ethyl alcohol and water) and those of PVP complexes with the cobalt ions in water were determined. Unperturbed dimensions of PVP coils were shown to be dependent on the solvent nature, and those of polymer-metal complexes on metal concentration.

Reactions of phenol with N-vinylcarbazole and N-vinylpyrrolidone copolymers in solution

1. The methods of viscosimetry and PMR spectroscopy have been used to show the existence of thermally induced conformational transformations between poly-N-vinylpyrrolidone, on the one hand, and the N-vinylpyrrolidone-N-vinylcarbazole copolymer, on the other, in benzene solution and at temperatures in the 40–55°C range. 2. The increase in chain rigidity accompanying passage from the poly-N-vinylpyrrolidine to the copolymer at 25–50°C (at temperatures too low for conformational transition in the macromolecule) reduces the complex equilibrium constant. The thermodynamic parameters of the complexes are essentially unaffected by alteration in the complex composition at the higher temperatures.

Effect of lyophilization on the degree of polymerization and the immunological properties of deoxyribonucleoproteins

A method of viscosimetry was used to compare the molecular weight of the crude and lyophilized desoxynucleoproteids (DNP) and DNA preparations at various stages of their purification from protein. As demonstrated, lyophilization leads to a marked reduction of polymerity of the preparations, especially in the DNA lyophilized preparations. However, the immunological activity of the DNP preparations remained unchanged after lyophilization. The study of the DNP by means of the quantitative complement fixation reaction has shown that crude and lyophilized DNP preparations had an equal initial antigenic and serological activity which could be explained by their sufficiently high polymerity.