Volume 26, Issue 2

A synthesized graft copolymer from polystyrene (PS) and polyvinyl propionate (PVPr) with polyaniline (PANi) with suitable electrical properties, thermal resistance, solubility and processability was optimized. Samples were prepared in the form of smooth and thin films. Four-point probe method was adapted to examine electrical DC conductivity. It was found that the electrical conductivity and thermal stability of copolymers were increased, but their processability and solubility decreased when PANi increased. Thermal stability of copolymers was investigated by Differential Scanning Calorimetry (DSC) and Thermal Gravimetrical Analysis (TGA). The prepared copolymers were much more thermally stable, soluble, flexible and ability to form a film than polyaniline, polystyrene and polyvinyl propionate. An irreversible exothermic transition was observed by DSC, which is believed to be an indication of cross-linking. Percentage of grafted PANi electrical conductivities of PS-g-PANi and PVPr-g-PANi have been examined and produced conductivities, 3.3 × 10 −2 and 4.6 × 10 −2 S/cm respectively.

This work studies the opto-thermo-mechanical properties of two different surgical sutures using interferometry. The polarizing Pluta interference microscope combined with opto-thermo-mechanical (OTM) device were used to study the effect of drawing on monofilament polyester (PET) and polyamide (PA) surgical sutures at room temperature. The variation of the refractive indices and the birefringence of both PET and PA sutures with different draw ratios were determined. The resulting data was used to calculate the optical orientation function and the average work per chain. The stress–strain curve was studied to estimate some mechanical parameters; yield stress, yield strain, Young's modulus and strain optical coefficient. The variations of the refractive the index profile were calculated for different draw ratios. In addition we studied the effect of temperature, during the drawing process, on monofilament PET suture. The obtained results provide important data for better characterization of suture materials.

Vibration injection molding technology has achieved some good properties, such as high impact strength and high tensile strength. Although many researchers have proved that the short-time mechanical properties of the polymer could be improved by vibration-injection molding technology, the long-time mechanical properties, such as the creep behavior, have not been paid enough attention. In this paper, the creep behavior of the calcium carbonate filled polypropylene (PP/CaCO 3 ) prepared at various vibration conditions has been observed. The influences of the vibration pressure and the frequency on the mechanical properties and creep behavior were investigated via creep test and tensile test. Firstly, the tensile fracture strain reached the maximum (11%) at 0.72 Hz. Moreover, with the increasing vibration pressure amplitude, the tensile fracture strain would decrease. The changing tendency of tensile strength is basically contrary with the change of the tensile fracture strain. Secondly, when the vibration frequency reaches the 0.72 Hz, the tensile creep is larger than that of other frequencies samples at 50 MPa; meanwhile, the tensile creep of these PP/CaCO 3 parts, which has been prepared at 0.48 Hz, decreases with the increasing vibration pressure amplitude. Finally, the dynamic mechanics analysis (DMA) and the wide-angle X-ray diffraction (WAXD) were adopted to analyze the reason of the creep behavior change. The different macromolecular chains mobility caused the different creep behavior.

In powder injection molding (PIM) barrel temperature, injection pressure and injection rate are important parameters for the molding of powder-binder mixtures. Improperly selected parameters lead to undesired problems such as separation of the powder-binder mixture and formation of collapses and cracks on the structure of the molded parts. In this study, steatite feedstocks based on PEG (polyethylene glycol) binders were injection molded into rectangular shape, ordered thickness with steps and zig-zag shaped mold cavities. The effects of the temperature and pressure of injection, rate of filling, temperature of the mold wall and geometry of the mold cavities were investigated. The optimum molding parameters of the feedstocks for the zig-zag shaped mold were determined to be an injection pressure of 80 to 140 MPa, a barrel temperature of 190 to 230°C, an injection rate of 5–25 · 10 −6 m 3 s −1 and a mold wall temperature of 32°C.

In order to optimize the melt spinning process of biodegradable as-spun linear aliphatic-aromatic co-polyester fibres, a fractional factorial experimental design and appropriate statistical analysis for the thirty-two screening trials involving five control parameters were used. Depending on previous studies (Younes and Fotheringham, 2011a, Younes, et al., 2009, 2010, Younes, et al., 2011b), the low melt flow index grade has been utilized in this work. Die head pressure of the extrusion machine, a range of crystallographic orders presented as full-width half-maximum of an X-ray scattering of as-spun fibres and thermo-graphic measurement of extruded filament in the air quench cooling window were investigated. Statistical analyses explained the relationship between, on the one hand, throughput flow rate and spinning temperature of filaments and, on the other hand, the crystallographic structure of the as-spun filaments. It has been found that spinning temperature and metering pumps speed are by far the most important factors affecting the die head pressure. Low spinning temperature leads to higher viscosity, higher flow resistance through the spinneret's nozzle and high die head pressure. Crystallographic order is affected significantly by metering pump speed, and the interaction between spinning temperature and quench air cooling speed. Metering pump speed, spinning temperature, winding speed and quench air cooling speed affect the filaments' temperature average. The obtained optimization helps to produce the most satisfactory properties in the biodegradable fibre based textiles, as environmentally-friendly attractive materials alternative to commercial chemical fibres for different applications.

The present article reports the processing, mechanical characterization and solid particle erosion response of a new class of multi phase composites consisting of epoxy resin reinforced with E-glass fiber and SiC particulates. The SiC powder synthesized from bamboo leaf employing DC extended thermal plasma technique has been used as the filler in this glass-epoxy composite. It is observed that with increasing percentage of filler particles, there is a decline in tensile and flexural strength, but there is significant improvement in hardness and erosion wear performance. It is also observed that, among all the factors, impact velocity is the most significant factor followed by filler percentage and impingement angle, while erodent size has the least significance on erosion of the hybrid composite. Taguchi's orthogonal arrays have been used to identify the controlling factors influencing the erosion wear rate.

Polyethylene terephthalate (PET) has been widely used in the stretch blow moulding (SBM) process for packaging applications. Finite element analysis has become extensively useful for assessing container designs and enabling the designers to perform analyses earlier in the design cycle to determine the best material and the best structure. However, there are several challenging issues due to various processing parameters and complex material behaviour, which is both temperature and strain-rate dependent. In this paper, we generalize the G'Sell-Jonas law in the three-dimensional (3D) case to model and simulate the elasto-visco-plastic (EVP) behaviour of PET, taking into account strain-hardening and strain-softening. In addition, it is observed that the internal pressure (inside the preform) is significantly different from the nominal pressure (imposed in the blowing device upstream) since the internal pressure and the enclosed volume of the preform are fully coupled. In order to accurately simulate this phenomenon, a thermodynamic model was used to characterize the pressure-volume relationship (PVR). The predicted pressure evolution is therefore more realistic when imposing only the machine power of the blowing device (air compressor or vacuum pump). Mechanical and temperature equilibrium equations are fully nonlinear and solved separately with implicit schemes on the current deformed configuration, which is updated at each time step. Biaxial characterization tests were used to determine the model parameters in order to simulate the SBM process using the PVR. Three industrial case studies, comparing simulated thickness predictions to experimental measurements, will be presented in order to illustrate the applicability of the proposed model.

The melting of an ABS resin was simulated using a three-dimensional finite element simulation of the two-phase flow in the compression section of a single-screw extruder. Screw freezing experiments were also conducted to compare the numerical predictions with the corresponding experimental data. Numerical simulations as well as experiments exhibited the Maddock melting mechanism and numerical predictions were in good agreement with the corresponding experimental data. The sensitivity of the melting profile to various material properties and processing conditions was numerically analyzed. With a constant flow rate enforced at the entrance of the screw channel, the screw and barrel temperature were found to have a minor effect on the melting profile. However, these parameters were found to have a significant effect on the predicted pressure profile along the screw channel. When the zero-traction boundary condition was imposed at the entrance of the screw channel, a change in the screw or barrel temperature affected the flow rate in the screw channel, which resulted in a significant change in the solid fraction at the same cross-section.

Telechelic poly(ethylene-ran-butylene) initiator terminated with [tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino] nitroxide groups (PEB-(SG1) 2 ) was used to initiate the controlled radical copolymerization of maleic anhydride (MA) and styrene (ST). The ST/MA copolymerizations were performed in 1,4-dioxane at 110°C and resulted in PEB-b-P(ST-ran-MA) 2 triblock copolymers with relatively narrow molecular weight distributions (M¯m/M¯n≈1.5). Gel permeation chromatography (GPC) indicated that the initiator used was ≈93% efficient. The resulting copolymers were then blended as 20 wt.% dispersions in nylon 6 (PA6) at 230°C. With as little as 10 mol.% of MA in the feed to make the PEB-b-P(ST-ran-MA) 2 , blends were deemed dynamically compatibilized based on the reduced particle size. All of the PEB-b-P(ST-ran-MA) 2 /PA6 blends resulted in a minor phase particle size D¯vs=0.1 μm while the PEB-b-P(ST)/PA6 blend had D¯vs=1.15 μm (i.e. no MA in the copolymer). Tensile testing revealed yield stresses and strains decreased steadily from pure PA6 to non-reactive PEB-b-P(ST) 2 /PA6 to PEB-b-P(ST-ran-MA) 2 /PA6. However, no difference in tensile properties was observed between PEB-b-P(ST-ran-MA) 2 /PA6 samples made from PEB-b-P(ST-ran-MA) 2 copolymer of varying MA content.

Intensive development of packing industry in response to the needs of modern society has aggravated the global situation with recovery of polymer wastes. One of the trends that may alleviate this problem is manufacture of ecologically friendly biodegradable polymeric films. Such films undergo accelerated destruction after burial under the action of soil microorganisms. The factor that speeds up biodestruction of the films in soil is the electric field of their own. The available experimental data have proved that the kinetics of biodestruction of polyethylene films, including starch-filled and inorganic salt-filled ones, alters significantly after such film transfer to electret state.

The offline Microstructure of nanocomposites based on Poly-Propylene (PP), Ethylene-Propylene Diene Monomer (EPDM) and Cloisite 15A along the twin screw extruder barrel was investigated by X-Ray diffraction, Transmission Electron Microscopy (TEM) and rheological measurements. To assess the effect of screw zones, the microstructural development of nanocomposites along the screw was investigated. Accordingly, dead-stop experiment samples were taken at four different positions of the extruder after abruptly stopping the machine and opening the barrel. Effect of clay loading on the evolution of morphology in the extruder was studied. X-Ray diffraction results showed that at lower clay contents (up to ∼7 wt.%), the intercalation process is independent of screw geometry and accomplishes as soon as the matrix is melted; and on the other hand, excessive melt mixing of the samples containing higher clay loadings (10 wt.%) might lead to the collapse of silicate layers and consequently poor degrees of intercalation/exfoliation. Results were confirmed by TEM micrographs and also XRD patterns of the nanocomposites sensitively detecting the microstructural changes of the samples.

Polyethylene terephthalate (PET) nanocomposite films (with 3 wt.% Cloisite 30B) were prepared by cast extrusion followed by uniaxial stretching, using chill rolls. Two screw profiles with different mixing elements under different screw speeds (N) and feeding rates (Q) were used to prepare PET/clay nanocomposite (PCN) films. Transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD) showed that the clay layers were aligned in the machine direction (MD). XRD patterns depicted that the interlayer distance of clay platelets in the state of intercalation is somehow independent of the processing conditions, but the macro-scale characterization, including barrier and mechanical properties, showed that the level of clay layer delamination was affected by processing conditions. The results reveal that the applied strain has stronger effect than residence time on the barrier and mechanical properties. At the highest screw speed (N = 250 min −1 ), 27% reduction in oxygen permeability and 30% improvement in tensile modulus were obtained for the more severe screw profile.

Nanocomposites based on melt blending of an organoclay and a thermoplastic matrix have end-use properties directly controlled by the state of dispersion of the clay and the resulting nanostructure. It is thus very important to be able to correctly quantify the levels of intercalation and exfoliation of these systems. For the exfoliation, rheological measurements in small amplitude oscillatory shear are very powerful because they put clearly in evidence the interactions between nanofillers. We show in this paper how it is possible to interpret the experimental results, we indicate the advantages and drawbacks of current methods used in the literature and we strongly suggest to use the melt yield stress to characterize exfoliation level.