Abstract
High density polyethylene and high density polyethylene-clay nanocomposites were produced using direct solvent polymerization and a Ziegler catalyst system (TiCl4 and triethylaluminum in hexane). The produced polymer has a high average molecular weight and a multimodal molecular weight distribution composed of four distributions including a very high molecular weight component. The laboratory polymer has a thermal stability in inert atmosphere similar to the commercial high density polyethylene produced by Braskem. In oxidant atmosphere the produced polymer presents three thermal oxidation events above 400ºC due to the combustion of low, medium and high molecular weight molecules. The thermal oxidation of the nanocomposites is shifted and reduced for high temperatures indicating an improvement in the thermal stability of the polymeric matrix due to the clay barrier effect for gases and volatile compounds.
Highlights
Polymer-clay nanocomposites have received considerable attention in recent years due to their excellent mechanical and barrier properties
The results indicated that the crystallization temperatures of the nanocomposites were significantly higher than that of pure polyethylene
The commercial samples present a melting temperature of 131 and 133°C, respectively, and the laboratory samples 133 and 134°C, which confirm the production of high molecular weight polyethylene
Summary
Polymer-clay nanocomposites have received considerable attention in recent years due to their excellent mechanical and barrier properties. Nowadays melt and solution intercalation are the most popular methods for nanocomposite production using a polymeric matrix that contains polar groups[3,4,5]. For a polyolefin matrix the in situ polymerization is the most effective method in clay exfoliation and in the production of nanocomposites[1]. The thermal degradation of polyethyleneclay nanocomposites produced by melt processing improves the stability and reduces inflammability due to the barrier effect and the charring process[1,6]. The thermal stability of high density polyethylene-clay nanocomposites produced by in situ polymerization has received less attention and only a few papers discuss this topic
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