Composites particulate filled

Ghassemieli, E. and Nassehi, V., 2001b. rediction of failure and fracture mechanisms of polymeric composites using finite clement analysis. Part 1 particulate filled composites. Poly- Compos. 22, 528-541. 

Hancock M Filled Thermoplastics. In Rothon R (ed) Particulate filled polymer composites. Longman Scientific Technical, Harlow (UK), p 279... 

The growth rate of the use of particulate filled polymers is very fast in all fields of application [ 1 ]. Household articles and automotive parts are equally prepared from them. In the early stages, the sole reason for the introduction of fillers was to decrease the price of the polymer. However, as a result of filling all properties of the polymer change, a new polymer is in fact created. Some characteristics improve, while others deteriorate, and properties must be optimized to utilize all potentials of particulate filling. Optimization must include all aspects of the composites from component properties, through structure and especially interactions. 

The characteristics of particulate filled polymers are determined by the properties of their components, composition, structure and interactions [2]. These four factors are equally important and their effects are interconnected. The specific surface area of the filler, for example, determines the size of the contact surface between the filler and the polymer, thus the amount of the interphase formed. Surface energetics influence structure, and also the effect of composition on properties, as well as the mode of deformation. A relevant discussion of adhesion and interaction in particulate filled polymers cannot be carried out without defining the role of all factors which influence the properties of the composite and the interrelation among them. 

This chapter focuses its attention on the discussion of the most relevant questions of interfacial adhesion and its modification in particulate filled polymers. However, because of the reasons mentioned in the previous paragraph, the four factors determining the properties of particulate filled polymers will be discussed in the first section. Interactions can be divided into two groups, parti-cle/particle and matrix/filler interactions. The first is often neglected although it may determine the properties of the composite and often the only reason for surface modification is to hinder its occurrence. Similarly important, but a very contradictory question is the formation and properties of the interphase a separate section will address this question. The importance of interfacial adhesion... 

As was mentioned above, four main factors determine the properties of particulate filled polymers characteristics of the components, composition, structure and component interactions. All four are equally important and must be adjusted to achieve optimum properties and economics. 

Fig.1. Effect of matrix properties on the tensile yield stress of particulate filled composites. Symbols (O) PVC, (A) LDPE filler CaC03,r=1.8 pm... 

The structure of particulate filled polymers seems to be simple, homogeneous distribution of particles is assumed in most cases. This, however, rarely occurs and often special, particle related structures develop in the composites. The... 

As was mentioned in the previous section two types of interactions must be considered in particulate filled polymers particle/particle and matrix/filler interaction. The first is often neglected even by compounders, in spite of the fact that its presence may cause composite properties to deteriorate significantly especially under the effect of dynamic loading conditions [18]. Many attempts have been made to change both interactions by the surface treatment of the filler, but the desired effect is often not achieved due to improper use of incorrect ideas. 

Table 1. Forces Acting During the Homogenization of Particulate Filled Composites Calculated for Particles of 20 pm Diameter...

The interaction of two substrates, the bond strength of adhesives are frequently measured by the peel test [76]. The results can often be related to the reversible work of adhesion. Due to its physical nature such a measurement is impossible to carry out for particulate filled polymers. Even interfacial shear strength widely applied for the characterization of matrix/fiber adhesion cannot be used in particulate filled polymers. Interfacial adhesion of the components is usually deduced indirectly from the mechanical properties of composites with the help of models describing composition dependence. Such models must also take into account interfacial interactions. 

Recently, stress analysis has been carried out for the determination of stress distribution around inclusions in particulate filled composites. A model based on the energy analysis has led to the determination of debonding stress [8]. This stress, which is necessary for the separation of the matrix and filler, was shown to depend on the reversible work of adhesion (see Eq. 16) and it is closely related to parameter B. 

Rothon R (1995) Particulate-filled polymer composites. Longman, Harlow Schlumpf HP (1983) Kunststoffe 73 511... 

Structure Development in Melt Processed Particulate-Filled Polymer Composites 207... 

Contrary to particulate-filled composites, fibres induce an increase in strength. Again on the basis of data from technical brochures, it can be concluded that the tensile strength is raised by a factor between 1.5 and 3.5 at 20 vol % glass fibres. Apparently the fibres play such an important load-carrying role, that the polymer itself is considerably less stressed. The strain at break, however, strongly decreases. 

Particulate-filled composites generally have greater elastic moduli compared to the unfilled resin, and starch-filled composites are no exception. Various models have been developed to describe this effect, and are generally of the form ... 

Source Reprinted in part from Rothon, R.N., Particulate Filled Polymer Composites, 2nd edn., Rapra Technology Ltd., Shawbury, U.K., 2003, Chapter 6. With permission. 

Rothon, R.N., Effects of particulate fillers on flame-retardant properties of composites, in Particulate-Filled Polymer Composites, Rothon, R. (Ed.), John Wiley Sons, New York, 1995, Chapter 6, pp. 207-234. 

Lewis, X B. and Nielsen, L. E. 1970. Dynamic mechanical properties of particulate-filled composites. J. Appl. Polym. Sci. 14 1449-1471. 

These remarks evaluate the effect of filler-related phenomena on failure of plastic materials. Several reasons for the failure ofplastics are filler related. They include delamination of laminated composite materials, debonding in particulate filled materials, stress cracking of filler particles, yielding, cavitation, and corrosion. 

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