Effect of calcium carbonate particle size and content on polyamide 6 processing and properties

Abstract

Abstract. Three different types of calcium carbonates, including a nanosize one, were incorporated into polyamide 6, at different contents (5, 10 and 20 wt%) using a corotating twin-screw extruder connected to a Haake torque rheometer. Spherical-like nanosize CaCO3 particles and needle-like precipitated CaCO3 showed to consist of calcite crystals, whereas needle-like naturally occurring CaCO3 particles consisted of both calcite and aragonite. Specimens were injection molded and subjected to tensile, bending and impact testing. XRD, SEM and DSC analyses were also carried out. Both conventional and nanocalcium carbonate reduced torque, with the nano resulting in lower values. All investigated calcium carbonates increased PA6 tensile and flexural strength and elastic modulus.

Effect of injection molding conditions on the properties of polyamide 6/calcium carbonate nanocomposite

“…The fracture surface of the PA6NPCC sample (Figure 5b) is smoother than that of neat PA6 (Figure 5a), indicating a more brittle behavior. Similar effects of low NPCC content on PA6 properties have also been observed by Bonse and Molina 16 . However, the authors noticed a decrease in the degree of crystallinity, attributing the phenomenon to fillers interfering with chain packing.…”

“…However, temperatures as low as 10°C can be used where applicable. The lower V inj (20 cm 3 s −1 ) was chosen based on the work of Bonse and Molina, 16 whereas the higher one (100 cm 3 s −1 ) was a velocity that still allowed obtaining test specimens without visible defects. The third factor is the incorporation of NPCC (Inc), 0 or 3 wt%, a fraction expected to increase mechanical properties while preserving part density due to the high specific area of the nanofiller.…”

“…Prior to specimen injection molding, the obtained pellets were dried in a vacuum oven at 100 C for 24 h. Injection molding occurred in a Battenfeld HM 60/350 E machine with the following fixed parameters: injection pressure of 700 bar, barrel temperature profile of 262/255/245/230 C, packing pressure of 600 bar, and packing time of 10 s. All processing variables were adjusted from earlier work on PA6NPCC by Bonse and Molina. 16 To study the effect of injection molding conditions on material properties, mold temperature (T mold ) was set at 25 C or 85 C and injection velocity (V inj ) at 20 or 100 cm 3 s À1 , according to a 2 3 design of experiments (Table 1). Chen et al 2 and Doagou-Rad et al 6 reported that these variables affect the properties of polyamide nanocomposites.…”

“…Similar effects of low NPCC content on PA6 properties have also been observed by Bonse and Molina. 16 However, the authors noticed a decrease in the degree of crystallinity, attributing the phenomenon to fillers interfering with chain packing. For the present investigation, however, the effect of incorporation on this property was statistically not significant (Figure 1a).…”

“…In their study of PA6/CaCO 3 composites, both conventional and nanostructured, Bonse and Molina 16 observed that the use of nanofiller led to a reduction in torque during extrusion. This reduction in torque, in turn, increased productivity.…”