JOURNAL OF MATERIALS SCIENCE 40 (2 0 0 5 ) 1785 – 1788 LETTERS Development of amorphous PLA-montmorillonite nanocomposites J. L. FEIJOO ∗ Departamento de Ciencia de los Materiales, Grupo de Pol´ ımeros, Universidad Sim ´ on Bol´ıvar, Caracas, 89000, Venezuela E-mail: jfeijoo@usb.ve L. CABEDO, E. GIM ´ ENEZ* Departamento de Tecnolog´ ıa, Area de Materiales, Universidad Jaime I, Campus Riu Sec, Castell ´ on 12071, Spain E-mail: gimenezt@tec.uji.es J. M. LAGARON Packaging Lab, IATA-CSIC, Apdo. Correos 73, 46100 Burjassot, Spain J. J. SAURA Departamento de Tecnolog´ ıa, Area de Materiales, Universidad Jaime I, Campus Riu Sec, Castell ´ on 12071, Spain The large amounts of plastics that are produced mainly from fossil fuels, once they are consumed and dis- carded into the environment, finally end up as un- degradable wastes, and therefore contribute greatly to global pollution. For this reason, there is an urgent need to produce renewable source-based environmen- tally benign plastic materials, specially in short term packaging and disposable applications that could al- low the composting of naturally occurring degradation products. One of the most promising candidates in this di- rection is poly(lactic acid) (PLA), produced from re- newable resources and readily biodegradable. PLA is a linear thermoplastic polyester produced by the ring- opening polymerization of lactide. Lactide is a cyclic dimmer prepared by the controlled depolymerization of lactic acid, which is obtained from the fermentation of sugar feedstocks, corn, etc. [1, 2]. In general commercial PLA grades are copolymers of poly(L-lactic acid) and poly(D,L-lactic acid), which are produced from L-lactides and D,L-lactides respec- tively. The ratio of L-enantiomers to D,L-enantiomers is known to affect the properties of PLA [3], i.e. if the materials are semicrystalline or amorphous; until now all the efforts reported in order to improve the proper- ties of PLA are focused on the semicrystalline material [3], e.g. D-content less than 6%. There is increasing interest in using PLA for dis- posable degradable plastic articles; however, there are properties such as flexural properties, gas permeabil- ity, impact strength, processability, etc. that are of- ten not good enough for some end use applications [4]. On the other hand confinement of polymer in a two-dimensional silicate gallery, so-called polymer nanocomposite, is one of the effective ways to improve material performance [5]. The most widely utilized clay is the montmorillonite (MMT) for its large cation exchange capacity [5]. Ogata et al. [4] first prepared ∗ Author to whom all correspondence should be addressed. blends of PLA and organically modified montmoril- lonite by solution casting method; several authors since then have prepared PLA/modified monmorillonite us- ing different techniques [3]. The melt intercalation process is a very convenient approach to make polymer layered silicate nanocom- posites by using a conventional polymer extrusion pro- cess widely spread in the polymer processing industry [6]. In this process, the clay is intercalated and dispersed in the polymer melt by application of shear forces dur- ing compounding. In this work, we report about our early efforts to develop new nanocomposites comprising completely amorphous PLA and montmorillonite with the main objective of obtaining new materials. The PLA used in this work was a commercial product (GALASTIC  R , containing 12 mol% D-lactide, manu- factured by GALACTIC (Belgium). The montmoril- lonite used was supplied by LAVIOSA MINERARIA (Livorno-Italy): DELLITE 72T and DELLITE 43B. The two different types of organically modified mont- morillonite (OMM) used in this study were synthesized by replacing Na + ions in different silicate layers by alkyl ammonium cations by ion exchange: dimethyl- hydrogenated tallow ammonium and dimethyl-benzyl- dihydrogenated tallow ammonium used in DELLITE 72T (OMMT) and DELLIT E 43B (OMMB), respec- tively. Before processing, PLA was dried at 50 ◦ C for 4 hrs under reduced pressure and then stored in the presence of humidity absorbent. For nanocomposite preparation, OMM (DELLITE in powder form) and PLA (pellets form) were first dry-mixed by shaking them in a bag. Melt blending of PLA with clay particles was conducted on an internal mixer (Rheomix-Haake) with a rotation speed of 20 rpm for 4 min, then at 60 rpm for another 4 min, at a temperature of 150 ◦ C. Compositions with 4wt% OMM were compounded. From these materials, 0022–2461 C  2005 Springer Science + Business Media, Inc. 1785