Preparation of anionic polymerized polyamide 6 using internal mixer: The effect of styrene maleic anhydride as a macroactivator

The effect of styrene maleic anhydride (SMA) on the anionic polymerization of ɛ-caprolactam was investigated. Poly-caprolactam (PA6) was prepared at three levels of hexamethylene diisocyanate (HDI) as the microactivator and three levels of SMA in an internal mixer at 200 °C. Then, the polymerization characteristics obtained from the mixing torque curves were compared. With increasing HDI content, reaction time decreased and the reaction rate increased. Final torque, which is attributed to the molecular weight of the synthesized polymer, showed a peak in the average level of HDI. In the presence of SMA, final torque had the same trend, but reaction time increased and reaction rate decreased. Monomer conversion increased by raising both the HDI and SMA contents. In solvent separation by formic acid, samples were found to behave differently. Anionic polymerized polyamides with no SMA formed a uniform and transparent solution, while SMA-containing samples turned into a canescent solution having a colloidal suspension part. The remaining small amount of SMA after solvent separation proved the attribution of SMA in the reaction. FTIR spectra of samples indicated that SMA acts as a macroactivator in the anionic polymerization of ɛ-caprolactam. Also, samples containing SMA showed only one glass transition temperature which was higher than that of samples without SMA, suggesting the existence of a copolymer of SMA and PA6, which raises the Tg.