Dynamic properties in aluminum filled PMMA S. Cerveny a , *, S.N. Goyanes a , A.J. Marzocca a , G.H. Rubiolo a,b a Departamento de Fı ´sica, FCEN, University of Buenos Aires, Cdad. Universitaria, Pab. I, 1428 Buenos Aires, Argentina b Departamento de Materiales, CNEA, Av. del Libertador 8250, 1424 Buenos Aires, Argentina Received 17 October 1997; revised 24 April 1998; accepted 7 May 1998 Abstract The dynamic mechanical properties of polymethyl methacrylate reinforced with different amounts of aluminum filler were investigated. The internal friction and the shear storage modulus were measured with an automated damped torsional pendulum in the temperature range between 200 and 375 K in an argon atmosphere. An increase in the glass transition temperature occurred at higher filler contents. The amount of filler in the matrix seems to modify the b relaxation of the composite. The dynamic modulus increases with the aluminum percentages for low filler content. These results were explained in terms of a model presented in the literature for the elastic modulus.  1998 Elsevier Science Ltd. All rights reserved. Keywords: Dynamic mechanical properties; Filled PMMA; Main and secondary relaxation 1. Introduction In recent years, the conductive polymer field has increased. One of the methods used to attain these materials is adding rather large amounts of a conductive filler in a polymer matrix [1,2]. This kind of material was prepared by Yang and Schruben [2] who investigated several metal filled composites made of polymethyl methacrylate (PMMA) with aluminum and nickel powder. Besides the importance from the point of view of elec- trical properties, it is interesting to analyze this class of material in terms of its dynamic mechanical properties. As it is known, the mechanical properties depended on the type, concentration, size, and shape of the filler. Other important factors that affect the mechanical behavior of filled systems are the strength of the adhesive bond between different phases, the type of dispersion and the kind of agglomeration. Several researchers studied different mechanical proper- ties of metal filler composite but the interest was focused mainly on tensile properties [3–6]. Using a method analo- gous to the theory of the dependence of Young’s modulus of the composites with the filler content [4,7,8], a relationship for the dynamic modulus can be given as G  c G  p ¼ (1 þ kf29 (1) where G  c and G  p are the dynamic modulus of the composite and the polymer matrix respectively, f is the volume frac- tion of filler and k is an adhesion factor. k ¼ 2.5 represents perfect adhesion between the filler and the polymer matrix while k ¼ 1 indicates a weak adhesion [4]. G* is calculated as G  ¼  p G' 2 þ G'' 2 with G' and G' the shear storage and shear loss modulus, respectively. The loss tangent or inter- nal friction is defined as the ratio between G and G', i.e. IF ¼ tand ¼ G'' G' (2) The objective of this paper is to study the dynamic proper- ties of a composite made of PMMA with several contents of aluminum powder and to analyze its associated relaxation in the range of temperatures between 200 and 375 K. 2. Experimental procedure 2.1. Materials The material used in this investigation was PMMA as a matrix and aluminum powder of a mean diameter between 10 mm and 40 mm. Aluminum powder was pre-dried into vacuum chamber at 393 K during 1 h before incorporation into PMMA matrix. Test samples were prepared by dissol- ving the polymer using 350 ml of methylene chloride as a solvent for each 70 g of solid PMMA. Then, certain amounts of aluminum powder were added to the solution, 0032-3861/98/$ - see front matter  1998 Elsevier Science Ltd. All rights reserved. PII: S0032-3861(98)00361-9 * Corresponding author. Tel: 782-1007; Fax: 782-7647; E-mail: lpmuba@df.uba.ar Polymer 40 (1999) 1495–1500