Very high modulus high‐density polyethylene and high‐modulus polypropylene obtained by solid‐state roll drawing

Ajji, Abdellah; Dumoulin, M. M.

doi:10.1002/app.21556

Cited by 8 publications

(4 citation statements)

References 26 publications

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“…The mechanical properties of the final thermoplastic part can be improved by modified structure via plastic deformation in a solid state. Numerous common methods exist for this purpose such as uniaxial and biaxial drawing, rolling, die drawing, combination of drawing with rolling, and solid state extrusion [1][2][3][4][5]. The ram extrusion process is a process that allows for the achievement of uniaxial orientation [6].…”

Section: Introductionmentioning

confidence: 99%

Axial‐feed thermoforming of oriented polypropylene tubes

Elnagmi

Bruhis

Jain

2009

Polymer Engineering & Sci

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The effect of newly developed axial feed thermoforming process (AFTF) on mechanical properties and morphology were investigated to gain a better understanding of structure-properties-process relationship. The starting material for AFTF is an oriented polypropylene tube (OPP) produced in uniaxial direction by using solid state extrusion process. Morphological changes from solid-state extrusion are briefly reported. A die-less bulge testing system was designed to bulge OPP tube at a high temperature in biaxial direction. Wide-angle X-ray diffraction, field emission scanning electron microscope, and optical microscopy were used to characterize the microstructure of the extruded and bulged samples of OPP. In addition, tensile tests were carried out at room temperature of samples machined from the extruded and bulged tubes along the axial and hoop directions. The results show that tensile strength increases with draw ratio in extruded samples as well as improvements in ductility were obtained in die-less bulge tests with an increase in axial feed.

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Section: Introductionmentioning

confidence: 99%

Axial‐feed thermoforming of oriented polypropylene tubes

Elnagmi

Bruhis

Jain

2009

Polymer Engineering & Sci

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“…The polymer used in the present study was HDPE Hiplex HHM 5502 (=0.955 g/cm 3 , M w =300 000). Isotropic sheets of different thickness were prepared by 20 min compression molding in a Carver laboratory press at 160 °C and a gradual increase in pressure up to 3.28 MPa.…”

Section: Experimental Sample Preparationmentioning

confidence: 99%

“…Orientation of an isotropic polymer, aligning the polymer macromolecules parallel to the direction of greatest anticipated stress, usually by drawing, rolling or extrusion, produces a material with a high degree of anisotropy in its physical properties due to molecular chain orientation [1][2][3][4]. For instance, mechanical properties such as strength and stiffness increase rapidly in the direction of molecular orientation [4,5].…”

Section: Introductionmentioning

confidence: 99%

Structural Changes and Dielectric Relaxation Behavior of Uniaxially Oriented High Density Polyethylene

Suljovrujić

Mićić

Miličević

2013

Journal of Engineered Fibers and Fabrics

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The molecular relaxation behavior of an ice-quenched high density polyethylene (HDPE) subjected to solid-state stretching at elevated temperature (100 °C) to various draw ratios (up to Λ=13.7) was examined by means of dielectric spectroscopy. All relaxation zones (α, β and γ, in order of decreasing temperature) between 25 K and melting temperature were studied in the frequency range from 1 kHz to 1 MHz. The changes observed in different dielectric relaxations were related to the orientation-induced modifications of the structural and morphological parameters. In order to investigate orientation-induced structural changes, optical microscopy (OM), scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), and differential scanning calorimetry (DSC) were employed. Herman's orientation function (fc) was used to quantify the degree of crystal orientation. Complete disappearance of the already weak β relaxation with orientation is attributed to the increase in crystallinity, but the contribution due to a more restricted chain segment mobility in the interlamellar regions of oriented specimens should also be taken into account. Presented results also reveal two different orientation-induced dynamics in the evolution of the dielectric α and γ relaxations connected with the main transformation stages in the drawing of crystalline polymers. The transformation of the initial isotropic into a fully oriented fibrillar structure introduces large changes in the dielectric relaxation spectra of HDPE, especially in the α relaxation zone; by contrast, with further increase in the draw ratio much smaller changes are observed due to the deformation of the fiber structure by longitudinal sliding motions of microfibrils and/or by fibrils slipping past each other.

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“…This structure is very important from industrial viewpoint because it is structural origin of ultra‐high strength and ultra‐high modulus fiber. Although considerable researches have been performed in flexible polymers, only ultra‐high modulus polyethylene fiber11, 12 has already been available in industry. One reason is that shear‐induced molding process is very complicated, in which many factors have significant influence on the final microstructure that directly dominates the final mechanical property of molded products.…”

Section: Introductionmentioning

confidence: 99%

The effect of multiple variables on tensile property of injection‐molded polypropylene through the combination of orthogonal design and variance analysis

Gao

Chen

et al. 2012

J of Applied Polymer Sci

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In this article, a combination of orthogonal design and variance analysis was used to study the systematical effect of vibration pressure, melt temperature, packing cycle, and mold temperature on the tensile property of polypropylene in dynamic packing injection molding (DPIM). The tensile measurement results show that all variables had significant influence on the final tensile property under the present molding condition. Meanwhile, the optimal molding condition to achieve high tensile strength was also obtained in the investigated ranges. Further quantitative statistical analysis revealed the degree of influence of four variables on the tensile property of polypropylene in DPIM. The sequence of the degree of influence from maximum to minimum is as follow: vibration pressure, melt temperature, packing cycle, and mold temperature. These findings provide the experimental and statistical evidences to illustrate that the application of orthogonal design and variance analysis might be an effective approach to systematically study the effect of multiple variables on the final mechanical property.

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Very high modulus high‐density polyethylene and high‐modulus polypropylene obtained by solid‐state roll drawing

Cited by 8 publications

References 26 publications

Axial‐feed thermoforming of oriented polypropylene tubes

Axial‐feed thermoforming of oriented polypropylene tubes

Structural Changes and Dielectric Relaxation Behavior of Uniaxially Oriented High Density Polyethylene

The effect of multiple variables on tensile property of injection‐molded polypropylene through the combination of orthogonal design and variance analysis

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