Ultimate Tensile Properties Research Articles

Performance and environmental impact of biodegradable polymers as agricultural mulching films.

In the aim of resolving environmental key issues such as irreversible soil pollution by non-biodegradable and non-recoverable polyethylene (PE) fragments, a full-scale field experiment was set up to evaluate the suitability of four biodegradable materials based on poly(butylene adipate-co-terephtalate) (PBAT) to be used as sustainable alternatives to PE for mulching application in vineyard. Initial ultimate tensile properties, functional properties during field ageing (water vapour permeability and radiometric properties), biodegradability and agronomical performance of the mulched vines (wood production and fruiting yield) were studied. In spite of their early loss of physical integrity that occurred only five months after vine planting, the four materials satisfied all the requested functional properties and led to agronomic performance as high as polyethylene. In the light of the obtained results, the mulching material lifespan was questioned in the case of long-term perennial crop such as grapevine. Taking into account their mulching efficiency and biodegradability, the four PBAT-based studied materials are proven to constitute suitable alternatives to the excessively resistant PE material.

Simulation of the Elastic and Ultimate Tensile Properties of Diamond, Graphene, Carbon Nanotubes, and Amorphous Carbon Using a Revised ReaxFF Parametrization.

In light of the enduring interest in using nanostructured carbon materials as reinforcing elements in composite materials, there is a significant need for a reliable computational tool capable to predict the mechanical properties, both elastic properties and properties at the point of fracture, in large-scale atomistic simulations. A revised version of the ReaxFF reactive force field parametrization for carbon, ReaxFFC-2013, was recently published and is notable because of the inclusion of density functional theory (DFT)-derived mechanical data for diamond and graphite in the fitting set. The purpose of the present work is to assess the accuracy of this new force field for predicting the mechanical properties for several allotropes of carbon, both in the elastic regime and during fracture. The initial discussion focuses on the performance of ReaxFFC-2013 for diamond and graphene, the two carbon forms for which mechanical properties were included in the parametrization data set. After it is established that simulations conducted with the new force field yield results that agree well with DFT and experimental data for most properties of interest, its transferability to amorphous carbon and carbon nanotubes is explored. ReaxFFC-2013 is found to produce results that, for the most part, compare favorably with available experimental data for single and multiwalled nanotubes and for amorphous carbon models prepared over a range of densities. Although there is opportunity for improvement in some predicted properties, the ReaxFFC-2013 parametrization is shown to generally perform well for each form of carbon and to compare favorably with DFT and experimental data.

Scenarios of crack propagation in bast fibers: Combining experimental and finite element approaches

This work investigates the rupture of bast fiber type from hemp, to attain better control over the ultimate tensile and fracture strength properties of hemp composites. Crack propagation in both individualized and bundles of hemp fibers is studied. Crack initiation is controlled using generated defects within fibers. A non-contact-ablation apparatus creates these defects using a laser beam directed by high-precision optics. V- and U-type notches are processed, with sizes ranging from 2 to 30μm in depth. The micromechanical testing of damaged fibers is coupled to a high-speed camera, allowing for the measurement of ultimate properties as well as monitoring of the crack propagation.Finite element simulation is developed to identify possible damage scenarios for bundles and elementary fibers. Microcracks are allowed to initiate, grow and coalesce based on non-prescribed crack propagation (i.e., not imposed or with direction update) and stress criteria. High speed camera recording indicate a wide variability in crack propagation speed in the range 2–149m/s. Both longitudinal and transverse cracking are observed depending on the notch geometry. Our results demonstrate that the damage kinetics is a combination of growth and coalescence of microcracks. These damage mechanisms compete depending on the notch geometry and fiber element dimensions.

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 (PEg-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 PEg-MAH to ATNAL at 8. Achievable draw ratio (Dra) values of UHMWPE/NAL (F100Ay), UHMWPE/ATNAL (F100Ax%-8-y) and/or UHMWPE/FNAL (F100Ax%-8FPEzy) 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 Dra values of F100Ax%-8FPEz0.075 as-prepared fiber specimens were significantly higher than those of F100A0.1 and F100Ax%-8-0.1 as-prepared fiber specimens. In which, the maximal Dra values obtained for F100Ax%-8FPEz0.075 as-prepared fibers reached another maximal value as FNAL fillers were modified using an optimal weight ratio of PEg-MAH to ATNAL at 8. The ultimate tensile strength value of F100A2%-8FPE80.075 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

Sustainable food packaging: Valorising wheat straw fibres for tuning PHBV-based composites properties

The present work aims at investigating the impact of wheat straw fibres (WSF) size, morphology and content on the process-ability and functional properties (mechanical properties and water vapour permeability) of PHBV-based composites. For that purpose, three types of fibres obtained by successive grindings (from the micrometric up to the millimetric scale) were used. It was shown that the highest possible filler level was all the more high when decreasing fibre size (over 50wt% in the case of micrometric fibres), due to reduced film heterogeneity and improved fibre wetting by the polymer. As regards functional properties, increasing fibre size and/or content led to a significant degradation of ultimate tensile properties, while Young’s modulus was not significantly affected. At the same time, water vapour transmission rate was significantly increased from 11 up to 110gm−2day−1, which could extend the applicability of PHBV/WSF composites as food packaging materials to respiring fresh products.

Ultradrawing and Ultimate Tenacity Properties of Ultrahigh Molecular Weight Polyethylene Composite Fibers Filled with Nanosilica Particles with Varying Specific Surface Areas

Original and/or functionalized nanosilica particles with a quoted specific surface area of 100, 300, and 600 m2/g, respectively, were used to investigate the influence of specific surface areas of nanosilica particles on ultradrawing and ultimate tensile properties of ultrahigh molecular weight polyethylene (UHMWPE), UHMWPE/nanosilica, and UHMWPE/functionalized nanosilica fibers. The specific surface areas of well‐dispersed functionalized nanosilica particles in UHMWPE/functionalized nanosilica fibers can positively affect their ultradrawing, orientation, ultimate tensile properties, and “micro‐fibrils” morphologies. Excellent orientation and ultimate tensile properties of UHMWPE/nanofiller fibers can be prepared by ultradrawing the UHMWPE/functionalized nanosilica as‐prepared fibers with optimal contents of the best prepared functionalized nanosilica particles well dispersing in the as‐prepared fibers. The ultimate tensile strength value of the best prepared UHMWPE/functionalized nanosilica drawn fiber reaches 7.6 GPa, which is about 2.3 times of those of the best prepared UHMWPE drawn fiber without addition of any nanofiller. Specific surface area, morphological and Fourier transform infrared analyses of original and functionalized nanosilica particles, and/or investigations of thermal, orientation factor, and ultimate tensile properties of as‐prepared and/or drawn UHMWPE/functionalized nanosilica fibers were performed to understand the above improved ultradrawing and ultimate tensile properties of the UHMWPE/functionalized nanosilica as‐prepared and/or drawn fibers.

Investigations on the Structural and Mechanical Properties of Polyurethane Resins Based on Cu(II)phthalocyanines

This work report was reported on the effect of the addition of organic filler, that is, 2(3),9(10),16(17),23(24)-octahydroxycopper(II)phthalocyanine [(OH)8CuPc] (3), on the thermal, tensile, and morphological properties of a polyurethane matrix. The mechanical and dynamic mechanical thermal tests together with microstructural characterization of CuPc/PU composites were performed. The three PU composite films containing up to 1, 15, and 30 wt% of CuPc have different behaviors in terms of their morphological issues, thermal properties, and tensile behavior in comparison with the PU film as the reference material. Very high elongations at break from 910% to 1230%, as well as high tensile strengths, illustrate excellent ultimate tensile properties of the prepared samples. The best mechanical and thermomechanical properties were found for the sample filled with 30 wt% of CuPc.

Design, polymerization, and properties of polyurethane elastomers from miscible, immiscible, and hybridized seed‐oil derived soft segment blends

ABSTRACTPolyester seed‐oil derived polyols have been prepared and blended with conventional polyols for making polyurethane elastomers. Miscibility was complete for polypropylene oxide/polyethylene oxide and polytetramethylene oxide (PTMEG). Blends of polyester seed‐oil derived polyols with conventional polyester polyols (polybutylene adipate and ɛ‐polycaprolactone) were immiscible or nearly so. Furthermore, the phase behavior (miscible vs. immiscible) did not change appreciably for each blend composition explored as a function of temperature at relevant ranges (up to the polyether ceiling temperature). This counter‐intuitive result is found to be actually consistent with calculated solubility parameters for each polyol type and the phase diagrams computed on their basis. The phase behavior of the polyols is shown to have significant effects on the properties of polyurethane elastomers where immiscible polyols cause broadening of the glass transition distribution and significant reduction of ultimate tensile properties. However, here it is shown that immiscible systems containing polyester seed‐oil derived polyols can be transesterified with the appropriate polyol partner of interest to create a new single phase polyol or that the polyester polyol monomers can also be copolymerized to make new single phase polyols, both of which result in improved polyurethane elastomer properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 93–102

Effect of Shoulder Surface Dimension and Geometries on FSW of AA7039

AbstractIn the present study, friction stir welding of AA7039 butt plates were investigated with respect to threaded probed tools having different shoulder diameters and shoulder surface geometries. The ultimate tensile properties, micro hardness and grain size of the welds were investigated with respect to the varying tool geometries. The mechanical properties of the welded joints were observed to be influenced by the shoulder diameter and shoulder surface geometry. With the increase in the shoulder diameter, the effect of shoulder concavity on refining the weld grain size diminished. Good quality welds were produced by using tools with semi-concave shoulder surface having shoulder and probe diameters of 19 mm and 7 mm respectively. The fracture surfaces of AA7039 weld samples were dimpled and the crack front energy-dispersive X-ray spectroscopy analysis exhibited absence of segregation of Zn.

Experimental Study on Mechanical Properties of Steel and Polypropylene Fiber-Reinforced Concrete

The mechanical tests of normal concrete (NC) specimens, steel fiber reinforced concrete (SFRC) specimens and polypropylene fiber reinforced concrete (PPFRC) specimens have been carried out. Fiber-reinforced concretes containing different volume fraction and aspect ratio of steel and polypropylene fibers were compared in terms of compressive, splitting tensile, ultimate tensile properties. Test results indicate that the mechanical properties of NC can be improved by addition of steel fibers and can be enhanced with the increase of fiber content. However, polypropylene fiber may cause opposite effect, if volume fraction too high.

Synthesis of Oligo(butylene succinate)-based Polyurethanes

Biobased oligo(butylene succinate)-based thermoplastic polyurethanes (TPUs) were prepared following a two-step polymerization process: condensation of succinic acid and butanediol and the chain extension of resulting hydroxyl-terminated butylene succinate oligomers (OBS) in the presence of butanediol as chain extender and isophorone diisocyanate (IPDI) as coupling agent. Mechanical and thermal properties of the elaborated TPUs were evaluated in terms of hard segment and compared with those of commercial polybutylene succinate (PBS), Bionolle 1001. Whatever the compositions, the ultimate tensile properties of OBS-based TPUs and Bionolle 1001 were found to exhibit similar values (e ≈400%, σ ≈40 MPa), which can be explained by their close molecular weight (60000 g.mol-1 equiv. PS). Interestingly, a higher content of hard segments within OBS-based TPUs leads to materials exhibiting higher rigidity, smaller degree of crystallization, lower melting temperature and weaker stability of the materials with temperature. Such a trend was attributed to the presence of urethane functions and their ability to set up strong H-bonding interchain interactions.

Thermoplastic elastomers blends based on linear low density polyethylene, ethylene-1-octene copolymers and ground rubber tire

Blends of linear low density polyethylene (LLDPE) ethylene-1-octene copolymers (EOC), with different 1-octene (OC) content, and ground rubber tire (GRT) were prepared by melt mixing in a twin screw extruder. Five different compositions of LLDPE/EOC/GRT blends were processed in the extruder to evaluate the effect of EOC addition to the LLDPE/GRT blends. The addition of EOC to LLDPE/GRT blends improves the mechanical properties. Besides, the replacement of 5% of GRT by EOC grades (OC = 20 or 30 wt %) in the 50/50 LLDPE/GRT blend, leads to a significant increase of ultimate tensile properties. The EOC comonomer content affects the properties of LLDPE/EOC and LLDPE/EOC/GRT blends. Dynamical-mechanical analyses showed that, with the addition of EOC to LLDPE/GRT blends, the Tg of GRT and the Tg of EOC are closer. This effect is more pronounced when the EOC with the highest content of comonomer (30 wt %) is added to LLDPE/GRT blend. In this case, only one peak related to the Tg of the rubber phase can be visualized in the amorphous region. These findings indicate that EOC may act as compatibilizer agent for LLDPE/GRT blends.

Application of the taguchi approach to investigate the effects of clay content and saponification parameters on the tensile properties of poly(vinyl alcohol)/clay nanocomposites

Poly(vinyl alcohol) (PVA)/montmorillonite nanocomposites were prepared via solution polymerization. The nanocomposites were formed either by first hydrolyzing poly(vinyl acetate) (PVAc) to PVA and then preparing the PVA/clay, or by initially preparing PVAc/clay and then hydrolyzing the matrix to PVA. The morphology of the nanocomposites was examined by X‐ray diffraction and transmission electron microscopy, which suggested the proper dispersion of silicate layers within the PVA matrix. The influences of some variables including method of preparation, clay content, and time and temperature of saponification on the tensile properties (elastic modulus, stress and elongation at break) of the nanocomposite samples were investigated by using the Taguchi experimental design approach. The results indicated that the tensile properties of the nanocomposites improved as clay content, and the temperature and time of saponification increased. Effect of each factor on the ultimate properties of as prepared nanocomposites are discussed in detail. The analysis of variance (ANOVA) showed that the method of preparation did not influence the ultimate tensile properties of the nanocomposite samples. Thermal degradation of the nanocomposites was studied by thermogravimetric analysis, which showed that their thermal stability was higher than that of virgin polymer. J. VINYL ADDIT. TECHNOL., 19:276–284, 2013. © 2013 Society of Plastics Engineers

Abrasion and fatigue resistance of PDMS containing multiblock polyurethanes after accelerated water exposure at elevated temperature

Segmented polyurethane multiblock polymers containing polydimethylsiloxane and polyether soft segments form tough and easily processed thermoplastic elastomers (PDMS-urethanes). Two commercially available examples, PurSil 35 (denoted as P35) and Elast-Eon E2A (denoted as E2A), were evaluated for abrasion and fatigue resistance after immersion in 85 °C buffered water for up to 80 weeks. We previously reported that water exposure in these experiments resulted in a molar mass reduction, where the kinetics of the hydrolysis reaction is supported by a straight forward Arrhenius analysis over a range of accelerated temperatures (37–85 °C). We also showed that the ultimate tensile properties of P35 and E2A were significantly compromised when the molar mass was reduced. Here, we show that the reduction in molar mass also correlated with a reduction in both the abrasion and fatigue resistance. The instantaneous wear rate of both P35 and E2A, when exposed to the reciprocating motion of an ethylene tetrafluoroethylene (ETFE) jacketed cable, increased with the inverse of the number averaged molar mass (1/Mn). Both materials showed a change in the wear surface when the number-averaged molar mass was reduced to ≈16 kg/mole, where a smooth wear surface transitioned to a ‘spalling-like’ pattern, leaving the wear surface with ≈0.3 mm cracks that propagated beyond the contact surface. The fatigue crack growth rate for P35 and E2A also increased in proportion to 1/Mn, after the molar mass was reduced below a critical value of ≈30 kg/mole. Interestingly, this critical molar mass coincided with that at which the single cycle stress–strain response changed from strain hardening to strain softening. The changes in both abrasion and fatigue resistance, key predictors for long term reliability of cardiac leads, after exposure of this class of PDMS-urethanes to water suggests that these materials are susceptible to mechanical compromise in vivo.

Tensile properties of fumed silica filled polydimethylsiloxane networks

Tensile properties of fumed silica filled hydroxylated polydimethylsiloxane (PDMS) networks were investigated in the current work. Similar to unfilled bimodal networks, unimodal networks filled with concentrated fumed silica exhibit non-Gaussian effect and improved ultimate tensile properties. The concept of “hierarchical network” was proposed to depict the networks exhibiting non-Gaussian effect at sufficiently high strains. It was found that the reinforcing effect originates from both the effective volume effect from filler volume and polymer–filler interaction and the synergistic effect between network chains within the “hierarchical network”. Experimental results showed that filler’s dispersion, concentration, specific surface area and surface chemistry have a great influence on the tensile properties, which could be interpreted by analyzing the variation of both effective volume effect and synergistic effect.

Compatibilization efficiency of carboxylated nitrile rubber and epoxy pre-polymer in nitrile/acrylic rubber blends.

An investigation has been made of the effects from a compatibilizer, viz. carboxylated nitrile rubber (XNBR), on several properties of nitrile rubber (NBR) and acrylic rubber (ACM) blends, including curing characteristics, mechanical, dynamic mechanical and dielectric properties. The presence of XNBR until 10 phr resulted in an improvement of the ultimate tensile properties, especially elongation at break. The mechanical properties associated to the volume fraction of rubber in the network (Vr) and torque values suggest the co-vulcanization phenomenon imparted by the compatibilization. The oil resistance of NBR/ACM (50:50 wt. (%)) blends (compatibilized and non compatibilized) was similar to that observed for pure ACM and significantly higher than NBR. The addition of small amounts of epoxy pre-polymer in combination with XNBR resulted in an additional improvement of the tensile properties. The dynamic mechanical and dielectric properties of the blends were also investigated. The loss modulus values of the compatibilized blends were significantly lower indicating an increase of the elastic characteristics. All blends presented two dielectric relaxation peaks confirming the heterogeneity of the compatibilized blends

Influence of Natural Weathering on the Physical Properties of Compatibilized Blends of Poly(propylene)/Polyamide‐6

AbstractSummary: The present paper deals with the effects of natural weathering on the properties of poly(propylene)/polyamide‐6 blends (70/30 wt %) without and with PP‐g‐MA used as the compatibilizer at various content ratios (2, 4 and 6 wt%). The resulted changes in the chemical structure, morphology and mechanical properties of the different blends were analyzed by Fourier transform infrared (FT‐IR) spectroscopy, scanning electron microscopy (SEM), and tensile tests. After one year of outdoor exposure, no important changes in the chemical structure are observed by FT‐IR spectroscopy for both virgin and compatibilized blends. SEM analysis revealed the effectiveness of PP‐g‐MA to improve the compatibility of PP/PA‐6 blends. However, the weathering effect on the morphology of both virgin and compatibilized blends resulted in the formation of voids and cracks on the fracture surfaces, while the ultimate tensile properties decreased considerably. The overall results indicated clearly that the presence of PP‐g‐MA compatibilizer in PP/PA‐6 blends had no influence on the photo‐oxidation process.

Thermo-mechanical properties of high density polyethylene – fumed silica nanocomposites: effect of filler surface area and treatment

High density polyethylene was melt compounded with various untreated (hydrophilic) or surface treated (hydrophobic) fumed silica nanoparticles, having different surface areas. The thermo-mechanical properties of the resulting nanocomposites have been thoroughly investigated. Field emission scanning electron microscopy revealed that nanofiller aggregation was more pronounced as the silica surface area increased, while nanofiller dispersion improved with a proper filler functionalization. The homogeneous distribution of fumed silica aggregates at low filler content allowed us to reach remarkable improvements of thermal stability, evidenced by an increase of the degradation temperature and a decrease of the mass loss rate with respect to neat matrix, especially when surface treated nanoparticles were utilized. Interestingly, the stabilizing effect produced by fumed silica nanoparticles was accompanied by noticeable enhancements of the ultimate tensile mechanical properties, both under quasi-static and impact conditions. Concurrently, a progressive enhancement of both elastic modulus and tensile stress at yield with the filler amount, was observed.

A comparative study on curing characteristics and thermomechanical properties of elastomeric nanocomposites: The effects of eggshell and calcium carbonate nanofillers

AbstractAfter‐hatching eggshell (AHES) nanobiofiller and nanocalcium carbonate (nano‐CA) were separately added to various elastomers, such as acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), and natural rubber (NR), in various amounts of 5, 10, and 15 phr. The effect of particle size and dispersion of such nanofillers on thermomechanical properties and curing characteristics were then investigated. The ultimate tensile properties of SBR and NR nanocomposites were improved to some extent when 5 phr of AHES nanofiller was added to the rubber compound compared to CA. In the case of NBR nanocompounds, however, the mechanical properties were seemingly comparable, irrespective of the type of nanofiller. This contradictive behavior could be attributed to the alteration of crosslink density due to particular filler–matrix interaction while using mineral and natural fillers. The results of the rheometric study revealed that using AHES rather than CA slightly increases the scorch time of all types of prepared nanocomposites, whereas a significant drop in the optimum curing time was seen for NBR nanocomposites containing AHES biofiller. Moreover, thermogravimetric analysis showed similar thermal stability for SBR nanocomposites containing AHES and CA fillers. Finer particle size of CA and higher porosity of AHES at high and low loading levels were respectively the main reasons for improvement of ultimate properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Experimental Investigation on Vertical Tension Property of Laminated Rubber Bearings

In order to study the vertical tension properties of laminated rubber bearings under different shear strain, pure tension test and shear-tension test on two groups of natural rubber bearings and lead core rubber bearings with 800mm diameter are present in this paper, and the initial stiffness, yield stiffness and yield stress and ultimate tensile properties (limit stress, limit strain) of the rubber isolation bearing in different shear strain are analyzed. The results of the tests provide the reference for the application of rubber bearings on large-scale complex structures or high building structures.