Structure development in melt spinning of poly(ethylene‐co‐octene) filaments with various comonomer contents

An experimental study of the spinnability and the variation in crystallinity and orientation of melt spinning of poly(ethylene‐co‐octene) with different contents of comonomers was carried out. The spinning behavior of these polymers was investigated under different draw‐down ratios and temperatures and correlated to spinline stress. The melt‐spun filaments were characterized by wide‐angle X‐ray diffraction birefringence, and differential scanning calorimetry. S‐1 is a high‐density polyethylene and S‐2, S‐3, and S‐4 have 16, 22, and 38 wt % octene. An orthorhombic unit cell was found in all four polymers, but a dominant hexagonal structure (perhaps mesophase) was found for the highest octene level (S‐4). The orientation factors for the a‐, b‐, and c‐axis of the orthorhombic crystal structure and a‐axis of the hexagonal phase were then calculated. The crystalline orientation behavior of the lower octene copolymers (S‐1, S‐2, and S‐3) are similar and can be represented as a “row‐nucleated“ structure. However, the orientation behavior of S‐4 was different. The uniaxial mechanical properties were also measured. The Young's modulus and tensile strength generally increased with birefringence for all polymers. With increasing content of octene, the Young's modulus showed a decrease from semicrystalline thermoplastic toward an elastomer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 9–22, 2004     

Film formation from pigmented latex systems: Mechanical and surface properties of ground calcium carbonate/functionalized poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) latex blend films

The mechanical and surface properties of films prepared from model latex/pigment blends were studied using tensile tests, surface gloss measurements, and atomic force microscopy. Functionalized poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) [P(BMA/BA)] and ground calcium carbonate (GCC) were used as latex and extender pigment particles, respectively. The critical pigment volume concentration of this pigment/latex blend system was found to be between 50 and 60 vol % as determined by surface gloss measurement and tensile testing of the blend films. As the pigment volume concentration increased in the blends, the Young's modulus of the films increased. Nielsen's equations were found to fit the experimental data very well. When the surface coverage of carboxyl groups on the latex particles was increased, the yield strength and Young's modulus of the films both increased, indicating better adhesion at the interfaces between the GCC and latex particles. When the carboxyl groups were neutralized during the film formation process, regions with reduced chain mobility were formed. These regions acted as a filler to improve the modulus of the copolymer matrix and the modulus of the resulting films. The carboxyl groups on the latex particle surfaces increased the surface smoothness of the films as determined by surface gloss measurement. When the initial stabilizer coverage of the latex particles was increased, the mechanical strength of the resulting films increased. At the same time, rougher film surfaces also were observed because of the migration of the stabilizer to the surface during film formation. With smaller‐sized latex particles, the pigment/latex blends had higher yield strength and Young's modulus. Higher film formation temperatures strengthen the resulting films and also influence their surface morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4550–4560, 2006     

High‐tensile‐strength polyvinyl alcohol films prepared from freeze/thaw cycled gels

The mechanical properties and molecular structure of a poly(vinyl alcohol) (PVA) film, which was obtained by eliminating water from a PVA hydrogel using repeated freeze/thaw cycles, were investigated by tensile tests, thermal analysis, and X‐ray diffraction measurements. The mechanical properties of PVA with 99.9% saponification were measured as a function of the number of freeze/thaw cycles performed. The tensile strength and Young's modulus increased and the elongation at break decreased with increasing freeze/thaw cycles. The tensile strength and Young's modulus of PVA films obtained after seven freeze/thaw cycles were as high as 255 MPa and 13.5 GPa after annealing at 130°C. Thermal analysis and X‐ray diffraction measurements revealed that this is because of a high crystallinity and a large crystallite size. A good relationship between the tensile strength and the glass transition temperature was obtained, regardless of the degree of saponification and annealing conditions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40578.     

Monomer cast polyamide 6 composites and their treatment with high‐energy electrons

At first, the impact of selected spherically structured nanofillers made of different polar materials (carbon, silicon carbide, surface‐modified silica, 2 wt % each) on mechanical properties of monomer cast polyamide 6 (MCPA6) was examined. Only the low‐polar carbon‐based nanofiller showed an average particle size below 100 nm in the liquid phase before polymerization was initiated. With regard to neat MCPA6, mechanical properties of the composite loaded with the carbon nanoparticles like tensile strength, Young's modulus, and heat distortion temperature could be improved by 6.4%, 13.5%, and 27.5%, respectively. The efficiency of carbon as filler material for MCPA6 was also shown for carbon short‐cut fibers. A fiber content of 15% improved tensile strength from 78 to 93 MPa (19%) and Young's modulus could be doubled from 2660 MPa to nearly 5300 MPa. Regardless of the improved mechanical properties, the composites showed reduced degrees of crystallinity. Therefore, electron beam irradiation was applied to crosslink the polymer chains as an alternative to improve material properties. Crosslinking was supported by the application of a curing agent (CA). Two strategies for crosslinking experiments were tested: (1) Irradiation of CA‐containing neat MCPA6 to find the most effective dose and subsequent treatment of the composites under this special condition; (2) Optimization of the properties by irradiation of the composites itself at graduated dose values. The second way was more convenient and showed, with regard to the composites without CA, improvements of tensile strength and Young's modulus of 6% each. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Transparent,flexible, and high‐strength regenerated cellulose/saponite nanocomposite films with high gas barrier properties

Regenerated cellulose‐saponite nanocomposite films were prepared from LiOH/urea solutions, and exhibited high optical transparency and flexibility. The saponite platelets formed intercalated nanolayered structures in the composites. The longitudinal directions of both the cellulose II crystallites and the saponite platelets were preferentially oriented parallel to the film surface in the composites. The good nanodispersibility and high orientation of the saponite platelets in the composite films resulted in high mechanical strength, high Young's modulus, and good thermal dimensional stabilities, and gas barrier properties in the composites, compared with a reference cellulose film. Moreover, the tensile strength and Young's modulus of the composite film reached 241 MPa and 7.7 GPa, respectively, when a simple drawing process was applied to the wet composite film; this is probably owing to the improvement in the orientation of the cellulose II crystallites and saponite platelets in the composites. The composite films also showed high toughness and ductility. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3168–3174, 2013     

Addition of 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl) imide to improve the thermal stability of regenerated cellulose

This article reports the influence of 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl) imide (BMITFSI) addition on the thermal and mechanical properties of regenerated cellulose. Scanning electron microscopy, Young's modulus values, thermogravimetric analysis, glass‐transition temperature values, and ultraviolet–visible spectroscopy were used to assess the effect of BMITFSI addition on the properties of regenerated cellulose. The addition of a room‐temperature ionic liquid, BMITFSI, during the dissolution of cellulose was found to enhance the thermal stability of regenerated cellulose. Compared to other reported plasticizers for regenerated cellulose, such as glycerol, glycols, water, mineral oil, and α‐monoglycerides, the low vapor pressure of BMITFSI led to a long performance with the least evaporation or leaching. In addition, the immiscible nature of BMITFSI in water and its stability against moisture made BMITFSI an effective plasticizer for regenerated cellulose over a broad range of surrounding humidities and temperature conditions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

High strength poly(vinyl alcohol) films obtained by drying and then stretching freeze/thaw cycled gel

The mechanical properties of stretched poly(vinyl alcohol) (PVA), which is formed by stretching a film prepared from a freeze/thaw cycled gel, were investigated as a function of the stretching ratio. The tensile strength and Young's modulus of 800% stretched PVA annealed at 130°C were 3.4 and 119 GPa, respectively. These values were much higher than those for a PVA film prepared without freeze/thaw cycling. For a film stretched more than 600% before annealing, two melting peaks, assignable to folded and extended chain crystals, were observed around 220°C and 230°C, respectively. This indicates that a shish‐kebab structure is formed as the stretching ratio increases. After annealing at 130°C, the folded‐chain crystal transformed to an extended‐chain crystal if an extended‐chain crystal was present in the stretched film before annealing. High tensile strength and Young's modulus after annealing were due to the formation of extended‐chain crystal. Therefore, the presence of extended‐chain crystal for annealing is important to provide good mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41318.     

On the nonlinear behavior of Young's modulus of carbon‐bonded alumina at high temperatures

The origin of the nonlinear behavior of the Young's modulus (E) of carbon‐bonded alumina at high temperatures was addressed, based on the microstructural changes observed during processing and their thermo‐mechanical properties. Impulse excitation technique, thermogravimetric analysis, porosity measurement, and scanning electron microscopy were conducted in order to highlight and explain the E behavior. The finite element model of a virtual microstructure was simulated and the results attained are in good agreement with the experimental data. The tests revealed that the Young's modulus of a cured sample heated from room temperature up to 500°C was governed by the release of volatiles. Above this temperature, the thermal expansion mismatch among alumina, graphite, and the carbon matrix is dominant resulting in an increase in the effective Young's modulus. During cooling, crack networks and gaps between alumina particles and the carbon matrix were developed. The former were induced by volatile release and by the graphite's highly anisotropic thermal expansion. The latter was derived by the thermal expansion mismatch between the alumina and the carbon matrix. The closure of the gaps and cracks governed the expansion behavior during the second heating cycle and a nonlinear effective Young's modulus increase as a function of temperature was observed.     

On the structure‐properties relationship in montmorillonite‐filled polyamide 6 nanocomposites

Polyamide 6/montmorillonite (MMT) nanocomposites were prepared by melt compounding method comprising 1–7.5 wt % of Nanomer I.24 TL or 5 and 10 wt % of Cloisite 15A organically modified nanoclays. The composite samples were characterized by synchrotron X‐ray, thermal and FT‐IR spectroscopy methods looking for changes in the micro‐ and nanostructure of both PA6 matrix and MMT reinforcement as a function of the clay content and type. These data were discussed in conjunction with the mechanical properties of the respective nanocomposites. Generally, the Young's modulus was found to increase proportionally to the clay content being the highest in samples with strong aggregation of MMT at micron length scale. The tensile strength passed through a maximum at 2.5 wt % clay load presenting a homogeneous microstructure with almost no agglomeration. Increasing the amount of MMT produced less crystalline PA6 matrices, richer in γ‐PA6 polymorph and resulted in larger long spacings of PA6 due to expansion of both crystalline and amorphous domains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Birefringence in injection‐compression molding of amorphous polymers: Simulation and experiment

The influence of the processing variables on the residual birefringence was analyzed for polystyrene and polycarbonate disks obtained by injection‐compression molding under various processing conditions. The processing variables studied were melt and mold temperatures, compression stroke, and switchover time. The modeling of flow‐induced residual stresses and birefringence of amorphous polymers in injection‐compression molded center‐gated disks was carried out using a numerical scheme based on a hybrid finite element/finite difference/control volume method. A nonlinear viscoelastic constitutive equation and stress‐optical rule were used to model frozen‐in flow stresses in moldings. The filling, compression, packing, and cooling stages were considered. Thermally‐induced residual birefringence was calculated using the linear viscoelastic and photoviscoelastic constitutive equations combined with the first‐order rate equation for volume relaxation and the master curves for the Young's relaxation modulus and strain‐optical coefficient functions. The residual birefringence in injection‐compression moldings was measured. The effects of various processing conditions on the measured and simulated birefringence distribution Δn and average transverse birefringence <n_rr?n_θθ> were elucidated. Comparison of the birefringence in disks manufactured by the injection molding and injection‐compression molding was made. The predicted and measured birefringence is found to be in fair agreement. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Predictions of young's modulus of inorganic fibrous particulate‐reinforced polymer composites

In this study, the factors affecting the Young's modulus of inorganic fibrous particulate‐reinforced polymer composites were analyzed, and a new expression of the Young's modulus was derived and was based on a simplified mechanical model. This equation was used to estimate the composite Young's modulus. The estimated relative Young's modulus increased nonlinearly with increasing filler volume fraction. Finally, we verified the equation preliminarily by quoting the measured Young's modulus values of poly(butylene terephthalate)/wollastonite, polypropylene/wollastonite, and nylon 6/wollastonite composites reported in the literature. Good agreement was shown between the predictions and the experimental data of the relative Young's modulus values for these three composite systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2957–2961, 2013     

Simultaneously enhanced cryogenic mechanical behaviors of cyanate ester/epoxy resins by poly(ethylene oxide)‐co‐poly(propylene oxide)‐co‐poly(ethylene oxide) (PEO‐PPO‐PEO) block copolymer and clay

Cryogenic mechanical properties are important parameters for thermosetting resins used in cryogenic engineering areas. The hybrid nanocomposites were prepared by modification of a cyanate ester/epoxy/poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) (PEO‐PPO‐PEO) system with clay. It is demonstrated that the cryogenic tensile strength, Young's modulus, ductility (failure strain), and fracture resistance (impact strength) are simultaneously enhanced by the addition of PEO‐PPO‐PEO and clay. The results show that the tensile strength and Young's modulus at 77 K of the hybrid nanocomposite containing 5 wt% PEO‐PPO‐PEO and 3 wt% clay were enhanced by 31.0% and 14.6%, respectively. The ductility and impact resistance at both room temperature and 77K are all improved for the hybrid composites. The fracture surfaces of the neat BCE/EP and its nanocomposites were examined using scanning electron microscopy (SEM). Finally, the dependence of the coefficients of thermal expansion (CTE) on the clay and PEO‐PPO‐PEO contents was examined by thermal dilatometer. POLYM. COMPOS., 38:2237–2247, 2017. © 2015 Society of Plastics Engineers     

Effects of process conditions on Young's modulus and strength of extrudate in short‐fiber‐reinforced polypropylene

We examined the effects of process conditions on Young's modulus and tensile strength of extruded short‐fiber reinforced thermoplastics. With increasing extrusion ratio and decreasing extrusion temperature, the fiber alignment increases, the mean fiber length decreases, and the mechanical properties of the matrix are improved. The orientation parameter, mean fiber length, Young's modulus, and tensile strength of the matrix are described as a function of extrusion ratio and extrusion temperature. The models proposed by Fukuda and Kawata, and Fukuda and Chou are applied to predict Young's modulus and tensile strength of the composites using orientation parameter. By comparing the predicted Young's modulus and tensile strength with experimental results, the validity of the models is examined. The prediction of Young's modulus agreed quit with the experimental results. The tensile strength of composite extruded below the melting point nearly matched that of the neat matrix. There is no the strengthening effect of the fiber since the angle between fracture surface and fiber direction is very small. POLYM. COMPOS. 28:29–35, 2007. © 2007 Society of Plastics Engineers     

Compilation of mechanical properties for the structural analysis of solid oxide fuel cell stacks. Constitutive materials of anode-supported cells

The mechanical failure of one cell is sufficient to lead to the end of service of a solid oxide fuel cell (SOFC) stack. Therefore, there is growing interest in gaining knowledge on the mechanical properties of the cell materials for stress analysis.This study compiles available data from the literature on the mechanical properties of the most common materials used in intermediate-temperature anode-supported cells: nickel and yttria-stabilized zirconia (Ni–YSZ) anodes, YSZ electrolytes, yttria (YDC) or gadolinia-doped ceria (GDC) compatibility layers and lanthanum strontium manganite (LSM) or lanthanum strontium cobalt ferrite (LSCF) cathodes. The properties for the simulation of stresses, i.e. coefficient of thermal expansion (CTE), Young's modulus, Poisson's ratio, creep behaviour and strength are reported, with an emphasis on temperature and porosity dependence and the evolution upon aging or cycling when available. Measurements of our Ni(O)–YSZ anode material includes the CTE (oxidised and reduced state), Young's modulus and strength at room temperature (oxidised and reduced) and 1073 K (oxidised).     

Effect of silica nanoparticle size on toughening mechanisms of filled epoxy

The addition of silica nanoparticles (23 nm, 74 nm, and 170 nm) to a lightly crosslinked, model epoxy resin, was studied. The effect of silica nanoparticle content and particle size on glass transition temperature (T_g), coefficient of thermal expansion (CTE), Young's modulus (E), yield stress (σ), fracture energy (G_IC) and fracture toughness (K_IC), were investigated. The toughening mechanisms were determined using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and transmission optical microscopy (TOM). The experimental results revealed that the addition of silica nanoparticles did not have a significant effect on T_g or the yield stress of epoxy resin, i.e. the yield stress and T_g remained constant regardless of silica nanoparticle size. As expected, the addition of silica nanoparticles had a significant impact on CTE, modulus and fracture toughness. The CTE values of nanosilica-filled epoxies were found to decrease with increasing silica nanoparticle content, which can be attributed to the much lower CTE of the silica nanoparticles. Interestingly, the decreases in CTE showed strong particle size dependence. The Young's modulus was also found to significantly improve with addition of silica nanoparticles and increase with increasing filler content. However, the particle size did not exhibit any effect on the Young's modulus. Finally, the fracture toughness and fracture energy showed significant improvements with the addition of silica nanoparticles, and increased with increasing filler content. The effect of particle size on fracture toughness was negligible. Observation of the fracture surfaces using SEM and TOM showed evidence of debonding of silica nanoparticles, matrix void growth, and matrix shear banding, which are credited for the increases in toughness for nanosilica-filled epoxy systems. Shear banding mechanism was the dominant mechanism while the particle debonding and plastic void growth were the minor mechanisms.     

Compatibilizing effect of starch‐grafted‐poly(L‐lactide) on the poly(ε‐caprolactone)/starch composites

The poly(ε‐caprolactone) (PCL)/starch blends were prepared with a coextruder by using the starch grafted PLLA copolymer (St‐g‐PLLA) as compatibilizers. The thermal, mechanical, thermo‐mechanical, and morphological characterizations were performed to show the better performance of these blends compared with the virgin PCL/starch blend without the compatibilizer. Interfacial adhesion between PCL matrix and starch dispersion phases dominated by the compatibilizing effects of the St‐g‐PLLA copolymers was significantly improved. Mechanical and other physical properties were correlated with the compatibilizing effect of the St‐g‐PLLA copolymer. With the addition of starch acted as rigid filler, the Young's modulus of the PCL/starch blends with or without compatibilizer all increased, and the strength and elongation were decreased compared with pure PCL. Whereas when St‐g‐PLLA added into the blend, starch and PCL, the properties of the blends were improved markedly. The 50/50 composite of PCL/starch compatibilized by 10% St‐g‐PLLA gave a tensile strength of 16.6 MPa and Young's modulus of 996 MPa, respectively, vs. 8.0 MPa and 597 MPa, respectively, for the simple 50/50 blend of PCL/starch. At the same time, the storage modulus of compatibilized blends improved to 2940 MPa. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of different film preparation procedures on the thermal,morphological and mechanical properties of pure and calcite‐filled HDPE films

The effect of different film preparation procedures on the thermal, morphological and mechanical properties of high density polyethylene (HDPE) films have been studied using differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and ultimate tensile testing. Film preparation procedures included variation in cooling methods, including quenching, forces (fanning) and natural cooling and techniques such as extrusion followed by melt squeezing and compression molding. The heat of fusion (from DSC), the degree of crystallinity (from WAXRD) and the crystallite size (from WAXRD and AFM) were found to be highest for naturally cooled specimens, followed by fan‐cooled and quenched ones. AFM images of surface topology exhibit stacked lamellar morphology for forcefully cooled (fan‐cooled and quenched) samples and spherulitic ‘lozenges’ for naturally cooled ones. The Young's modulus and yield stress [from the universal testing machine (UTM)] were highest for naturally cooled samples, followed by fan‐cooled and quenched ones. Among the calcite‐filled composites, the ‘base film,’ which was prepared by extrusion followed by melt squeezing and natural cooling, exhibited the lowest heat of fusion and degree of crystallinity and a similar crystallite size relative to compression‐molded films. Lower yield stress, tensile strength and Young's modulus and higher elongation at break were observed for the base film in comparison to the naturally cooled composite film. The low degree of crystallinity and crystallite size in the ‘base film’ explain all of its mechanical and morphological properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1427–1434, 2004     

A study of nano‐mechanical and macro‐mechanical properties of ethylene vinyl acetate

Nano‐ and macro‐mechanical properties of ethylene vinyl acetate (EVA) with various amounts of vinyl acetate (VA) have been investigated. Nano‐mechanical properties (modulus and hardness) were obtained using nano‐indentation measurements while macro‐mechanical properties were determined using tensile test measurements. A decrease in Young's modulus and hardness was observed with increasing VA content for both nano‐ and macro‐mechanical measurements. An increase in Young's modulus and hardness was observed as a function of the draw ratio keeping the VA content constant. The difference between macro‐ and nano‐mechanical properties as a function of VA content and draw ratio is explained in terms of crystallinity and chain orientation. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers     

Strength and Young's modulus change in concrete due to long-term drying and heating up to 90 °C

Understanding changes in the strength and Young's modulus of concrete under long-term drying or heating less than or equal to 90 °C is crucial for managing the aging of industrial buildings. We collected experimental data on changes in the physical properties of concrete components, aggregates, cement pastes, and concretes containing different aggregates and mortar under different heating and drying conditions. The change in compressive strength of concretes under various drying or heating conditions was explained by the behavior of the cement paste matrix and damage accumulation caused by differences in volume changes between the aggregate and mortar. In contrast, the variation in the Young's modulus of concrete caused by the drying or heating conditions was mainly explained by the increase in the number of voids due to internal cracking in the concrete.     

Mechanical Properties of Anisotropic Metaphosphate Glass

The effect of anisotropy on the mechanical properties was investigated for a chain‐structured metaphosphate glass (12.5Li₂O–12.5Na₂O–12.5K₂O–12.5Cs₂O–50P₂O₅ mol%). Anisotropic glasses with different birefringence values were prepared with a fiber elongation method. The strength and Young's moduli of the glasses were measured with a three‐point bending method. It was found that the strength and Young's modulus increased with increasing birefringence, reaching about 160% and 140%, respectively, compared with the values for the isotropic glass. The enhancement of the mechanical properties was attributed to the orientation of ‐P‐O‐P‐ chains in the glass.