No abstract

Nanocomposites based on biodegradable poly(3-caprolactone) organo-modified clay have been prepared by melt intercalation using a twin-screw extruder. The screw configuration developed allowed us to obtain an intercalated/exfoliated nanocomposite structure using a modified montmorillonite containing no polar groups, in contrast to previous work using mainly alkyl ammonium containing hydroxyl polar groups in poly(3-caprolactone). Montmorillonite nanocomposites were prepared using a specific extrusion profile from a 30 wt% masterbatch of organo-modified clay, which was then diluted at 1, 3 and 5%. Intercalated and/or exfoliated nanocomposites structures were assessed using rheological procedures and confirmed by transmission electron microscopy analysis. Mechanical and thermal properties were found to be strongly dependent on morphology and clay percentage. Crystallinity was only slightly affected by the clay addition. Effect of exfoliation on Young's modulus and thermal stability was investigated. Young's modulus increased significantly and onset degradation temperature measured by TGA was significantly reduced for an exfoliated nanocomposite composition containing 5 wt% organoclay.

Nanometric aluminum oxide particles were modified by phosphonic acid‐based oligomers of aromatic polyester, polyether, or polydimethylsiloxane (PDMS). The grafting process was characterized by FTIR spectroscopy and thermogravimetric analysis (TGA) showing that covalent bonds must have formed between the oxide and oligomers. The highest yield of grafting was achieved in dichloromethane (CH2Cl2) solvent. Then, nanocomposites were prepared by melt‐blending in a poly(methyl methacrylate) (PMMA) matrix. The best results in terms of thermal stability and flammability were obtained with the bis‐phosphonicpolydimethylsiloxane‐based formulation. With this latter, the peak of heat released rate (pHRR) decreased during the combustion, whereas PyGC/MS experiments led to the conclusion that PDMS‐covered nanoparticles played a role in the composition of the gaseous phase as well. Copyright © 2008 John Wiley & Sons, Ltd.