Marc Poorteman

Eugenol-based benzoxazine: from straight synthesis to taming of the network properties

Mixed benzoxazine precursors were synthesized using a blend of eugenol, a natural renewable product, and phenol. The structures of these mixed benzoxazine precursors with different phenol:eugenol compositions were attested by 1H NMR. Their polymerization and degradation were investigated and monitored by DSC and TGA and showed an enhancement of the crosslinking ability with the phenol content. Depending on its relative content, the phenol moiety proved to limit the thermal degradation of the bis-benzoxazine “hybrid” monomer and allowed the formation of crosslinked networks with high thermomechanical stabilities. The properties of the networks were closely dependent on the phenol:eugenol ratio, which allowed for adjustment of the crosslinking density and fine tuning of the glass transition temperature (Tg) within a wide temperature range. A comparison between the polymerized hybrid precursors and blend of two pure monomers displaying the same overall composition showed the same material properties increasing the tunability of the system. The eugenol/phenol combination for the preparation of mixed/hybrid benzoxazines or corresponding blends clearly paves the way to new sustainable high performance bio-based materials.

Arbutin-based benzoxazine : en route to an intrinsic water soluble biobased resin

A novel benzoxazine monomer containing a carbohydrate moiety was synthesized using a solventless approach from the reaction of arbutin, a naturally occurring phenolic compound, furfurylamine and formaldehyde. The chemical structure of this fully bio-based benzoxazine monomer was confirmed by 1H NMR and FTIR. Its polymerization has been investigated and monitored by DSC showing the ring opening polymerization of benzoxazine functions with a network densification thanks to the reaction of the furan group. The high hydroxyl content of the monomer allows its easy solubilisation in water paving the way to a wide range of possible “environmentally friendly” applications especially in the fields of coatings, paintings and adhesives.

Impedance Spectroscopy for Non Destructive Characterisation of Ceramic Compacts

Introduction Non destructive testing of ceramic pieces is usually carried out for final quality control of outgoing industrial products, i.e. on fired products which are difficult to recycle and energy consuming. Few non destructive performant tests are available for early stage control, for instance after the forming step, which could lower the cost of the presence of defects in materials, avoiding expensive drying and/or firing steps and giving the possibility of recycling. In this paper we studied the feasibility to use impedance spectroscopy as a tool for non destructive characterisation of ceramic compacts. Several kinds of forming processes have been investigated: first, uniaxial or isostatic pressing with or without binder and, finally, extrusion.

Anisotropic Properties in Hot Pressed Silicon Nitride - Silicon Carbide Platelet Reinforced Composites

The anisotropic properties (microstructure, mechanical properties) of a hot-pressed platelet reinforced silicon nitride composite were compared with those of the monolithic material. The platelets appeared to be orientated with their basal plane in the compressive plane, and to be embedded in a silicon nitride matrix consisting of interlocked elongated b-Si3N4 grains with their c axis orientated in this plane. TEM analysis showed an interface, consisting of glassy phase and graphite at the platelet‐matrix grain boundary. Moreover the interfacial tensile stresses are in favour of a crack deflection mechanism. It was shown by TEM analysis that crack deflection occurs not only at the silicon nitride‐platelet interface, but also at silicon nitride‐silicon nitride grain boundaries. The eAciency of this reinforcing mechanism is highly orientation dependent. Because of their two dimensional geometry compared to the one-dimensional b-Si3N4 grains, platelets increase the toughness in two dimensions. # 1999 Elsevier Science Ltd. All rights reserved.