Oxidative destruction of polyolefins under stress. The action of ozone on polyethylene and polypropylene

Tensile stresses accelerate the rate of oxidation by ozone of films of polyolefins, high-density and low-density polyethylene, and isotactic polypropylene. Experiments have been performed on thin (up to 20 μm) uniaxially oriented films under constant stress σ, under conditions where the chemical kinetics rather than diffusion dominates. It is found that the oxidation rate is proportional to exp(γ′σ/RT) where γ′ is an empirical constant. The effects of unimolecular chain scission and the change of molecular polymer parameters under stress on this dependence are negligible. An analogy with the kinetics of oxidation of stressed cycloparaffins by ozone is noted. A mechanism is suggested to explain the accelerating effect of tensile deformations on chemical processes involving rehybridization of carbon atoms in the main chain from the sp³ to the sp² state. An ESR study with a stable nitroxyl radical probe revealed a change in the segmental mobility of polymer chains in the course of loading.     

Investigation of heterocyclic quinones

A general method for the synthesis of substituted 8-amino-2-quinolono-5,6-quinones by oxidation with simultaneous animation of 6-hydroxy-2-quinolones is described. The stepwise course of the process and several properties of the compounds obtained are studied.For Communication X, see [10].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1376–1380, October, 1970.     

About the Principal Necessity of Accounting for the Second Order of Smallness in Quantum-Kinetic Problems

Russian Physics Journal -     

Influence of drug on the structure and segmental mobility of poly(3-hydroxybutyrate) ultrafine fibers

Ultrafine fibers of biodegradable natural polyester such as poly(3-hydroxybutyrate) containing dipyridamole at various concentrations as a drug are prepared by the electrospinning method. It is shown by scanning electron microscopy that the absence of dipyridamole or its low concentrations (from 0 to 1%) provide the complex morphology of fibers composed of cylindrical regions 1–3 μm in diameter and thickened spindle-like ones 5–7 μm in average diameter. An increase in the concentration of dipyridamole in fibers leads to disappearance of the latter regions, with the morphology being cylindrical. The features of the crystalline and amorphous structures of poly(3-hydroxybutyrate) and its mixtures with dipyridamole are examined via DSC and EPR probe techniques. It is shown that the addition of dipyridamole to the poly(3- hydroxybutyrate) polymer matrix results in a sharp increase in the crystallinity and a slowdown of the molecular mobility in amorphous regions of ultrafine fibers. The heat treatment (annealing) of fibers leads to a sharp increase in the polymer crystallinity and a reduction of the segmental mobility in intercrystalline regions of the initial poly(3-hydroxybutyrate) fibers and those containing 1% of dipyridamole. All results including the influence of the drug concentration on the shape of fibers and their dynamic characteristics agree well with the thermal and physical parameters and should be used in the design of therapeutic systems for targeted and sustained delivery of bioactive compounds.     

Stress-strain state of plates with point fixing

Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Prikladnaya Mekhanika, Vol. 25, No. 7, pp. 80–85, July, 1989.