Effect of different dispersing additives on the morphology and the properties of polyethylene-based nanocomposite films

Abstract

It has been reported that thermoplastics filled with nanometer-sized materials show properties different from those of thermoplastics filled with conventional microsized particles. The incorporation of nanosized fillers has, indeed, been shown to have significant effects not only on some mechanical and thermomechanical properties e.g. elastic modulus, heat deflection temperature, but also on the transparency and haze characteristics of the polymers films. It is well documented that nanoclay incorporation into polymer films significantly enhances transparency, reduces haze and sizeably increases the film barrier properties. Clays, being hydrophilic, are easier to be nano-disperded in polar polymers. On the other hand preparation of clay-based nanocomposites by melt processing of polyolefins (PO's), thermoplastic olefins (TPO's) and other non-polar polymers is a technologically challenging task as the clay silicate layers have to be exfoliated by pure mechanical shear during the extrusion of the polymer. Extrusion conditions, extruder screw type and design strongly affect the exfoliation extent. In order to improve exfoliation, use of the more polar Abstract. In this work, the use of a polar wax, e.g. amphiphilic Tegomer ® E 525 (TEG) is investigated with the aim of modifying, and possibly improving, the dispersion of an organically modified nanoclay (OMMT), loaded at 5 wt%, in a polyethylene matrix (PE) at relatively low loading levels. We have indeed found that the incorporation of low loadings, e.g. 0.5 wt%, of TEG, an amphiphilic block co-polymer, into a PE/OMMT sample results in a substantial improvement of the clay dispersion in the nanocomposite and, consequently, of the mechanical and thermomechanical properties of the films. The achieved results are comparable to those obtained for systems containing traditional dispersing agents such as maleated PE (PEgMA) and ethylene-acrylic acid copolymer (EAA), at higher loadings, i.e. at 5 wt%. It has also been found that by increasing the polar wax content, i.e. 1-5 wt%, no useful improvement in the mechanical behaviour and morphology of the PE films was obtained. At high loadings of the polar wax relatively the short chains are arranged into the clay particles galleries and intercalation of the polyethylene chains between the clay platelets may be hindered. Additionally at high TEG loadings, the presence of the new polar groups of the wax also on external surfaces of the clay particles is expected to promote aggregation of the clay particles, with a loss of the beneficial effect of the more dispersed clay particles on the polymer mechanical/thermomechanical properties. The reported results strongly indicate that the amphiphilic TEG dispersing additive, may advantageously be used, at substantially lower loadings, as an alternative to incumbent PEgMA in the formulation of nanocomposites to improve their macroscopic performances.

Compatibilizer Polarity Parameters as Tools for Predicting Organoclay Dispersion in Polyolefin Nanocomposites

“…e most commonly used compatibilizers are obtained by grafting polar groups on polymers and copolymers. Examples of these compatibilizers include maleic anhydride grafted on polyethylene (PE-g-MA) [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], on linear low density polyethylene (LLDPE-g-MA) [28][29][30], on polypropylene (PPg-MA) [8,10,19,, and on styrene/ethylene-butylene/ styrene (SEBS-g-MA) [51,56,57]. Other polar groups grafted on polymers are itaconic acid [58][59][60], glycidyl methacrylate (GMA) [54], and acrylic acid (AA) [54,61,62].…”

Materials for food packaging applications based on bio-based polymer nanocomposites

“…To promote interaction between phases, use of an adhesion promoter named as a compatibilizing agent, a compatibilizer or an interfacial agent is necessary to achieve good adhesion between matrix and particles as a result of successful intercalation or exfoliation. 18 Compatibilizers provide a convenient method to improve thermal, mechanical or chemical properties of polymer materials without synthesizing new ones. 19 A large number of experiments have been conducted in order to decrease the phase separation and to improve interfacial adhesion, such as the addition of chemical or physical compatibilizers (block copolymer or a third homopolymer or graft) to act as a bond between the two phases through the introduction of covalent bonds between the homopolymer phases and interfacial modification.…”

Polystyrene nanocomposites produced by melt-compounding with polymer-coated magnesium carbonate nanoparticles

“…In order to avoid agglomeration phenomena with preformed particles during melt blending, various strategies have been recommended. Some of them are based on the knowledge gained with traditional fillers (e.g., additional use of dispersing agents, 5 surface coating by silane compounds 1,2 ); others benefit from multiple processing with and without previous masterbatch preparation, 6 again others follow the water-assisted melt-compounding, whereby the water swelling/water dispersion capability of some nanofillers are exploited. 7–9 However, providing the nanofillers with a thick polymer coating, which effectively hampers the reagglomeration, is a completely other way which is rarely practiced.…”