Other Filler Systems

A series of additional filler systems merit brief discussion, not because of their reinforcement qualities but because of their high consumption. These include kaolin clay (hydrous aluminum silicate), mica (potassium aluminum silicate), talc (magnesium silicate), limestone (calcium carbonate), and titanium dioxide. 

Such clays show improved tear strength, an increase in modulus, improved component-to-component adhesion in multicomponent products, and improved aging properties. 

Calcium carbonate is used as a low-cost filler in rubber products for static applications such as carpet underlay. Titanium dioxide finds extensive use in white products such as white tire sidewalls where appearance is important. 

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The selection of mix ingredients may depend heavily on the type of adhesive applieation equipment used. The main types of equipment for plywood and LVL are roll coaters, spray systems, eurtain coaters, and foam extruders. When foam extruders are used, animal blood and surfactants are usually added to the mill mix. For other application systems, resin producers typieally supply the non-filler additives as part of the resin eomposition. 

Ammonium polyphosphates, on the other hand, are relatively water insoluble, nonmelting solids with very high phosphorus contents (up to about 30%). There are several crystalline forms and the commercial products differ in molecular weights, particle sizes, solubilities, and so on. They are also widely used as components of intumescent paints and mastics where they function as the acid catalyst (i.e., by producing phosphoric acid upon decomposition). They are used in paints with pentaerythritol (or with a derivative of pentaerythritol) as the carbonific component and melamine as the spumific compound.22 In addition, the intumescent formulations typically contain resinous binders, pigments, and other fillers. These systems are highly efficient in flame-retarding hydroxy-lated polymers. 

The notched Izod impact strength of the kenaf system is much lower than that of the glass fiber-filled PP but about the same as all other fillers and mica systems. Short fiber lengths present in the kenaf system due to the compounding system used and molding are probably responsible for the poor impact strengths [30]. 

Strength and most important commercial fillers for a particular polymer have a lower reduction in these properties at a given volume fraction than other fillers. The applications of composites that depend primarily on mechanical property specifications are too numerous to list some examples are airplane and automotive components. Other important mechanical properties that often justify the use of a filled system vs. one without a filler are abrasion resistance, for instance, automobile tires and resistance to creep, e.g., weightbearing structural components. 

The addition of aluminum trihydrate improved fire resistance of glass epoxy laminates but, because of the high loading required, it decreased the mechanical properties of the laminate. Various components of formulation were studied to improve performance. It was found that the curing agent and impact modifier help to improve the mechanical properties of the laminates. Other fillers were also studied in order to understand the impact of filler on properties. It was found that all fillers (glass beads, quartz, calcium carbonate, mica) reduce mechanical properties of laminates, not just aluminum trihydrate. " Aluminum trihydrate was found to be one of better performers in this system. 

Manufacturers of various fillers continue studies on altemative systems. Most antimony oxide used as a fire retardant can be replaced by a combination of zinc borate without the loss of other properties (in some cases improvements are reported). Another option is to use the same filler systems which are used in polyethylene insulated cables and wires. These are based on magnesium hydroxide and aluminum hydroxide. These systems pcrfoim as flame retardants but require a high filler concentration which affects jacket resistance and mechanical performance. Recently, new coated grades have been developed which can be used at up to 65 wt% without the loss of properties or productivity (extrusion rates 2,500 m/min of cable are possible). ... 

Jet Fil . [Luzenac R.T. Vanderbilt] Talc filler for PP and other resin systems. 

Observed values of permeability may also be expected to deviate from predictions based on a simple two-component model of an impermeable, noninteracting filler embedded in a permeable matrix (see Section 12.1.3.1). If an interphase exists, it may be more permeable than the matrix, as in some pigmented paint films (Funke et ai, 1969 Michaels 1965), or less permeable, as in several other filler-polymer systems now to be discusses. 

Clays compatibilized and evenly dispersed in a polymer matrix tend to build networks at low concentration. Rheological measurements, performed on RCN based on various types of rubbers, revealed the pronounced rubber-clay interaction, when measurements were taken at zero shear. The filler networking phenomenon was observed as well in matrices based on various other rubber systems. At zero shear, the viscosity of RCN is thus higher than the one of... 

Compared with other adhesives systems, the formulation of the rubber-based adhesives is very complex considerable training and practical experience is necessary before they can be successfully formulated (see Rubber-based adhesives compounding). The properties of the elastomeric adhesives depend on both the chemical type and particular grade of the natural or synthetic elastomer and on the modifying additives that may be incorporated into the adhesive formulation (tackifiers, reinforcing resins, fillers, plasticizers, curing agents, etc.). 

This is similar to the system described above except that particles of inorganic filler are also mixed into the polymer before extrusion. The particles of filler are removed together with the plasticizer. The advantage of this system is that it is able to form larger pores than the other two systems, providing greater ion mobility. 

Figure 2 shows that the average value of s in the first high density layers is markedly negative. Similar curves are found for the other simulated systems, indicating in all cases a comprehensible tendency of chain segments in contact with the filler particles to run parallel to the surfaces of the particles. It is concluded that the polymer units at the interface with the filler are arranged in densely packed and partly ordered shells of thickness approximately 2cr similar to the layers found for the same model polymers near planar solid surfaces in Refs. [22-24] and... 

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