Anionic Polymerization of Lactams in Thermoplastic Composites
Summary
Anionic polymerization of lactams has emerged as a versatile route to manufacture high-performance thermoplastic composites, combining rapid in situ polymer growth with excellent fibre wet-out and recyclability. Central to the method is the activated ring-opening of cyclic amide monomers—most commonly ε-caprolactam—by anionic initiators and activators. This approach yields polyamide 6 matrices that cure at relatively low temperatures and viscosities, enabling impregnation of high-volume-fraction fibres or fabrics without the processing challenges of conventional thermoplastics. Key advantages include short cycle times, precise control over molecular weight and crystallinity, and the ability to incorporate functional comonomers or nanofillers in a single step. The resulting composites exhibit high stiffness and strength, tailored thermal transitions and enhanced interfacial adhesion, making them suitable for automotive, aerospace and sustainable-materials applications. Advances in reaction modelling, moisture management and process optimisation have further broadened design freedom, supporting the transition from thermoset to recyclable thermoplastic platforms and accelerating industrial uptake of in situ polymerisation technologies.
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Anionic Polymerization of Lactams in Thermoplastic Composites publication trend
The graph below shows the total number of articles in anionic polymerization of lactams in thermoplastic composites across all publications each year (not limited to Nature Index journals).
Technical terms
Anionic ring-opening polymerisation: A chain-growth mechanism in which anionic initiators open cyclic lactam monomers to form polyamide chains without significant termination events.
Lactam: A cyclic amide monomer (for example ε-caprolactam) that undergoes ring-opening to produce polyamide structures.
Thermoplastic resin transfer moulding (T-RTM): A processing technique where low-viscosity reactive monomer is injected into a fibre preform and polymerised in situ to yield a consolidated thermoplastic composite.
Activator and initiator: Chemical species that generate and stabilise the anionic active centre required to trigger and propagate the ring-opening polymerisation of lactams.
References
- Polymers and Related Composites via Anionic Ring-Opening Polymerization of Lactams: Recent Developments and Future Trends. Polymers (2018).
- The Effect of the Parameters of T-RTM on the Properties of Polyamide 6 Prepared by in Situ Polymerization. Materials (2019).
- Moisture Adsorption and Desorption Behavior of Raw Materials for the T-RTM Process. Journal of Composites Science (2021).
- Compensation of Water Influence on Anionic Polymerization of ε-Caprolactam: 1. Chemistry and Experiments. Journal of Composites Science (2020).
- Thermoplastic Composite Materials Approach for More Circular Components: From Monomer to In Situ Polymerization, a Review. Journal of Composites Science (2022).
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