From PET Nanofibrils to Nanofibrillar Single- Polymer Composites Stoyko Fakirov,* Miro Duhovic, Philipp Maitrot, Debes Bhattacharyya Introduction In their recent review ‘‘How Nano are Nanocomposites’’ Schaefer and Justice [1] concluded that ‘‘with the exception of reinforced elastomers, nanocomposites have not lived up to expectations.’’ In other words, nowadays we could hardly be satisfied with the mechanical performance of polymer composites reinforced with nanosized fillers of various origins. For this reason, as recently suggested, [2] in addition to the attempts to overcome the encountered problems, new routes to create polymeric materials with improved properties have to be explored. An attractive alternative route seems to be the preparation of intrinsically nanosized polymers, as provided, for example, by electrospinning. [3] At the same time, this elegant technique has the disadvantage that the fine nanofibers are of limited practical use. In this article, the results of attempts to prepare nanofibrillar composite (NFC) materials starting from nanofibrils are presented. This approach is based (i) on the concept of polymer/polymer NFCs, which have recently been manufactured by Fakirov et al. [4] and which represent a significant development for microfibril-reinforced com- posites, [5–7] and (ii) on the opportunity to isolate neat nanofibrils through selective dissolving of the second blend component. Experimental Part Commercial fiber grade poly(ethylene terephthalate) (PET) and commercial polypropylene (PP) (type Novolen with MFI 5, as well as Novolen 1100L, provided by Basell, Germany) were used for manufacturing of PET nanofibrils. For this purpose the dried PET pellets were dry-mixed with PP to give a weight ratio of PP:PET 80:20. The melt blending was performed in a twin-screw Brabender extruder. The temperature profile, starting from the feeding zone to the die, was 260, 270, 260 and 245 8C. The extruded bristles (2 mm in diameter) were cooled down to room temperature and pelletised. To this PP/PET blend (80:20 by wt) were added 20 wt% chips of PP type Novolen 1100L so that the effective amount of PET in the blend was reduced to 16.7 wt.-%. Communication S. Fakirov, D. Bhattacharyya, M. Duhovic, P. Maitrot, Department of Mechanical Engineering, Centre for Advanced Composite Materials, The University of Auckland, Private Bag 92019, Auckland, New Zealand E-mail: s.fakirov@auckland.ac.nz The preparation of nanofibrillar composite (NFC) materials using single-polymer nanofibrils as starting materials is described. Such a possibility is offered by (i) the concept of polymer/ polymer NFCs, which have recently been manufactured and represent a further development in the field of microfibril-reinforced com- posites, and (ii) the opportunity to iso- late neat nanofibrils through selective dissolving of the second blend com- ponent. The resulting nanofibrillar single-polymer composites are charac- terized by superior mechanical proper- ties (the tensile modulus and strength are improved up to 350%), competing with glass-fiber-reinforced PET. Macromol. Mater. Eng. 2010, 295, 515–518 ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mame.200900387 515