Preparation, physical and mechanical characterization of several montmorillonite-polyethylene nanocomposites

VALERIA PETTARIN; VICTOR PITA; FRANCISCO VALENZUELA DIAZ; STELLA MOSCHIAR; LAURA FASCE; ROCÍO SELTZER; MARCOS LOPES DIAS; PATRICIA FRONTINI

Sydney, Australia

Workshop; International Workshop "Fracture of Materials: Moving Forwards"; 2006

In this work composites based on high-density polyethylene (HDPE) and organophilic montmorillonite (OMMT) were prepared by melt compounding. Melt processing is the most appropriate technique for the industrial preparation of these composites because it is compatible with existing processes. Their mechanical and physical properties were characterized. Several compositions were scanned: (a) three Na+-montmorillonites (Argentinian (Arg), Brazilian (Bra) and Wyoming (SW)) were modiffied by replacing the cation originally present in the galleries with one organic cation containing one long n-alkyl ammonium chain (HDTMA), producing ‘organoclays’; (b) two grades of HDPE ((HDPE-Arg) and Brazilian (HDPE-Bra)) were used as composite matrixes. An ethylene/methacrilic acid copolymer (Nu) was added to some composites to verify its effectiveness as a compatibilizer to favour the exfoliation of OMMT in HDPE, and its effect on morphology and mechanical properties was evaluated. The extent of clay platelet exfoliation in the composites was confirmed by X-ray diffraction. Intercalated and exfoliated nanocomposites were obtained depending on the compositions used. Mechanical properties under static and impact conditions were evaluated. Young’s modulus, tensile strength, and ultimate stress of prepared composites are enhanced by the presence of clay while the best performance was achieved by the HDPE-Arg based composites. Elongation at break is only improved in the exfoliated composites. The addition of an ethylene/methacrilic acid copolymer does not improve exfoliation, because it may not act as a compatibilizer agent. Therefore tensile properties and impact strength of ‘compatibilized’ composites are lower than those of ‘uncompatibilized’ composites. The large array of improved mechanical properties attained at very low filler content (3%) together with the ease of production through a simple process such as melt intercalation, make HDPE/OMMT nanocomposites a very promising material.