Morphology and Properties of Polyethylene/Clay Nanocomposite Drawn Fibers

Abstract

The influence of an elongational flow on the morphology of PE/clay nanocomposite drawn fibers was studied. An increase of the elastic modulus and the tensile strength as well as a decrease of the elongation at break are observed with increasing draw ratio. The applied elongational gradient orients the polymer chains and the clay particles along the spinning direction. When the applied flow results in the formation and the orientation of exfoliated nanoparticles, a pronounced increase of the mechanical properties is observed. The dispersed clay particles can be broken and oriented by the extensional flow, which might indicate a flow‐induced intercalated/exfoliated morphology transition.

High performance polyethylene nanocomposite fibers

“…These results are in good agreement with the conclusions reported by La Mantia et al [30]. Therefore, the experienced increase of the mechanical properties due to nanosilica introduction cannot be attributed to different chain orientation in the tested materials.…”

“…Also Ruan et al [32] reported that the addition of MWCNT at a concentration of 5 wt% had a nucleating effects on polyethylene crystals, particularly in the highly aligned fibers, but the crystallinity of the composite fibers was slightly lower than that of the pristine fibers. On the other hand, La Mantia et al [30] found that organomodified layered silicates did not have any effect on the crystallization properties of LLDPE fibers and hypothesized that the orientation in both crystalline and amorphous phases were similar for filled and unfilled fibers. According to our previous works on polyethylene based nanocomposites [20,21,23], we can hypothesize that the limited influence played by fumed silica nanoparticles on the crystallization properties of our HDPE matrix could be probably ascribed to their dispersion state.…”

“…It is widely reported in literature how the increase of the elastic properties of the drawn fibers can be due both to the crystallinity increase induced by the molecular orientation and to possible changes in the crystal size/morphology promoted by the cold drawing process [38]. Also nanoparticles can alter crystallization behaviour of the nanofilled fibers [30,32,33]. In our case, DSC tests on the nanofilled fibers excluded any effect on the overall crystallinity degree due to the nanofiller introduction, but it is possible to hypothesize that crystal size could be altered by the presence of silica aggregates within the matrix.…”

“…Moreover, it was recently found that the introduction of small amounts of layered silicates in polyethylene matrices may lead to substantial improvements of the mechanical performances of the resulting fibers, in terms of elastic modulus and tensile properties at break [29]. Many efforts were devoted by La Mantia and his group in the investigation of the influence of the elongational flow on the morphology of PE/clay nanocomposite drawn fibers [30]. It was demonstrated how an increase of the elastic modulus and of tensile strength with respect to the neat matrix could be obtained when elevated draw ratios are reached.…”

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.…”