Polypropylene/wood flour composites:: treatments and properties

In this research, the variations produced on the mechanical, morphological and thermal properties and on the melt index (MI) of a composite of polypropylene and wood flour (WF) by the modification of the filler were studied. The filler was treated with sodium hydroxide at different immersion times and with vinil-tris-(2-metoxietoxi)-silane. Polypropylenes functionalized with maleic anhydride (maleated polypropylene, MAPP) were also used as compatibilizers. All the treatments showed the same tendency to slightly increase tensile modulus and tensile strength of the composites, but they did not affect their MFI. Morphological studies showed that the MAPP and silane improve the polymer-WF adhesion and the dispersion of the particles, while the alkaline treatment only improves the dispersion. The silane-modified samples and the use of MA-PP produced samples with lower water absorption than those of untreated WF composites. The addition of the filler and the treatments carried out on it caused an increase in the crystallization temperature. (C) 2001 Elsevier Science Ltd. All rights reserved.