Intrinsic Viscosity Of Solutions Research Articles

Termooxidaition destruction of butadiene-nitrile rubbers and industrial waste

The process of thermooxidation destruction of industrial butadiene-nitrile copolymers of the grades SKN-18, SKN-26 and substandard products is investigated. The process is carried out in aromatic solvents (toluene in the xylene) under the influence of air oxygen in the presence of an adduct of the radical initiator azodiisobutyronitrile with N-metilpirrolidone. The mass-average molecular weights of the resulting products were determined by gel permeation chromatography, and molecular weight distribution calculations were performed. The influence of the temperature and the content of the initiator on the change in the intrinsic viscosity of solutions of the resulting degradation products, depending on the time of the process, is considered. Based on a comparative analysis of the destruction parameters using toluene and xylene at 80 °C and an initiator concentration of 0.8% by weight. It was found that the type of solvent and the time of destruction practically do not affect the process of thermooxidative destruction with the production of low molecular weight polymers with a molecular weight of 40 ? 103. It is shown that in the course of the destruction of industrial rubbers differing in the content of acrylonitrile, the process proceeds with the formation of higher molecular weight compounds in rubbers with a higher content of acrylonitrile units. When carrying out the destruction of substandard rubber SKN-26SNT with high Defoe hardness, it is necessary to increase the concentration of the initiator to 1.1% of the mass. and temperature. The mechanism of thermooxidative destruction of the studied polymers is considered. According to the data of IR spectroscopy and chemical analysis, it was found that the products of thermooxidative destruction of nitrile butadiene rubbers contain oxygen-containing functional groups. Thus, a simple commercially method for producing low-molecular-weight butadiene-nitrile polymers based on special-purpose rubbers and substandard product with functional hydroxyl, carboxyl and epoxy groups has been developed.

Analogy between Swelling of Gels and Intrinsic Viscosity of Polymer Solutions for Ion-Complexed Poly(vinyl alcohol) in Aqueous Medium

The swelling/shrinking behavior of chemically cross-linked poly(vinyl alcohol) (PVA) gel complexed with borate ions in aqueous medium and the intrinsic viscosity behavior of the corresponding polymer solutions were compared as a function of the boric acid concentration, b. The equilibrium swelling ratio of the gels, Q/Q 0 , and the intrinsic viscosity ratio of the solutions, [η]/[η] 0 , were in good accordance when the NaOH concentration, [NaOH], is high enough, where Q 0 and [η] 0 are the equilibrium swelling volume of the gel and the intrinsic viscosity of the solution without borate ions, respectively. NaOH was added so as to ionize boric acid. However, a significant difference was observed when [NaOH] was lowered. The comparison of Q/Q 0 and [η]/[η] 0 allowed one to elucidate the essential difference in the swelling (or expansion) behavior of polymer chains, which is the presence (in a gel) and absence (in a dilute polymer solution) of the Donnan potential. A free energy function for ion-complexed polymer gels is proposed.

Interaction between polyvinylpyrrolidone and surfactant from viscosimetric data

The intrinsic viscosities of solutions of polyvinylpyrrolidone (PVP) in water-sodium dodecyl sulphate have been measured, for four different molecular weights of PVP, and different concentrations of sodium dodecyl sulphate at temperatures between 20 and 35°C. The exponent a of the Mark-Houwink-Sakurada equation has been determined, and the values of the short range interaction parameter Kθ, and expansion factor αη derived. Above a certain concentration the sodium dodecyl sulphate is adsorbed on the polymer by means of hydrophobic attractions, and the consequent repulsion between anionic heads provokes expansion of the macromolecule.

Investigation of the viscosity of solutions of graft copolymers

AbstractLiving polystyrene was grafted on fractions of poly(methyl methacrylate) by an anionic grafting reaction. Unreacted polystyrene was separated by fractional precipitation. The composition of copolymer, i.e., the molecular weight of main chains and side chains, was determined. The influence of molecular weight and structure of graft copolymers on the intrinsic viscosity of solutions was examined. This may be expressed in the form [η] = KMagn. The dependence between a and n in this equation was established.

Non‐newtonian viscosity of dilute polymer solutions

AbstractA model is developed to calculate the influence of the shear rate on the intrinsic viscosity of dilute solutions of nondraining polymer coils. The polymer molecule is substituted by an equivalent ellipsoid with internal flow currents such that the macromolecule yields to the liquid flow and follows it up to a certain extent. The dimensions of the ellipsoid are obtained by equating the hydrodynamic deforming forces to the statistical restoring forces of the polymer chain. The intrinsic viscosity of the solution can then be calculated as a function of the shear rate.

Role of molecular motions in polymer reactions. Part 2.—Low-temperature free-radical polymerization of vinyl bromide and of N-vinyl carbazole

The individual rate constants for propagation and termination have been determined for the low-temperature solution free-radical polymerization of vinyl bromide and N-vinyl carbazole. The propagation rate constants can be expressed in the Arrhenius form: kP,V.B.= 4.8 × 107 exp (–7,100/RT), kP,N.V.C.= 1.2 × 106 exp (–6,900/RT). The termination rate constant for vinyl bromide can be written in the form, (2ktc+2ktd)V.B.= 2.8 × 1011 exp (–3,900/RT). However, the termination rate constant for N-vinyl carbazole polymerization, like that of methyl methacrylate,3 does not satisfy the Arrhenius relationship, and becomes markedly reduced as the temperature is lowered from +10 to –30°C. These results are interpreted in terms of the cessation of backbone rotation in dissolved “stiff” macroradicals, which cessation markedly retards diffusion-controlled termination. The fact that the intrinsic viscosities of solutions of polymethyl methacrylate and poly N-vinyl carbazole are independent of temperature in these regions can be interpreted as confirmation of this phenomenon.