Novel Anionic Polymerization of varepsilon-Caprolactam Towards Polyamide 6 Containing Nanofibrils

Anionic ring-opening polymerization of ه-caprolactam leads to the formation of polyamide 6 (PA6). This reaction takes place at a significantly faster reaction rate and gives a narrower molecular weight distribution than the other techniques. Due to this advantage, anionic polymerization of ه-caprolactam towards PA6 in melt blending was investigated in this work. PA6 was prepared in an internal mixer via melt polymerization of ه-caprolactam as a monomer with sodium caprolactam as its catalyst and hexamethylene diisocyanate as an activator. The effects of various concentrations of catalyst and activator on the initiation time of the reaction and on the residual monomer were determined. The residual monomer was collected using a solvent extraction method and determined by GC-mass technique. The physical and mechanical properties of the PA6 prepared via melt blending and of a commercial PA6 prepared were determined by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), tensile and impact tests. The experimental results showed that addition of 3% catalyst and 3% activator to the formulation gave the best properties. These conditions led to the lowest residual monomer and better mechanical properties as well. The other novel aspect of this investigation was the formation of nanofibril during melt polymerization of ه-caprolactam. Mechanical properties showed that the PA6 prepared by using this technique and the above formulation were similar to the PA6 commercial grade.