Reinforcing Fillers and Liquid Additives

Particulate fillers are divided into two types, inert fillers and reinforcing fillers. The term inert filler is something of a misnomer as many properties may be affected by incorporation of such a filler. For example, in a plasticised PVC compound the addition of an inert filler will reduce die swell on extrusion, increase modulus and hardness, may provide a white base for colouring, improve electrical insulation properties and reduce tackiness. Inert fillers will also usually substantially reduce the cost of the compound. Amongst the fillers used are calcium carbonates, china clay, talc, and barium sulphate. For normal uses such fillers should be quite insoluble in any liquids with which the polymer compound is liable to come into contact. 

In addition to the broad categories of TPs and TSs, TPs can be further classified in terms of their structure, as either crystalline, amorphous, or liquid crystalline. Other classes (terms) include elastomers, copolymers, compounds, commodity resins, engineering plastics, or neat plastics. Additives, fillers, and reinforcements are other classifications that relate directly to plastics properties and performance. 

The remaining tetrachlorosilane is predominantly used for the production of firmed silica [20], which finds wide use in a variety of industrial applications. Most important are reinforcement of silicone elastomers as active filler and thickening of liquids as a rheological additive. A highly dispersed particle structure, high surface area and surface energy are the main characteristics of firmed silica. 

Gaseous additives are incorporated into polymer exclusively in processing, while liquid additives and those which become liquids in the compounding step due to their good solubility are easily incorporated. That is why compounding mainly deals with the incorporation of solid additives, especially with colorants, fillers, and reinforcements. 

The gluability of the lignin-epoxy resin adhesives was found to be improved by the addition of calcium carbonate (50% by weight) to the liquid resin. This must be attributed to the nature of the weak alkali in calcium carbonate as a cure accelerator, and to the reinforcement effect of fillers. Since wood surfaces are acidic, the addition of alkaline fillers effectively alters the pH of the glue line. 

Although FEP is available as a liquid dispersion, the commonly used material in liquid dispersion coatings are PFA and PVDF. Both materials are used in various ways such as filled or unfilled. T q)ical fillers for PFA are mica flakes. PVDF can be reinforced with fiberglass cloth or carbon fabric for additional permeation protection. T q)ical thicknesses achieved are up to 80 milli-inches (2 mm). PFA coatings are used with wire mesh reinforcment for additional protection from delamination. 

When compared to injection molding (IM) that processes a plastic compound, RIM uses two liquid PUR chemical monomer components (polyol and isocyanate) that are mixed to produce the polymer (plastic). Additives such as catalysts, surfactants, fillers, reinforcements, and/or blowing agents are also incorporated in the reactive system that produces the basic polymer. Their purpose is to propagate the reaction and form a finished product possessing the desired properties (Table 5.9). 

As the organic polymer or its residual char are removed by the ablative aspects of the hyper-environment, the reinforcing fibers or particle fillers are left exposed and unsupported. If vitreous in composition, they undergo melting. The resultant molten material covers the surface as liquid droplets, irregular globules, or a thin film. Continued addition of heat to the surface causes the melt to be vaporized. A fraction of the melt may be splattered by internal pressure forces, or sloughed away when acted upon by external pressure and shear forces of the dynamic environment. 

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