Filler Characteristics

The mechanical behaviour of a two-phase composite system depends partly on the filler characteristics, such as the geometry of inclusions, their size, the size distribution, the orientation of inclusions, the filler volume-fraction, the relative positions between the inclusions, the physical state of the filler, etc. and partly on the matrix characteristics, which are related to the physico-chemical state of the matrix, the degree of its polymerization, the crystallinity, the degree of cross-linking, etc. 

The importance of the use of mineral fillers to the growth of applications for thermoplastic polymers has already been described. The addition of such materials affects most of the significant properties of the matrix, some beneficially, others detrimentally. Only some of these altered properties are important to the use of thermoplastics, and an appreciation of what these are is critical to identifying those filler characteristics that are important and in understanding how certain filler types and production methods have come to dominate the market. 

Numerous filler characteristics influence the properties of composites [14,15]. Chemical composition and, in particular, purity of the filler both have a direct and an indirect effect on its application possibilities and performance. Traces of heavy-metal contamination decrease stability. Insufficient purity leads to discoloration, high purity CaC03 has the advantage of a white color, while the grey shade of talc filled composites excludes them from some fields of application. 

Although a number of filler characteristics influence composite properties, particle size, specific surface area, and surface energetics must again be mentioned here. All three also influence interfacial interactions. In the case of large particles and weak adhesion, the separation of the matrix/ filler interface is easy, debonding takes place under the effect of a small external load. Small particles form aggregates which cause a deterioration in the mechanical properties of the composites. Specific surface area, which depends on the particle size distribution of the filler, determines the size of the contact surface between the polymer and the filler. The size of this surface plays a crucial role in interfacial interactions and the formation of the interphase. 

Both adhesive and hydrodynamic forces depend on the size of the particles. The two forces were calculated for CaC03 fillers of various particle sizes homogenized in a PP matrix. The results are presented in Fig. 3. At a certain particle size adhesion exceeds shear forces, aggregation of the particles takes place in the melt. Since commercial fillers have a relatively broad particle size distribution, most fillers show some degree of aggregation and the exact determination of the particle size, or other filler characteristics where aggregation appears, is difficult. Experiments carried out with 11 different CaC03 showed this limit to be around 6 m /g specific surface area [25]. 

The IAF is thus designed to represent the filler characteristics [R3 (1 + s2)/a2b] that surfaced in (16). Thus, the corrective function, ( 1 ). introduced to accommodate the shape and aggregation effects, can be defined as ... 

The concept of the free volume of disperse systems can also be correlated with the change in the structure of the composite of the type solid particles — liquid — gas during its compaction. In that case the value of the maximum packing fraction of filler (p in Eq. (80b) remains valid also for systems containing air inclusions, and instead of the value of the volume fraction of filler, characteristic for a solid particles — liquid dispersion-system solid particles — liquid — gas should be substituted. This value can be calculated as follows the ratio of concentrations Cs x g/Cs, to the first approximation can be substituted by the ratio of the densities of uncompacted and compacted composites, i.e. by parameter Kp. Then Eq. (80b) in view of Eq. (88), for uncompacted composites acquires the form ... 

As can be seen on Fig. 1, the filler characteristics have a considerable effect on the material behaviour the crack opening displacement is increased from 1 to more than 4 mm as a function of the filler size. 

The effect of fillers on the gel point of thermosets has not been studied extensively. Ng and Manas-Zloczower (1993) used isothermal dynamic time tests to measure the crossover point for a silica-filled epoxy resin. They noted a decrease in gel time with increasing filler loading. Metzner (1985) also noted that the storage modulus and loss modulus increased by different amounts with filler loading. Therefore, the gel-point tests for highly filled systems must involve knowledge of the effect of filler characteristics at various levels. 

Electrical properties. Fillers and additives significantly increase the porosity of polytetrafluoroethylene compounds. Electrical properties are affected by the void content as well as the filler characteristics. Dielectric strength drops while dielectric constant and dissipation factor rise. Metals, carbon, and graphite increase the thermal conductivity of PTFE compounds. Tables 3.19 and 3.20 present electrical properties of a few common compounds. 

A generalized table of fundamental filler characteristics is given in Table 6.1 for a range of carbonate and kaolin grades as well as typical filler titanium, talc and precipitated silica. By developing an understanding of how these fundamental... 

In summary, it is of paramount importance for the papermaker to have a clear idea of the performance attributes which are to be achieved by filler. With that information and a cursory understanding of how the fundamental filler characteristics scale up to application performance, cost-effective paper grade design is possible. 

Yang L, et al (2004) Revised Kubelka-Munk Theory. II. Unified framework for homogeneous and inhomogeneous optical media. Journal Opt. Soc. Am. A 21(10) 1942 McLain L, Wygant R (2005) Fundamental Filler Characteristics for Maximum Sheet Performance, Paper presented at AEL Metsko s Stock Preparation and Uses of Various Pulps Workshop, Munich, Germany, November 2005... 

Fillers are those materials added to a matrix in order to improve its properties. The filler characteristics that affect the composite s properties are particle size, size distribution, specific surface area and particle shape and interfacial interactions. The shape of most mineral filler particles can be approximated as a sphere, cube, block, plate, needle or fibre. Some fillers contain a mixture of shapes. ... 

It is now well established that the extent of reinforcement highly depends on the filler characteristics, especially surface characteristics and morphology. In addition, the dispersion of the nanofillers is considered to be one of the most important determining factors of physical properties of the polymer composites. Therefore, it is desirable to investigate metal oxide filled micro/nano-composites of NR for the structural analysis by XRD and morphology by TEM, SEM, FE-SEM and AFM. 

Key filler characteristics include density, particle shape, size and size distribution, surface chemistry, oil absorption capacity, hardness, and refractive index. Oil absorption is frequently measured in a few fillers such as carbon black. It is usual to measure the uptake of dibutyl phthalate under standard conditions this gives some information about the surface of the... 

Effect of filler characteristics on composite properties LIVE GRAPH Flexural modulus (QPa)... 

The most important filler characteristics determining the properties of PP composites are particle size, particle size distribution, specific surface area and shape. None of these influence stiffness very much the reinforcing effect is a result of the orientation of the anisotropic particles. All other properties are considerably affected by these filler characteristics. Yield stress and strength usually increase with decreasing particle size and increasing surface area, while deformability and impact resistance change in the opposite direction. 

The thermophysical properties of multiphase systems are affected by matrix and filler characteristics. In the case of the polymer phase, the microstructure is the most important feature that influences thermal conduction ability. When discussing the filler, one must take into consideration filler physicochanical properties but also several microstructural parameters, such as the diameter, length, shape, distribution, volume fraction, the alignment, and the packing arrangement. Fillers may be in the form of fibers or particles uniformly or randomly placed in the polymer matrix material. Therefore, thermal conduction of particle-filled polymers is isotropic, although... 

There are several filler characteristics that strongly affect the conduction abilities of polymer composites. The most studied aspects include the size, hardness, shape, distribution, and wetting with regard to composite conductivity (Strumpler and Glatz-Reichenbach 1999 Boudenne et al. 2011). 

Ecological considerations and investigations of fire hazards such as CO and smoke production target the inert filler characteristics of nanocomposites. The rather physical mechanisms proposed for nanocomposites are advantageous for such considerations. Nanocomposites appear to be a promising eco-friendly approach to fire retardancy in polymers. 

Abstract This chapter deals with the non-linear viscoelastic behaviour of rubber-rubber blend composites and nanocomposites with fillers of different particle size. The dynamic viscoelastic behaviour of the composites has been discussed with reference to the filler geometry, distribution, size and loading. The filler characteristics such as particle size, geometry, specific surface area and the surface structural features are found to be the key parameters influencing the Payne effect. Non-Unear decrease of storage modulus with increasing strain has been observed for the unfilled vulcanizates. The addition of spherical or near-spherical filler particles always increase the level of both the linear and the non-linear viscoelastic properties. However, the addition of high-aspect-ratio, fiber-like fillers increase the elasticity as well as the viscosity. 

The nonlinear viscoelastic behavior of the composites of natural rubber filled with surface-modified nanosilica was studied with reference to silica loading [191]. The effect of temperature on the nonlinear viscoelastic behavior has been investigated. It was observed that Payne effect becomes more pronounced at higher silica loading. The filler characteristics such as particle size, specific surface area, and the surface structural features were found to be the key parameters influencing the Payne effect. A nonlinear decrease in storage modulus with increasing strain was observed for unfilled compounds also. The results reveal that the mechanism includes the breakdown of different networks namely the filler — filler network, the... 

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