Use of Pyrolysed Oil Shale as Filler in Poly(ethylene-co- vinyl Alcohol) Ronilson Vasconcelos Barbosa, Ricardo Baumhardt-Neto, Raquel Santos Mauler, Carlos José, Perez Gorga, Cla ´udia Gazzana Schneider Instituto de Quı ´mica, Universidade Federal do Rio Grande do Sul, Departamento de Quı ´mica Orga ˆnica, Avenida Bento Gonc ¸alves, 9500, Porto Alegre, Rio Grande do Sul, Caixa Postal 15003, CEP 91501–970, Brazil Received 23 June 2003; accepted 27 October 2003 ABSTRACT: The pyrolysed oil shale (POS) obtained from the pyrolysis of bituminous rock was used as filler in poly- (ethylene-co-vinyl alcohol) (EVAL). The effects of vinyl al- cohol content in the EVAL and the particle size of pyrolysed oil shale in the mechanical properties were investigated. The EVAL was prepared by hydrolysis of poly(ethylene-co-vinyl acetate) (EVA) with 8 and 18 wt % of vinyl alcohol content. The composites were prepared in a rotor mixer at 180°C with concentration of pyrolysed oil shale up to 5 wt %. Stress–strain plots of compression-molded composites showed a synergic behavior in the mechanical properties for low concentrations (1–5 wt %) of POS in all particle sizes and EVAL used. Such behavior indicates a close packing and strong interactions between the inorganic filler and the poly- mer. Increasing of the vinyl alcohol content of EVAL im- proved the compatibility between the polymer and filler, but decreasing the POS particle size had no effect on the properties. The modulus and the ultimate tensile strength also increased in all concentrations of POS for both EVAL. Mechanical properties and dynamic mechanical analysis also demonstrated the compatibility between EVAL and POS. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1658 –1665, 2004 Key words: composites; fillers; mechanical properties INTRODUCTION Pyrolysed oil shale (POS) is an inorganic material that originates from the oil extraction of bituminous rock, through pyrolysis at approximately 400°C. POS, with low oil concentration (between 12% wt), goes back to the mines after extraction, increasing production costs and requiring appropriate environmental control. During the pyrolysis process the organic material con- tained in the rock is transformed into oil and gas, and another part produces a coke that is retained in the mineral matrix. POS is a black mineral consisting of a consolidated organic–inorganic mixture with most of the inorganic part constituted of silicates. Many of the mineral fillers currently being used in plastics, such as clay, mica, and talc, also consist of silicate. 1 The use of mineral as fillers in polymeric materials is an eco- nomic practice in the polymer industry today. Most mineral fillers are used in industry to reduce produc- tion costs; among them the most important are alu- mina, calcium carbonate, talc, clay, and others. The use of POS as filler in polymer materials is new and few works referring to the subject are found in the specialized literature. 1 According to the literature, the objective of blending oil shale with polymer is to promote the decomposition of the oil shale in the pyrolysis process. 2,3 In previous work we showed the role of surface organic compounds on pyrolysed oil shale in promot- ing a better dispersion between high-density polyeth- ylene (HDPE) andPOS. 4 These interactions are also responsible for better phase dispersion and the lost of ultimate tensile strength and elongation at break with the decrease of particle size of pyrolysed oil shale. 4,5 The results of mechanical properties of poly(ethylene- co-vinyl acetate) (EVA)-8/POS and EVA-18/POS showed that three factors were related to the mechan- ical properties of the mixtures of polymer/POS: (a) POS particle size: the smaller the particle size, the better the mechanical properties of the composites compared to the pure polymer. This behavior may be explained by the best dispersion of the particle in the polymer matrix; (b) concentration of POS: the amount of POS or any other filler is very important for the mechanical properties. The increase of filler content tends to determine losses in the mechanical properties, mainly when the interface polymer/filler shows poor dispersion; (c) the polarity of the polymer: when the polymer polarity (vinyl alcohol (VA) content) was increased, the mechanical properties remained almost the same at higher filler content compared with the pure polymer. Correspondence to: R. V. Barbosa (Ronilson@iq.ufrgs.br). Contract grant sponsor: CNPq, FAPERGS, ANP/CTPE- TRO, and TECPOL-Tecnologia em Polı ´meros. Journal of Applied Polymer Science, Vol. 92, 1658 –1665 (2004) © 2004 Wiley Periodicals, Inc.