Fillers performance

In engineering applications we routinely incorporate inorganic fillers, such as glass fibers and mineral particles, into nylons. In general, fillers perform three functions they reduce the cost of the product, they increase its stiffness, and they reduce shrinkage and warpage in molded products. 

This definition implies the existence of two ways in which a filler performs in a system -through its own properties (e.g., hardness, particle size, particle shape, etc.) and through interactions with the material (the extent of which can vary from strong chemical/physical interaction to almost no interaction at all). This allows us to include all existing fillers (even the degrading fillers which have too large a particle size and too small an interaction to combine with the material in an economical manner)... 

Most medical plastics must be kept scrupulously clean and are handled only in a clean room environment. Static charge built up on these parts will attract contaminants therefore it is critical that static charges be dissipated. Fillers perform this function because fillers, unlike organic antistatics, have no tendency to migrate and contaminate the surroundings. 

The above aspects of fillers performance are discussed in detail in specialized monograph on fillers. The most common method of estimation of plasticizer uptake by a filler is by measurement of oil absorption." ... 

Fillers take the space of more expensive polymer in a formulation while reinforcers strengthen the formulation. Reinforcing fillers perform both functions. Processing aids allow lower energy, lower temperature, or lower defect rate formation of objects from a formidation. Dyes change the reflectance spectrum of a formulation so that objects made from it have the correct color. 

This chapter has reviewed both the types and the properties of elastomers, compounding with a range of filler or reinforcement systems such as carbon black, and enhancement of filler performance by novel use of compounding ingredients such as silane coupling agents. Other issues such as antioxidant systems and vulcanization systems were also discussed. The role of the modem materials scientist in the tire and rubber industry is to use materials to improve current products and develop new products. Four key parameters govern this development process ... 

Table 13.12 Comparison of filler performance in polyester gel coat after aging [18]. ...

Some fillers perform valuable specialist functions and some are discussed in other sections of this report. One example is aluminium trihydroxide (ATH), discussed under the heading of Flame Retardants and Smoke Suppressants, rather than Fillers. Carbon black has several roles, improving polymer conductivity, electrostatic dissipation and UV stabihsation. Antimony trioxide is a flame retardant synergist. 

L.A. Acquarulo, Jr., C. O Neil, and J. Xu, Optimizing nano-filler performance in polymers, US Patent 7 034071, assigned to Foster Corporation (Putnam, CT), April 25,2006. 

Some data included in the tables for inorganic antiblocking agents are taken from a monograph on fillers. Performance characteristics are adjusted to reflect properties required for antiblocking agents, if they differ from general purpose fillers. A handbook on fillers contains additional information on particular materials, which is not repeated in this book. 

As with most elastomers, various fillers have different effects on the properties of the compoimd. Because of the potential for the formation of ionic crosslinks with the terpolymer, some fillers are not suitable for use with terpolymers. Table 6.9 is a brief overview of filler performance when incorporated into Vamac. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

The properties of fillers which induence a given end use are many. The overall value of a filler is a complex function of intrinsic material characteristics, eg, tme density, melting point, crystal habit, and chemical composition and of process-dependent factors, eg, particle-si2e distribution, surface chemistry, purity, and bulk density. Fillers impart performance or economic value to the compositions of which they are part. These values, often called functional properties, vary according to the nature of the appHcation. A quantification of the functional properties per unit cost in many cases provides a vaUd criterion for filler comparison and selection. The following are summaries of key filler properties and values. 

True Density or Specific Gravity. The average mass per unit volume of the individual particles is called the tme density or specific gravity. This property is most important when volume or mass of the filled composition is a key performance variable. The tme density of fillers composed of relatively large, nonporous, spherical particles is usually determined by a simple Hquid displacement method. Finely divided, porous, or irregular fillers should be measured using a gas pycnometer to assure that all pores, cracks, and crevices are penetrated. 

In a flexible PVC compound, ingredients in the recipe are chosen based on cost and/or thein contribution to physical and other properties and performance. Typical ingredients (16,17) are stabilizers, fillers, plasticizers, colorants, and lubricants. 

---