Organic-acid mediated bulk polymerization of ε-caprolactam and its copolymerization with ε-caprolactone

Abstract

Polyamides (PA) constitute one of the most important classes of polymeric materials and have gained strong position in different areas, such as textiles, fibers, and construction materials. Whereas most PA are synthesized by step‐growth polycondensation, PA 6 is synthesized by ring opening polymerization (ROP) of ε‐caprolactam (ε‐CLa). The most popular ROP methods involve the use of alkaline metal catalyst difficult to handle at large scale. In this article, we propose the use of organic acids for the ROP of ε‐CLa in bulk at 180 °C (below the polymer's melting point). Among evaluated organic acids, sulfonic acids were found to be the most effective for the polymerization of ε‐CLa , being the Brønsted acid ionic liquid: 1‐(4‐sulfobutyl)−3‐methylimidazolium hydrogen sulfate the most suitable due to its higher thermal stability. End‐group analysis by 1H nuclear magnetic resonance and model reactions provided mechanistic insights and suggested that the catalytic activity of sulfonic acids was a function of not only the acid strength, but of the nucleophilic character of conjugate base as well. Finally, the ability of sulfonic acid to promote the copolymerization of ε‐CLa and ε‐caprolactone is demonstrated. As a result, poly(ε‐caprolactam‐co‐ε‐caprolactone) copolymers with considerably randomness are obtained. This benign route allows the synthesis of poly(ester amide)s with different thermal and mechanical properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2394–2402

Nucleation and Crystallization of PA6 Composites Prepared by T-RTM: Effects of Carbon and Glass Fiber Loading

“…The products used for anionic ring opening polymerization of polyamide 6 (PA6) are the ε-caprolactam monomer, purchased from BASF (Rhein, Germany), sodium aluminum lactate, as initiator, and a commercial mixture of isocianates, as an activator [33,34,35,36]. The reinforcement fabrics used were glass fibers (GF) and carbon fibers (CF) fabrics.…”

“…The CAPROCAST process developed at TECNALIA [33,34,35,36] consists of a device for polymerizing lactams directly in a mold. In a pressurized vessel connected to the mold, the reaction mixture was prepared by melting the reactants at 125 °C under stirring.…”

“…In the present work, we have used a new technology, adapted from thermoplastic resin transfer molding (T-RTM), named and patented as CAPROCAST, and developed at TECNALIA [33,34,35,36]. This process is based on the capacity of ε-caprolactam (the monomer of polyamide 6) to polymerize in situ with an anionic reactive reaction.…”

Effect of Composition on the Crystallization, Water Absorption, and Biodegradation of Poly(ε-caprolactam-co-ε-caprolactone) Copolymers

“…For poly(ε-caprolactam-co-ε-caprolactone) (P(CLA-co-CLO)), the current researches mainly focus on the synthesis and structure characterizations of copolymers. Many synthetic methods have been reported, such as anionic copolymerization, interfacial copolymerization, hydrolytic ring-opening polymerization, and polycondensation [7][8][9][10][11][12][13][14]. Regardless of the synthesis method and feeding sequence, the final products obtained are almost random or multiblock copolymers so far.…”

“…Deshayes and According to the DSC and WAXS results, Michell et al [5,9,[15][16][17] found that only the CLA sequence of P(CLA-co-CLO) copolymers could crystallize except for C 55 -ran-A 45 , and the crystallization temperature (T c ) shifts were affected by microstructure and the dilution effect due to the CLO interruptions. Sanchez et al [11] reported that only in the case of P(CLA 19 -co-CLO 81 ), both CLA and CLO sequences could crystallize, but only a single melting peak. Though the above works found both CLA and CLO sequence could crystallize through DSC melting curves, no extensive studies were carried out.…”