Organically modified hydrotalcite for compounding and spinning of polyethylene nanocomposites

Abstract

Abstract.Organically modified hydrotalcite is a recent class of organoclay based on layered double hydroxides (LDH), which is anionically modified with environmental friendly ligands such as fatty acids. In this paper the influence of hydrotalcite compounded/dispersed by means of two different processes for production of plates and fibers of polyolefin nanocomposites will be compared. A polyethylene matrix, suitable for fiber production, was firstly compounded with various amounts of hydrotalcite in the range of 0.5-5% by weight, and then compression moulded in plates whose thermomechanical properties were evaluated. Similar compositions were processed by using a co-rotating twin screw extruder in order to directly produce melt-spun fibers. The incorporation of clay into both bulk and fiber nanocomposites enhanced the thermal stability and induced heterogeneous nucleation of polyethylene crystals. Hydrotalcite manifested a satisfactory dispersion into the polymer matrix, and hence positively affected the mechanical properties in term of an increase of both Young's modulus and tensile strength. Tenacity of nanocomposite as spun fibers was increased up to 30% with respect to the neat polymer. Moreover, the addition of LDH filler induced an increase of the tensile modulus of drawn fibers from 5.0 GPa (neat HDPE) up to 5.6-5.8 GPa.

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

“…DSC results of the nonisothermal crystallization at different cooling rate between −0.3°C/min and −40°C/min are summarized in Table . Higher crystallization temperatures of the LDH nanocomposites seem to confirm a nucleating effect of hydrotalcite …”

“…All composition were easy to spun in single monofilaments of 500 micron diameter, with a linear density of about 190 tex, as described in the previous paper. 35 Thermogravimetric analysis of fibers evidenced a shift of the degradation curve at higher temperature after introduction of LDH, as shown in Figure 1.…”

“…In our previous paper we have described the compounding of hydrotalcite with HDPE (either internal mixing or mixing in twin‐screw extruder) and the preliminary melt spinning of fibers and drawing at 100°C . In this article, the production of polyethylene/organically modified hydrotalcite fibers was developed and detailed on a wider scale.…”

“…29 If properly processed, the organically modified hydrotalcite can easily be melt dispersed into a polymer and exfoliated forming a true nanocomposite resulting in improved properties such as thermo-mechanical, flame retardant, barrier and rheological (better thermoforming properties). [28][29][30][31][32] In our previous paper we have described the compounding of hydrotalcite with HDPE (either internal mixing or mixing in twin-screw extruder) and the preliminary melt spinning of fibers and drawing at 100 C. 35 In this article, the production of polyethylene/organically modified hydrotalcite fibers was developed and detailed on a wider scale. In particular, the effects of the drawing temperature (between 100 and 140 C) and of the draw ratio (up to 20) are reported.…”

Spinning, drawing and physical properties of polypropylene nanocomposite fibers with fumed nanosilica

“…TOT ) of selected fibers were reported in Table 3. As previously defined by Dabrowska et al [28], the mechanical draw ratio (! MEC ), is calculated by Equation (3): (3) where # b is the strain at break expressed in percentage.…”