Preparation, chemical and mechanical properties of microcomposite materials based on Fe powder and phenol-formaldehyde resin

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 180; no. 15; pp. 343 - 353
• Main Authors: Strečková, M., Sopčák, T., Medvecký, Ľ., Bureš, R., Fáberová, M., Batko, I., Briančin, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-01-2012
• Subjects: Additives; Byproducts; chemical engineering; Coating; coatings; Core–shell structure; Curing; Fe powder; hardness; Iron; Magnetic materials; mechanical properties; Morphology; Nanostructure; Phenol-formaldehyde resin; Polymers; Resins; spectroscopy; Thermal degradation; Additives; Core–shell structure; Fe powder; Phenol-formaldehyde resin; Morphology; Thermal degradation
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2011.11.036

► Core–shell microcomposite is prepared from Fe powder and phenol-formaldehyde resin. ► SiO
2 and ZnSO
4 additives prevent foaming and formation of microvoids. ► ZnSO
4 additive provokes polymerization to fine fibers of nanometer size. ► SiO
2 and ZnSO
4 additives increase a hardness of prepared microcomposites. ► Electrical resistivity of microcomposites is much greater than that of Fe sample.
Preparation of microcomposite materials based on Fe powder and the modified phenol-formaldehyde resin (PFR) was investigated with the aim to design a new class of prospective soft magnetic materials. Undesirable evolution of water and other volatile by-products during curing process was eliminated by modification of resol prepolymer coating with two different inorganic additives – SiO
2 and ZnSO
4. The structure of synthesized PFR was confirmed by
13C-NMR spectroscopy. The effect of both additives on thermal degradation, structure and morphology was studied by employing TG, DSC, IR and SEM analysis. The addition of ZnSO
4 into PFR caused a significant change in the polymer structure, which is constituted by nano-fibers linking Fe particles. The observed unusual structure of PFR–ZnSO
4 coating on Fe particles results in a higher mechanical hardness and flexural strength compared to the Fe particles coated by the pure PFR or PFR–SiO
2. It is shown that the microcomposites with a few percentages of PFR coatings exhibit a substantial increase of the specific resistivity and they still belong to soft magnetic materials with low enough coercivity.