Filler nonreinforcing

As it will be discussed later, the size of the filler is probably one of the most important properties for reinforcement. So, particulate fillers obtained by grinding of minerals or by coarse precipitation are usually nonreinforcing fillers because of their size they are too big. Such fillers can even be used in elastomers but just confer them a very slight increase in modulus and a very significant drop in break properties occurs. 

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Mineral fillers are used for light-colored compounds. Talc has a small particle size and is a semireinforcing filler. It reduces air permeabihty and has htde effect on cure systems. Calcined clay is used for halobutyl stoppers in pharmaceutical appHcations. Nonreinforcing fillers, such as calcium carbonate and titanium dioxide, have large particle sizes and are added to reduce cost and viscosity. Hydrated siUcas give dry, stiff compounds, and their acidity reduces cure rate hence, their content should be minimized. 

Many properties of composites filled with nonreinforcing fillers, such as coefficient of expansion, heat deflection, and specific heat, may be estimated from the rule of mixtures. Thus the coefficient of expansion of the composite, ae, is related to the sum of the coefficients of expansion of the continuous phase or resin matrix m and the discontinuous phase or filler/times their fractional volumes V and (1 — V)% respectively, as follows ... 

Although glass spheres are classified as nonreinforcing fillers, the addition of 40 g of these spheres to 60 g of nylon 66 increases the flexural modulus, the compressive strength, and the melt index of the polymer. The tensile strength, the impact strength, the creep resistance, and the elongation of these composites are less than those of the unfilled nylon 66. 

Figure 9. Reinforcing and nonreinforcing filler (volume fraction = 0.5) in poly(l,2-oxypropylene)-type polyurethane rubber. I = 0.74 min. 1 T =...

Nonreinforcing Filler-Elastomer System, I. Experiments Based on Model Systems , JA-PolymSci 1974, 18(1), 1-20 CA80, 109562 (1974) 5) A.J. Hammond H.R. Lobowitz,... 

Nonreinforcing Filler-Elastomer Systems—2. Silane-Treated Ammonium Perchlorate in Polybutadiene , JApplPolymSci 18 (1), 21—43... 

In parallel with this increase, certain undesirable properties which indicate viscoelastic behaviour become more marked as the proportion of carbon black is raised. These include stress-softening, compression set, hysteresis and heat build-up. Only comparatively insignificant increases become apparent, if at all, when nonreinforcing fillers are used. 

All elastomer can be removed from nonreinforcing fillers by any solvent at all temperatures. While the author cannot quote the literature for this statement, direct and indirect evidence for the complete separation of cured elastomer from fillers such as chalk, talk and clay, when swollen in solvents7) make this statement more than probably true. 

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