Results 1 - 10 of 13201
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[en] The process of saturation of high-density polyethylene and polyethylene terephthalate with suband supercritical freons and supercritical carbon dioxide was investigated for the first time. The subcritical freon R22 was shown to be absorbed by these polymers in much larger amounts compared to subcritical freon R410a, as well as supercritical R23 and carbon dioxide, which makes it promising for use in the processes of impregnation and sterilization of polymers.
[en] A wide range of infinite urethane polymer networks were prepared from poly (ethylene glycol) (PEG) and hexamethylene disocyanate (HMDI) using 1,1,1, tris (hydroxymethyl) ethane (THME) as crosslinking agent. Differential scanning calorimetry showed that the hydrate formation depends quantitatively upon the weight fraction on poly(ethylene oxide) in the gel. It has been shown that the crosslinked polyurethanes crystallize only with definite ranges of chain length between the knots. In this range with the increase of the degree of crosslinking and crystallinity on the swelling character of the polymeric materials has also been discussed. (author)
[en] Polyethylene oxide solution containing multi-walled carbon nanotubes have been electrospun onto a rotating collector to produce highly aligned arrays of electrospun nanofibers ranging in diameters from (200 – 360) nanometres. The addition of a surfactant (Triton X-100) is highly effective in dispersing carbon nanotube within an aqueous solution of polyethylene oxide and the resulting mixture can be electrospun without excessive clumping to produce nanofibers containing high loadings of nanotubes; in this case up to 5% wt thereby providing an effective route to electrically conductive nanofibres. (paper)
[en] The authors' experience with clinical use of a radiosterilized polyethylene finger joint prepared from Alkatane BPM-90 is described. The material was first tested in the laboratory for toxicity to mammalian cells, followed by tests on laboratory animals. Afterwards, it was successfully implanted to humans. (author)
[en] A comparative analysis of radio-and electro-thermoluminescence phenomena in crystallizing polymers and nano composites based on super molecular polyethylene (UHMWPE) and nano-SiO2 is carried out. The effect of low doses of γ-radiation on the electrophysical properties (ε ', ε '', Te) of UHMWPE/ a- SiO2 nano composites was studied. It was found that the dispersion of nanoparticles and crystallization conditions of the composite significantly affect the ETL and RTL features. It is shown that as in the creation of nano composite UHMWPE / α- SiO2 and y-exposure decrease the intensity of y, P -relaxation processes.
[en] Electrohydrodynamic 3D printing is a promising strategy to controllably fabricate hierarchical fibrous architectures that mimic the structural organizations of native extracellular matrix. However, most of the existing investigations are mainly based on viscous melted biopolymers which make it difficult to uniformly incorporate bioactive or functional nanobiomaterials into the printed microfibers for functionization. Here we investigated the feasibility of employing solution-based electrohydrodynamic 3D printing to fabricate microscale poly ( ε -caprolactone) (PCL) scaffolds with multi-walled carbon nanotubes (MWCNTs). The effect of polyethylene oxide (PEO) content in the acetic acid solution of PCL on the 3D profile and dimension of the electrohydrodynamically printed walls was studied for an optimal PEO-PCL composition. When the contents of PEO and PCL are 8 w/v % and 5 w/v %, respectively, 3D fibrous lactic structures with different MWCNTs content could be stably printed with the fiber diameter about 10 μ m, close to the size of living cells. Biological experiments showed that although the addition of MWCNTs negatively affected cellular attachment compared with PEO-PCL scaffolds, the electrohydrodynamically printed PEO-PCL-MWCNT scaffolds facilitated cell alignment. It is envisioned that the presented electrohydrodynamic 3D printing might provide a new strategy to flexibly incorporate various nanobiomaterials into microscale fibrous structures for specific functionality or mimicking of hierarchically organized nanocomposites in vivo . (paper)
[en] In this paper we considered the behaviour of the conformational probes introduced in polymer blends. The temperatures of the secondary relaxation transitions of the binary blends of polyvinyl butyral and polyethylene glycol were determined by FTIR spectra. The assignment of the secondary relaxation transitions to the types of local molecular mobility in the blend of polymers was carried out. (paper)
[en] The thermodynamics, kinetics, and computer simulations of crystallization and melting is discussed. The thermodynamics is shown to be well understood, although for many specific crystals not enough details for full description are available. Experiments on the crystallization kinetics of poly(ethylene) and poly(oxyethylene) in the presence of crystal nuclei as a function of molecular mass revealed that with increasing mass, the crystallization behavior deviates increasingly from that of small, rigid molecules. Instead of showing a continuously changing, linear crystallization rate with temperature through the equilibrium melting temperature, Tm0, these flexible macromolecules show a region of practically zero crystallization rate between Tm0 and about (Tm0 - 15) K, creating a temperature region of metastability in the melt that cannot be broken by nucleation with pregrown crystals. Molecular Nucleation was proposed as a cooperative process to be of overriding importance for the description of polymer crystallization, and to be at the center of segregation of molecules of lower molecular mass by growing crystal fronts. Initial efforts to model sufficiently large crystals using Monte Carlo and molecular dynamics methods are presented. Some of the short-time intermediates in the melting, crystallization, and annealing processes seem to have little similarity to commonly assumed models of crystallization and melting and are presented as discussion topics