Thermoplastic Medium Research Articles

Study of the Potential Employment of Malvaceae Species in Composites Materials

The employ of vegetal fibers for textiles and composites represents a great potential in economic and social sustainable development. Some Malvaceae species are considered tropical cosmopolitans, such as from Sida genus. Several species of this genus provide excellent textile bast fibers, which are very similar in qualities to the jute textile fiber. The objective of the present study is present the physicochemical characterization of six Brazilian vegetal fibers: Sida rhombifolia L.; Sida carpinifolia L. f.; Sidastrum paniculatum (L.) Fryxell; Sida cordifolia L.; Malvastrum coromandelianum (L.) Gurck; Wissadula subpeltata (Kuntze) R.E.Fries. Respectively the two first species are from Brazilian Atlantic Forest biome and the four remaining from Brazilian Cerrado biome, despite of present in other regions of the planet. The stems of these species were retted in water at 37oC for 20 days. The fibers were tested in order to determine tensile rupture strength, tenacity, elongation, Young’s modulus, cross microscopic structure, Scanning Electronic Microscopy (SEM), regain, combustion, acid, alkali, organic solvent and cellulase effects, pH of the aqueous extract, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The obtained values were compared with those from fibers of recognized applicability in the textile industry including hemp. The results are promising in terms of their employment in thermoset and thermoplastic medium resistance composites.

Self-assembled block copolymer micelles with silver-carbon nanotube hybrid fillers for high performance thermal conduction.

The development of polymer-filled composites with an extremely high thermal conductivity (TC) that is competitive with conventional metals is in great demand due to their cost-effective process, light weight, and easy shape-forming capability. A novel polymer composite with a large thermal conductivity of 153 W m(-1) K(-1) was prepared based on self-assembled block copolymer micelles containing two different fillers of micron-sized silver particles and multi-walled carbon nanotubes. Simple mechanical mixing of the components followed by conventional thermal compression at a low processing temperature of 160 °C produced a novel composite with both structural and thermal stability that is durable for high temperature operation up to 150 °C as well as multiple heating and cooling cycles of ΔT = 100 °C. The high performance in thermal conduction of our composite was mainly attributed to the facile deformation of Ag particles during the mixing in a viscous thermoplastic medium, combined with networked carbon nanotubes uniformly dispersed in the nanoscale structural matrix of block copolymer micelles responsible for its high temperature mechanical stability. Furthermore, micro-imprinting on the composite allowed for topographically periodic surface micropatterns, which offers broader suitability for numerous micro-opto-electronic systems.

Pyrophthalones as Blue Wavelength Absorbers in Thermoplastic Media

We have explored the utility of pyrophthalones as violet-blue light filtering dyes in polymer matrices for wavelengths below 450 nm. Further, we have investigated the photodegradation of these molecules in thermoplastic media and the mechanisms behind their degradation. Finally, a range of additives have been explored to improve the photostability of these molecules to achieve the desired performance.

The cell bases of honeybee combs

Pirk et al. [Naturwissenschaften 91, 350–353 (2004)] posited that beeswax is a thermoplastic medium that softens with increasing temperature and literally flows among an array of close-packed cylinders, which are actually the self-heated building bees and so hexagonal cells arise quite passively. But, it was further argued that the three apparent rhomboids of the cell base arise as optical artefacts. A re-examination of the cell bases of freshly drawn comb, old comb, and the silk residues of wax-extracted old combs prepared from a silicone-based moulding rubber preparation showed that three perfect rhomboids are seen to form the trihedral pyramid in the cell base (Fig. 1), those of old combs show hemispheres inside the cell bases (Fig. 2). Longitudinal sections of old combs clearly show the parabolic curvature of the inside of the cell base; but the edges of rhomboids are clearly visible on the outside of the cell base (Fig. 3). The silken cell “ghosts” exhibit rhomboids on the outside of the cells (Fig. 4) but a hemispherical base on the inside of the “ghost cell” (Fig. 3). Three rhomboids would be expected as a product of thermodynamic equilibrium in precisely the same way that soap bubbles form angular, not hemispherical, contact faces because the wax moves to a more probable state resulting in rhomboids, or a trihedral pyramid, which forms the cell base. Thus, the underlying geometry of the cell walls and bases are in keeping with mathematical laws on surface minima.

Characterization of microholograms recorded in a thermoplastic medium for three-dimensional optical data storage

A three-dimensional optical data storage system that combines a new recording material with a microholographic data format in which data are stored as single-bit microholograms is presented. This format offers less sensitivity to environmental conditions than the page-based holographic approach in addition to an increased compatibility with current storage technologies. The new recording material is based on a thermoplastic material. The results presented indicate that the dimensions of the microholograms are larger than those calculated by use of simple laser beam waist approximations and that multiple layers of microholograms would significantly affect signal levels. Data densities achievable with the microholographic format will likely be limited by those effects.

Yielding behaviour of thermoplastic/elastomer blends cured by gamma irradiation

AbstractMechanical blends of thermoplastic medium density polyethylene (MDPE) and elastomeric ethylene propylene diene monomer (EPDM) have been prepared with a fixed composition of 60/40 wt%. They have been used either in their gum form or loaded with two different reinforcing fillers, high abrasion furnace (HAF) carbon black or precipitated SiO2 (Hi Sil) of concentration 25–100 phr (parts per hundred parts of resin) with respect to the blend. Curing was achieved by gamma irradiation. Yielding properties (yield stress, yield strain and cold drawing) have been followed as a function of irradiation dose for different blend compositions. Yield stress values increased with irradiation dose and with the content of the reinforcing filler, but yield strain and cold drawing values decreased with irradiation dose and also with the filler content. The data obtained reveal that Hi Sil is more effective as a reinforcing filler, and the prepared blends are suitable for load‐bearing applications.© 2001 Society of Chemical Industry

Modeling an Optimal Temperature Field in a Thermoplastic Medium

We consider the problem of constructing an optimal temperature field in a medium with the use of thin films of polymeric semiconductors when visualizing a hidden image.

Some properties of thermoplastic mixtures for forming ceramics by extrusion

The change in the rheological properties of mixtures for plastic forming based on cordierite and aluminum nitride as a function of the composition of the thermoplastic binder and the temperature is considered. A supposition on the influence of the ratio between the crystalline and the amorphous components of the thermoplastic dispersion medium on the properties of the mixture is made. Some recommendations on forming of ceramic pieces are given.

On the wavefront distortion in holograms recorded in thermoplastic films

This letter analyzes the quality of reproduction of holograms recorded in thermoplastic media as a function of the variations in coating thickness of the different layers. The fidelity of reproduction is investigated by means of a phase sampling interferometric technique. It is found that the distortion depends on the processing parameters. A criterion for the optimization of the coating thickness of the layers is given.

Low charge-voltage frost recording on a photosensitive thermoplastic medium

Low charge-voltage frost recording on a photosensitive thermoplastic medium

Absorption of phthalocyanines in thermoplastic media in the 0.5 to 0.8μ region

Absorption of phthalocyanines in thermoplastic media in the 0.5 to 0.8μ region

On Wave Propagation in Thermoplastic Media

The dynamic behavior of a medium, according to the uncoupled thermoplastic theory, is presented and is compared to the behavior that would be obtained from an uncoupled quasi-static analysis. Since the inertia terms are retained in the equations of motion, wave fronts (or surfaces of discontinuity) are produced in the medium. The normal velocity of the wave front separating the elastic and plastic regions is determined. General closed-form solutions of the displacement (according to both the dynamic and the quasi-static approaches) are obtained; their unique forms are found for the semi-infinite region, and an illustrative numerical example is then presented.