Effects of surface modification on filler properties

Attachment of molecules to the surface of a solid filler in polymeric biocomposites affects a variety of innate properties, particularly those related to the surface of (he filler material. An overview of the surface modification techniques and how they alter specific filler properties is outlined in Table 3.3. The attachment of molecules affects the immediate physical and chemical composition of a surface, which can alter secondary surface properties related to surface interactions, such as wetting, zeta potential, suiface solution reactions including dissolution/degradation, as well as cellular interactions. These primary and secondary properties do not necessarily alter how the filler interacts with polymer binders in a biocomposite setting, but these properties can change the inherent overall properties of the resultant filler. 

Zeta potential is the potential difference between the dispersion medium (eg, polymer) and the layer of fluid attached to the dispersed particle (eg, soUd filler). This value is used to quantity the electrokinetic potential in a colloidal system and is used to evaluate the stabihty of colloidal dispersions. The modification of HA powder with methoxysilane coupling agents (possessing a variety of functionalities) was shown to significantly increase the zeta potential (Dupraz et al., 1996). 

Category Surface modification Parameter Effect References 

Filler properties Silane Surface topography Smoothed surface, as determined by SEM Koleganova et al. (2006) 

Filler incorporation into polymer binder Filler surface polymer adhesion 

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