High-density Polyethylene Fibers Research Articles

Effect of Acetylation and MAPE on the Properties of Steam-Exploded Acacia mangium Fiber—HDPE Composites

Composites of high-density polyethylene (HDPE) and alkali-extracted steam-exploded Acacia mangium fiber (AEF) were prepared using 2-roll mill and compression molding. AEF was acetylated (AAEF) to three different wt% gains (WPG) and maleic anhydride grafted polyethylene (MAPE) was used as compatibilizer. Acetylation of AEF (AAEF) did not improve the tensile properties, particularly tensile strength of the composites. Addition of maleic anhydride-grafted polyethylene (MAPE) to either HDPE—AEF or HDPE—AAEF composites improved the composite strength. The effectiveness of MAPE, however, was limited by the weight percent gain (WPG) of AAEF resulting in a decrease in composite strength and stiffness. Sorption kinetics and characteristics of water absorption of the composites immersed in distilled water at room temperature for 30 days were determined and compared. All composites were found to exhibit Fickian diffusion process. Results showed that acetylation and MAPE reduced equilibrium water uptake as well as rate of water absorption (diffusion coefficient) of the composites. A synergistic effect, however, was only observed for the equilibrium water uptake when both were considered in a composite formulation.

Toughening of recycled polystyrene used for TV backset

AbstractThe recycled polystyrene (rPS) was toughened with ethylene‐octylene copolymer thermoplastic elastomer (POE) and high‐density polyethylene (HDPE) with various melt flow index (MFI), compatibilized by styrene‐butadiene‐styrene copolymer (SBS) to enhance the toughness of rPS for use as TV backset. The rPS/POE binary blends exhibited an increased impact strength with 5–10 wt % POE content followed by a decrease with the POE content up to 20 wt %, which could be due to poor compatibility between POE and rPS. For rPS/POE/SBS ternary blends with 20 wt % of POE content, the impact strength increased dramatically and a sharp brittle‐ductile transition was observed as the SBS content was around 3–5 wt %. Rheological study indicated a possible formation of network structure by adding of SBS, which could be a new mechanism for rPS toughening. In rPS/POE/HDPE/SBS (70/20/5/5) quaternary blends, a fibril‐like structure was observed as the molecular weight of HDPE was higher (with lower MFI). The presence of HDPE fibers in the blends could not enhance the network structure, but could stop the crack propagation during fracture process, resulting in a further increase of the toughness. The prepared quaternary blend showed an impact strength of 9.3 kJ/m2 and a tensile strength of 25 MPa, which can be well used for TV backset to substitute HIPS because this system is economical and environmental friendly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Thermal diffusivity, thermal conductivity, and specific heat of flax fiber–HDPE biocomposites at processing temperatures

There is increasing work on the use of flax fibers as reinforcement for manufacturing composites because of their lower cost and environmental benefit. During manufacturing of such natural fiber–plastic composites, heat transfer is involved, but information about the thermal conductivity and thermal diffusivity at the processing temperatures is not available. In this study, the thermal conductivity, thermal diffusivity, and specific heat of flax fiber–high density polyethylene (HDPE) biocomposites were determined in the temperature range of 170–200 °C. The fiber contents in biocomposites were 10%, 20%, and 30% by mass. Using the line-source technique, the instrumental setup was developed to measure the thermal conductivity of biocomposites. It was found that the thermal conductivity, thermal diffusivity, and specific heat decreased with increasing fiber content, but thermal conductivity and thermal diffusivity did not change significantly with temperature in the range studied. The specific heat of the biocomposites increased gradually with temperature.

Determining the opto-mechanical and geometrical properties of high-density polyethylene fibres

A method is described to determine the opto-mechanical and geometrical properties of high-density polyethylene, HDPE, fibres at the same time for the same region from the fibre. Variations of the transverse sectional shapes, areas, optical and mechanical properties of fibres during the cold drawing process were investigated. A rotator-mechanical drawing device was used for rotating the fibre around its longitudinal axis during the cold drawing process. The Pluta polarizing two-beam interference microscope was attached with the rotator-mechanical drawing device for detecting these variations under the interferometer. The rotator-mechanical drawing device permits determining the tensile stress–strain curve, Poisson's ratio and strain optical coefficient for HDPE fibres. Also, it permits determining the refractive index profile of the drawn fibres taking into considering the transverse sectional area and the enclosed area under the fringe shift. The optical orientation factor and orientation angle was calculated for HDPE fibre to clarify the orientation of molecules during the cold drawing process. Microinterferograms are utilized for illustrations.

High strength polyethylene fibers from high density polyethylene/organoclay composites

AbstractHigh strength fibers were prepared from high density polyethylene (HDPE)/organically modified montmorillonite (OMMT) composites. X‐ray diffraction study revealed that the composites were of conventional or phase‐separated type. As‐spun composite fibers were found to have higher drawability than as‐spun HDPE fiber. As a result of an increased drawability, fibers with much higher mechanical properties were obtained. The highest modulus and tensile strength obtained in the present study were 38 GPa and 1.7 GPa, respectively. Study of internal morphology suggests that the role of OMMT is to suppress a defect formation and allows the fiber to be drawn to higher draw ratio. Analysis of the mechanical properties of the fibers using a Griffith type relationship suggested that the fibers have much smaller defects and the predicted attainable strength for the fiber is much higher than that previously predicted for melt‐spun and hot drawn fiber. POLYM. ENG. SCI., 47:943–950, 2007. © 2007 Society of Plastics Engineers

Estimating crystallinity in high density polyethylene fibers using online Raman spectroscopy

AbstractOnline Raman spectra, obtained at different points along the spin line during pilot‐scale nonisothermal melt spinning of high density polyethylene (HDPE) fibers, are presented for the first time. The fraction of the crystalline phase corresponding to each spectrum was determined from the normalized integrated intensity of the 1418 cm−1 Raman band. It is well established that this band represents the orthorhombic crystalline phase in polyethylene. The estimates of percent crystallinity obtained from decomposition of the Raman spectrum were compared with the percent crystallinity from differential scanning calorimetry (DSC) measurements. It is concluded that online Raman spectroscopy can be successfully used to monitor the development of crystallinity in HDPE fibers as a function of distance from the spinneret. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 545–549, 2003

Effects of different treatments on the interface of HDPE/lignocellulosic fiber composites

We studied the chemical and mechanical characteristics of composites made up of HDPE (high-density polyethylene) and lignocellulosic fibers (in the presence or absence of a coupling agent). Interfacial morphology and esterification reactions between aspen fibers and the coupling agent were analyzed by means of Fourier Transform Infrared Spectrophotometry (FTIR) and Scanning Electron Microscopy (SEM). The variation of absorption in spectral bands (related to water absorption, glycosidic bonds in the cellulose backbone, hydroxyl and vinyl contents, and the formation of ether bonds) was determined in order to assess the influence of the coupling agents as well as the lignocellulosic fiber content. SEM micrographs were used in order to show the “bridge effect”, brought about by the coupling agent between the HDPE matrix and the reinforcement of lignocellulosic fibers. Mechanical properties, such as tensile strength, Young modulus, elongation at breaking point and toughness, were also analyzed. Finally, the differences observed between the various composites studied were explained by some specific adhesion mechanisms (including interdiffusion, adsorption-wettability and chemical bonds).

Effect of non‐isothermal oriented crystallization on the velocity and elongational viscosity profiles during the melt spinning of high density polyethylene fibers

AbstractBased on the experimental data of spine line temperature and percent crystallization, a time‐integral constitutive equation has been used together with the degree of phase transformation theory to predict the velocity and elongational viscosity profiles. For the velocity profile, our predicted results are compared to experimental data and good agreement is found. Under a drawing force, the elongational viscosity profile shows a stress softening due to the molecular alignment; then the fiber hardens close to the take‐up point, owing to filament crystallization.

Fine-structure and physical properties of polyethylene fibers in high-speed spinning. I. Effect of melt-flow rate in the high-density polyethylene

High-density polyethylene (HDPE) fibers, obtained from a melt-flow rate (g/10 min) of 11 and 28, was produced by a high-speed melt-spinning method in the range of take-up velocity from 1 to 8 km/min and from 1 to 6 km/min, respectively. The change of fiber structure and physical properties with increasing take-up velocity was investigated through birefringence, wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), a Rheovibron, and a Fafegraph-M. With an increase in take-up velocity, the birefringence showed a sigmoidal increase, which has distinct changes in the range of 1–5 km/min. Throughout the whole take-up velocities, the birefringence of HDPE(11) was higher than that of HDPE(28). With increasing take-up velocity, the crystalline orientation was transformed from a-axis orientation to c-axis orientation. These crystalline relaxations are confirmed by the tan δ peak of high-speed spun HDPE fibers. The intensity of the crystalline relaxation peak decreases with increasing take-up velocity in both HDPE(11) and HDPE(28). As above, the crystalline relaxation peaks shift to lower temperature with increasing take-up velocity. With increasing take-up velocity, the ultimate strain decreases while both specific stress and the initial modulus increase. The mechanical behavior may be closely related to, as investigated by birefringence, orientation of the amorphous region, etc., the take-up velocity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1182–1195, 2000

Double yield in tensile deformation of high-density polyethylene fiber

Fiber-grade high-density polyethylene (HOPE) was melt spun into a multifilament yam that, after quenching in air, was wound at speeds in the range 450 m/min to 1000 m/min. Tensile tests on these anisotropic yarns showed two yield points of varying intensity, similar to those reported in the literature for compression molded, isotropic HOPE sheets and films. However, unlike the sheets, the second yield in the case of fibers always occurred at a stress higher than that for the first yield. More detailed studies on the yam spun at 450 m/ min showed that these characteristics persisted at different strain rates and test temperatures and were also present in the heat-set as-spun samples. The applicability of the existing models to explain the double-yield phenomenon has been critically examined in the light of the results obtained. For this, the necessary structural and morphological characterization of the samples was also done.

Tribological Properties of Model Polymer Blends

Tribological properties such as the coefficient of friction and the specific wear rate of the model polymer blends consist of two different epoxy resin matrices and high density polyethylene (HDPE) fibers unidirectionally dispersed in the matrix to a stainless steel disk were investigated by using a pin-on-disk type friction tester. Further the morphology of the abraded surfaces were studied by SEM photomicrographs. When the modulus of the matrix epoxy resin is high, both the coefficient of friction and the specific wear rate monotonically decreased with HDPE fiber contents to those of neat HDPE. On the other hand, when the modulus of the matrix is low, HDPE or HDPE/epoxy resin mixture covers the sample surface resulted in the sudden drop of the coefficient of friction and in the specific wear rate lower than those of both epoxy resin and neat HDPE. It was further found that the HDPE fiber so oriented to the friction direction that HDPE can more efficiently make the lubrication film onto the metal surface reduces the coefficient of friction of the model polymer blends.

Molecular Orientation of High-Density Polyethylene Fibers Characterized by Polarized Raman Spectroscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular Orientation of High-Density Polyethylene Fibers Characterized by Polarized Raman SpectroscopyMario J. Citra, D. Bruce Chase, Richard M. Ikeda, and Kenncorwin H. GardnerCite this: Macromolecules 1995, 28, 11, 4007–4012Publication Date (Print):May 1, 1995Publication History Published online1 May 2002Published inissue 1 May 1995https://doi.org/10.1021/ma00115a037RIGHTS & PERMISSIONSArticle Views831Altmetric-Citations88LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (665 KB) Get e-Alerts Get e-Alerts

520 PB 480 USE OF TYVEK HOUSEWRAP FOR POLLINATION BAGS IN BREEDING OF HAZELNUT

Tyvek housewrap (Du Pont, Wilmington, Delaware), an air-infiltration barrier for use in house construction, has been put to a novel use for making pollination bags for breeding hazelnuts (Corylus avellana L.). Bagged flowers are used in making crosses and incompatiblity testing and remain receptive for up to 3 months. Tyvek has outperformed paper and plastic materials we have tried in terms of durability and cost. Tyvek is a spun-bonded, nondirectionally oriented film of highdensity polyethylene fibers that is permeable to water vapor and air, but is water resistant and pollen-proof, and can be made into bags of any size needed.

Radiation‐grafting of acrylic acid onto ultrahigh molecular, high‐strength polyethylene fibers

AbstractRadiation‐induced grafting of acrylic acid onto ultrahigh molecular weight (UHMW) high‐strength polyethylene fibers to impart heat resistance and dyeability was undertaken. A preirradiation method was employed for grafting in an aqueous solution of acrylic acid containing a small amount of Mohr's salt as inhibitor. The grafting rate for UHMW high‐strength polyethylene fibers is one‐tenth of that for high‐density polyethylene fibers currently in use, and one‐hundredth, for high‐density polyethylene film. It has become clear that the preirradiation dose should be as low as 1 Mrad to keep the high strength of the starting fibers. The starting UHMW high‐strength polyethylene fiber begins to shrink remarkably at around 145°C, showing a maximum shrinkage of 90%, and then breaks at 154°C. When a 24% acrylic acid graft is converted to calcium salt, the grafted fiber retains the fiber form even at 300°C and gives only a maximum shrinkage of 11%. The less than 1% acrylic acid graft UHMW high‐strength polyethylene fibers and their calcium salt can be dyed to a deep shade with cationic dyes, whereas the starting fibers cannot be dyed with usual dyes including the cationic dye. © 1993 John Wiley & Sons, Inc.

Orientation and morphology of high‐density polyethylene film produced by the tubular blowing method and its relationship to process conditions

AbstractThe orientation and crystallinity of a series of high‐density polyethylene (HDPE) tubular films is characterized using wide‐angle x‐ray scattering pole‐figure analysis and birefringence. The films ranged from uniaxial to equal biaxial. The data were used to compute biaxial orientation factors which were then plotted on an orientation‐factor triangle diagram. It was shown, within the range of conditions studied, that both the crystalline biaxial orientation factors were unique functions of the stresses exerted on the bubble at the freeze line. Both correlations are the same as those developed by Dees and Spruiell for melt‐spun HDPE fibers. SAXS measurements on the films suggest lamellar structures in both uniaxial and biaxial films.

Microhardness of extruded high density polyethylene fibers

AbstractHigh‐density polyethylene of high tensile modulus has been produced by solid state extrusion using an Instron capillary rheometer. Microhardness measurements on these ultraoriented fibers have been made to assess their perfection from values of the tensile elastic modulus and shear strength. The microhardness tests were measured using a Vickers square diamond. The microhardness increased with the common temperature for crystallization and extrusion, likely due to improvement in the lateral packing of microfibrils. The variation of microhardness with draw ratio is also illustrated.

Physical and mechanical properties of ultra‐oriented high‐density polyethylene fibers

AbstractUltra‐oriented high‐density polyethylene fibers (HDPE) have been prepared by solid‐state extrusion over 60–140°C range using capillary draw ratios up to 52 and extrusion pressures of 0.12 to 0.49 GPa. The properties of the fibers have been assessed by birefringence, thermal expansivity, differential scanning calorimetry, x‐ray analysis, and mechanical testing. A maximum birefringence of 0.0637 ± 0.0015 was obtained, greater than the calculated value of 0.059 for the intrinsic birefringence of the orthorhombic crystal phase. The maximum modulus obtained was 70 GPa. The melting point, density, crystallinity, and negative thermal expansion coefficient parallel to the fiber axis all increase rapidly with draw ratio and at draw ratios of 20–30 attain limiting values comparable with those of a polyethylene single crystal. The properties of the fibers have been analyzed using the simple rule of mixtures, assuming a two‐phase model of crystalline and noncrystalline microstructure. The orientation of the noncrystalline phase with draw ratio was determined by birefringence and x‐ray measurements. Solid‐state extrusion of HDPE near the ambient melting point produced a c‐axis orientation of 0.996 and a noncrystalline orientation function of 0.36. Extrusion 50°C below the ambient melting point produced a decrease in crystallinity, c‐axis orientation, melting point, and birefringence, but the noncrystalline orientation increased at low draw ratios and was responsible for the increased thermal shrinkage of the fibers.

The Influence of Initial Morphology on the Physical and Mechanical Properties of Extruded High Density Polyethylene Fibers

Abstract Ultra-oriented high density polyethylene fibers have been produced by solid state extrusion of various polyethylene morphologies prepared in the reservoir of an Instron Rheometer. A constant extrusion temperature and pressure were used in the following studies: (a) high density polyethylene melted at 170°C and then cooled at ∼1°C min−1 to the desired extrusion temperature below the ambient melting point; (b) a molten sample removed from the rheometer and quenched into an ice-water bath and subsequently extruded; (c) a chain-extended polyethylene prepared by crystallization at 0.49 GPa and 200°C; (d) various chain-folded morphologies prepared by isothermal crystallization between 134°C and 200°C and pressures from 0.12 to 0.49 GPa. The properties of the fibers have been assessed by birefringence, thermal expansivity, differential scanning calorimetry, small angle X-ray scattering, modulus, and tensile strength. Fibers produced from the various isothermally-crystallized morphologies attained, at de...

Formation properties of solid‐state extruded high density polyethylene fibers

AbstractExtrusion rates have been measured for high density polyethylene fibers prepared by solid‐state extrusion through a conical die with maximum draw ratio of 52, using constant pressure and temperatures ranging from 0.12 to 0.49 GPa and 60° to 140°C and molecular weights from 5 × 104 to 6 × 106. The processing variables are reported in terms of an apparent elongational viscosity. The logarithm of the extrusion rate was proportional to the applied pressure. Deviation from the Eyring theory of viscosity was found, since lowering of the extrusion temperature to 60°C produced an anomalous decrease in the extrusion rates. The anomaly was explained by the increased friction between die and polymer, the pressure dependence of the yield stress, and by the pressure dependence of the α‐relaxation mechanism. Apparent activation energies of 60 and 100 kcal/mole were calculated for the solid‐state extrusion in the region 100°–130°C and 80–100°C. Three modes of deformation were observed for each extrusion, consisting of an unsteady state, a second stage of drawing in which the extrusion rate approached a constant value, and a fracture region. The first mode corresponded to orientation and rotation of the crystalline lamellae, as shown by the rapid increase and plateau region of the crystalline and noncrystalline orientation functions. During the second stage of deformation, the apparent elongational viscosity ηE increased linearly with draw ratio, as did the modulus, and this mode was found necessary for the attainment of high modulus fibers. The second mode of deformation was associated with the deformation of the crystalline lamellae and strain hardening in which ηE‐approached that for a glass. Strain hardening readily occurred with decreasing temperature, and increasing draw ratio and molecular weight. Continuous extrusion producing uniform modulus fibers was only possible when the maximum draw ratio of the die was less than the fiber draw ratio, where strain hardening occurred. The third mode of deformation limited the maximum modulus obtainable and consisted of fracture or kink planes oblique to the fiber axis. The relations between the processing variables used in the solid‐state extrusion and the resulting fiber properties are discussed.

The influence of drawing, twisting, heat setting, and untwisting on the structure and mechanical properties of melt-spun high-density polyethylene fiber

The variation of crystalline morphology and mechanical properties of polyethylene fibers was studied as they were sequentially melt spun, drawn, twisted, heat set, and untwisted. Twisting of as-melt spun fibers was also investigated. The morphology was characterized using wideangle x-ray diffraction, small-angle x-ray diffraction, and scanning electron microscopy techniques. Drawing results in high crystalline orientation, fibrillation, and large increases in modulus and tensile strength. Effects due to variation of spinning conditions were noted. Twisting either as-spun or drawn fibers decreased the axial orientation, modulus, tensile strength, and usually also the elongation to break. The changes in these properties increased with twist angle. Twisting also caused transformation of a small fraction of the sample to the monoclinic form of polyethylene. Heat setting caused healing of voids generated during drawing and increased the perfection and periodicity of the stacking of lamellar crystals along the fiber axis. Heat setting also caused the monoclinic polyethylene to transform back to the orthorhombic form, and it increased the modulus and tensile strength. Untwisting returned the orientation in the fiber to essentially that which it would have if it had not been twisted, but untwisting also resulted in the formation of kink bands.