DEVELOPMENT AND THERMOMECHANICAL CHARACTERIZATION OF THERMOPLASTIC NANOCOMPOSITES BASED ON THE IN-SITU ANIONIC POLYMERIZATION OF POLYAMIDE 6
Topic(s) : Material science
Co-authors :
Lorenzo BROGGIO (ITALY), Giulia FREDI (ITALY), Andrea DORIGATO (ITALY), Alessandro PEGORETTI (ITALY)Abstract :
An interesting technique for creating thermoplastic nanocomposites with high mechanical and functional properties is the in-situ anionic polymerization of polyamide 6 (PA6). This study aims to investigate the thermomechanical properties of anionic PA6-matrix (aPA6) nanocomposites, establish a correlation with microstructural attributes like the degree of crystallinity and the dispersion of nanofiller and look into promising ways to improve them towards high end applications.
The nanocomposites were prepared in a lab-made small-scale polymerization plant as follows. Caprolactam (CL)(AP-Nylon, Bruggeman S.A.), was melted at 110 °C in a round-bottom flask under nitrogen flow, followed by the addition of a commercial initiator and activator (C10 and C20P, Bruggeman S.A.) in variable concentrations and the layered nanofiller (expanded graphite nanoplatelets (xGnPs), organomodified nanoclays) in proper amount. The stirred mixture was then injected into a mold preheated at varying temperatures (140-170 °C) through a thermoplastic resin transfer molding (tRTM) facility, and left to polymerize for 20 minutes.
While all the investigated nanofillers mostly increased the elastic modulus, the quasi-static properties at break and the impact properties resulted to be strongly affected by the nanofiller dispersion. The mechanical properties of the nanocomposites were found to be influenced by the processing parameters such as the temperature and the concentration of the initiator and activator, mostly due to the profound impact of these parameters on the matrix crystallinity. Tensile tests on the PA6 samples showed that optimal mechanical properties were found at intermediate polymerization temperatures (150-160 °C) and low initiator and activator concentrations. All the investigated nanocomposites presented a high degree of conversion with little (<2%) residual caprolactam, as investigated by thermogravimetric analysis.
The use of a compatibilizer between the matrix and the nanoplatelets and the ultrasonication of the reactive mixture was found to be effective in order to improve of the nanofiller dispersion.
This study provides valuable insights into the properties and behavior of thermoplastic nanocomposites based on aPA6. While the results suggest that these nanocomposites have potential for use in various applications where improved mechanical, thermal, and electrical properties are required, further research is needed to fully characterize the interfacial interactions between the fillers and the matrix and to improve the filler dispersion, also with the introduction of surface functionalization.
The nanocomposites were prepared in a lab-made small-scale polymerization plant as follows. Caprolactam (CL)(AP-Nylon, Bruggeman S.A.), was melted at 110 °C in a round-bottom flask under nitrogen flow, followed by the addition of a commercial initiator and activator (C10 and C20P, Bruggeman S.A.) in variable concentrations and the layered nanofiller (expanded graphite nanoplatelets (xGnPs), organomodified nanoclays) in proper amount. The stirred mixture was then injected into a mold preheated at varying temperatures (140-170 °C) through a thermoplastic resin transfer molding (tRTM) facility, and left to polymerize for 20 minutes.
While all the investigated nanofillers mostly increased the elastic modulus, the quasi-static properties at break and the impact properties resulted to be strongly affected by the nanofiller dispersion. The mechanical properties of the nanocomposites were found to be influenced by the processing parameters such as the temperature and the concentration of the initiator and activator, mostly due to the profound impact of these parameters on the matrix crystallinity. Tensile tests on the PA6 samples showed that optimal mechanical properties were found at intermediate polymerization temperatures (150-160 °C) and low initiator and activator concentrations. All the investigated nanocomposites presented a high degree of conversion with little (<2%) residual caprolactam, as investigated by thermogravimetric analysis.
The use of a compatibilizer between the matrix and the nanoplatelets and the ultrasonication of the reactive mixture was found to be effective in order to improve of the nanofiller dispersion.
This study provides valuable insights into the properties and behavior of thermoplastic nanocomposites based on aPA6. While the results suggest that these nanocomposites have potential for use in various applications where improved mechanical, thermal, and electrical properties are required, further research is needed to fully characterize the interfacial interactions between the fillers and the matrix and to improve the filler dispersion, also with the introduction of surface functionalization.