Mechanical,thermal and morphological properties of environmentally degradable ABS and poly(vinyl alcohol) blends

Blends of acrylonitrile–butadiene–styrene (ABS) with 5, 10, 15, and 20 wt % of poly(vinyl alcohol) (PV) were prepared by extruding in a corotating twin screw extruder. The ABS material was blended with PVA with the objective to enhance the degradability of ABS. The extrudate strands were cut into pellets and injection molded to make test specimens. These ABS/PVA blend specimens were tested for physicomechanical properties like tensile strength, elongation, modulus of elasticity, abrasion resistance, density, and water absorption, These blends were further characterized by melt flow Index, differential scanning calorimetry, thermogravimetry analysis, and scanning electron microscopy. The morphological analysis reveals the existence of PVA domains in the ABS matrix. Differential scanning calorimetry thermograms indicates the chemical interaction between ABS and PVA domains. The prepared blends show enhanced environmental and thermal degradation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Relationship between crystalline structure and mechanical behavior in isotropic and oriented polyamide 6

Polyamide 6 (PA6) isotropic films and oriented cables were prepared by compression molding or by consecutive extrusion and cold‐drawing. These samples were isothermally annealed in the 120–200°C range and were then subjected to tensile tests at room temperature. Synchrotron wide‐angle X‐ray scattering (WAXS) and small‐angle X‐ray scattering (SAXS) patterns were obtained before and after mechanical failure. These data were related with the mechanical properties of the respective PA6 samples. The annealing of isotropic PA6 resulted in an increase in the Young's modulus (E) and yield stress (σ_y) values, which was attributed to the observed proportional reduction of the d‐spacings of the intersheet distances in both the α‐PA6 and γ‐PA6 polymorphs. Analysis of the WAXS and SAXS patterns of isotropic PA6 after break allowed the supposition of structural changes in the amorphous phase, with these being better pronounced with increasing annealing temperature; this made the samples less ductile. In oriented PA6 samples, annealing resulted in a drastic increase in the E and σ_y values accompanied by a phase transition from γ‐PA6 to α‐PA6 and a well‐pronounced reduction in the intersheet distances of both polymorphs. The stretching of the oriented samples led to an additional γ‐to‐α transition, whose extent was also related to structural changes in the amorphous phase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2242–2252, 2007     

Influence of the cross‐sectional shape on the structure and properties of polyester fibers

The effects of the fiber cross‐sectional shape on the structure and properties of polyester fibers were investigated. Fully drawn yarn (FDY) polyester fibers (167 dtex and 48 filaments) were produced under the same spinning conditions used in a spinning plant. The only difference between the fibers was their cross‐sectional shapes. Four different cross‐sectional shapes were chosen for the experimental work: round, hollow‐round, trilobal, and hollow‐trilobal. The crystallinity and values of the maximum stress, maximum strain, modulus, yield stress, shrinkage in boiling water, and unevenness of the fibers were determined. The difference in the cross‐sectional shapes influenced the modulus, maximum strain, yield stress, and shrinkage in boiling water. No effects on the crystallinity and maximum stress were observed. The results suggested that the hollow fibers had higher amorphous orientation than the full fibers. The hollow‐round fiber had the highest unevenness value. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2615–2621, 2007     

Mechanical and tribological properties of glass–epoxy composites with and without graphite particulate filler

The objectives of this research article is to evaluate the mechanical and tribological properties of glass‐fiber‐reinforced epoxy (G–E) composites with and without graphite particulate filler. The laminates were fabricated by a dry hand layup technique. The mechanical properties, including tensile strength, tensile modulus, elongation at break, and surface hardness, were investigated in accordance with ASTM standards. From the experimental investigation, we found that the tensile strength and dimensional stability of the G–E composite increased with increasing graphite content. The effect of filler content (0–7.5 wt %) and sliding distance on the friction and wear behavior of the graphite‐filled G–E composite systems were studied. Also, conventional weighing, determination of the coefficient of friction, and examination of the worn surface morphological features by scanning electron microscopy (SEM) were done. A marginal increase in the coefficient of friction with sliding distance for the unfilled composites was noticed, but a slight reduction was noticed for the graphite‐filled composites. The 7.5% graphite‐filled G–E composite showed a lower friction coefficient for the sliding distances used. The wear loss of the composites decreased with increasing weight fraction of graphite filler and increased with increasing sliding distance. Failure mechanisms of the worn surfaces of the filled composites were established with SEM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2472–2480, 2007     

Investigation on process parameters of electrospinning system through orthogonal experimental design

Electrospinning is a very simple and versatile method of creating polymer‐based high‐functional and high‐performance nanofibers. But most of the investigations are not systematic and describe the electrospinning process without quantitative accuracy. Inconsistent and even opposite results have been reported, which has hindered the consistent interpretation of the experiments. Orthogonal experimental method was used to investigate qualitative and quantitative correlations between fiber characteristics (diameters and morphologies) and the processing and materials parameters. Uniform fibers can be obtained without any beads by proper selection of the processing parameters, and a lower glass transition temperature was observed for electrospun fibers than that of native polymer. Results of statistical analysis showed that significant influences were observed for polymer molecular weight and solution concentration on fiber diameters, and there were significant effects of polymer molecular weight, solution concentration, and solvent system on fiber morphologies. Meanwhile, solution concentration and polymer molecular weight, and polymer molecular weight and solvent system had obvious interaction effects. Regression analysis revealed quantitative relations of fiber diameters and beads percent, that is, Y₁ = 72.8X₁ ? 8.1X₂ + 138.8, Y₂ = ?3.2X₁ + 0.4X₂ + 60.5, where Y₁ is fiber diameter (nm), Y₂ beads percent (%), X₁ solution concentration (%, w/w), and X₂ polymer molecular weight (kDa). Validation test showed that the experimental values of fiber size and beads percent were in good agreement with the calculated ones. Based on these results, optimal conditions could be obtained for predetermined diameters and morphologies for electrospun fibers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3105–3112, 2007     

The effect of citrate esters as plasticizers on the thermal and mechanical properties of poly(methyl methacrylate)

Plasticizers play a key role in the formulation of polymers and in determining their physical properties and processability. This study examines the effects of citrate esters, triethylcitrate, and triacetine as plasticizers on the thermal and mechanical properties of poly(methyl methacrylate). The samples were characterized by differential scanning calorimetry, dynamical mechanical analysis, and mechanical testing under different plasticizer contents. Both citrate esters proved to be effective as plasticizers, DSC data for the triacetine additive fits with Fox equation. Microstructure and relaxation properties were studied by dynamic mechanical analysis where loss modulus shows clearly that absorbed plasticizer shifts the α‐transition to lower temperature and β‐relaxations associated to ester side groups are unchanged even up to 30 wt % plasticizer. Mechanical properties were evaluated with an Instron testing machine. Both additives produced (1) an initial plasticization, with a decrease in tensile strength and modulus; (2) an antiplasticization, reflected as an increase in tensile strength; and modulus and (3) a final plasticization, with a notable decrease in tensile strength and modulus and an increase in elongation where a 35 wt % of triethylcitrate added to the poly(methyl methacrylate) increased in 200% its elongation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Peroxide crosslinking of rigid poly(vinyl chloride)

The optimum conditions for crosslinking rigid poly(vinyl chloride) with trimethylolpropane trimethacrylate (TMPTMA) and peroxide have been examined. The extent of crosslinking was measured by determining gel content by Soxhlet extraction in tetrahydrofuran. Mechanical properties were measured at 130°C and dynamic viscoelastic measurements were carried out to detect changes in the glass transition temperature (T_g). It was found that 15 phr of TMPTMA and 0.3 phr of peroxide were optimum concentrations for maximizing the extent of crosslinking, tensile strength, and T_g. The lower molding temperature of 170°C was preferred to minimize thermal degradation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2904–2909, 2007     

Influence of pigment properties on UV‐curing efficiency

The curable formulations containing monomer‐diacrylate, photoinitiator‐p‐methoxybenzoyldiphenylphosphine oxide/benzyldimethylketal, additive reactive‐triethylamine, and inorganic thermoresistant pigments‐white, red, green, and blue were cured by UV exposure films. A series of experiments was carried out to investigate the relationship between the particle size distribution of the inorganic pigment and the colorimetric and mechanical properties of the UV acrylic curable coatings. Pendulum hardness and appearance of the films depend on the content and particle size distribution of the pigment. Optimal particle size distribution and pigment content were established to obtain the best films concerning their pendulum hardness and chromatic parameters. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 247–252, 2007     

Shape‐memory behavior of thermally stimulated polyurethane for medical applications

Shape memory polymers (SMPs) have been of great interest because of their ability to be thermally actuated to recover a predetermined shape. Medical applications in clot extracting devices and stents are especially promising. We investigated the thermomechanical properties of a series of Mitsubishi SMPs for potential application as medical devices. Glass transition temperatures and moduli were measured by differential scanning calorimetry and dynamic mechanical analysis. Tensile tests were performed with 20 and 100% maximum strains, at 37 and 80°C, which are respectively, body temperature and actuation temperature. Glass transitions are in a favorable range for use in the body (35–75°C), with high glassy and rubbery shear moduli in the range of 800 and 2 MPa respectively. Constrained stress–strain recovery cycles showed very low hysteresis after three cycles, which is important to know for preconditioning of the material to ensure identical properties during applications. Isothermal free recovery tests showed shape recoveries above 94% for MP5510 thermoset SMP cured at different temperatures. One material exhibited a shape fixity of 99% and a shape recovery of 85% at 80°C over one thermomechanical cycle. These polyurethanes appear particularly well suited for medical applications in deployment devices such as stents or clot extractors. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3882–3892, 2007     

Dynamic mechanical properties and morphology of high‐density polyethylene/CaCO3 blends with and without an impact modifier

Dynamic mechanical analysis and differential scanning calorimetry were used to investigate the relaxations and crystallization of high‐density polyethylene (HDPE) reinforced with calcium carbonate (CaCO₃) particles and an elastomer. Five series of blends were designed and manufactured, including one series of binary blends composed of HDPE and amino acid treated CaCO₃ and four series of ternary blends composed of HDPE, treated or untreated CaCO₃, and a polyolefin elastomer [poly(ethylene‐co‐octene) (POE)] grafted with maleic anhydride. The analysis of the tan δ diagrams indicated that the ternary blends exhibited phase separation. The modulus increased significantly with the CaCO₃ content, and the glass‐transition temperature of POE was the leading parameter that controlled the mechanical properties of the ternary blends. The dynamic mechanical properties and crystallization of the blends were controlled by the synergistic effect of CaCO₃ and maleic anhydride grafted POE, which was favored by the core–shell structure of the inclusions. The treatment of the CaCO₃ filler had little influence on the mechanical properties and morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3907–3914, 2007