Drawing and tensile properties of polyamide 6/calcium chloride composite fibers

The influence of calcium chloride (CaCl₂) contents on the drawing and tensile properties of polyamide 6 (PA6)/CaCl₂ composite fibers prepared at varying drawing temperatures were investigated. At any fixed drawing temperature, the achievable draw ratio (D_ra) values of PA6_x(CaCl₂)_y as-spun fiber specimens approach a maximum value, as their CaCl₂ contents are close to the 3 wt% optimum value. The maximum D_ra values obtained for PA6_x(CaCl₂)_y as-spun fiber specimens prepared at the optimum CaCl₂ content reach another maximum as their drawing temperatures approach the optimum drawing temperature at 120 °C. The initial modulus, tensile strength and birefringence values of the PA6 and PA6_x(CaCl₂)_y fiber specimens were found to improve consistently with D_ra or with drawing temperatures when they were stretched to a fixed D_ra. Similar to those found for their achievable drawing properties, the ultimate initial modulus, tensile strength and birefringence values of PA6_x(CaCl₂)_y fiber specimens approach a maximum value, as their CaCl₂ contents and drawing temperatures approach the 3 wt% and 120 °C optimum values, respectively. Experiments including thermal, FTIR, melt shear viscosity and wide angle X-ray diffraction experiments were performed on the PA6_x(CaCl₂)_y resin and/or fiber specimens to clarify the possible reasons accounting for the interesting drawing, tensile and birefringence properties found for the PA6_x(CaCl₂)_y fiber specimens.     

Drawing and ultimate tensile properties of nylon 6/nylon 6 clay composite fibers

This study systematically investigated the drawing and ultimate tenacity properties of the Nylon 6 (NY6)/nylon 6 clay (NYC) composite fiber specimens prepared at varying NYC contents and drawing temperatures. The achievable draw ratio (D_ra) values of NY6_x(NYC)_y as‐spun fiber specimens initially increase in conjunction with NYC content, and then approach a maximum value, as their NYC contents and drawing temperature approach the 0.5 wt% and 120°C, respectively. The percentage crystallinity (X_c) values of NY6_x(NYC)_y as‐spun fiber specimens increased significantly, as their NYC contents increased from 0 to 2 wt%. As revealed by high power wide angle X‐ray diffraction analysis, α form NY6 crystals grew at the expense of γ form NY6 crystals originally present in NY6_x(NYC)_y as‐spun fiber specimens as their draw ratios increased. The ultimate modulus, tenacity, and orientation factor values of NY6_x(NYC)_y fiber specimens approach a maximum value, as their NYC contents and drawing temperatures approach the 0.5 wt% and 120°C optimum values, respectively. The thermal and melt shear viscosity experiments were performed on NY6_x(NYC)_y resins and/or fiber specimens to determine the optimum NYC content and possible deformation mechanisms accounting for the interesting drawing, orientation, and ultimate tenacity properties found above. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Drawing and ultimate tensile properties of modified polyamide 6 fibers

The drawing and ultimate tensile properties of the modified PA 6 (MPA) fiber specimens prepared at varying drawing temperature were systematically investigated, wherein the MPA resins were prepared by reactive extrusion of PA 6 with the compatibilizer precursor (CP). At any fixed drawing temperature, the achievable draw ratio (D_ra) values of MPA as‐spun fiber specimens increase initially with increasing CP contents, and then approach a maximum value, as their CP contents are close to the 5 wt% optimum value. The maximum D_ra values obtained for MPA as‐spun fiber specimens prepared at the optimum CP content reach another maximum as their drawing temperatures approach the optimum drawing temperature at 120°C. The tensile and birefringence values of PA 6 and MPA fiber specimens improve consistently as their draw ratios increase. Similar to those found for their achievable drawing properties, the ultimate tensile and birefringence values of MPA fiber specimens approach a maximum value, as their CP contents and drawing temperatures approach the 5 wt% and 120°C optimum values, respectively. Investigations including Fourier transform infrared, melt shear viscosity, gel content, thermal and wide angle X‐ray diffraction experiments were performed on the MPA resin and/or fiber specimens to clarify the optimum CP content and possible deformation mechanisms accounting for the interesting drawing, birefringence, and ultimate tensile properties found for the MPA fiber specimens prepared in this study. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Ultradrawing properties of ultrahigh‐molecular‐weight polyethylene/attapulgite fibers

An investigation of the influence of the contents of original and modified attapulgite (ATP) on the ultradrawing properties of ultrahigh‐molecular‐weight polyethylene (UHMWPE)/ATP (FA_x) and UHMWPE/modified ATP (FA_mx) as‐prepared fibers is reported. Similar to what is found for the orientation factor values, the achievable draw ratios (D_ra) of the FA_x and FA_mx as‐prepared fibers approach a maximum value as the original ATP and/or modified ATP contents reach their corresponding optimum values. The maximum D_ra value obtained for FA_mx as‐prepared fiber specimens is significantly higher than that for FA_x as‐prepared fiber specimens prepared at the optimum original ATP content. Similar to what is found for the orientation factors and achievable drawing properties, the tensile strength (σ_f) and initial modulus (E) of both drawn F₂A_x and F₂A_mx fiber series specimens with a fixed draw ratio reach maximum values as the original and/or modified ATP contents approach the optimum values, respectively. The σ_f and E values of the F₂A_mx fiber specimens are always significantly higher than those of the corresponding F₂A_x fiber specimens prepared at the same draw ratios and ATP contents but without being modified. To understand the interesting ultradrawing, orientation and tensile properties of FA_x and FA_mx fiber specimens, Fourier transform infrared spectral, specific surface area, transmission electron microscopic and elemental analyses of the original and modified ATPs were performed. Copyright © 2012 Society of Chemical Industry     

Ultradrawing properties of ultra‐high molecular weight polyethylene/functionalized carbon nanotube fibers

Systemic investigation of the influence of the plain and functionalized carbon nanotube (CNT) contents on the ultradrawing properties of ultrahigh molecular weight polyethylene/carbon nanotubes (UHMWPE/CNTs, FC_y) and UHMWPE/functionalized CNTs (FC_fx‐y) as‐prepared fibers are reported. In a way similar to those found for the orientation factor values, the achievable draw ratios (D_ra) of the FC_y and FC_fx‐y as‐prepared fibers approached a maximum value as their CNT and/or functionalized CNT contents reached their corresponding optimum values. The maximum D_ra values obtained for FC_fx‐0.001 as‐prepared fiber specimens prepared at varying maleic anhydride grafted polyethylene (PE_‐g‐MAH)/modified CNTs weight ratios were significantly higher that of the FC_0.0015 as‐prepared fiber specimen prepared at the optimum plain CNT content. Tensile property analysis further suggested that excellent orientation and tensile properties of the drawn FC_y and FC_fx‐y fibers can be obtained by ultradrawing the fibers prepared at their optimum plain CNT and/or functionalized CNT contents. To understand the interesting orientation, ultradrawing and tensile properties of FC_y and FC_fx‐y fiber specimens, FTIR, specific surface area, and SEM morphology analysis of the plain and functionalized CNTs were performed in this study. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Ultradrawing properties of ultrahigh‐molecular weight polyethylene/functionalized carbon nanotube fibers and transmittance properties of their gel solutions

The influences of the dispersion level of carbon nanotubes (CNTs) and functionalized CNTs on the transmittance properties of ultrahigh‐molecular weight polyethylene (UHMWPE) gel solutions and on ultradrawing properties of their as‐prepared fibers are reported. The transmittance properties suggest that the dispersion level of functionalized CNTs in UHMWPE/functionalized CNTs gel solution is significantly better than plain CNTs in UHMWPE/CNTs gel solutions. The orientation factors, achievable draw ratios, tensile strength (σ_f), and modulus (E) values of UHMWPE/CNTs (F_xC_y) and UHMWPE/functionalized CNTs (F_xC_f‐y) as‐prepared fiber specimens reached a maximum value as their CNT and functionalized CNT contents approached optimum contents at 0.00015 and 0.0001 wt%, respectively. The σ_f and E values of both F_xC_0.0012 and F_xC_f‐0.001 series fiber specimens prepared at their optimum CNT and functionalized CNT contents reached another maximum as their UHMWPE approached optimum UHMWPE concentration of 1.7 wt%. Possible reasons accounting for these interesting properties are proposed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Preparation and characterization of novel ultra‐high molecular weight polyethylene composite fibers filled with nanosilica particles

Ultrahigh molecular weight polyethylene (UHMWPE)/nanosilica (F₂S_y) and UHMWPE/modified nanosilica (F₂S_mx‐y) as‐prepared fibers were prepared by spinning of F₂S_y and F₂S_mx‐y gel solutions, respectively. Modified nanosilica particles were prepared by grafting maleic anhydride grafted polyethylenes onto nanosilica particles. The achievable draw ratios (D_ra) of F₂S_y and F₂S_mx‐y as‐prepared fibers approached a maximal value as the original and modified nanosilica contents reached corresponding optimum values; the maximal D_ra value obtained for F₂S_mx‐y as‐prepared fiber specimens was significantly higher than that of the F₂S_y as‐prepared fiber specimens prepared at the optimum nanosilica content. The melting temperature and evaluated lamellar thickness values of F₂S_y and F₂S_mx‐y as‐prepared fiber series specimens decrease, but crystallinity values increase significantly, as their original and modified nanosilica contents respectively increase. Similar to the achievable drawing properties of the as‐prepared fibers, the orientation factor, tensile strength (σ_f) and initial modulus (E) values of both drawn F₂S_y and F₂S_mx‐y fiber series specimens with a fixed draw ratio reach a maximal value as the original and/or modified nanosilica contents approach the optimum values; the σ_f and E values of the drawn F₂S_mx‐y fiber specimens are significantly higher than those of the corresponding drawn F₂S_y fiber specimens prepared at the same draw ratios and nanosilica contents but without being modified. To understand the interesting ultradrawing, thermal, orientation and tensile properties of F₂S_y and F₂S_mx‐y fiber specimens, Fourier transform infrared, specific surface area and transmission electron microscopy analyses of the original and modified nanosilica were performed in this study. © 2012 Society of Chemical Industry     

Ultrahigh molecular weight polyethylene fibers prepared using conical dies with varying dimensions

Dimensions of conical dies were found to have a significant influence on thermal, morphological, orientation, ultradrawing, and dynamic mechanical properties of the as‐prepared and/or drawn ultrahigh molecular weight polyethylene (UHMWPE) fiber specimens prepared in this study. Many demarcated “micro‐fibrils” were found paralleling to fiber direction of the as‐prepared UHMWPE fiber specimens. The percentage crystallinity, melting temperatures, orientation factor (f_o) and achievable draw ratio (D_ra) values of each as‐prepared UHMWPE fiber specimen prepared at a fixed length of outlet land reach a maximum value, as the entry angles of the conical die approach the optimum value at 75°. The maximum f_o and D_ra values obtained for each F₂₀^75‐y as‐prepared fiber series specimens prepared using the optimum entry angle reach another maximum value as their length of outlet land approach the optimum value of 6.5 mm. The ultimate tensile strengths and moduli of the drawn UHMWPE fibers prepared at the optimum entry angle and length of outlet land are significantly higher than those of fibers prepared at other conditions but stretched to the same draw ratio. Possible reasons accounting for the above interesting properties were discussed in this study. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Ultradrawing and ultimate tensile properties of ultrahigh molecular weight polyethylene composite fibers filled with functionalized nanoalumina fillers

Ultradrawing and ultimate tensile properties of ultrahigh molecular weight polyethylene (UHMWPE) composite fibers were successfully improved by the addition of nanoalumina (NAL), acid treated nanoalumina (ATNAL), and/or functionalized nanoalumina (FNAL). As evidenced by FTIR and TEM analyses, maleic anhydride grafted polyethylene (PE_g‐MAH) molecules were successfully grafted onto ATNAL fillers. The specific surface areas of FNAL fillers reached a maximal value at 516 m²/g, as they were modified using an optimal weight ratio of PE_g‐MAH to ATNAL at 8. Achievable draw ratio (D_ra) values of UHMWPE/NAL (F₁₀₀A_y), UHMWPE/ATNAL (F₁₀₀A_x%‐8‐y) and/or UHMWPE/FNAL (F₁₀₀A_x%‐8FPE^z_y) as‐prepared fibers approached a maximal value as NAL, ATNAL, and/or FNAL contents reached an optimal value at 0.1, 0.1, and 0.075 phr, respectively. The maximal D_ra values of F₁₀₀A_x%‐8FPE^z_0.075 as‐prepared fiber specimens were significantly higher than those of F₁₀₀A_0.1 and F₁₀₀A_x%‐8‐0.1 as‐prepared fiber specimens. In which, the maximal D_ra values obtained for F₁₀₀A_x%‐8FPE^z_0.075 as‐prepared fibers reached another maximal value as FNAL fillers were modified using an optimal weight ratio of PE_g‐MAH to ATNAL at 8. The ultimate tensile strength value of F₁₀₀A_2%‐8FPE⁸_0.075 drawn fiber reached 6.4 GPa, which was about 2.4 times of that of the UHMWPE drawn fibers prepared at the same optimal UHMWPE concentration and drawing condition. POLYM. ENG. SCI., 55:2205–2214, 2015. © 2015 Society of Plastics Engineers     

Ultradrawing properties of ultrahigh‐ molecular‐weight polyethylene/carbon nanotube fibers prepared at various formation temperatures

The influence of formation temperature on the ultradrawing properties of ultrahigh‐molecular‐weight polyethylene/carbon nanotube (UHMWPE/CNT) fiber specimens is investigated. Gel solutions of UHMWPE/CNT with various CNT contents were gel‐spun at the optimum concentration and temperature but were cooled at varying formation temperatures in order to improve the ultradrawing and tensile properties of the UHMWPE/CNT composite fibers. The achievable draw ratio (D_ra) values of UHMWPE/CNT as‐prepared fibers reach a maximum when they are prepared with the optimum CNT content and formation temperature. The D_ra value of UHMWPE/CNT as‐prepared fibers produced using the optimum CNT content and formation temperature is about 33% higher than that of UHMWPE as‐prepared fibers produced using the optimum concentration and formation temperature. The percentage crystallinity (W_c) and melting temperature (T_m) of UHMWPE/CNT as‐prepared fiber specimens increase significantly as the formation temperature increases. In contrast, W_c increases but T_m decreases significantly as the CNT content increases. Dynamic mechanical analysis of UHMWPE and UHMWPE/CNT fiber specimens exhibits particularly high α‐transition and low β‐transition, wherein the peak temperatures of α‐transition and β‐transition increase dramatically as the formation temperature increases and/or CNT content decreases. In order to understand these interesting drawing, thermal and dynamic mechanical properties of the UHMWPE and UHMWPE/CNT as‐prepared fiber specimens, birefringence, morphological and tensile studies of as‐prepared and drawn fibers were carried out. Possible mechanisms accounting for these interesting properties are proposed. Copyright © 2010 Society of Chemical Industry     

The compatible and mechanical properties of biodegradable poly(Lactic Acid)/ethylene glycidyl methacrylate copolymer blends

The Fourier transform infrared results suggest that the carboxylic acid groups of poly(lactic acid) (PLA) molecules react with the epoxy groups of molecules of Ethylene Glycidyl Methacrylate Copolymer (EGMC) during the reactive extrusion processes of PLA_xEGMC_y specimens. The tensile and tear strength values of PLA_xEGMC_y blown-film specimens in machine and transverse directions improve significantly, and reach their maximal values as their EGMC contents approach an optimum value of 6 wt.%. The melt shear viscosity values of PLA_xEGMC_y resins, measured at varying shear rates, are significantly higher than those of the PLA resin, and increase consistently with their EGMC contents. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) of PLA and PLA_xEGMC_y specimens reveal that the percentage crystallinity, peak melting temperature, and onset re-crystallization temperature values of PLA_xEGMC_y specimens reduce gradually as their EGMC contents increase. In contrast, the glass transition temperatures of PLA_xEGMC_y specimens increase gradually in conjunction with their EGMC contents. Demarcated porous morphology with several connected fungi-decomposed cavities was found on the surfaces of the PLA_xEGMC_y specimens after being buried for specific amounts of time, in which the sizes of the fungi-decomposed cavities found on the surfaces of buried PLA_xEGMC_y specimens reduce significantly as their EGMC contents increase. Further DMA and morphological analysis of PLA_xEGMC_y specimens reveal that the EGMC molecules are compatible with PLA molecules at EGMC contents equal to or less than 2 wt.% because no phase-separated EGMC droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLA_xEGMC_y specimens, respectively. The possible reasons for these remarkable properties of the PLA/EGMC specimens are proposed in this study.     

Properties of polyamide 6,10/poly(vinyl alcohol) blends and impact on oxygen barrier performance

The oxygen transmission rate, average volume of free‐volume cavities (V_f) and fractional free volume (F_v) of polyamide 6,10 (PA610)/poly(vinyl alcohol) (PVA) (i.e. PA610_xPVA⁰⁵_y, PA610_xPVA⁰⁸_y and PA610_xPVA¹⁴_y) blend films reduced to minimum values when their PVA contents reached corresponding optimal values. Oxygen transmission rate, V_f and F_v values obtained for optimal PA610_xPVA^z_y blown films were reduced considerably with decreasing PVA degrees of polymerization. The oxygen transmission rate of the optimal bio‐based PA610₈₀PVA⁰⁵₂₀ blown film was only 2.4 cm³ (m²·day·atm)^?1, which is about the same as that of the most often used high‐barrier polymer, ethylene–vinyl alcohol copolymer. Experimental findings from dynamic mechanical analysis, differential scanning calorimetry, wide‐angle X‐ray diffraction and Fourier transform infrared spectroscopy of the PA610_xPVA^z_y blends indicate that PA610 and PVA in the blends are miscible to some extent at the molecular level when the PVA contents are less than or equal to the corresponding optimal values. The considerably enhanced oxygen barrier properties of the PA610_xPVA^z_y blend films with optimized compositions are attributed to the significantly reduced local free‐volume characteristics. © 2017 Society of Chemical Industry     

Direct electrochemical detection of pyruvic acid by cobalt oxyhydroxide modified indium tin oxide electrodes

An enzyme-free electrode was fabricated by anodic electrodeposition of cobalt oxyhydroxide film on an ITO electrode (CoO_x(OH)_y/ITO) for direct electrochemical detection of pyruvic acid (PA) in solution. Scanning electron microscopy (SEM) and atom force microscopy (AFM) were employed to characterize the morphology of CoO_x(OH)_y film. Cyclic voltammetry (CV) was used to investigate the electrochemical properties of PA on CoO_x(OH)_y/ITO in order to select the optimal potential for the chronoamperometric detection of PA. It was found that the CoO_x(OH)_y/ITO electrode served as an excellent PA sensor with a linear detection range of 1.00 μM to 1.91 mM, a detection limit of 0.55 μM, and a high sensitivity of 417.1 μA mM⁻¹ cm⁻². Moreover, the response time of CoO_x(OH)_y/ITO to PA is less than 10 s, which is the shortest for PA detection reported in literature using electrochemical method. These properties and the high stability of CoO_x(OH)_y/ITO made it a good candidate for developing electrochemical enzyme-free PA sensing device.     

Negative air ion releasing properties of tourmaline/bamboo charcoal compounds containing ethylene propylene diene terpolymer/polypropylene composites

The average concentrations of negative air ions (C_ion?) emitted from tourmaline (T), bamboo charcoal (B) particles, and tourmaline/bamboo charcoal (T/B) compounds containing polypropylene (PP) and ethylene propylene diene terpolymer/polypropylene (EPDM/PP) composite specimens under varying testing conditions were investigated in this study. The C_ion? values emitted from T or B filled PP and EPDM/PP composite specimens reached a maximum value as their T or B contents approached the 5 and 3 wt % optimum values, respectively. In contrast, the C_ion? values of T/B compounds filled PP and EPDM/PP composite specimens were significantly higher than their theoretical C_ion? values estimated using the “simple mixing rule,” and reached a maximum value as the weight ratio of T to B reaches an optimum value. At this optimum T/B weight ratio, the C_ion? values of T/B compounds filled PP and EPDM/PP composite specimens reached another maximum as their total compound loadings reached the optimum loading of 6 and 4 wt %, respectively. The C_ion? values of the PP/T/B and EPDM/PP/T/B specimens increased significantly as they were tested under dynamic mode or by increasing the testing temperatures. The T and/or T/B powders filled PP and EPDM/PP specimens exhibited significantly higher tensile strength (σ_f) and elongation at break (ε_f) values than did the B filled PP and EPDM/PP specimens with the same filler loadings, respectively. Energy dispersive X‐rays, particle size, and SEM morphology analysis of the filler particles present in the T, B, and T/B filled composite specimens were performed to understand these interesting negative air ion and tensile properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Oxygen barrier,free volume,and blending properties of fully bio-based polyamide 11/poly(vinyl alcohol) blends

Fully bio-based polyamide 11 (PA11) was melt-blended with poly(vinyl alcohol) (PVA) with varying degrees of polymerization (DP) to prepare PA11_xPVA^z_y. The PA11_xPVA^z_y films demonstrated the lowest oxygen transmission rates (OTR) and free volume characteristics, when PVA contents of each PA11_xPVA^z_y series reached a corresponding critical concentration. The minimum OTR and free volume characteristics obtained for the optimal PA11_xPVA^z_y films reduced significantly with decreasing PVA DPs. The OTR of the optimal PA11_xPVA^z_y blown film was 1.07 cm³ m⁻² day⁻¹ atm⁻¹, which is near to that of the ethylene-vinyl alcohol copolymer high-barrier polymer. The results of dynamical, mechanical, and other experimental characterizations demonstrated that PA11 and PVA are compatible to some extent when PVA concentrations are less-than or equal to the respective critical values. The enhanced oxygen permeation resistance and free volume characteristics for optimal PA11_xPVA^z_y films are at least partly ascribed to the improved hydrogen-bonded molecular interactions between PA11 CO groups and PVA O─H groups. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48562.     

Properties of polyamide 612/poly(vinyl alcohol) blends and their impact on free volume and oxygen barrier properties

Oxygen transmission rates and free volume properties (i.e. average volumes of free-volume-cavities (V_f), mean number of the free volume cavities per unit volume (I₃) and fractional free volume (F_v)) values of bio-based polyamide 612 (PA612)/poly(vinyl alcohol) (PVA) (i.e. PA612_xPVA⁰³_y, PA612_xPVA⁰⁵_y, PA612_xPVA⁰⁸_y and PA612_xPVA¹⁴_y) blend films were reduced to a minimum value, when their PVA content reached corresponding optimal values of 25, 20, 15 and 10 wt%, respectively. The minimum oxygen transmission rate, V_f, I₃ and F_v value obtained for the best PA612₉₀PVA¹⁴₁₀, PA612₈₅PVA⁰⁸₁₅, PA612₈₀PVA⁰⁵₂₀ and PA612₇₅PVA⁰³₂₅ bio-based blown films reduced considerably with decreasing PVA degrees of polymerization. As evidenced by the results of dynamical mechanical analysis, differential scanning calorimetry, wide angle X-ray diffraction and Fourier transform infrared spectroscopic experiments, PA612 and PVA are miscible to some extent at the molecular level when their PVA contents are ≤ the corresponding optimal values. The significantly improved oxygen barrier and free volume properties for the PA612_xPVA^z_y blend films with optimized compositions is at least in part to the enhanced intermolecular interactions between PA612 carbonyl groups and PVA hydroxyl groups.     

Plasticized properties of poly (lactic acid) and triacetine blends

Systematically investigations of the plasticizing effects of triacetine (TAc) on crystallization, chain mobility, microstructure, and tensile properties of the Poly (lactic acid)/triacetine (PLA/TAc) blends are reported. A new transition hump was observed on the tan δ curve of PLA_xTAc_y specimens at temperatures ranging from ?80 to ?20°C. Thermal, wide angle X‐ray diffraction (WAXD) and dynamic mechanical analysis properties of PLA and PLA_xTAc_y series specimens suggest that PLA and PLA_xTAc_y series specimens can hardly crystallize by cooling the melt in room temperature. However, significant recrystallization of α form PLA crystals was found during the annealing processes of PLA_xTAc_y series specimens. Some “less perfect” β form PLA crystals were found as the TAc contents of PLA_xTAc_y specimens reach 30 wt %. Further morphological analysis show that the inherent brittle deformation behavior of the PLA specimen was successfully transformed into relatively ductile fracture behavior after blending sufficient but optimum amounts of TAc in PLA resins. Possible reasons accounting for this interesting recrystallization, thermal, microstructure and tensile properties of PLA_xTAc_y specimens are proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ultradrawing behavior of gel films of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends at varying drawing conditions

A systematic study of the influence of the drawing temperature and rate on the ultradrawing properties of film samples prepared from gel solutions of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends is reported. At a fixed drawing rate, the achievable draw ratios reached a maximum value when each film specimen was drawn at a temperature near its optimum temperature (T_op). It is interesting to note that the T_op values of each film sample increased consistently with the drawing rate. The achievable draw ratio of each film sample drawn at a constant rate and a temperature near T_op is referred to as the D_raop, which reached another maximum value as the drawing rates approached an optimum value. Dynamic mechanical analysis of the film sample exhibited an extraordinary high transition peaked at temperature near 95°C, which is again very close to the T_op value found for the film sample drawn at a relatively low rate. On the other hand, the birefringence values and tensile strengths of the film specimen were found to improve significantly with the draw ratios, although the improvement of these properties reduced significantly at high draw ratios. Moreover, both the drawing temperature and rate showed beneficial influence on the birefringence, and tensile strengths of the drawn film specimens. Possible mechanisms accounting for these interesting deformation properties are suggested.     

Electrochemical characterization of praseodymia doped zircon. Catalytic effect on the electrochemical reduction of molecular oxygen in polar organic solvents

The voltammetry of microparticles and scanning electrochemical microscopy methodologies are applied to characterize praseodymium centers in praseodymia-doped zircon (Pr_xZr_(1−y)Si_(1−z)O₄; y + z = x; 0.02 < x < 0.10) specimens prepared via sol–gel synthetic routes. In contact with aqueous electrolytes, two overlapping Pr-centered cathodic processes, attributable to the Pr (IV) to Pr (III) reduction of Pr centers in different sites are obtained. In water-containing, air-saturated acetone and DMSO solutions as solvent, Pr_xZr_(1−y)Si_(1−z)O₄ materials produce a significant catalytic effect on the electrochemical reduction of peroxide radical anion electrochemically generated. These electrochemical features denote that most of the Pr centers are originally in its 4+ oxidation state in the parent Pr_xZr_(1−y)Si_(1−z)O₄ specimens. The variation of the catalytic performance of such specimens with potential scan rate, water concentration and Pr loading suggests that Pr is not uniformly distributed within the zircon grains, being concentrated in the outer region of such grains.     

The effect of poly(vinyl alcohol) hydrolysis on the properties of its blends with nylon 6

An investigation of the properties of the blends of nylon 6 (PA6) and poly(vinyl alcohol) (PVA) with varying degrees of hydrolysis was conducted. A near disappearance of the characteristics of the α‐form PVA crystals, crystallization exotherms, and hydrogen‐bonded hydroxyl groups and the tensile properties originally associated with the PVA molecules of PA6_xPVA PA6_xPVA, and PA6_xPVA specimens was observed as the PVA contents of the specimens became equal to or less than their corresponding ‘‘critical’’ values at 16.7 wt%, 33.3 wt%, and 50 wt%, respectively. These results support the idea that PVA molecules are miscible with PA6 molecules to some extent at the molecular level as the PVA contents of the blends become equal to or less than their corresponding critical PVA contents. In this article, we have proposed the possible reasons accounting for these properties of the PA6_xPVA_y series specimens with a varying degree of hydrolysis. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers