Mechanism of low-temperature plastic deformation in structural steel

It has been discovered that grade 30KhGSA steel after a high-temperature thermomechanical treatment is more plastic at –196°C than at room temperature, unlike in the case of quenched steel and uncharacteristically for metals or alloys with a bcc crystal lattice. A study has, therefore, been made to establish the temperature characteristic of the resistance to deformation and, especially, to its reversible component, both after an anneal and after a heat treatment of steel. The activation energy and volume of the thermally induced deformation were measured, whereupon the results were analyzed on the basis of the Payerls mechanism with dislocations frozen by interstitial impurities. No differentiation was made between the behavior of steel after a quench and after a high-temperature thermomechanical treatment, respectively, so that differences in the low-temperature diagrams could be related to the peculiarities of nonthermal deformation and to the resistance to brittle fracture.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 26–33, September, 1974.     

Radiation induced oxidative degradation of poly[bis(p-tolylamino)] phosphazene in chlorinated hydrocarbons

Degradation induced by ionizing radiations on polyphosphazenes, dissolved in chlorinated methanes, is the subject of this investigation. Both steady gamma and pulse radiolysis techniques have been employed.The labile sites for radical attack in poly[bis(p-tolylamino)] phosphazene were identified as the aniline N-H and benzyl C-H bonds of the pendant groups. All the primary radicals, by themselves or after peroxidation, can give rise to macroradicals by hydrogen abstraction from the polymer molecules. Appreciable crosslinking appeared only in the presence of quite a high concentration of oxygen, whereas, in its absence or after it had been consumed, practically no $\text{M}{}_{\mathrm{<mtext>w</mtext>}}$ changes were detected. Optical spectra of intermediates formed after pulse radiolysis are reported and attributed to radical-polymer charge transfer complexes, anilinium ions and toluidine radicals. p-Toluidine is formed as an end-product by hydrogen abstraction from polymer molecules. In solvents where hydrogen chloride can be formed, the amino functional group is affected.     

Application of a calorimetric method in radiation-induced polymerization—V. Determination of propagation and termination rate constants for iso-butyl- and dodecyl-methacrylates

The gamma induced polymerizations of iso-butyl- (i-BMA) and dodecyl-(DMMA) methacrylates under non-stationary conditions have been studied, utilizing a calorimetric method already used for other methacrylates.For both monomers, the polymerization rate was found to vary linearly with $\text{(}\text{dose rate}\text{)}\text{1}\text{2}$ at the dose rates and temperatures examined. The rate constants for propagation and termination are compared with those of methyl-, ethyl-, n-butyl- and cyclohexyl methacrylate; the results are discussed.     

Nanomorphology of polymer frameworks and their role as templates for generating size-controlled metal nanoclusters

The microporous (gel-type) functional resin co-poly-N,N-dimethylacrylamide (DMAA) (88 % mol)/methacrylic acid (MAA) (8 % mol)/N,N'-methylenebisacrylamide (MBAA) (4 % mol) (MPIF(H)) is employed as the hosting framework for the production of resin-supported Pd(0) nanoclusters. The obtained composite MPIF(-)Na(+)/Pd(0) is prepared upon reducing, in ethanol, MPIF(-)Pd(2+) (0.5), obtained upon previous homogeneous dispersion of "Pd(2+)" inside the resin particles (XRMA control) through ion-exchange. Metal nanoclusters appear to be size-controlled (2.0+/-0.2 nm) and are seen to reasonably fit the predominant resin "nanopores" diameter, determined in ethanol (3.2 nm) by means of inverse steric exclusion chromatography (ISEC).     

Hydrogels obtained by radiation-induced polymerization as delivery systems for peptide and protein drugs

The controlled release of peptides and proteins from hydrogels obtained by radiation-induced polymerization of 2-hydroxyethyl methacrylate at a low temperature was studied. It was found that the extent of release progressively decreased as protein molecular weight increased until no further release occurred above a critical value of the latter. However, an increasing rate of protein release was found if the polymerization was carried out in the presence of poly(ethylene glycol), PEG. Moreover, only with high molecular weight PEGs were large proteins released. The release data as a function of swellability and porosity of polymer matrices were discussed.