Fillers surface energy

CaCO EPR rubber rubber silicone maleates fatty acid silanes PDMS decreased disperse component of the surface energy filler surface energy approaches surface energy of matrix decreased tensile strength and flexural cracking increased green strength, Mooney viscosity, and tensile properties surface hydrophobization resistance to solvent extraction and water 21 49 49 37... 

This justifies the use of inverse gas chromatography (IGC) for filler surface energy characterization. This technique can be used in two very different modes infinite or finite dilution. 

As discussed earlier, dispersibility and so dispersion is mainly controlled by the strength of interaction between agglomerates and/or aggregates, which is a direct consequence of their surface energy. The influence of surface energy on dispersion has been clearly demonstrated by the use of different matrices when matrix surface energy increases and becomes closer to filler surface energy, dispersion is facilitated. 

Influence of filler surface energy and morphology (Kraus, Donnet, Wagner, Wolf, Gespacher, Lablanc, Niedermeier, Wang). 

Surface treatment of fillers is common to minimise particle interaction and to facilitate dispersion. Additionally, appropriate treatment will lower the filler surface energy, thereby increasing compatibility with the polymer phase. This will aid wet-out hy the melt and may result in enhanced physical properties depending on the relative interaction between surface modifier, filler and polymer. It will be evident from the previous discussion that dispersion will be determined by the level of shear stress experienced hy the filler particles, which in turn is dependent on process-operating conditions and above all, hy compounding machinery design (Figure 5.1). 

EPR maleates decreased disperse component of the surface energy filler surface energy approaches surface energy of matrix 21... 

D.M. Ansari, G.J. Price. Correlation of the material properties of calcium carbonate filled polypropylene with the filler surface energies. /. Appl. Polym. Sci, 88, 1951-1955,2003. 

Permanent Set. When an elastomer is stretched and then allowed to relax, it will not completely recover its original dimensions. This divergence from its original form is called its permanent set. It is principally affected by the affinity of the elastomer for the filler surface and is, therefore, primarily a function of the surface energy or wetting of the filler. 

The adsorption of gas onto a solid surface can also be used to estimate surface energy. Both inverse gas chromatography (IGC) and isotherm measurement using the BET method [19] have been used. Further discussion and detailed references are given by Lucic et al. [20] who compare the application of IGC, BET and contact angle methods for characterising the surface energies of stearate-coated calcium carbonate fillers. 

Filler/polymer surface energy ratio Equilibrium work of 1.14 0.87 0.76... 

Styrene-butadiene-styrene (SBS) block copolymers are adequate raw materials to produce thermoplastic mbbers (TRs). SBS contains butadiene—soft and elastic—and styrene— hard and tough—domains. Because the styrene domains act as cross-links, vulcanization is not necessary to provide dimensional stability. TRs generally contain polystyrene (to impart hardness), plasticizers, fillers, and antioxidants processing oils can also be added. Due to their nature, TR soles show low surface energy, and to reach proper adhesion a surface modification is always needed. 

The surface of silica is covered by a layer of acidic silanol and siloxane groups. This highly polar and hydrophilic character of the filler surface results in a low compatibihty with the rather apolar polymer. Besides, highly attractive forces between silica particles result in strong agglomeration forces. The formation of a hydrophobic shell around the silica particle by the sUica-sUane reaction prevents the formation of a filler-filler network by reduction of the specific surface energy [3]. 

Aid in the uniform dispersion of additives. Make powdered solids (e.g. particulate fillers with high energy and hydrophilic surface) more compatible with polymers by coating their surfaces with an adsorbed layer of surfactant in the form of a dispersant. Surface coating reduces the surface energy of fillers, reduces polymer/filler interaction and assists dispersion. Filler coatings increase compound cost. Fatty acids, metal soaps, waxes and fatty alcohols are used as dispersants commonly in concentrations from 2 to 5 wt %. 

Composite-based PTC thermistors are potentially more economical. These devices are based on a combination of a conductor in a semicrystalline polymer—for example, carbon black in polyethylene. Other fillers include copper, iron, and silver. Important filler parameters in addition to conductivity include particle size, distribution, morphology, surface energy, oxidation state, and thermal expansion coefficient. Important polymer matrix characteristics in addition to conductivity include the glass transition temperature, Tg, and thermal expansion coefficient. Interfacial effects are extremely important in these materials and can influence the ultimate electrical properties of the composite. 

As Table 2 shows, non-treated fillers and reinforcements have high energy surfaces. During the almost exclusively used melt mixing procedure, the forces discussed in the previous section lead to the adsorption of polymer chains onto the active sites of the filler surface. The adsorption of polymer molecules results in the development of a layer which has properties different from those of the matrix polymer [43-47]. Although the character, thickness and properties of this interlayer or interphase are much discussed topics, its existence is now an accepted fact. 

The dispersive and polar parts of the surface energies were calculated from contact angle measurements with test liquids of different surface tension and polarity, using a modified Wihelmy technique [79] Organoclay filler yF = + = 24.3 mJ m + 1.0 mJ m 2 EPDM = I = 24.2 mj... 

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