Polyethylene composite fibers. I. Composite fibers of high‐density polyethylene

Abstract

Polymer matrix composites are generally studied in the form of bulk solids, and very few works have examined composite fibers. The research described here extended such bulk studies to fibers. The question is whether or not what has been reported for bulk polymers will be the same in fibers. In this article are reported studies of high-density polyethylene (HDPE), whereas those of linear low-density polyethylene are reported in part II of this article series. Two types of filler were used, that is, organically modified montmorillonite (OMMT), in which the nanosized filler particles had a high aspect ratio, and microsized calcium carbonate (CaCO 3 ), with an aspect ratio nearer to unity. Composite fibers of both as-spun and highly drawn forms were prepared, and their structures, morphology, and mechanical properties were studied. It was found that the microsized particles gave HDPE composite fibers with mechanical properties that were the same as those of the neat polymer. In the case of clay composite fibers, the clay interfered with the yield process, and the usual yield point could not be observed. The particle shape did not affect the mechanical properties. The fibers showed different deformation morphologies at low draw ratios. The CaCO 3 composite fibers showed cavities, which were indicative of low interaction between the polymer and the filler. The OMMT composite fibers showed platelets aligned along the fibers and good polymer-filler interaction.

Melt spinning and drawing of polyethylene nanocomposite fibers with organically modified hydrotalcite

“…These effects can be explained in terms of filler dispersion, as reported by Costa et al in the case of polyethylene/Mg‐Al LDH nanocomposites, describing a critical concentration range of 2.5–5 wt % above which the LDH particles do not show strong interfacial adhesion with the matrix . The existence of an optimal amount of the nanofiller was already observed by several authors . In this article, the critical concentration of LDH in HDPE for fiber spinning was found at 2%.…”

“…For instance, PP fibers were produced with various types of nanofillers, for example, layered silicates, carbon nanotubes, and montmorillonite . In the case of HDPE, composites fibers containing calcium carbonate, carbon nanotubes, silica, and layered silicates were reported . Owing to the alignment of the nanofiller particles along the strain direction, which induced a stronger interfacial load transfer, enhanced stiffness, and tensile strength of the composite fibers were achieved …”

“…[13][14][15][16][17][18] In the case of HDPE, composites fibers containing calcium carbonate, carbon nanotubes, silica, and layered silicates were reported. [19][20][21][22][23][24][25] Owing to the alignment of the nanofiller particles along the strain direction, which induced a stronger interfacial load transfer, enhanced stiffness, and tensile strength of the composite fibers were achieved. [20][21][22][23][24] Recently many articles on synthetic layered double hydrotalcite (LDH) have been published.…”

Organically modified hydrotalcite for compounding and spinning of polyethylene nanocomposites

“…However, it should be noted that even in the case of low molecular weight polymers, the presence of nanofiller and sometimes the lower level of chain extension determine the formation of various type of defects, and hence relatively low modulus and strength values of the spun fibers. In the case of polyethylene fibers, both linear low density and high density polymers at very low melt flow, between 0.27 and 0.9 dg/min (190°C, 2.16 kg), were spun with various organo-modified clays or with fumed silica [14][15][16][17][18]. The high molecular weight of polymers allowed an efficient drawing process and the achievement of higher mechanical properties of drawn nanocomposite fiber with respect to those of neat polymer.…”

“…The high molecular weight of polymers allowed an efficient drawing process and the achievement of higher mechanical properties of drawn nanocomposite fiber with respect to those of neat polymer. In particular, the organo-modified clay was considered responsible for the reduction of the fiber defects during drawing and for the higher attainable draw ratios [17]. On the other hand, various authors described the production of isotactic polypropylene fibers containing organo-modified clay with a double-step process consisting in a preliminary melt compounding with or without compatibilizer, followed by fiber spinning [19][20][21][22] or melt-spun bonding [23].…”