Experimental study of polymerization and crystallization kinetics of polyamide 6 obtained by anionic ring opening polymerization of ε-caprolactam

Abstract

To adapt liquid reactive processes to thermoplastic composite manufacturing, synthesis kinetics of PA6 from ε-caprolactam monomer have been investigated. This reaction involves simultaneously polymerization of monomers and crystallization of growing chains. It has been studied by DSC over a wide range of isothermal and non-isothermal conditions, and TGA, DSC and WAXS experiments were performed on polymerized samples. Shape of DSC curves allowed to identify the degree of interaction between polymerization and crystallization. At high temperature or high heating rate, polymerization occurs first and crystallization is delayed because of the low supercooling. When phenomena are fully decoupled, the final properties are close to conventional PA6. For lower conditions, crystallization depends on the availability of chains and polymerization controls the synthesis time. The high mobility of the environment favors the final degree of conversion and the properties of the crystalline phase. At very low temperature, a two-step crystallization is observed, due to a critical molecular weight that is required for nucleation and the degree of conversion could be affected by entrapment of reactive species in crystals.

The reactive compatibilization effect of copolymer macroactivator for immiscible anionic polyamide 6/polystyrene blends via in situ polymerization

“…The data are summarized in Table in detail. From second heating DSC scans, for the samples of M3 and M5, two peaks are observed as denoted by T m 1 and T m 2 referring to the melting of unstable γ‐phase at about 210 °C followed by the melting of stable α‐phase at about 217 °C, respectively . In addition, with the increase of IEM, the T m 1 and T m 2 also drop slightly.…”

Effect of thermoplastic resin transfer molding process and flame surface treatment on mechanical properties of carbon fiber reinforced polyamide 6 composite

“…In the range from 120 to 160°C, the dD/dt for the AROP of the T‐RTM process showed a similar result to that with the thermoset resin. In cases where the curing temperature was lower than 160°C, the polymerization and crystallization of the PA 6 occurred simultaneously; therefore, the dD/dt represented only one maximum peak (curing initiation point) and negative peak (gelation initiation point), as shown in Figure A. When the curing (polymerization and crystallization) is initiated, the ion viscosity also begins to be reduced; therefore, the dD/dt has a maximum peak point.…”

“…In the last decade, demand of fiber‐reinforced polymer (FRP) composites for lightweight structures has exploded in the automotive, aerospace, and energy industries . Thermoset polymer composites are mostly used in industry due to the ease of the manufacturing process based on the liquid state (resin transfer molding, infusion, filament‐winding, and so on) . Currently, researchers are focusing more attention on carbon fiber reinforced thermoplastic polymer composites (CFRTP) due to the recycling, heat and impact resistance issues of thermoset polymer composites.…”

“…The curing temperature has a direct influence on the crystallinity and physical properties of PA6. This is because the polymerization and crystallization of PA6 synthesis via the AROP process occurs simultaneously due to the polymerization temperature being lower (>120°C) than the melting temperature of PA6 (220°C) . Therefore, the curing temperature is the most important processing parameter.…”

“…This is because the polymerization and crystallization of PA6 synthesis via the AROP process occurs simultaneously due to the polymerization temperature being lower (>120 C) than the melting temperature of PA6 (220 C). [3,18,19] Therefore, the curing temperature is the most important processing parameter. There are many studies about the activator and catalyst (type and concentration) and curing conditions.…”