Synthesis and Characterization of Chrysotile/Polyethylene Nanocomposites

Polyethylene/chrysotile nanocomposites with different amount (0.4 to 6.7 wt%) of filler were prepared by in situ polymerization method using the metallocene Cp2ZrCl2 as catalyst and methylaluminoxane (MAO) as co-catalyst. Previous to polymerization, raw chrysotile was treated by three different methods that used thermal treatment and acid leaching. In method A, raw chrysotile was treated thermally at 800 °C and the catalyst supported directly. In methods B and C the brucite sheet was totally or partially removed from chrysotile by acid treatment and the filler treated with MAO before adding the catalyst. The catalytic activities of the polymerizations were, in generally, very good, in some cases superior to the obtained with the neat polymer. In method C, the Al/Zr ratio was varied from 200 to 1000 and the best result obtained was 300, what it was a very interesting achievement taking into account the vantages of reducing the amount of MAO. Melting temperatures of the nanocomposites were very close between them, being in the range of temperature of a high density polyethylene. SEM and TEM micrographs showed that morphologies of the treated chrysotiles are dependent on the method used and that the filler was well dispersed in the nanocomposites. TGA showed an improved thermal stability of the nanocomposites. The novelty and importance of this contribution was the use of commodities, chrysotile and polyethylene, to increase the aggregate value of both materials by the method of adding the filler during the polymerization to obtain nanocomposites.