Particulate Fillers in Thermoplastics

Abstract

The characteristics of particulate filled thermoplastics are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape, while the main matrix property is stiffness. Segregation, aggregation and the orientation of anisotropic particles determine structure. Interfacial interactions lead to the formation of a stiff interphase considerably influencing properties. Interactions are changed by surface modification, which must be always system specific and selected according to its 2 goal. Under the effect of external load inhomogeneous stress distribution develops around heterogeneities, which initiate local micromechanical deformation processes determining the macroscopic properties of the composites. INTRODUCTUIONParticulate filled polymers are used in very large quantities in all kinds of applications. The total consumption of fillers in Europe alone is currently estimated as 4.8 million tons (Table 1) [6]. In spite of the overwhelming interest in nanocomposites, biomaterials and natural fiber reinforced composites, considerable research and development is done on particulate filled polymers even today. The reason for the continuing interest in traditional composites lays, among others, in the changed role of particulate fillers. In the early days fillers were added to the polymer to decrease price.However, the ever increasing technical and aesthetical requirements as well as soaring material and compounding costs require the utilization of all possible advantages of fillers.Fillers increase stiffness and heat deflection temperature, decrease shrinkage and improve the appearance of the composites [9][10][11][12][13]. Productivity can be also increased in most thermoplastic processing technologies due to their decreased specific heat and increased heat conductivity [9,10,[14][15][16][17]. Fillers are very often introduced into the polymer to create new functional properties not possessed by the matrix polymer at all like flame retardancy or conductivity [18][19][20][21]. Another reason for the considerable research activity is that new fillers and reinforcements emerge continuously among others layered silicates [7,[22][23][24][25][26][27][28][29], wood flour [30][31][32][33][34][35][36][37], sepiolite [38][39][40][41][42][43][44][45][46][47][48][49], etc.The properties of all heterogeneous polymer systems are determined by the same four factors: component properties, composition, structure and interfacial interactions [9,50]. Although certain fillers and reinforcements including layered silicates, other nanofillers, or natural fibers possess special characteristics, the effect of these four factors is universal and valid for all particulate filled materials. As a consequence, in this paper 3 we focus our attention on them and discuss the most important theoretical and practical aspects of composite preparation and use accordingly. The general rules of h...

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