Increase In Percentage Elongation Research Articles

Morphological, mechanical, and thermal characterization of electrospun three‐dimensional graphite nanoplatelets/polystyrene ultra‐fine fibril composite fabrics

AbstractUltra‐fine fibril composites were produced by electrospinning of a polymer solution containing polystyrene (PS)/dimethylformamide (DMF) with different concentrations of three‐dimensional graphite nanoplatelets (3D‐GNPs). Berry's number of PS/DMF polymer solution was extensively studied to produce minimum electrospun PS fiber diameters. Three‐dimensional GNPs of different weight percentages were dispersed in the optimized PS/DMF to produce ultrafine fibril composite fabric. The electrospun average diameters decreased from 1.5 μm for PS fibers to 890 nm for 3D‐GNPs/PS fibril composites, respectively, at 12 and 9.8 Berry's number. High‐resolution transmission electron microscopy samples' micrographs confirm a homogenous dispersion and alignment of 3D‐GNPs in PS fibril composites. Thermal and mechanical characteristics of fabrics were determined using thermogravimetric analysis, thermomechanical Analysis, and dynamic mechanical analysis (DMA). It was found that there was an increase in percentage elongation, tensile strength, thermal stability, and glass‐transition temperature for 3D‐GNPs PS fibril composite fabrics compared to PS fabrics. Diminishing the value of loss tangent, measured by DMA, was used as an approach to predict the maximum amount of 3D‐GNPs weight percent dispersion in electrospun PS/dimethylformamide solution. One of the most important potential applications of the electrospun 3D‐GNPs/PS fibril composite fabrics is in the interiors of vehicles and aerospace industries as it characterizes by its good thermal and mechanical properties as well as its low density.

Elongation Patterns of the Anterior and Posterior Borders of the Anterolateral Ligament of the Knee

To compare the elongation patterns of the anterior and posterior borders of the anterolateral ligament (ALL) at varying knee flexion angles with the knee in a neutral position without any external forces and with external forces applied, including anterior-posterior translation, internal-external rotation, and varus-valgus angulation. Eight cadaveric knees were tested in a custom knee testing system. Elongation of the anterior and posterior borders of the ALL was measured using a MicroScribe 3DLX system at knee flexion angles of 0°, 30°, 60°, and 90° and after the application of internal-external rotation, anterior-posterior translation, and varus-valgus angulation. The anterior border showed a slight noncontinuous increase in percentage elongation (0.8% ± 2.2%) whereas the posterior border showed a continuous decrease in percentage elongation (-12.0% ± 2.8%) as knee flexion increased (P < .001). Apart from the elongation of the posterior border at 90° of knee flexion, internal rotation, varus angulation, and anterior translation resulted in a significant increase in the percentage elongation of the anterior and posterior borders at each flexion angle compared with external rotation, valgus angulation, and posterior translation, respectively. The ALL shows different elongation patterns between the anterior and posterior borders, with a continuous decrease in the percentage elongation of the posterior border as knee flexion increases. This study presents useful evidence to resolve the uncertainty regarding the change in length of the ALL at various degrees of knee flexion. This information may be helpful for deciding the optimal knee flexion angle during ALL graft fixation. The findings from this study suggest that graft fixation during ALL reconstructions should be performed at close to full extension of the knee.

Investigation of carbon black and metakaolin cofillers content on mechanical and thermal behaviors of natural rubber compounds

A series of natural rubber (NR) vulcanizates have been prepared by partially replacing the carbon black by metakaolin (MK). The effect of MK content on the physicomechanical properties and cure characteristics of NR composites was investigated. The effect of with and without silane (Si-69)-modified MK content on the mechanical behaviors of the NR systems has been reported. The physicomechanical properties of the rubber vulcanizates were determined before and after heat aging at 90°C for 72 h and aging with brake fluid for 1 week. NR/MK composites exhibit increase in percentage elongation as increase in the MK filler content.

Ageing behavior of a Cu-bearing ultrahigh strength steel

On ageing at different temperatures a various combination of properties has been obtained for this Cu-bearing ultrahigh strength steel. A substantial increase in strength has been obtained at 450 °C, accompanied by a drop in percentage elongation, percentage reduction in area and toughness. At 550 °C temperature extensive ɛ-Cu precipitates have been observed. The increased strength value retained in the temperature range of 450–600 °C and a secondary hardening peak obtained at 600 °C is probably due to the formation of fine Mo carbide precipitates. The decrease in strength at 650 °C along with an increase in percentage elongation, percentage reduction in area and toughness is due to the coarsening of Cu particles and a partial recovery of matrix. At 700 °C most of the Cu precipitates become rod shaped and formation of fresh martensite with a dark contrast is observed at the lath boundaries.

Molecular weight effects on solution rheology of pullulan and mechanical properties of its films

The effects of molecular weight on solution rheology of pullulan, and on thermomechanichal properties of sorbitol and/or water-plasticized pullulan specimens, prepared by either hot pressing or casting of aqueous solutions, were studied. Pullulan samples differing in molecular weight were characterized by 13C NMR spectroscopy and size exclusion chromatography combined with a multiangle laser light scattering and a refractive index detector. For samples with weight average molecular weight ( M w) ranging between 100 and 560×10 3, the values of limiting viscosity ([η]), critical concentration ( c ∗) and coil overlap parameter ( c ∗[η]) were within the range 0.38–0.70 dl/g, 1.4–3.1 g/dl and 1.0–1.2 dl/g, respectively. The thermomechanical properties of five molecular weight grades of pullulan, either alone or with sorbitol (plasticized at a 10% d.b. level) were examined by dynamic mechanical thermal analysis (DMTA). A large drop in storage modulus E′ (∼10 1.5–10 3 Pa) and a peak in tan δ in the DMTA traces accompanied the glass–rubber transition ( T g) or the α-relaxation ( T α) of pullulan; the magnitude of the drop in E′ and the tan δ peak height increased with increasing water content. The plasticizing action of water and sorbitol was evident in the DMTA curves, and the T g vs. moisture content data were fitted to the Gordon–Taylor empirical model. Within the range of molecular weights tested there was no effect of polymer molecular weight on T g. A β-relaxation detected by DMTA was shifted to lower temperature with increasing moisture content and to higher temperature with addition of sorbitol. Apparent activation energies for α-relaxation ( E αα) and β-relaxation ( E αβ) processes, estimated from multifrequency measurements, were within 171–640 and 118–256 kJ/mol, respectively; the values for E αα and ‘fragility’ parameter decreased with increasing moisture content. Analysis of viscoelasticity data using the time–temperature superposition principle with the Williams–Landel–Ferry equation was successful over the range T g to T g+40 °C, provided that the coefficients C 1 and C 2 are optimized and not allowed to assume their ‘universal’ values. Large deformation mechanical tests demonstrated large decreases in tensile (Young's) modulus ( E) and strength ( σ max), and an increase in percentage elongation with increasing water content and/or addition of sorbitol in pullulan films. Relationships between the tensile parameters ( E and σ max) and water content showed an increase in stiffness of the films from 3 to 7% moisture, and a strong softening effect at higher water contents. The tensile tests revealed some relationships between mechanical properties under uniaxial load and the molecular characteristics of pullulan, e.g. E, σ max, and elongation values increased with increasing molecular weight.

Structure Properties correlation in copolymers of Methyl Methacrylate and Alkyl Methacrylates

The result of a study on the copolymerisation of methacrylate (MMA) with varying mol fractions of octyl methacrylate, decyl methacrylate (DMA), lauryl methacrylate (LMA) and stearyl methacrylate (SMA) by free radical polymerisation using benzoyl peroxide as the initiator are presented. It was anticipated that incorporation of alkyl methacrylate (AMA) having a long alkyl side chain in poly(methyl methadrylate) (PMMA) backbone may lead to an improvement in the toughness of the cast sheets. Such copolymers can be used for low temperature applications in defence. The glass transition temperature of the polymers determined using differential scanning calorimetry was found to decrease with increase in length of the alkyl side chain and the comonomer content. A significant increase in percentage elongation and decrease in tensile strength, modulus and per cent transmittance was observed on incorporation of AMA in PMMA backbone. In the copolymers of SMA and MMA, significant opacity was observed.

Edible films made from natural resources; microcrystalline cellulose (MCC), methylcellulose (MC) and corn starch and polyols—Part 2

Aqueous blends of microcrystalline cellulose (MCC) or methyl cellulose (MC) and corn starch with or without polyols were extruded, hot pressed and studied, after their conditioning at different relative humidities, in terms of their thermal, mechanical and water and gas permeability properties. An increase in water or polyol content showed a considerable increase in percentage elongation but also a decrease in the tensile strength of films. The presence of high cellulose contents increased the tensile strength and decreased the water vapour transmission of films. The development of crystallinity with time resulted in a decrease of both gas and water permeability. Several semiempirical models for calculation of gas permeability and tensile strength and tensile and flexural moduli were applied. The obtained values were compared to those experimentally determined and with the ones reported in the literature. On several occasions, quite significant discrepancies were found which were attributed to differences in molecular weight, percentage crystallinity and polymorphism.

The Effect of the Degree of Substitution on Some Textile Properties of Jute and Cotton Fibres

An investigation is reported in which the effects of the degree of alkyl substitution on percentage elongation, bundle strength and moisture regain were studied. A remarkahle increase in percentage elongation was achieved with partially substituted jute fibre within a 1–2-hour reaction time